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 /*
  * The Lean Mean C++ Option Parser
  *
  * Copyright (C) 2012 Matthias S. Benkmann
  *
  * The "Software" in the following 2 paragraphs refers to this file containing
  * the code to The Lean Mean C++ Option Parser.
  * The "Software" does NOT refer to any other files which you
  * may have received alongside this file (e.g. as part of a larger project that
  * incorporates The Lean Mean C++ Option Parser).
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software, to deal in the Software without restriction, including
  * without limitation the rights to use, copy, modify, merge, publish,
  * distribute, sublicense, and/or sell copies of the Software, and to permit
  * persons to whom the Software is furnished to do so, subject to the following
  * conditions:
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
 
 /*
  * NOTE: It is recommended that you read the processed HTML doxygen documentation
  * rather than this source. If you don't know doxygen, it's like javadoc for C++.
  * If you don't want to install doxygen you can find a copy of the processed
  * documentation at
  *
  * http://optionparser.sourceforge.net/
  *
  */
 
 /**
  * @file
  *
  * @brief This is the only file required to use The Lean Mean C++ Option Parser.
  *        Just \#include it and you're set.
  *
  * The Lean Mean C++ Option Parser handles the program's command line arguments 
  * (argc, argv).
  * It supports the short and long option formats of getopt(), getopt_long() 
  * and getopt_long_only() but has a more convenient interface.
  * The following features set it apart from other option parsers:
  *
  * @par Highlights:
  * <ul style="padding-left:1em;margin-left:0">
  * <li> It is a header-only library. Just <code>\#include "optionparser.h"</code> and you're set.
  * <li> It is freestanding. There are no dependencies whatsoever, not even the
  *      C or C++ standard library.
  * <li> It has a usage message formatter that supports column alignment and
  *      line wrapping. This aids localization because it adapts to
  *      translated strings that are shorter or longer (even if they contain
  *      Asian wide characters).
  * <li> Unlike getopt() and derivatives it doesn't force you to loop through
  *     options sequentially. Instead you can access options directly like this:
  *     <ul style="margin-top:.5em">
  *     <li> Test for presence of a switch in the argument vector:
  *      @code if ( options[QUIET] ) ... @endcode
  *     <li> Evaluate --enable-foo/--disable-foo pair where the last one used wins:
  *     @code if ( options[FOO].last()->type() == DISABLE ) ... @endcode
  *     <li> Cumulative option (-v verbose, -vv more verbose, -vvv even more verbose):
  *     @code int verbosity = options[VERBOSE].count(); @endcode
  *     <li> Iterate over all --file=&lt;fname> arguments:
  *     @code for (Option* opt = options[FILE]; opt; opt = opt->next())
  *   fname = opt->arg; ... @endcode
  *     <li> If you really want to, you can still process all arguments in order:
  *     @code
  *   for (int i = 0; i < p.optionsCount(); ++i) {
  *     Option& opt = buffer[i];
  *     switch(opt.index()) {
  *       case HELP:    ...
  *       case VERBOSE: ...
  *       case FILE:    fname = opt.arg; ...
  *       case UNKNOWN: ...
  *     @endcode
  *     </ul>
  * </ul> @n
  * Despite these features the code size remains tiny. 
  * It is smaller than <a href="http://uclibc.org">uClibc</a>'s GNU getopt() and just a
  * couple 100 bytes larger than uClibc's SUSv3 getopt(). @n
  * (This does not include the usage formatter, of course. But you don't have to use that.)
  *
  * @par Download:
  * Tarball with examples and test programs:
  * <a style="font-size:larger;font-weight:bold" href="http://sourceforge.net/projects/optionparser/files/optionparser-1.4.tar.gz/download">optionparser-1.4.tar.gz</a> @n
  * Just the header (this is all you really need):
  * <a style="font-size:larger;font-weight:bold" href="http://optionparser.sourceforge.net/optionparser.h">optionparser.h</a>
  *
  * @par Changelog:
  * <b>Version 1.4:</b> Fixed 2 printUsage() bugs that messed up output with small COLUMNS values @n
  * <b>Version 1.3:</b> Compatible with Microsoft Visual C++. @n
  * <b>Version 1.2:</b> Added @ref ATOOLS::Option_Parser::Option::namelen "Option::namelen" and removed the extraction
  *                     of short option characters into a special buffer. @n
  *                     Changed @ref ATOOLS::Option_Parser::Arg::Optional "Arg::Optional" to accept arguments if they are attached
  *                     rather than separate. This is what GNU getopt() does and how POSIX recommends
  *                     utilities should interpret their arguments.@n
  * <b>Version 1.1:</b> Optional mode with argument reordering as done by GNU getopt(), so that
  *                     options and non-options can be mixed. See
  *                     @ref ATOOLS::Option_Parser::Parser::parse() "Parser::parse()".
  *
  * @par Feedback:
  * Send questions, bug reports, feature requests etc. to: <tt><b>optionparser-feedback<span id="antispam">&nbsp;(a)&nbsp;</span>lists.sourceforge.net</b></tt>
  * @htmlonly <script type="text/javascript">document.getElementById("antispam").innerHTML="@"</script> @endhtmlonly
  *
  *
  * @par Example program:
  * (Note: @c option::* identifiers are links that take you to their documentation.)
  * @code
  * #error EXAMPLE SHORTENED FOR READABILITY. BETTER EXAMPLES ARE IN THE .TAR.GZ!
  * #include <iostream>
  * #include "optionparser.h"
  *
  * enum  optionIndex { UNKNOWN, HELP, PLUS };
  * const option::Descriptor usage[] =
  * {
  *  {UNKNOWN, 0,"" , ""    ,option::Arg::None, "USAGE: example [options]\n\n"
  *                                             "Options:" },
  *  {HELP,    0,"" , "help",option::Arg::None, "  --help  \tPrint usage and exit." },
  *  {PLUS,    0,"p", "plus",option::Arg::None, "  --plus, -p  \tIncrement count." },
  *  {UNKNOWN, 0,"" ,  ""   ,option::Arg::None, "\nExamples:\n"
  *                                             "  example --unknown -- --this_is_no_option\n"
  *                                             "  example -unk --plus -ppp file1 file2\n" },
  *  {0,0,0,0,0,0}
  * };
  *
  * int main(int argc, char* argv[])
  * {
  *   argc-=(argc>0); argv+=(argc>0); // skip program name argv[0] if present
  *   option::Stats  stats(usage, argc, argv);
  *   option::Option options[stats.options_max], buffer[stats.buffer_max];
  *   option::Parser parse(usage, argc, argv, options, buffer);
  *
  *   if (parse.error())
  *     return 1;
  *
  *   if (options[HELP] || argc == 0) {
  *     option::printUsage(std::cout, usage);
  *     return 0;
  *   }
  *
  *   std::cout << "--plus count: " <<
  *     options[PLUS].count() << "\n";
  *
  *   for (option::Option* opt = options[UNKNOWN]; opt; opt = opt->next())
  *     std::cout << "Unknown option: " << opt->name << "\n";
  *
  *   for (int i = 0; i < parse.nonOptionsCount(); ++i)
  *     std::cout << "Non-option #" << i << ": " << parse.nonOption(i) << "\n";
  * }
  * @endcode
  *
  * @par Option syntax:
  * @li The Lean Mean C++ Option Parser follows POSIX <code>getopt()</code> conventions and supports
  *     GNU-style <code>getopt_long()</code> long options as well as Perl-style single-minus
  *     long options (<code>getopt_long_only()</code>).
  * @li short options have the format @c -X where @c X is any character that fits in a char.
  * @li short options can be grouped, i.e. <code>-X -Y</code> is equivalent to @c -XY.
  * @li a short option may take an argument either separate (<code>-X foo</code>) or
  *     attached (@c -Xfoo). You can make the parser accept the additional format @c -X=foo by
  *     registering @c X as a long option (in addition to being a short option) and
  *     enabling single-minus long options.
  * @li an argument-taking short option may be grouped if it is the last in the group, e.g.
  *     @c -ABCXfoo or <code> -ABCX foo </code> (@c foo is the argument to the @c -X option).
  * @li a lone minus character @c '-' is not treated as an option. It is customarily used where
  *     a file name is expected to refer to stdin or stdout.
  * @li long options have the format @c --option-name.
  * @li the option-name of a long option can be anything and include any characters.
  *     Even @c = characters will work, but don't do that.
  * @li [optional] long options may be abbreviated as long as the abbreviation is unambiguous.
  *     You can set a minimum length for abbreviations.
  * @li [optional] long options may begin with a single minus. The double minus form is always
  *     accepted, too.
  * @li a long option may take an argument either separate (<code> --option arg </code>) or
  *     attached (<code> --option=arg </code>). In the attached form the equals sign is mandatory.
  * @li an empty string can be passed as an attached long option argument: <code> --option-name= </code>.
  *     Note the distinction between an empty string as argument and no argument at all.
  * @li an empty string is permitted as separate argument to both long and short options.
  * @li Arguments to both short and long options may start with a @c '-' character. E.g.
  *     <code> -X-X </code>, <code>-X -X</code> or <code> --long-X=-X </code>. If @c -X
  *     and @c --long-X take an argument, that argument will be @c "-X" in all 3 cases.
  * @li If using the built-in @ref ATOOLS::Option_Parser::Arg::Optional "Arg::Optional", optional arguments must
  *     be attached.
  * @li the special option @c -- (i.e. without a name) terminates the list of
  *     options. Everything that follows is a non-option argument, even if it starts with
  *     a @c '-' character. The @c -- itself will not appear in the parse results.
  * @li the first argument that doesn't start with @c '-' or @c '--' and does not belong to
  *     a preceding argument-taking option, will terminate the option list and is the
  *     first non-option argument. All following command line arguments are treated as
  *     non-option arguments, even if they start with @c '-' . @n
  *     NOTE: This behaviour is mandated by POSIX, but GNU getopt() only honours this if it is
  *     explicitly requested (e.g. by setting POSIXLY_CORRECT). @n
  *     You can enable the GNU behaviour by passing @c true as first argument to
  *     e.g. @ref ATOOLS::Option_Parser::Parser::parse() "Parser::parse()".
  * @li Arguments that look like options (i.e. @c '-' followed by at least 1 character) but
  *     aren't, are NOT treated as non-option arguments. They are treated as unknown options and
  *     are collected into a list of unknown options for error reporting. @n
  *     This means that in order to pass a first non-option
  *     argument beginning with the minus character it is required to use the
  *     @c -- special option, e.g.
  *     @code
  *     program -x -- --strange-filename
  *     @endcode
  *     In this example, @c --strange-filename is a non-option argument. If the @c --
  *     were omitted, it would be treated as an unknown option. @n
  *     See @ref ATOOLS::Option_Parser::Descriptor::longopt for information on how to collect unknown options.
  *
  */
 
 #ifndef ATOOLS_Org_Option_Parser_H
 #define ATOOLS_Org_Option_Parser_H
 
 #include <cstdio>
 
 namespace ATOOLS
 {
 
 /** @brief The namespace of The Lean Mean C++ Option Parser. */
 namespace Option_Parser
 {
 
 #ifdef _MSC_VER
 #include <intrin.h>
 #pragma intrinsic(_BitScanReverse)
 struct MSC_Builtin_CLZ
 {
   static int builtin_clz(unsigned x)
   {
     unsigned long index;
     _BitScanReverse(&index, x);
     return 32-index; // int is always 32bit on Windows, even for target x64
   }
 };
 #define __builtin_clz(x) MSC_Builtin_CLZ::builtin_clz(x)
 #endif
 
 class Option;
 
 /**
  * @brief Possible results when checking if an argument is valid for a certain option.
  *
  * In the case that no argument is provided for an option that takes an
  * optional argument, return codes @c ARG_OK and @c ARG_IGNORE are equivalent.
  */
 enum ArgStatus
 {
   //! The option does not take an argument.
   ARG_NONE,
   //! The argument is acceptable for the option.
   ARG_OK,
   //! The argument is not acceptable but that's non-fatal because the option's argument is optional.
   ARG_IGNORE,
   //! The argument is not acceptable and that's fatal.
   ARG_ILLEGAL
 };
 
 /**
  * @brief Signature of functions that check if an argument is valid for a certain type of option.
  *
  * Every Option has such a function assigned in its Descriptor.
  * @code
  * Descriptor usage[] = { {UNKNOWN, 0, "", "", Arg::None, ""}, ... };
  * @endcode
  *
  * A CheckArg function has the following signature:
  * @code ArgStatus CheckArg(const Option& option, bool msg); @endcode
  *
  * It is used to check if a potential argument would be acceptable for the option.
  * It will even be called if there is no argument. In that case @c option.arg will be @c NULL.
  *
  * If @c msg is @c true and the function determines that an argument is not acceptable and
  * that this is a fatal error, it should output a message to the user before
  * returning @ref ARG_ILLEGAL. If @c msg is @c false the function should remain silent (or you
  * will get duplicate messages).
  *
  * See @ref ArgStatus for the meaning of the return values.
  *
  * While you can provide your own functions,
  * often the following pre-defined checks (which never return @ref ARG_ILLEGAL) will suffice:
  *
  * @li @c Arg::None @copybrief Arg::None
  * @li @c Arg::Optional @copybrief Arg::Optional
  *
  */
 typedef ArgStatus (*CheckArg)(const Option& option, bool msg);
 
 /**
  * @brief Describes an option, its help text (usage) and how it should be parsed.
  *
  * The main input when constructing an option::Parser is an array of Descriptors.
 
  * @par Example:
  * @code
  * enum OptionIndex {CREATE, ...};
  * enum OptionType {DISABLE, ENABLE, OTHER};
  *
  * const option::Descriptor usage[] = {
  *   { CREATE,                                            // index
  *     OTHER,                                             // type
  *     "c",                                               // shortopt
  *     "create",                                          // longopt
  *     Arg::None,                                         // check_arg
  *     "--create  Tells the program to create something." // help
  *   }
  *   , ...
  * };
  * @endcode
  */
 struct Descriptor
 {
   /**
    * @brief Index of this option's linked list in the array filled in by the parser.
    *
    * Command line options whose Descriptors have the same index will end up in the same
    * linked list in the order in which they appear on the command line. If you have
    * multiple long option aliases that refer to the same option, give their descriptors
    * the same @c index.
    *
    * If you have options that mean exactly opposite things
    * (e.g. @c --enable-foo and @c --disable-foo ), you should also give them the same
    * @c index, but distinguish them through different values for @ref type.
    * That way they end up in the same list and you can just take the last element of the
    * list and use its type. This way you get the usual behaviour where switches later
    * on the command line override earlier ones without having to code it manually.
    *
    * @par Tip:
    * Use an enum rather than plain ints for better readability, as shown in the example
    * at Descriptor.
    */
   const unsigned index;
 
   /**
    * @brief Used to distinguish between options with the same @ref index.
    * See @ref index for details.
    *
    * It is recommended that you use an enum rather than a plain int to make your
    * code more readable.
    */
   const int type;
 
   /**
    * @brief Each char in this string will be accepted as a short option character.
    *
    * The string must not include the minus character @c '-' or you'll get undefined
    * behaviour.
    *
    * If this Descriptor should not have short option characters, use the empty
    * string "". NULL is not permitted here!
    *
    * See @ref longopt for more information.
    */
   const char* const shortopt;
 
   /**
    * @brief The long option name (without the leading @c -- ).
    *
    * If this Descriptor should not have a long option name, use the empty
    * string "". NULL is not permitted here!
    *
    * While @ref shortopt allows multiple short option characters, each
    * Descriptor can have only a single long option name. If you have multiple
    * long option names referring to the same option use separate Descriptors
    * that have the same @ref index and @ref type. You may repeat
    * short option characters in such an alias Descriptor but there's no need to.
    *
    * @par Dummy Descriptors:
    * You can use dummy Descriptors with an
    * empty string for both @ref shortopt and @ref longopt to add text to
    * the usage that is not related to a specific option. See @ref help.
    * The first dummy Descriptor will be used for unknown options (see below).
    *
    * @par Unknown Option Descriptor:
    * The first dummy Descriptor in the list of Descriptors,
    * whose @ref shortopt and @ref longopt are both the empty string, will be used
    * as the Descriptor for unknown options. An unknown option is a string in
    * the argument vector that is not a lone minus @c '-' but starts with a minus
    * character and does not match any Descriptor's @ref shortopt or @ref longopt. @n
    * Note that the dummy descriptor's @ref check_arg function @e will be called and
    * its return value will be evaluated as usual. I.e. if it returns @ref ARG_ILLEGAL
    * the parsing will be aborted with <code>Parser::error()==true</code>. @n
    * if @c check_arg does not return @ref ARG_ILLEGAL the descriptor's
    * @ref index @e will be used to pick the linked list into which
    * to put the unknown option. @n
    * If there is no dummy descriptor, unknown options will be dropped silently.
    *
    */
   const char* const longopt;
 
   /**
    * @brief For each option that matches @ref shortopt or @ref longopt this function
    * will be called to check a potential argument to the option.
    *
    * This function will be called even if there is no potential argument. In that case
    * it will be passed @c NULL as @c arg parameter. Do not confuse this with the empty
    * string.
    *
    * See @ref CheckArg for more information.
    */
   const CheckArg check_arg;
 
   /**
    * @brief The usage text associated with the options in this Descriptor.
    *
    * You can use option::printUsage() to format your usage message based on
    * the @c help texts. You can use dummy Descriptors where
    * @ref shortopt and @ref longopt are both the empty string to add text to
    * the usage that is not related to a specific option.
    *
    * See option::printUsage() for special formatting characters you can use in
    * @c help to get a column layout.
    *
    * @attention
    * Must be UTF-8-encoded. If your compiler supports C++11 you can use the "u8"
    * prefix to make sure string literals are properly encoded.
    */
   const char* help;
 };
 
 /**
  * @brief A parsed option from the command line together with its argument if it has one.
  *
  * The Parser chains all parsed options with the same Descriptor::index together
  * to form a linked list. This allows you to easily implement all of the common ways
  * of handling repeated options and enable/disable pairs.
  *
  * @li Test for presence of a switch in the argument vector:
  *      @code if ( options[QUIET] ) ... @endcode
  * @li Evaluate --enable-foo/--disable-foo pair where the last one used wins:
  *     @code if ( options[FOO].last()->type() == DISABLE ) ... @endcode
  * @li Cumulative option (-v verbose, -vv more verbose, -vvv even more verbose):
  *     @code int verbosity = options[VERBOSE].count(); @endcode
  * @li Iterate over all --file=&lt;fname> arguments:
  *     @code for (Option* opt = options[FILE]; opt; opt = opt->next())
  *   fname = opt->arg; ... @endcode
  */
 class Option
 {
   Option* next_;
   Option* prev_;
 public:
   /**
    * @brief Pointer to this Option's Descriptor.
    *
    * Remember that the first dummy descriptor (see @ref Descriptor::longopt) is used
    * for unknown options.
    *
    * @attention
    * @c desc==NULL signals that this Option is unused. This is the default state of
    * elements in the result array. You don't need to test @c desc explicitly. You
    * can simply write something like this:
    * @code
    * if (options[CREATE])
    * {
    *   ...
    * }
    * @endcode
    * This works because of <code> operator const Option*() </code>.
    */
   const Descriptor* desc;
 
   /**
    * @brief The name of the option as used on the command line.
    *
    * The main purpose of this string is to be presented to the user in messages.
    *
    * In the case of a long option, this is the actual @c argv pointer, i.e. the first
    * character is a '-'. In the case of a short option this points to the option
    * character within the @c argv string.
    *
    * Note that in the case of a short option group or an attached option argument, this
    * string will contain additional characters following the actual name. Use @ref namelen
    * to filter out the actual option name only.
    *
    */
   const char* name;
 
   /**
    * @brief Pointer to this Option's argument (if any).
    *
    * NULL if this option has no argument. Do not confuse this with the empty string which
    * is a valid argument.
    */
   const char* arg;
 
   /**
    * @brief The length of the option @ref name.
    *
    * Because @ref name points into the actual @c argv string, the option name may be
    * followed by more characters (e.g. other short options in the same short option group).
    * This value is the number of bytes (not characters!) that are part of the actual name.
    *
    * For a short option, this length is always 1. For a long option this length is always
    * at least 2 if single minus long options are permitted and at least 3 if they are disabled.
    *
    * @note
    * In the pathological case of a minus within a short option group (e.g. @c -xf-z), this
    * length is incorrect, because this case will be misinterpreted as a long option and the
    * name will therefore extend to the string's 0-terminator or a following '=" character
    * if there is one. This is irrelevant for most uses of @ref name and @c namelen. If you
    * really need to distinguish the case of a long and a short option, compare @ref name to
    * the @c argv pointers. A long option's @c name is always identical to one of them,
    * whereas a short option's is never.
    */
   int namelen;
 
   /**
    * @brief Returns Descriptor::type of this Option's Descriptor, or 0 if this Option
    * is invalid (unused).
    *
    * Because this method (and last(), too) can be used even on unused Options with desc==0, you can (provided
    * you arrange your types properly) switch on type() without testing validity first.
    * @code
    * enum OptionType { UNUSED=0, DISABLED=0, ENABLED=1 };
    * enum OptionIndex { FOO };
    * const Descriptor usage[] = {
    *   { FOO, ENABLED,  "", "enable-foo",  Arg::None, 0 },
    *   { FOO, DISABLED, "", "disable-foo", Arg::None, 0 },
    *   { 0, 0, 0, 0, 0, 0 } };
    * ...
    * switch(options[FOO].last()->type()) // no validity check required!
    * {
    *   case ENABLED: ...
    *   case DISABLED: ...  // UNUSED==DISABLED !
    * }
    * @endcode
    */
   int type() const
   {
     return desc == 0 ? 0 : desc->type;
   }
 
   /**
    * @brief Returns Descriptor::index of this Option's Descriptor, or -1 if this Option
    * is invalid (unused).
    */
   int index() const
   {
     return desc == 0 ? -1 : (int)desc->index;
   }
 
   /**
    * @brief Returns the number of times this Option (or others with the same Descriptor::index)
    * occurs in the argument vector.
    *
    * This corresponds to the number of elements in the linked list this Option is part of.
    * It doesn't matter on which element you call count(). The return value is always the same.
    *
    * Use this to implement cumulative options, such as -v, -vv, -vvv for
    * different verbosity levels.
    *
    * Returns 0 when called for an unused/invalid option.
    */
   int count()
   {
     int c = (desc == 0 ? 0 : 1);
     Option* p = first();
     while (!p->isLast())
     {
       ++c;
       p = p->next_;
     };
     return c;
   }
 
   /**
    * @brief Returns true iff this is the first element of the linked list.
    *
    * The first element in the linked list is the first option on the command line
    * that has the respective Descriptor::index value.
    *
    * Returns true for an unused/invalid option.
    */
   bool isFirst() const
   {
     return isTagged(prev_);
   }
 
   /**
    * @brief Returns true iff this is the last element of the linked list.
    *
    * The last element in the linked list is the last option on the command line
    * that has the respective Descriptor::index value.
    *
    * Returns true for an unused/invalid option.
    */
   bool isLast() const
   {
     return isTagged(next_);
   }
 
   /**
    * @brief Returns a pointer to the first element of the linked list.
    *
    * Use this when you want the first occurrence of an option on the command line to
    * take precedence. Note that this is not the way most programs handle options.
    * You should probably be using last() instead.
    *
    * @note
    * This method may be called on an unused/invalid option and will return a pointer to the
    * option itself.
    */
   Option* first()
   {
     Option* p = this;
     while (!p->isFirst())
       p = p->prev_;
     return p;
   }
 
   /**
    * @brief Returns a pointer to the last element of the linked list.
    *
    * Use this when you want the last occurrence of an option on the command line to
    * take precedence. This is the most common way of handling conflicting options.
    *
    * @note
    * This method may be called on an unused/invalid option and will return a pointer to the
    * option itself.
    *
    * @par Tip:
    * If you have options with opposite meanings (e.g. @c --enable-foo and @c --disable-foo), you
    * can assign them the same Descriptor::index to get them into the same list. Distinguish them by
    * Descriptor::type and all you have to do is check <code> last()->type() </code> to get
    * the state listed last on the command line.
    */
   Option* last()
   {
     return first()->prevwrap();
   }
 
   /**
    * @brief Returns a pointer to the previous element of the linked list or NULL if
    * called on first().
    *
    * If called on first() this method returns NULL. Otherwise it will return the
    * option with the same Descriptor::index that precedes this option on the command
    * line.
    */
   Option* prev()
   {
     return isFirst() ? 0 : prev_;
   }
 
   /**
    * @brief Returns a pointer to the previous element of the linked list with wrap-around from
    * first() to last().
    *
    * If called on first() this method returns last(). Otherwise it will return the
    * option with the same Descriptor::index that precedes this option on the command
    * line.
    */
   Option* prevwrap()
   {
     return untag(prev_);
   }
 
   /**
    * @brief Returns a pointer to the next element of the linked list or NULL if called
    * on last().
    *
    * If called on last() this method returns NULL. Otherwise it will return the
    * option with the same Descriptor::index that follows this option on the command
    * line.
    */
   Option* next()
   {
     return isLast() ? 0 : next_;
   }
 
   /**
    * @brief Returns a pointer to the next element of the linked list with wrap-around from
    * last() to first().
    *
    * If called on last() this method returns first(). Otherwise it will return the
    * option with the same Descriptor::index that follows this option on the command
    * line.
    */
   Option* nextwrap()
   {
     return untag(next_);
   }
 
   /**
    * @brief Makes @c new_last the new last() by chaining it into the list after last().
    *
    * It doesn't matter which element you call append() on. The new element will always
    * be appended to last().
    *
    * @attention
    * @c new_last must not yet be part of a list, or that list will become corrupted, because
    * this method does not unchain @c new_last from an existing list.
    */
   void append(Option* new_last)
   {
     Option* p = last();
     Option* f = first();
     p->next_ = new_last;
     new_last->prev_ = p;
     new_last->next_ = tag(f);
     f->prev_ = tag(new_last);
   }
 
   /**
    * @brief Casts from Option to const Option* but only if this Option is valid.
    *
    * If this Option is valid (i.e. @c desc!=NULL), returns this.
    * Otherwise returns NULL. This allows testing an Option directly
    * in an if-clause to see if it is used:
    * @code
    * if (options[CREATE])
    * {
    *   ...
    * }
    * @endcode
    * It also allows you to write loops like this:
    * @code for (Option* opt = options[FILE]; opt; opt = opt->next())
    *   fname = opt->arg; ... @endcode
    */
   operator const Option*() const
   {
     return desc ? this : 0;
   }
 
   /**
    * @brief Casts from Option to Option* but only if this Option is valid.
    *
    * If this Option is valid (i.e. @c desc!=NULL), returns this.
    * Otherwise returns NULL. This allows testing an Option directly
    * in an if-clause to see if it is used:
    * @code
    * if (options[CREATE])
    * {
    *   ...
    * }
    * @endcode
    * It also allows you to write loops like this:
    * @code for (Option* opt = options[FILE]; opt; opt = opt->next())
    *   fname = opt->arg; ... @endcode
    */
   operator Option*()
   {
     return desc ? this : 0;
   }
 
   /**
    * @brief Creates a new Option that is a one-element linked list and has NULL
    * @ref desc, @ref name, @ref arg and @ref namelen.
    */
   Option() :
       desc(0), name(0), arg(0), namelen(0)
   {
     prev_ = tag(this);
     next_ = tag(this);
   }
 
   /**
    * @brief Creates a new Option that is a one-element linked list and has the given
    * values for @ref desc, @ref name and @ref arg.
    *
    * If @c name_ points at a character other than '-' it will be assumed to refer to a
    * short option and @ref namelen will be set to 1. Otherwise the length will extend to
    * the first '=' character or the string's 0-terminator.
    */
   Option(const Descriptor* desc_, const char* name_, const char* arg_)
   {
     init(desc_, name_, arg_);
   }
 
   /**
    * @brief Makes @c *this a copy of @c orig except for the linked list pointers.
    *
    * After this operation @c *this will be a one-element linked list.
    */
   void operator=(const Option& orig)
   {
     init(orig.desc, orig.name, orig.arg);
   }
 
   /**
    * @brief Makes @c *this a copy of @c orig except for the linked list pointers.
    *
    * After this operation @c *this will be a one-element linked list.
    */
   Option(const Option& orig)
   {
     init(orig.desc, orig.name, orig.arg);
   }
 
 private:
   /**
    * @internal
    * @brief Sets the fields of this Option to the given values (extracting @c name if necessary).
    *
    * If @c name_ points at a character other than '-' it will be assumed to refer to a
    * short option and @ref namelen will be set to 1. Otherwise the length will extend to
    * the first '=' character or the string's 0-terminator.
    */
   void init(const Descriptor* desc_, const char* name_, const char* arg_)
   {
     desc = desc_;
     name = name_;
     arg = arg_;
     prev_ = tag(this);
     next_ = tag(this);
     namelen = 0;
     if (name == 0)
       return;
     namelen = 1;
     if (name[0] != '-')
       return;
     while (name[namelen] != 0 && name[namelen] != '=')
       ++namelen;
   }
 
   static Option* tag(Option* ptr)
   {
     return (Option*) ((unsigned long long) ptr | 1);
   }
 
   static Option* untag(Option* ptr)
   {
     return (Option*) ((unsigned long long) ptr & ~1ull);
   }
 
   static bool isTagged(Option* ptr)
   {
     return ((unsigned long long) ptr & 1);
   }
 };
 
 /**
  * @brief Functions for checking the validity of option arguments.
  *
  * @copydetails CheckArg
  *
  * The following example code
  * can serve as starting place for writing your own more complex CheckArg functions:
  * @code
  * struct Arg: public option::Arg
  * {
  *   static void printError(const char* msg1, const option::Option& opt, const char* msg2)
  *   {
  *     fprintf(stderr, "ERROR: %s", msg1);
  *     fwrite(opt.name, opt.namelen, 1, stderr);
  *     fprintf(stderr, "%s", msg2);
  *   }
  *
  *   static option::ArgStatus Unknown(const option::Option& option, bool msg)
  *   {
  *     if (msg) printError("Unknown option '", option, "'\n");
  *     return option::ARG_ILLEGAL;
  *   }
  *
  *   static option::ArgStatus Required(const option::Option& option, bool msg)
  *   {
  *     if (option.arg != 0)
  *       return option::ARG_OK;
  *
  *     if (msg) printError("Option '", option, "' requires an argument\n");
  *     return option::ARG_ILLEGAL;
  *   }
  *
  *   static option::ArgStatus NonEmpty(const option::Option& option, bool msg)
  *   {
  *     if (option.arg != 0 && option.arg[0] != 0)
  *       return option::ARG_OK;
  *
  *     if (msg) printError("Option '", option, "' requires a non-empty argument\n");
  *     return option::ARG_ILLEGAL;
  *   }
  *
  *   static option::ArgStatus Numeric(const option::Option& option, bool msg)
  *   {
  *     char* endptr = 0;
  *     if (option.arg != 0 && strtol(option.arg, &endptr, 10)){};
  *     if (endptr != option.arg && *endptr == 0)
  *       return option::ARG_OK;
  *
  *     if (msg) printError("Option '", option, "' requires a numeric argument\n");
  *     return option::ARG_ILLEGAL;
  *   }
  * };
  * @endcode
  */
 struct Arg
 {
   //! @brief For options that don't take an argument: Returns ARG_NONE.
   static ArgStatus None(const Option&, bool)
   {
     return ARG_NONE;
   }
 
   //! @brief Returns ARG_OK if the argument is attached and ARG_IGNORE otherwise.
   static ArgStatus Optional(const Option& option, bool)
   {
     if (option.arg && option.name[option.namelen] != 0)
       return ARG_OK;
     else
       return ARG_IGNORE;
   }
 
   //! @brief Returns ARG_OK only if an argument is attached and ARG_ILLEGAL otherwise.
   static ArgStatus Required(const Option& option, bool msg)
   {
     if (option.arg != 0)
       return ARG_OK;
  
     if (msg) printError("Option '", option, "' requires an argument\n");
     return ARG_ILLEGAL;
   }
   static void printError(const char* msg1, const Option& opt, const char* msg2)
   {
     fprintf(stderr, "ERROR: %s", msg1);
     fwrite(opt.name, opt.namelen, 1, stderr);
     fprintf(stderr, "%s", msg2);
   }
 };
 
 /**
  * @brief Determines the minimum lengths of the buffer and options arrays used for Parser.
  *
  * Because Parser doesn't use dynamic memory its output arrays have to be pre-allocated.
  * If you don't want to use fixed size arrays (which may turn out too small, causing
  * command line arguments to be dropped), you can use Stats to determine the correct sizes.
  * Stats work cumulative. You can first pass in your default options and then the real
  * options and afterwards the counts will reflect the union.
  */
 struct Stats
 {
   /**
    * @brief Number of elements needed for a @c buffer[] array to be used for
    * @ref Parser::parse() "parsing" the same argument vectors that were fed
    * into this Stats object.
    *
    * @note
    * This number is always 1 greater than the actual number needed, to give
    * you a sentinel element.
    */
   unsigned buffer_max;
 
   /**
    * @brief Number of elements needed for an @c options[] array to be used for
    * @ref Parser::parse() "parsing" the same argument vectors that were fed
    * into this Stats object.
    *
    * @note
    * @li This number is always 1 greater than the actual number needed, to give
    * you a sentinel element.
    * @li This number depends only on the @c usage, not the argument vectors, because
    * the @c options array needs exactly one slot for each possible Descriptor::index.
    */
   unsigned options_max;
 
   /**
    * @brief Creates a Stats object with counts set to 1 (for the sentinel element).
    */
   Stats() :
       buffer_max(1), options_max(1) // 1 more than necessary as sentinel
   {
   }
 
   /**
    * @brief Creates a new Stats object and immediately updates it for the
    * given @c usage and argument vector. You may pass 0 for @c argc and/or @c argv,
    * if you just want to update @ref options_max.
    *
    * @note
    * The calls to Stats methods must match the later calls to Parser methods.
    * See Parser::parse() for the meaning of the arguments.
    */
   Stats(bool gnu, const Descriptor usage[], int argc, const char** argv, int min_abbr_len = 0, //
         bool single_minus_longopt = false) :
       buffer_max(1), options_max(1) // 1 more than necessary as sentinel
   {
     add(gnu, usage, argc, argv, min_abbr_len, single_minus_longopt);
   }
 
   //! @brief Stats(...) with non-const argv.
   Stats(bool gnu, const Descriptor usage[], int argc, char** argv, int min_abbr_len = 0, //
         bool single_minus_longopt = false) :
       buffer_max(1), options_max(1) // 1 more than necessary as sentinel
   {
     add(gnu, usage, argc, (const char**) argv, min_abbr_len, single_minus_longopt);
   }
 
   //! @brief POSIX Stats(...) (gnu==false).
   Stats(const Descriptor usage[], int argc, const char** argv, int min_abbr_len = 0, //
         bool single_minus_longopt = false) :
       buffer_max(1), options_max(1) // 1 more than necessary as sentinel
   {
     add(false, usage, argc, argv, min_abbr_len, single_minus_longopt);
   }
 
   //! @brief POSIX Stats(...) (gnu==false) with non-const argv.
   Stats(const Descriptor usage[], int argc, char** argv, int min_abbr_len = 0, //
         bool single_minus_longopt = false) :
       buffer_max(1), options_max(1) // 1 more than necessary as sentinel
   {
     add(false, usage, argc, (const char**) argv, min_abbr_len, single_minus_longopt);
   }
 
   /**
    * @brief Updates this Stats object for the
    * given @c usage and argument vector. You may pass 0 for @c argc and/or @c argv,
    * if you just want to update @ref options_max.
    *
    * @note
    * The calls to Stats methods must match the later calls to Parser methods.
    * See Parser::parse() for the meaning of the arguments.
    */
   void add(bool gnu, const Descriptor usage[], int argc, const char** argv, int min_abbr_len = 0, //
            bool single_minus_longopt = false);
 
   //! @brief add() with non-const argv.
   void add(bool gnu, const Descriptor usage[], int argc, char** argv, int min_abbr_len = 0, //
            bool single_minus_longopt = false)
   {
     add(gnu, usage, argc, (const char**) argv, min_abbr_len, single_minus_longopt);
   }
 
   //! @brief POSIX add() (gnu==false).
   void add(const Descriptor usage[], int argc, const char** argv, int min_abbr_len = 0, //
            bool single_minus_longopt = false)
   {
     add(false, usage, argc, argv, min_abbr_len, single_minus_longopt);
   }
 
   //! @brief POSIX add() (gnu==false) with non-const argv.
   void add(const Descriptor usage[], int argc, char** argv, int min_abbr_len = 0, //
            bool single_minus_longopt = false)
   {
     add(false, usage, argc, (const char**) argv, min_abbr_len, single_minus_longopt);
   }
 private:
   class CountOptionsAction;
 };
 
 /**
  * @brief Checks argument vectors for validity and parses them into data
  * structures that are easier to work with.
  *
  * @par Example:
  * @code
  * int main(int argc, char* argv[])
  * {
  *   argc-=(argc>0); argv+=(argc>0); // skip program name argv[0] if present
  *   option::Stats  stats(usage, argc, argv);
  *   option::Option options[stats.options_max], buffer[stats.buffer_max];
  *   option::Parser parse(usage, argc, argv, options, buffer);
  *
  *   if (parse.error())
  *     return 1;
  *
  *   if (options[HELP])
  *   ...
  * @endcode
  */
 class Parser
 {
   int op_count; //!< @internal @brief see optionsCount()
   int nonop_count; //!< @internal @brief see nonOptionsCount()
   const char** nonop_args; //!< @internal @brief see nonOptions()
   bool err; //!< @internal @brief see error()
 public:
 
   /**
    * @brief Creates a new Parser.
    */
   Parser() :
       op_count(0), nonop_count(0), nonop_args(0), err(false)
   {
   }
 
   /**
    * @brief Creates a new Parser and immediately parses the given argument vector.
    * @copydetails parse()
    */
   Parser(bool gnu, const Descriptor usage[], int argc, const char** argv, Option options[], Option buffer[],
          int min_abbr_len = 0, bool single_minus_longopt = false, int bufmax = -1) :
       op_count(0), nonop_count(0), nonop_args(0), err(false)
   {
     parse(gnu, usage, argc, argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   //! @brief Parser(...) with non-const argv.
   Parser(bool gnu, const Descriptor usage[], int argc, char** argv, Option options[], Option buffer[],
          int min_abbr_len = 0, bool single_minus_longopt = false, int bufmax = -1) :
       op_count(0), nonop_count(0), nonop_args(0), err(false)
   {
     parse(gnu, usage, argc, (const char**) argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   //! @brief POSIX Parser(...) (gnu==false).
   Parser(const Descriptor usage[], int argc, const char** argv, Option options[], Option buffer[], int min_abbr_len = 0,
          bool single_minus_longopt = false, int bufmax = -1) :
       op_count(0), nonop_count(0), nonop_args(0), err(false)
   {
     parse(false, usage, argc, argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   //! @brief POSIX Parser(...) (gnu==false) with non-const argv.
   Parser(const Descriptor usage[], int argc, char** argv, Option options[], Option buffer[], int min_abbr_len = 0,
          bool single_minus_longopt = false, int bufmax = -1) :
       op_count(0), nonop_count(0), nonop_args(0), err(false)
   {
     parse(false, usage, argc, (const char**) argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   /**
    * @brief Parses the given argument vector.
    *
    * @param gnu if true, parse() will not stop at the first non-option argument. Instead it will
    *            reorder arguments so that all non-options are at the end. This is the default behaviour
    *            of GNU getopt() but is not conforming to POSIX. @n
    *            Note, that once the argument vector has been reordered, the @c gnu flag will have
    *            no further effect on this argument vector. So it is enough to pass @c gnu==true when
    *            creating Stats.
    * @param usage Array of Descriptor objects that describe the options to support. The last entry
    *              of this array must have 0 in all fields.
    * @param argc The number of elements from @c argv that are to be parsed. If you pass -1, the number
    *             will be determined automatically. In that case the @c argv list must end with a NULL
    *             pointer.
    * @param argv The arguments to be parsed. If you pass -1 as @c argc the last pointer in the @c argv
    *             list must be NULL to mark the end.
    * @param options Each entry is the first element of a linked list of Options. Each new option
    *                that is parsed will be appended to the list specified by that Option's
    *                Descriptor::index. If an entry is not yet used (i.e. the Option is invalid),
    *                it will be replaced rather than appended to. @n
    *                The minimum length of this array is the greatest Descriptor::index value that
    *                occurs in @c usage @e PLUS ONE.
    * @param buffer Each argument that is successfully parsed (including unknown arguments, if they
    *        have a Descriptor whose CheckArg does not return @ref ARG_ILLEGAL) will be stored in this
    *        array. parse() scans the array for the first invalid entry and begins writing at that
    *        index. You can pass @c bufmax to limit the number of options stored.
    * @param min_abbr_len Passing a value <code> min_abbr_len > 0 </code> enables abbreviated long
    *               options. The parser will match a prefix of a long option as if it was
    *               the full long option (e.g. @c --foob=10 will be interpreted as if it was
    *               @c --foobar=10 ), as long as the prefix has at least @c min_abbr_len characters
    *               (not counting the @c -- ) and is unambiguous.
    *               @n Be careful if combining @c min_abbr_len=1 with @c single_minus_longopt=true
    *               because the ambiguity check does not consider short options and abbreviated
    *               single minus long options will take precedence over short options.
    * @param single_minus_longopt Passing @c true for this option allows long options to begin with
    *               a single minus. The double minus form will still be recognized. Note that
    *               single minus long options take precedence over short options and short option
    *               groups. E.g. @c -file would be interpreted as @c --file and not as
    *               <code> -f -i -l -e </code> (assuming a long option named @c "file" exists).
    * @param bufmax The greatest index in the @c buffer[] array that parse() will write to is
    *               @c bufmax-1. If there are more options, they will be processed (in particular
    *               their CheckArg will be called) but not stored. @n
    *               If you used Stats::buffer_max to dimension this array, you can pass
    *               -1 (or not pass @c bufmax at all) which tells parse() that the buffer is
    *               "large enough".
    * @attention
    * Remember that @c options and @c buffer store Option @e objects, not pointers. Therefore it
    * is not possible for the same object to be in both arrays. For those options that are found in
    * both @c buffer[] and @c options[] the respective objects are independent copies. And only the
    * objects in @c options[] are properly linked via Option::next() and Option::prev().
    * You can iterate over @c buffer[] to
    * process all options in the order they appear in the argument vector, but if you want access to
    * the other Options with the same Descriptor::index, then you @e must access the linked list via
    * @c options[]. You can get the linked list in options from a buffer object via something like
    * @c options[buffer[i].index()].
    */
   void parse(bool gnu, const Descriptor usage[], int argc, const char** argv, Option options[], Option buffer[],
              int min_abbr_len = 0, bool single_minus_longopt = false, int bufmax = -1);
 
   //! @brief parse() with non-const argv.
   void parse(bool gnu, const Descriptor usage[], int argc, char** argv, Option options[], Option buffer[],
              int min_abbr_len = 0, bool single_minus_longopt = false, int bufmax = -1)
   {
     parse(gnu, usage, argc, (const char**) argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   //! @brief POSIX parse() (gnu==false).
   void parse(const Descriptor usage[], int argc, const char** argv, Option options[], Option buffer[],
              int min_abbr_len = 0, bool single_minus_longopt = false, int bufmax = -1)
   {
     parse(false, usage, argc, argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   //! @brief POSIX parse() (gnu==false) with non-const argv.
   void parse(const Descriptor usage[], int argc, char** argv, Option options[], Option buffer[], int min_abbr_len = 0,
              bool single_minus_longopt = false, int bufmax = -1)
   {
     parse(false, usage, argc, (const char**) argv, options, buffer, min_abbr_len, single_minus_longopt, bufmax);
   }
 
   /**
    * @brief Returns the number of valid Option objects in @c buffer[].
    *
    * @note
    * @li The returned value always reflects the number of Options in the buffer[] array used for
    * the most recent call to parse().
    * @li The count (and the buffer[]) includes unknown options if they are collected
    * (see Descriptor::longopt).
    */
   int optionsCount()
   {
     return op_count;
   }
 
   /**
    * @brief Returns the number of non-option arguments that remained at the end of the
    * most recent parse() that actually encountered non-option arguments.
    *
    * @note
    * A parse() that does not encounter non-option arguments will leave this value
    * as well as nonOptions() undisturbed. This means you can feed the Parser a
    * default argument vector that contains non-option arguments (e.g. a default filename).
    * Then you feed it the actual arguments from the user. If the user has supplied at
    * least one non-option argument, all of the non-option arguments from the default
    * disappear and are replaced by the user's non-option arguments. However, if the
    * user does not supply any non-option arguments the defaults will still be in
    * effect.
    */
   int nonOptionsCount()
   {
     return nonop_count;
   }
 
   /**
    * @brief Returns a pointer to an array of non-option arguments (only valid
    * if <code>nonOptionsCount() >0 </code>).
    *
    * @note
    * @li parse() does not copy arguments, so this pointer points into the actual argument
    * vector as passed to parse().
    * @li As explained at nonOptionsCount() this pointer is only changed by parse() calls
    * that actually encounter non-option arguments. A parse() call that encounters only
    * options, will not change nonOptions().
    */
   const char** nonOptions()
   {
     return nonop_args;
   }
 
   /**
    * @brief Returns <b><code>nonOptions()[i]</code></b> (@e without checking if i is in range!).
    */
   const char* nonOption(int i)
   {
     return nonOptions()[i];
   }
 
   /**
    * @brief Returns @c true if an unrecoverable error occurred while parsing options.
    *
    * An illegal argument to an option (i.e. CheckArg returns @ref ARG_ILLEGAL) is an
    * unrecoverable error that aborts the parse. Unknown options are only an error if
    * their CheckArg function returns @ref ARG_ILLEGAL. Otherwise they are collected.
    * In that case if you want to exit the program if either an illegal argument
    * or an unknown option has been passed, use code like this
    *
    * @code
    * if (parser.error() || options[UNKNOWN])
    *   exit(1);
    * @endcode
    *
    */
   bool error()
   {
     return err;
   }
 
 private:
   friend struct Stats;
   class StoreOptionAction;
   struct Action;
 
   /**
    * @internal
    * @brief This is the core function that does all the parsing.
    * @retval false iff an unrecoverable error occurred.
    */
   static bool workhorse(bool gnu, const Descriptor usage[], int numargs, const char** args, Action& action,
                         bool single_minus_longopt, bool print_errors, int min_abbr_len);
 
   /**
    * @internal
    * @brief Returns true iff @c st1 is a prefix of @c st2 and
    * in case @c st2 is longer than @c st1, then
    * the first additional character is '='.
    *
    * @par Examples:
    * @code
    * streq("foo", "foo=bar") == true
    * streq("foo", "foobar")  == false
    * streq("foo", "foo")     == true
    * streq("foo=bar", "foo") == false
    * @endcode
    */
   static bool streq(const char* st1, const char* st2)
   {
     while (*st1 != 0)
       if (*st1++ != *st2++)
         return false;
     return (*st2 == 0 || *st2 == '=');
   }
 
   /**
    * @internal
    * @brief Like streq() but handles abbreviations.
    *
    * Returns true iff @c st1 and @c st2 have a common
    * prefix with the following properties:
    * @li (if min > 0) its length is at least @c min characters or the same length as @c st1 (whichever is smaller).
    * @li (if min <= 0) its length is the same as that of @c st1
    * @li within @c st2 the character following the common prefix is either '=' or end-of-string.
    *
    * Examples:
    * @code
    * streqabbr("foo", "foo=bar",<anything>) == true
    * streqabbr("foo", "fo=bar" , 2) == true
    * streqabbr("foo", "fo"     , 2) == true
    * streqabbr("foo", "fo"     , 0) == false
    * streqabbr("foo", "f=bar"  , 2) == false
    * streqabbr("foo", "f"      , 2) == false
    * streqabbr("fo" , "foo=bar",<anything>)  == false
    * streqabbr("foo", "foobar" ,<anything>)  == false
    * streqabbr("foo", "fobar"  ,<anything>)  == false
    * streqabbr("foo", "foo"    ,<anything>)  == true
    * @endcode
    */
   static bool streqabbr(const char* st1, const char* st2, long long min)
   {
     const char* st1start = st1;
     while (*st1 != 0 && (*st1 == *st2))
     {
       ++st1;
       ++st2;
     }
 
     return (*st1 == 0 || (min > 0 && (st1 - st1start) >= min)) && (*st2 == 0 || *st2 == '=');
   }
 
   /**
    * @internal
    * @brief Returns true iff character @c ch is contained in the string @c st.
    *
    * Returns @c true for @c ch==0 .
    */
   static bool instr(char ch, const char* st)
   {
     while (*st != 0 && *st != ch)
       ++st;
     return *st == ch;
   }
 
   /**
    * @internal
    * @brief Rotates <code>args[-count],...,args[-1],args[0]</code> to become
    *        <code>args[0],args[-count],...,args[-1]</code>.
    */
   static void shift(const char** args, int count)
   {
     for (int i = 0; i > -count; --i)
     {
       const char* temp = args[i];
       args[i] = args[i - 1];
       args[i - 1] = temp;
     }
   }
 };
 
 /**
  * @internal
  * @brief Interface for actions Parser::workhorse() should perform for each Option it
  * parses.
  */
 struct Parser::Action
 {
   /**
    * @brief Called by Parser::workhorse() for each Option that has been successfully
    * parsed (including unknown
    * options if they have a Descriptor whose Descriptor::check_arg does not return
    * @ref ARG_ILLEGAL.
    *
    * Returns @c false iff a fatal error has occured and the parse should be aborted.
    */
   virtual bool perform(Option&)
   {
     return true;
   }
 
   /**
    * @brief Called by Parser::workhorse() after finishing the parse.
    * @param numargs the number of non-option arguments remaining
    * @param args pointer to the first remaining non-option argument (if numargs > 0).
    *
    * @return
    * @c false iff a fatal error has occurred.
    */
   virtual bool finished(int numargs, const char** args)
   {
     (void) numargs;
     (void) args;
     return true;
   }
 };
 
 /**
  * @internal
  * @brief An Action to pass to Parser::workhorse() that will increment a counter for
  * each parsed Option.
  */
 class Stats::CountOptionsAction: public Parser::Action
 {
   unsigned* buffer_max;
 public:
   /**
    * Creates a new CountOptionsAction that will increase @c *buffer_max_ for each
    * parsed Option.
    */
   CountOptionsAction(unsigned* buffer_max_) :
       buffer_max(buffer_max_)
   {
   }
 
   bool perform(Option&)
   {
     if (*buffer_max == 0x7fffffff)
       return false; // overflow protection: don't accept number of options that doesn't fit signed int
     ++*buffer_max;
     return true;
   }
 };
 
 /**
  * @internal
  * @brief An Action to pass to Parser::workhorse() that will store each parsed Option in
  * appropriate arrays (see Parser::parse()).
  */
 class Parser::StoreOptionAction: public Parser::Action
 {
   Parser& parser;
   Option* options;
   Option* buffer;
   int bufmax; //! Number of slots in @c buffer. @c -1 means "large enough".
 public:
   /**
    * @brief Creates a new StoreOption action.
    * @param parser_ the parser whose op_count should be updated.
    * @param options_ each Option @c o is chained into the linked list @c options_[o.desc->index]
    * @param buffer_ each Option is appended to this array as long as there's a free slot.
    * @param bufmax_ number of slots in @c buffer_. @c -1 means "large enough".
    */
   StoreOptionAction(Parser& parser_, Option options_[], Option buffer_[], int bufmax_) :
       parser(parser_), options(options_), buffer(buffer_), bufmax(bufmax_)
   {
     // find first empty slot in buffer (if any)
     int bufidx = 0;
     while ((bufmax < 0 || bufidx < bufmax) && buffer[bufidx])
       ++bufidx;
 
     // set parser's optionCount
     parser.op_count = bufidx;
   }
 
   bool perform(Option& option)
   {
     if (bufmax < 0 || parser.op_count < bufmax)
     {
       if (parser.op_count == 0x7fffffff)
         return false; // overflow protection: don't accept number of options that doesn't fit signed int
 
       buffer[parser.op_count] = option;
       int idx = buffer[parser.op_count].desc->index;
       if (options[idx])
         options[idx].append(buffer[parser.op_count]);
       else
         options[idx] = buffer[parser.op_count];
       ++parser.op_count;
     }
     return true; // NOTE: an option that is discarded because of a full buffer is not fatal
   }
 
   bool finished(int numargs, const char** args)
   {
     // only overwrite non-option argument list if there's at least 1
     // new non-option argument. Otherwise we keep the old list. This
     // makes it easy to use default non-option arguments.
     if (numargs > 0)
     {
       parser.nonop_count = numargs;
       parser.nonop_args = args;
     }
 
     return true;
   }
 };
 
 inline void Parser::parse(bool gnu, const Descriptor usage[], int argc, const char** argv, Option options[],
                           Option buffer[], int min_abbr_len, bool single_minus_longopt, int bufmax)
 {
   StoreOptionAction action(*this, options, buffer, bufmax);
   err = !workhorse(gnu, usage, argc, argv, action, single_minus_longopt, true, min_abbr_len);
 }
 
 inline void Stats::add(bool gnu, const Descriptor usage[], int argc, const char** argv, int min_abbr_len,
                        bool single_minus_longopt)
 {
   // determine size of options array. This is the greatest index used in the usage + 1
   int i = 0;
   while (usage[i].shortopt != 0)
   {
     if (usage[i].index + 1 >= options_max)
       options_max = (usage[i].index + 1) + 1; // 1 more than necessary as sentinel
 
     ++i;
   }
 
   CountOptionsAction action(&buffer_max);
   Parser::workhorse(gnu, usage, argc, argv, action, single_minus_longopt, false, min_abbr_len);
 }
 
 inline bool Parser::workhorse(bool gnu, const Descriptor usage[], int numargs, const char** args, Action& action,
                               bool single_minus_longopt, bool print_errors, int min_abbr_len)
 {
   // protect against NULL pointer
   if (args == 0)
     numargs = 0;
 
   int nonops = 0;
 
   while (numargs != 0 && *args != 0)
   {
     const char* param = *args; // param can be --long-option, -srto or non-option argument
 
     // in POSIX mode the first non-option argument terminates the option list
     // a lone minus character is a non-option argument
     if (param[0] != '-' || param[1] == 0)
     {
       if (gnu)
       {
         ++nonops;
         ++args;
         if (numargs > 0)
           --numargs;
         continue;
       }
       else
         break;
     }
 
     // -- terminates the option list. The -- itself is skipped.
     if (param[1] == '-' && param[2] == 0)
     {
       shift(args, nonops);
       ++args;
       if (numargs > 0)
         --numargs;
       break;
     }
 
     bool handle_short_options;
     const char* longopt_name;
     if (param[1] == '-') // if --long-option
     {
       handle_short_options = false;
       longopt_name = param + 2;
     }
     else
     {
       handle_short_options = true;
       longopt_name = param + 1; //for testing a potential -long-option
     }
 
     bool try_single_minus_longopt = single_minus_longopt;
     bool have_more_args = (numargs > 1 || numargs < 0); // is referencing argv[1] valid?
 
     do // loop over short options in group, for long options the body is executed only once
     {
       int idx;
 
       const char* optarg;
 
       /******************** long option **********************/
       if (handle_short_options == false || try_single_minus_longopt)
       {
         idx = 0;
         while (usage[idx].longopt != 0 && !streq(usage[idx].longopt, longopt_name))
           ++idx;
 
         if (usage[idx].longopt == 0 && min_abbr_len > 0) // if we should try to match abbreviated long options
         {
           int i1 = 0;
           while (usage[i1].longopt != 0 && !streqabbr(usage[i1].longopt, longopt_name, min_abbr_len))
             ++i1;
           if (usage[i1].longopt != 0)
           { // now test if the match is unambiguous by checking for another match
             int i2 = i1 + 1;
             while (usage[i2].longopt != 0 && !streqabbr(usage[i2].longopt, longopt_name, min_abbr_len))
               ++i2;
 
             if (usage[i2].longopt == 0) // if there was no second match it's unambiguous, so accept i1 as idx
               idx = i1;
           }
         }
 
         // if we found something, disable handle_short_options (only relevant if single_minus_longopt)
         if (usage[idx].longopt != 0)
           handle_short_options = false;
 
         try_single_minus_longopt = false; // prevent looking for longopt in the middle of shortopt group
 
         optarg = longopt_name;
         while (*optarg != 0 && *optarg != '=')
           ++optarg;
         if (*optarg == '=') // attached argument
           ++optarg;
         else
           // possibly detached argument
           optarg = (have_more_args ? args[1] : 0);
       }
 
       /************************ short option ***********************************/
       if (handle_short_options)
       {
         if (*++param == 0) // point at the 1st/next option character
           break; // end of short option group
 
         idx = 0;
         while (usage[idx].shortopt != 0 && !instr(*param, usage[idx].shortopt))
           ++idx;
 
         if (param[1] == 0) // if the potential argument is separate
           optarg = (have_more_args ? args[1] : 0);
         else
           // if the potential argument is attached
           optarg = param + 1;
       }
 
       const Descriptor* descriptor = &usage[idx];
 
       if (descriptor->shortopt == 0) /**************  unknown option ********************/
       {
         // look for dummy entry (shortopt == "" and longopt == "") to use as Descriptor for unknown options
         idx = 0;
         while (usage[idx].shortopt != 0 && (usage[idx].shortopt[0] != 0 || usage[idx].longopt[0] != 0))
           ++idx;
         descriptor = (usage[idx].shortopt == 0 ? 0 : &usage[idx]);
       }
 
       if (descriptor != 0)
       {
         Option option(descriptor, param, optarg);
         switch (descriptor->check_arg(option, print_errors))
         {
           case ARG_ILLEGAL:
             return false; // fatal
           case ARG_OK:
             // skip one element of the argument vector, if it's a separated argument
             if (optarg != 0 && have_more_args && optarg == args[1])
             {
               shift(args, nonops);
               if (numargs > 0)
                 --numargs;
               ++args;
             }
 
             // No further short options are possible after an argument
             handle_short_options = false;
 
             break;
           case ARG_IGNORE:
           case ARG_NONE:
             option.arg = 0;
             break;
         }
 
         if (!action.perform(option))
           return false;
       }
 
     } while (handle_short_options);
 
     shift(args, nonops);
     ++args;
     if (numargs > 0)
       --numargs;
 
   } // while
 
   if (numargs > 0 && *args == 0) // It's a bug in the caller if numargs is greater than the actual number
     numargs = 0; // of arguments, but as a service to the user we fix this if we spot it.
 
   if (numargs < 0) // if we don't know the number of remaining non-option arguments
   { // we need to count them
     numargs = 0;
     while (args[numargs] != 0)
       ++numargs;
   }
 
   return action.finished(numargs + nonops, args - nonops);
 }
 
 /**
  * @internal
  * @brief The implementation of option::printUsage().
  */
 struct PrintUsageImplementation
 {
   /**
    * @internal
    * @brief Interface for Functors that write (part of) a string somewhere.
    */
   struct IStringWriter
   {
     /**
      * @brief Writes the given number of chars beginning at the given pointer somewhere.
      */
     virtual void operator()(const char*, int)
     {
     }
   };
 
   /**
    * @internal
    * @brief Encapsulates a function with signature <code>func(string, size)</code> where
    * string can be initialized with a const char* and size with an int.
    */
   template<typename Function>
   struct FunctionWriter: public IStringWriter
   {
     Function* write;
 
     virtual void operator()(const char* str, int size)
     {
       (*write)(str, size);
     }
 
     FunctionWriter(Function* w) :
         write(w)
     {
     }
   };
 
   /**
    * @internal
    * @brief Encapsulates a reference to an object with a <code>write(string, size)</code>
    * method like that of @c std::ostream.
    */
   template<typename OStream>
   struct OStreamWriter: public IStringWriter
   {
     OStream& ostream;
 
     virtual void operator()(const char* str, int size)
     {
       ostream.write(str, size);
     }
 
     OStreamWriter(OStream& o) :
         ostream(o)
     {
     }
   };
 
   /**
    * @internal
    * @brief Like OStreamWriter but encapsulates a @c const reference, which is
    * typically a temporary object of a user class.
    */
   template<typename Temporary>
   struct TemporaryWriter: public IStringWriter
   {
     const Temporary& userstream;
 
     virtual void operator()(const char* str, int size)
     {
       userstream.write(str, size);
     }
 
     TemporaryWriter(const Temporary& u) :
         userstream(u)
     {
     }
   };
 
   /**
    * @internal
    * @brief Encapsulates a function with the signature <code>func(fd, string, size)</code> (the
    * signature of the @c write() system call)
    * where fd can be initialized from an int, string from a const char* and size from an int.
    */
   template<typename Syscall>
   struct SyscallWriter: public IStringWriter
   {
     Syscall* write;
     int fd;
 
     virtual void operator()(const char* str, int size)
     {
       (*write)(fd, str, size);
     }
 
     SyscallWriter(Syscall* w, int f) :
         write(w), fd(f)
     {
     }
   };
 
   /**
    * @internal
    * @brief Encapsulates a function with the same signature as @c std::fwrite().
    */
   template<typename Function, typename Stream>
   struct StreamWriter: public IStringWriter
   {
     Function* fwrite;
     Stream* stream;
 
     virtual void operator()(const char* str, int size)
     {
       (*fwrite)(str, size, 1, stream);
     }
 
     StreamWriter(Function* w, Stream* s) :
         fwrite(w), stream(s)
     {
     }
   };
 
   /**
    * @internal
    * @brief Sets <code> i1 = max(i1, i2) </code>
    */
   static void upmax(int& i1, int i2)
   {
     i1 = (i1 >= i2 ? i1 : i2);
   }
 
   /**
    * @internal
    * @brief Moves the "cursor" to column @c want_x assuming it is currently at column @c x
    * and sets @c x=want_x .
    * If <code> x > want_x </code>, a line break is output before indenting.
    *
    * @param write Spaces and possibly a line break are written via this functor to get
    *        the desired indentation @c want_x .
    * @param[in,out] x the current indentation. Set to @c want_x by this method.
    * @param want_x the desired indentation.
    */
   static void indent(IStringWriter& write, int& x, int want_x)
   {
     int indent = want_x - x;
     if (indent < 0)
     {
       write("\n", 1);
       indent = want_x;
     }
 
     if (indent > 0)
     {
       char space = ' ';
       for (int i = 0; i < indent; ++i)
         write(&space, 1);
       x = want_x;
     }
   }
 
   /**
    * @brief Returns true if ch is the unicode code point of a wide character.
    *
    * @note
    * The following character ranges are treated as wide
    * @code
    * 1100..115F
    * 2329..232A  (just 2 characters!)
    * 2E80..A4C6  except for 303F
    * A960..A97C
    * AC00..D7FB
    * F900..FAFF
    * FE10..FE6B
    * FF01..FF60
    * FFE0..FFE6
    * 1B000......
    * @endcode
    */
   static bool isWideChar(unsigned ch)
   {
     if (ch == 0x303F)
       return false;
 
     return ((0x1100 <= ch && ch <= 0x115F) || (0x2329 <= ch && ch <= 0x232A) || (0x2E80 <= ch && ch <= 0xA4C6)
         || (0xA960 <= ch && ch <= 0xA97C) || (0xAC00 <= ch && ch <= 0xD7FB) || (0xF900 <= ch && ch <= 0xFAFF)
         || (0xFE10 <= ch && ch <= 0xFE6B) || (0xFF01 <= ch && ch <= 0xFF60) || (0xFFE0 <= ch && ch <= 0xFFE6)
         || (0x1B000 <= ch));
   }
 
   /**
    * @internal
    * @brief Splits a @c Descriptor[] array into tables, rows, lines and columns and
    * iterates over these components.
    *
    * The top-level organizational unit is the @e table.
    * A table begins at a Descriptor with @c help!=NULL and extends up to
    * a Descriptor with @c help==NULL.
    *
    * A table consists of @e rows. Due to line-wrapping and explicit breaks
    * a row may take multiple lines on screen. Rows within the table are separated
    * by \\n. They never cross Descriptor boundaries. This means a row ends either
    * at \\n or the 0 at the end of the help string.
    *
    * A row consists of columns/cells. Columns/cells within a row are separated by \\t.
    * Line breaks within a cell are marked by \\v.
    *
    * Rows in the same table need not have the same number of columns/cells. The
    * extreme case are interjections, which are rows that contain neither \\t nor \\v.
    * These are NOT treated specially by LinePartIterator, but they are treated
    * specially by printUsage().
    *
    * LinePartIterator iterates through the usage at 3 levels: table, row and part.
    * Tables and rows are as described above. A @e part is a line within a cell.
    * LinePartIterator iterates through 1st parts of all cells, then through the 2nd
    * parts of all cells (if any),... @n
    * Example: The row <code> "1 \v 3 \t 2 \v 4" </code> has 2 cells/columns and 4 parts.
    * The parts will be returned in the order 1, 2, 3, 4.
    *
    * It is possible that some cells have fewer parts than others. In this case
    * LinePartIterator will "fill up" these cells with 0-length parts. IOW, LinePartIterator
    * always returns the same number of parts for each column. Note that this is different
    * from the way rows and columns are handled. LinePartIterator does @e not guarantee that
    * the same number of columns will be returned for each row.
    *
    */
   class LinePartIterator
   {
     const Descriptor* tablestart; //!< The 1st descriptor of the current table.
     const Descriptor* rowdesc; //!< The Descriptor that contains the current row.
     const char* rowstart; //!< Ptr to 1st character of current row within rowdesc->help.
     const char* ptr; //!< Ptr to current part within the current row.
     int col; //!< Index of current column.
     int len; //!< Length of the current part (that ptr points at) in BYTES
     int screenlen; //!< Length of the current part in screen columns (taking narrow/wide chars into account).
     int max_line_in_block; //!< Greatest index of a line within the block. This is the number of \\v within the cell with the most \\vs.
     int line_in_block; //!< Line index within the current cell of the current part.
     int target_line_in_block; //!< Line index of the parts we should return to the user on this iteration.
     bool hit_target_line; //!< Flag whether we encountered a part with line index target_line_in_block in the current cell.
 
     /** 
      * @brief Determines the byte and character lengths of the part at @ref ptr and 
      * stores them in @ref len and @ref screenlen respectively.
      */
     void update_length()
     {
       screenlen = 0;
       for (len = 0; ptr[len] != 0 && ptr[len] != '\v' && ptr[len] != '\t' && ptr[len] != '\n'; ++len)
       {
         ++screenlen;
         unsigned ch = (unsigned char) ptr[len];
         if (ch > 0xC1) // everything <= 0xC1 (yes, even 0xC1 itself) is not a valid UTF-8 start byte
         {
           // int __builtin_clz (unsigned int x)
           // Returns the number of leading 0-bits in x, starting at the most significant bit
           unsigned mask = (unsigned) -1 >> __builtin_clz(ch ^ 0xff);
           ch = ch & mask; // mask out length bits, we don't verify their correctness
           while (((unsigned char) ptr[len + 1] ^ 0x80) <= 0x3F) // while next byte is continuation byte
           {
             ch = (ch << 6) ^ (unsigned char) ptr[len + 1] ^ 0x80; // add continuation to char code
             ++len;
           }
           // ch is the decoded unicode code point
           if (ch >= 0x1100 && isWideChar(ch)) // the test for 0x1100 is here to avoid the function call in the Latin case
             ++screenlen;
         }
       }
     }
 
   public:
     //! @brief Creates an iterator for @c usage.
     LinePartIterator(const Descriptor usage[]) :
         tablestart(usage), rowdesc(0), rowstart(0), ptr(0), col(-1), len(0), max_line_in_block(0), line_in_block(0),
         target_line_in_block(0), hit_target_line(true)
     {
     }
 
     /**
      * @brief Moves iteration to the next table (if any). Has to be called once on a new
      * LinePartIterator to move to the 1st table.
      * @retval false if moving to next table failed because no further table exists.
      */
     bool nextTable()
     {
       // If this is NOT the first time nextTable() is called after the constructor,
       // then skip to the next table break (i.e. a Descriptor with help == 0)
       if (rowdesc != 0)
       {
         while (tablestart->help != 0 && tablestart->shortopt != 0)
           ++tablestart;
       }
 
       // Find the next table after the break (if any)
       while (tablestart->help == 0 && tablestart->shortopt != 0)
         ++tablestart;
 
       restartTable();
       return rowstart != 0;
     }
 
     /**
      * @brief Reset iteration to the beginning of the current table.
      */
     void restartTable()
     {
       rowdesc = tablestart;
       rowstart = tablestart->help;
       ptr = 0;
     }
 
     /**
      * @brief Moves iteration to the next row (if any). Has to be called once after each call to
      * @ref nextTable() to move to the 1st row of the table.
      * @retval false if moving to next row failed because no further row exists.
      */
     bool nextRow()
     {
       if (ptr == 0)
       {
         restartRow();
         return rowstart != 0;
       }
 
       while (*ptr != 0 && *ptr != '\n')
         ++ptr;
 
       if (*ptr == 0)
       {
         if ((rowdesc + 1)->help == 0) // table break
           return false;
 
         ++rowdesc;
         rowstart = rowdesc->help;
       }
       else // if (*ptr == '\n')
       {
         rowstart = ptr + 1;
       }
 
       restartRow();
       return true;
     }
 
     /**
      * @brief Reset iteration to the beginning of the current row.
      */
     void restartRow()
     {
       ptr = rowstart;
       col = -1;
       len = 0;
       screenlen = 0;
       max_line_in_block = 0;
       line_in_block = 0;
       target_line_in_block = 0;
       hit_target_line = true;
     }
 
     /**
      * @brief Moves iteration to the next part (if any). Has to be called once after each call to
      * @ref nextRow() to move to the 1st part of the row.
      * @retval false if moving to next part failed because no further part exists.
      *
      * See @ref LinePartIterator for details about the iteration.
      */
     bool next()
     {
       if (ptr == 0)
         return false;
 
       if (col == -1)
       {
         col = 0;
         update_length();
         return true;
       }
 
       ptr += len;
       while (true)
       {
         switch (*ptr)
         {
           case '\v':
             upmax(max_line_in_block, ++line_in_block);
             ++ptr;
             break;
           case '\t':
             if (!hit_target_line) // if previous column did not have the targetline
             { // then "insert" a 0-length part
               update_length();
               hit_target_line = true;
               return true;
             }
 
             hit_target_line = false;
             line_in_block = 0;
             ++col;
             ++ptr;
             break;
           case 0:
           case '\n':
             if (!hit_target_line) // if previous column did not have the targetline
             { // then "insert" a 0-length part
               update_length();
               hit_target_line = true;
               return true;
             }
 
             if (++target_line_in_block > max_line_in_block)
             {
               update_length();
               return false;
             }
 
             hit_target_line = false;
             line_in_block = 0;
             col = 0;
             ptr = rowstart;
             continue;
           default:
             ++ptr;
             continue;
         } // switch
 
         if (line_in_block == target_line_in_block)
         {
           update_length();
           hit_target_line = true;
           return true;
         }
       } // while
     }
 
     /**
      * @brief Returns the index (counting from 0) of the column in which
      * the part pointed to by @ref data() is located.
      */
     int column()
     {
       return col;
     }
 
     /**
      * @brief Returns the index (counting from 0) of the line within the current column
      * this part belongs to.
      */
     int line()
     {
       return target_line_in_block; // NOT line_in_block !!! It would be wrong if !hit_target_line
     }
 
     /**
      * @brief Returns the length of the part pointed to by @ref data() in raw chars (not UTF-8 characters).
      */
     int length()
     {
       return len;
     }
 
     /**
      * @brief Returns the width in screen columns of the part pointed to by @ref data().
      * Takes multi-byte UTF-8 sequences and wide characters into account.
      */
     int screenLength()
     {
       return screenlen;
     }
 
     /**
      * @brief Returns the current part of the iteration.
      */
     const char* data()
     {
       return ptr;
     }
   };
 
   /**
    * @internal
    * @brief Takes input and line wraps it, writing out one line at a time so that
    * it can be interleaved with output from other columns.
    *
    * The LineWrapper is used to handle the last column of each table as well as interjections.
    * The LineWrapper is called once for each line of output. If the data given to it fits
    * into the designated width of the last column it is simply written out. If there
    * is too much data, an appropriate split point is located and only the data up to this
    * split point is written out. The rest of the data is queued for the next line.
    * That way the last column can be line wrapped and interleaved with data from
    * other columns. The following example makes this clearer:
    * @code
    * Column 1,1    Column 2,1     This is a long text
    * Column 1,2    Column 2,2     that does not fit into
    *                              a single line.
    * @endcode
    *
    * The difficulty in producing this output is that the whole string
    * "This is a long text that does not fit into a single line" is the
    * 1st and only part of column 3. In order to produce the above
    * output the string must be output piecemeal, interleaved with
    * the data from the other columns.
    */
   class LineWrapper
   {
     static const int bufmask = 15; //!< Must be a power of 2 minus 1.
     /**
      * @brief Ring buffer for length component of pair (data, length).
      */
     int lenbuf[bufmask + 1];
     /**
      * @brief Ring buffer for data component of pair (data, length).
      */
     const char* datbuf[bufmask + 1];
     /**
      * @brief The indentation of the column to which the LineBuffer outputs. LineBuffer
      * assumes that the indentation has already been written when @ref process()
      * is called, so this value is only used when a buffer flush requires writing
      * additional lines of output.
      */
     int x;
     /**
      * @brief The width of the column to line wrap.
      */
     int width;
     int head; //!< @brief index for next write
     int tail; //!< @brief index for next read - 1 (i.e. increment tail BEFORE read)
 
     /**
      * @brief Multiple methods of LineWrapper may decide to flush part of the buffer to
      * free up space. The contract of process() says that only 1 line is output. So
      * this variable is used to track whether something has output a line. It is
      * reset at the beginning of process() and checked at the end to decide if
      * output has already occurred or is still needed.
      */
     bool wrote_something;
 
     bool buf_empty()
     {
       return ((tail + 1) & bufmask) == head;
     }
 
     bool buf_full()
     {
       return tail == head;
     }
 
     void buf_store(const char* data, int len)
     {
       lenbuf[head] = len;
       datbuf[head] = data;
       head = (head + 1) & bufmask;
     }
 
     //! @brief Call BEFORE reading ...buf[tail].
     void buf_next()
     {
       tail = (tail + 1) & bufmask;
     }
 
     /**
      * @brief Writes (data,len) into the ring buffer. If the buffer is full, a single line
      * is flushed out of the buffer into @c write.
      */
     void output(IStringWriter& write, const char* data, int len)
     {
       if (buf_full())
         write_one_line(write);
 
       buf_store(data, len);
     }
 
     /**
      * @brief Writes a single line of output from the buffer to @c write.
      */
     void write_one_line(IStringWriter& write)
     {
       if (wrote_something) // if we already wrote something, we need to start a new line
       {
         write("\n", 1);
         int _ = 0;
         indent(write, _, x);
       }
 
       if (!buf_empty())
       {
         buf_next();
         write(datbuf[tail], lenbuf[tail]);
       }
 
       wrote_something = true;
     }
   public:
 
     /**
      * @brief Writes out all remaining data from the LineWrapper using @c write.
      * Unlike @ref process() this method indents all lines including the first and
      * will output a \\n at the end (but only if something has been written).
      */
     void flush(IStringWriter& write)
     {
       if (buf_empty())
         return;
       int _ = 0;
       indent(write, _, x);
       wrote_something = false;
       while (!buf_empty())
         write_one_line(write);
       write("\n", 1);
     }
 
     /**
      * @brief Process, wrap and output the next piece of data.
      *
      * process() will output at least one line of output. This is not necessarily
      * the @c data passed in. It may be data queued from a prior call to process().
      * If the internal buffer is full, more than 1 line will be output.
      *
      * process() assumes that the a proper amount of indentation has already been
      * output. It won't write any further indentation before the 1st line. If
      * more than 1 line is written due to buffer constraints, the lines following
      * the first will be indented by this method, though.
      *
      * No \\n is written by this method after the last line that is written.
      *
      * @param write where to write the data.
      * @param data the new chunk of data to write.
      * @param len the length of the chunk of data to write.
      */
     void process(IStringWriter& write, const char* data, int len)
     {
       wrote_something = false;
 
       while (len > 0)
       {
         if (len <= width) // quick test that works because utf8width <= len (all wide chars have at least 2 bytes)
         {
           output(write, data, len);
           len = 0;
         }
         else // if (len > width)  it's possible (but not guaranteed) that utf8len > width
         {
           int utf8width = 0;
           int maxi = 0;
           while (maxi < len && utf8width < width)
           {
             int charbytes = 1;
             unsigned ch = (unsigned char) data[maxi];
             if (ch > 0xC1) // everything <= 0xC1 (yes, even 0xC1 itself) is not a valid UTF-8 start byte
             {
               // int __builtin_clz (unsigned int x)
               // Returns the number of leading 0-bits in x, starting at the most significant bit
               unsigned mask = (unsigned) -1 >> __builtin_clz(ch ^ 0xff);
               ch = ch & mask; // mask out length bits, we don't verify their correctness
               while ((maxi + charbytes < len) && //
                   (((unsigned char) data[maxi + charbytes] ^ 0x80) <= 0x3F)) // while next byte is continuation byte
               {
                 ch = (ch << 6) ^ (unsigned char) data[maxi + charbytes] ^ 0x80; // add continuation to char code
                 ++charbytes;
               }
               // ch is the decoded unicode code point
               if (ch >= 0x1100 && isWideChar(ch)) // the test for 0x1100 is here to avoid the function call in the Latin case
               {
                 if (utf8width + 2 > width)
                   break;
                 ++utf8width;
               }
             }
             ++utf8width;
             maxi += charbytes;
           }
 
           // data[maxi-1] is the last byte of the UTF-8 sequence of the last character that fits
           // onto the 1st line. If maxi == len, all characters fit on the line.
 
           if (maxi == len)
           {
             output(write, data, len);
             len = 0;
           }
           else // if (maxi < len)  at least 1 character (data[maxi] that is) doesn't fit on the line
           {
             int i;
             for (i = maxi; i >= 0; --i)
               if (data[i] == ' ')
                 break;
 
             if (i >= 0)
             {
               output(write, data, i);
               data += i + 1;
               len -= i + 1;
             }
             else // did not find a space to split at => split before data[maxi]
             { // data[maxi] is always the beginning of a character, never a continuation byte
               output(write, data, maxi);
               data += maxi;
               len -= maxi;
             }
           }
         }
       }
       if (!wrote_something) // if we didn't already write something to make space in the buffer
         write_one_line(write); // write at most one line of actual output
     }
 
     /**
      * @brief Constructs a LineWrapper that wraps its output to fit into
      * screen columns @c x1 (incl.) to @c x2 (excl.).
      *
      * @c x1 gives the indentation LineWrapper uses if it needs to indent.
      */
     LineWrapper(int x1, int x2) :
         x(x1), width(x2 - x1), head(0), tail(bufmask)
     {
       if (width < 2) // because of wide characters we need at least width 2 or the code breaks
         width = 2;
     }
   };
 
   /**
    * @internal
    * @brief This is the implementation that is shared between all printUsage() templates.
    * Because all printUsage() templates share this implementation, there is no template bloat.
    */
   static void printUsage(IStringWriter& write, const Descriptor usage[], int width = 80, //
                          int last_column_min_percent = 50, int last_column_own_line_max_percent = 75)
   {
     if (width < 1) // protect against nonsense values
       width = 80;
 
     if (width > 10000) // protect against overflow in the following computation
       width = 10000;
 
     int last_column_min_width = ((width * last_column_min_percent) + 50) / 100;
     int last_column_own_line_max_width = ((width * last_column_own_line_max_percent) + 50) / 100;
     if (last_column_own_line_max_width == 0)
       last_column_own_line_max_width = 1;
 
     LinePartIterator part(usage);
     while (part.nextTable())
     {
 
       /***************** Determine column widths *******************************/
 
       const int maxcolumns = 8; // 8 columns are enough for everyone
       int col_width[maxcolumns];
       int lastcolumn;
       int leftwidth;
       int overlong_column_threshold = 10000;
       do
       {
         lastcolumn = 0;
         for (int i = 0; i < maxcolumns; ++i)
           col_width[i] = 0;
 
         part.restartTable();
         while (part.nextRow())
         {
           while (part.next())
           {
             if (part.column() < maxcolumns)
             {
               upmax(lastcolumn, part.column());
               if (part.screenLength() < overlong_column_threshold)
                 // We don't let rows that don't use table separators (\t or \v) influence
                 // the width of column 0. This allows the user to interject section headers
                 // or explanatory paragraphs that do not participate in the table layout.
                 if (part.column() > 0 || part.line() > 0 || part.data()[part.length()] == '\t'
                     || part.data()[part.length()] == '\v')
                   upmax(col_width[part.column()], part.screenLength());
             }
           }
         }
 
         /*
          * If the last column doesn't fit on the same
          * line as the other columns, we can fix that by starting it on its own line.
          * However we can't do this for any of the columns 0..lastcolumn-1.
          * If their sum exceeds the maximum width we try to fix this by iteratively
          * ignoring the widest line parts in the width determination until
          * we arrive at a series of column widths that fit into one line.
          * The result is a layout where everything is nicely formatted
          * except for a few overlong fragments.
          * */
 
         leftwidth = 0;
         overlong_column_threshold = 0;
         for (int i = 0; i < lastcolumn; ++i)
         {
           leftwidth += col_width[i];
           upmax(overlong_column_threshold, col_width[i]);
         }
 
       } while (leftwidth > width);
 
       /**************** Determine tab stops and last column handling **********************/
 
       int tabstop[maxcolumns];
       tabstop[0] = 0;
       for (int i = 1; i < maxcolumns; ++i)
         tabstop[i] = tabstop[i - 1] + col_width[i - 1];
 
       int rightwidth = width - tabstop[lastcolumn];
       bool print_last_column_on_own_line = false;
       if (rightwidth < last_column_min_width &&  // if we don't have the minimum requested width for the last column
             ( col_width[lastcolumn] == 0 ||      // and all last columns are > overlong_column_threshold
               rightwidth < col_width[lastcolumn] // or there is at least one last column that requires more than the space available
             )
           )
       {
         print_last_column_on_own_line = true;
         rightwidth = last_column_own_line_max_width;
       }
 
       // If lastcolumn == 0 we must disable print_last_column_on_own_line because
       // otherwise 2 copies of the last (and only) column would be output.
       // Actually this is just defensive programming. It is currently not
       // possible that lastcolumn==0 and print_last_column_on_own_line==true
       // at the same time, because lastcolumn==0 => tabstop[lastcolumn] == 0 =>
       // rightwidth==width => rightwidth>=last_column_min_width  (unless someone passes
       // a bullshit value >100 for last_column_min_percent) => the above if condition
       // is false => print_last_column_on_own_line==false
       if (lastcolumn == 0)
         print_last_column_on_own_line = false;
 
       LineWrapper lastColumnLineWrapper(width - rightwidth, width);
       LineWrapper interjectionLineWrapper(0, width);
 
       part.restartTable();
 
       /***************** Print out all rows of the table *************************************/
 
       while (part.nextRow())
       {
         int x = -1;
         while (part.next())
         {
           if (part.column() > lastcolumn)
             continue; // drop excess columns (can happen if lastcolumn == maxcolumns-1)
 
           if (part.column() == 0)
           {
             if (x >= 0)
               write("\n", 1);
             x = 0;
           }
 
           indent(write, x, tabstop[part.column()]);
 
           if ((part.column() < lastcolumn)
               && (part.column() > 0 || part.line() > 0 || part.data()[part.length()] == '\t'
                   || part.data()[part.length()] == '\v'))
           {
             write(part.data(), part.length());
             x += part.screenLength();
           }
           else // either part.column() == lastcolumn or we are in the special case of
                // an interjection that doesn't contain \v or \t
           {
             // NOTE: This code block is not necessarily executed for
             // each line, because some rows may have fewer columns.
 
             LineWrapper& lineWrapper = (part.column() == 0) ? interjectionLineWrapper : lastColumnLineWrapper;
 
             if (!print_last_column_on_own_line || part.column() != lastcolumn)
               lineWrapper.process(write, part.data(), part.length());
           }
         } // while
 
         if (print_last_column_on_own_line)
         {
           part.restartRow();
           while (part.next())
           {
             if (part.column() == lastcolumn)
             {
               write("\n", 1);
               int _ = 0;
               indent(write, _, width - rightwidth);
               lastColumnLineWrapper.process(write, part.data(), part.length());
             }
           }
         }
 
         write("\n", 1);
         lastColumnLineWrapper.flush(write);
         interjectionLineWrapper.flush(write);
       }
     }
   }
 
 }
 ;
 
 /**
  * @brief Outputs a nicely formatted usage string with support for multi-column formatting
  * and line-wrapping.
  *
  * printUsage() takes the @c help texts of a Descriptor[] array and formats them into
  * a usage message, wrapping lines to achieve the desired output width.
  *
  * <b>Table formatting:</b>
  *
  * Aside from plain strings which are simply line-wrapped, the usage may contain tables. Tables
  * are used to align elements in the output.
  *
  * @code
  * // Without a table. The explanatory texts are not aligned.
  * -c, --create  |Creates something.
  * -k, --kill  |Destroys something.
  *
  * // With table formatting. The explanatory texts are aligned.
  * -c, --create  |Creates something.
  * -k, --kill    |Destroys something.
  * @endcode
  *
  * Table formatting removes the need to pad help texts manually with spaces to achieve
  * alignment. To create a table, simply insert \\t (tab) characters to separate the cells
  * within a row.
  *
  * @code
  * const option::Descriptor usage[] = {
  * {..., "-c, --create  \tCreates something." },
  * {..., "-k, --kill  \tDestroys something." }, ...
  * @endcode
  *
  * Note that you must include the minimum amount of space desired between cells yourself.
  * Table formatting will insert further spaces as needed to achieve alignment.
  *
  * You can insert line breaks within cells by using \\v (vertical tab).
  *
  * @code
  * const option::Descriptor usage[] = {
  * {..., "-c,\v--create  \tCreates\vsomething." },
  * {..., "-k,\v--kill  \tDestroys\vsomething." }, ...
  *
  * // results in
  *
  * -c,       Creates
  * --create  something.
  * -k,       Destroys
  * --kill    something.
  * @endcode
  *
  * You can mix lines that do not use \\t or \\v with those that do. The plain
  * lines will not mess up the table layout. Alignment of the table columns will
  * be maintained even across these interjections.
  *
  * @code
  * const option::Descriptor usage[] = {
  * {..., "-c, --create  \tCreates something." },
  * {..., "----------------------------------" },
  * {..., "-k, --kill  \tDestroys something." }, ...
  *
  * // results in
  *
  * -c, --create  Creates something.
  * ----------------------------------
  * -k, --kill    Destroys something.
  * @endcode
  *
  * You can have multiple tables within the same usage whose columns are
  * aligned independently. Simply insert a dummy Descriptor with @c help==0.
  *
  * @code
  * const option::Descriptor usage[] = {
  * {..., "Long options:" },
  * {..., "--very-long-option  \tDoes something long." },
  * {..., "--ultra-super-mega-long-option  \tTakes forever to complete." },
  * {..., 0 }, // ---------- table break -----------
  * {..., "Short options:" },
  * {..., "-s  \tShort." },
  * {..., "-q  \tQuick." }, ...
  *
  * // results in
  *
  * Long options:
  * --very-long-option              Does something long.
  * --ultra-super-mega-long-option  Takes forever to complete.
  * Short options:
  * -s  Short.
  * -q  Quick.
  *
  * // Without the table break it would be
  *
  * Long options:
  * --very-long-option              Does something long.
  * --ultra-super-mega-long-option  Takes forever to complete.
  * Short options:
  * -s                              Short.
  * -q                              Quick.
  * @endcode
  *
  * <b>Output methods:</b>
  *
  * Because TheLeanMeanC++Option parser is freestanding, you have to provide the means for
  * output in the first argument(s) to printUsage(). Because printUsage() is implemented as
  * a set of template functions, you have great flexibility in your choice of output
  * method. The following example demonstrates typical uses. Anything that's similar enough
  * will work.
  *
  * @code
  * #include <unistd.h>  // write()
  * #include <iostream>  // cout
  * #include <sstream>   // ostringstream
  * #include <cstdio>    // fwrite()
  * using namespace std;
  *
  * void my_write(const char* str, int size) {
  *   fwrite(str, size, 1, stdout);
  * }
  *
  * struct MyWriter {
  *   void write(const char* buf, size_t size) const {
  *      fwrite(str, size, 1, stdout);
  *   }
  * };
  *
  * struct MyWriteFunctor {
  *   void operator()(const char* buf, size_t size) {
  *      fwrite(str, size, 1, stdout);
  *   }
  * };
  * ...
  * printUsage(my_write, usage);    // custom write function
  * printUsage(MyWriter(), usage);  // temporary of a custom class
  * MyWriter writer;
  * printUsage(writer, usage);      // custom class object
  * MyWriteFunctor wfunctor;
  * printUsage(&wfunctor, usage);   // custom functor
  * printUsage(write, 1, usage);    // write() to file descriptor 1
  * printUsage(cout, usage);        // an ostream&
  * printUsage(fwrite, stdout, usage);  // fwrite() to stdout
  * ostringstream sstr;
  * printUsage(sstr, usage);        // an ostringstream&
  *
  * @endcode
  *
  * @par Notes:
  * @li the @c write() method of a class that is to be passed as a temporary
  *     as @c MyWriter() is in the example, must be a @c const method, because
  *     temporary objects are passed as const reference. This only applies to
  *     temporary objects that are created and destroyed in the same statement.
  *     If you create an object like @c writer in the example, this restriction
  *     does not apply.
  * @li a functor like @c MyWriteFunctor in the example must be passed as a pointer.
  *     This differs from the way functors are passed to e.g. the STL algorithms.
  * @li All printUsage() templates are tiny wrappers around a shared non-template implementation.
  *     So there's no penalty for using different versions in the same program.
  * @li printUsage() always interprets Descriptor::help as UTF-8 and always produces UTF-8-encoded
  *     output. If your system uses a different charset, you must do your own conversion. You
  *     may also need to change the font of the console to see non-ASCII characters properly.
  *     This is particularly true for Windows.
  * @li @b Security @b warning: Do not insert untrusted strings (such as user-supplied arguments)
  *     into the usage. printUsage() has no protection against malicious UTF-8 sequences.
  *
  * @param prn The output method to use. See the examples above.
  * @param usage the Descriptor[] array whose @c help texts will be formatted.
  * @param width the maximum number of characters per output line. Note that this number is
  *        in actual characters, not bytes. printUsage() supports UTF-8 in @c help and will
  *        count multi-byte UTF-8 sequences properly. Asian wide characters are counted
  *        as 2 characters.
  * @param last_column_min_percent (0-100) The minimum percentage of @c width that should be available
  *        for the last column (which typically contains the textual explanation of an option).
  *        If less space is available, the last column will be printed on its own line, indented
  *        according to @c last_column_own_line_max_percent.
  * @param last_column_own_line_max_percent (0-100) If the last column is printed on its own line due to
  *        less than @c last_column_min_percent of the width being available, then only
  *        @c last_column_own_line_max_percent of the extra line(s) will be used for the
  *        last column's text. This ensures an indentation. See example below.
  *
  * @code
  * // width=20, last_column_min_percent=50 (i.e. last col. min. width=10)
  * --3456789 1234567890
  *           1234567890
  *
  * // width=20, last_column_min_percent=75 (i.e. last col. min. width=15)
  * // last_column_own_line_max_percent=75
  * --3456789
  *      123456789012345
  *      67890
  *
  * // width=20, last_column_min_percent=75 (i.e. last col. min. width=15)
  * // last_column_own_line_max_percent=33 (i.e. max. 5)
  * --3456789
  *                12345
  *                67890
  *                12345
  *                67890
  * @endcode
  */
 template<typename OStream>
 void printUsage(OStream& prn, const Descriptor usage[], int width = 80, int last_column_min_percent = 50,
                 int last_column_own_line_max_percent = 75)
 {
   PrintUsageImplementation::OStreamWriter<OStream> write(prn);
   PrintUsageImplementation::printUsage(write, usage, width, last_column_min_percent, last_column_own_line_max_percent);
 }
 
 template<typename Function>
 void printUsage(Function* prn, const Descriptor usage[], int width = 80, int last_column_min_percent = 50,
                 int last_column_own_line_max_percent = 75)
 {
   PrintUsageImplementation::FunctionWriter<Function> write(prn);
   PrintUsageImplementation::printUsage(write, usage, width, last_column_min_percent, last_column_own_line_max_percent);
 }
 
 template<typename Temporary>
 void printUsage(const Temporary& prn, const Descriptor usage[], int width = 80, int last_column_min_percent = 50,
                 int last_column_own_line_max_percent = 75)
 {
   PrintUsageImplementation::TemporaryWriter<Temporary> write(prn);
   PrintUsageImplementation::printUsage(write, usage, width, last_column_min_percent, last_column_own_line_max_percent);
 }
 
 template<typename Syscall>
 void printUsage(Syscall* prn, int fd, const Descriptor usage[], int width = 80, int last_column_min_percent = 50,
                 int last_column_own_line_max_percent = 75)
 {
   PrintUsageImplementation::SyscallWriter<Syscall> write(prn, fd);
   PrintUsageImplementation::printUsage(write, usage, width, last_column_min_percent, last_column_own_line_max_percent);
 }
 
 template<typename Function, typename Stream>
 void printUsage(Function* prn, Stream* stream, const Descriptor usage[], int width = 80, int last_column_min_percent =
                     50,
                 int last_column_own_line_max_percent = 75)
 {
   PrintUsageImplementation::StreamWriter<Function, Stream> write(prn, stream);
   PrintUsageImplementation::printUsage(write, usage, width, last_column_min_percent, last_column_own_line_max_percent);
 }
 
 }
 // namespace Option_Parser
 
 }
 // namespace ATOOLS
 
 #endif /* ATOOLS_Org_Option_Parser.H */
 

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