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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*
 *******************************************************************************
 *   Copyright (C) 2010-2012, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *******************************************************************************
 *   file name:  ucharstrie.h
 *   encoding:   UTF-8
 *   tab size:   8 (not used)
 *   indentation:4
 *
 *   created on: 2010nov14
 *   created by: Markus W. Scherer
 */
 
 #ifndef __UCHARSTRIE_H__
 #define __UCHARSTRIE_H__
 
 /**
  * \file
  * \brief C++ API: Trie for mapping Unicode strings (or 16-bit-unit sequences)
  *                 to integer values.
  */
 
 #include "unicode/utypes.h"
 
 #if U_SHOW_CPLUSPLUS_API
 
 #include "unicode/unistr.h"
 #include "unicode/uobject.h"
 #include "unicode/ustringtrie.h"
 
 U_NAMESPACE_BEGIN
 
 class Appendable;
 class UCharsTrieBuilder;
 class UVector32;
 
 /**
  * Light-weight, non-const reader class for a UCharsTrie.
  * Traverses a char16_t-serialized data structure with minimal state,
  * for mapping strings (16-bit-unit sequences) to non-negative integer values.
  *
  * This class owns the serialized trie data only if it was constructed by
  * the builder's build() method.
  * The public constructor and the copy constructor only alias the data (only copy the pointer).
  * There is no assignment operator.
  *
  * This class is not intended for public subclassing.
  * @stable ICU 4.8
  */
 class U_COMMON_API UCharsTrie : public UMemory {
 public:
     /**
      * Constructs a UCharsTrie reader instance.
      *
      * The trieUChars must contain a copy of a char16_t sequence from the UCharsTrieBuilder,
      * starting with the first char16_t of that sequence.
      * The UCharsTrie object will not read more char16_ts than
      * the UCharsTrieBuilder generated in the corresponding build() call.
      *
      * The array is not copied/cloned and must not be modified while
      * the UCharsTrie object is in use.
      *
      * @param trieUChars The char16_t array that contains the serialized trie.
      * @stable ICU 4.8
      */
     UCharsTrie(ConstChar16Ptr trieUChars)
             : ownedArray_(nullptr), uchars_(trieUChars),
               pos_(uchars_), remainingMatchLength_(-1) {}
 
     /**
      * Destructor.
      * @stable ICU 4.8
      */
     ~UCharsTrie();
 
     /**
      * Copy constructor, copies the other trie reader object and its state,
      * but not the char16_t array which will be shared. (Shallow copy.)
      * @param other Another UCharsTrie object.
      * @stable ICU 4.8
      */
     UCharsTrie(const UCharsTrie &other)
             : ownedArray_(nullptr), uchars_(other.uchars_),
               pos_(other.pos_), remainingMatchLength_(other.remainingMatchLength_) {}
 
     /**
      * Resets this trie to its initial state.
      * @return *this
      * @stable ICU 4.8
      */
     UCharsTrie &reset() {
         pos_=uchars_;
         remainingMatchLength_=-1;
         return *this;
     }
 
     /**
      * Returns the state of this trie as a 64-bit integer.
      * The state value is never 0.
      *
      * @return opaque state value
      * @see resetToState64
      * @stable ICU 65
      */
     uint64_t getState64() const {
         return (static_cast<uint64_t>(remainingMatchLength_ + 2) << kState64RemainingShift) |
             (uint64_t)(pos_ - uchars_);
     }
 
     /**
      * Resets this trie to the saved state.
      * Unlike resetToState(State), the 64-bit state value
      * must be from getState64() from the same trie object or
      * from one initialized the exact same way.
      * Because of no validation, this method is faster.
      *
      * @param state The opaque trie state value from getState64().
      * @return *this
      * @see getState64
      * @see resetToState
      * @see reset
      * @stable ICU 65
      */
     UCharsTrie &resetToState64(uint64_t state) {
         remainingMatchLength_ = static_cast<int32_t>(state >> kState64RemainingShift) - 2;
         pos_ = uchars_ + (state & kState64PosMask);
         return *this;
     }
 
     /**
      * UCharsTrie state object, for saving a trie's current state
      * and resetting the trie back to this state later.
      * @stable ICU 4.8
      */
     class State : public UMemory {
     public:
         /**
          * Constructs an empty State.
          * @stable ICU 4.8
          */
         State() { uchars=nullptr; }
     private:
         friend class UCharsTrie;
 
         const char16_t *uchars;
         const char16_t *pos;
         int32_t remainingMatchLength;
     };
 
     /**
      * Saves the state of this trie.
      * @param state The State object to hold the trie's state.
      * @return *this
      * @see resetToState
      * @stable ICU 4.8
      */
     const UCharsTrie &saveState(State &state) const {
         state.uchars=uchars_;
         state.pos=pos_;
         state.remainingMatchLength=remainingMatchLength_;
         return *this;
     }
 
     /**
      * Resets this trie to the saved state.
      * If the state object contains no state, or the state of a different trie,
      * then this trie remains unchanged.
      * @param state The State object which holds a saved trie state.
      * @return *this
      * @see saveState
      * @see reset
      * @stable ICU 4.8
      */
     UCharsTrie &resetToState(const State &state) {
         if(uchars_==state.uchars && uchars_!=nullptr) {
             pos_=state.pos;
             remainingMatchLength_=state.remainingMatchLength;
         }
         return *this;
     }
 
     /**
      * Determines whether the string so far matches, whether it has a value,
      * and whether another input char16_t can continue a matching string.
      * @return The match/value Result.
      * @stable ICU 4.8
      */
     UStringTrieResult current() const;
 
     /**
      * Traverses the trie from the initial state for this input char16_t.
      * Equivalent to reset().next(uchar).
      * @param uchar Input char value. Values below 0 and above 0xffff will never match.
      * @return The match/value Result.
      * @stable ICU 4.8
      */
     inline UStringTrieResult first(int32_t uchar) {
         remainingMatchLength_=-1;
         return nextImpl(uchars_, uchar);
     }
 
     /**
      * Traverses the trie from the initial state for the
      * one or two UTF-16 code units for this input code point.
      * Equivalent to reset().nextForCodePoint(cp).
      * @param cp A Unicode code point 0..0x10ffff.
      * @return The match/value Result.
      * @stable ICU 4.8
      */
     UStringTrieResult firstForCodePoint(UChar32 cp);
 
     /**
      * Traverses the trie from the current state for this input char16_t.
      * @param uchar Input char value. Values below 0 and above 0xffff will never match.
      * @return The match/value Result.
      * @stable ICU 4.8
      */
     UStringTrieResult next(int32_t uchar);
 
     /**
      * Traverses the trie from the current state for the
      * one or two UTF-16 code units for this input code point.
      * @param cp A Unicode code point 0..0x10ffff.
      * @return The match/value Result.
      * @stable ICU 4.8
      */
     UStringTrieResult nextForCodePoint(UChar32 cp);
 
     /**
      * Traverses the trie from the current state for this string.
      * Equivalent to
      * \code
      * Result result=current();
      * for(each c in s)
      *   if(!USTRINGTRIE_HAS_NEXT(result)) return USTRINGTRIE_NO_MATCH;
      *   result=next(c);
      * return result;
      * \endcode
      * @param s A string. Can be nullptr if length is 0.
      * @param length The length of the string. Can be -1 if NUL-terminated.
      * @return The match/value Result.
      * @stable ICU 4.8
      */
     UStringTrieResult next(ConstChar16Ptr s, int32_t length);
 
     /**
      * Returns a matching string's value if called immediately after
      * current()/first()/next() returned USTRINGTRIE_INTERMEDIATE_VALUE or USTRINGTRIE_FINAL_VALUE.
      * getValue() can be called multiple times.
      *
      * Do not call getValue() after USTRINGTRIE_NO_MATCH or USTRINGTRIE_NO_VALUE!
      * @return The value for the string so far.
      * @stable ICU 4.8
      */
     inline int32_t getValue() const {
         const char16_t *pos=pos_;
         int32_t leadUnit=*pos++;
         // U_ASSERT(leadUnit>=kMinValueLead);
         return leadUnit&kValueIsFinal ?
             readValue(pos, leadUnit&0x7fff) : readNodeValue(pos, leadUnit);
     }
 
     /**
      * Determines whether all strings reachable from the current state
      * map to the same value.
      * @param uniqueValue Receives the unique value, if this function returns true.
      *                    (output-only)
      * @return true if all strings reachable from the current state
      *         map to the same value.
      * @stable ICU 4.8
      */
     inline UBool hasUniqueValue(int32_t &uniqueValue) const {
         const char16_t *pos=pos_;
         // Skip the rest of a pending linear-match node.
         return pos!=nullptr && findUniqueValue(pos+remainingMatchLength_+1, false, uniqueValue);
     }
 
     /**
      * Finds each char16_t which continues the string from the current state.
      * That is, each char16_t c for which it would be next(c)!=USTRINGTRIE_NO_MATCH now.
      * @param out Each next char16_t is appended to this object.
      * @return the number of char16_ts which continue the string from here
      * @stable ICU 4.8
      */
     int32_t getNextUChars(Appendable &out) const;
 
     /**
      * Iterator for all of the (string, value) pairs in a UCharsTrie.
      * @stable ICU 4.8
      */
     class U_COMMON_API Iterator : public UMemory {
     public:
         /**
          * Iterates from the root of a char16_t-serialized UCharsTrie.
          * @param trieUChars The trie char16_ts.
          * @param maxStringLength If 0, the iterator returns full strings.
          *                        Otherwise, the iterator returns strings with this maximum length.
          * @param errorCode Standard ICU error code. Its input value must
          *                  pass the U_SUCCESS() test, or else the function returns
          *                  immediately. Check for U_FAILURE() on output or use with
          *                  function chaining. (See User Guide for details.)
          * @stable ICU 4.8
          */
         Iterator(ConstChar16Ptr trieUChars, int32_t maxStringLength, UErrorCode &errorCode);
 
         /**
          * Iterates from the current state of the specified UCharsTrie.
          * @param trie The trie whose state will be copied for iteration.
          * @param maxStringLength If 0, the iterator returns full strings.
          *                        Otherwise, the iterator returns strings with this maximum length.
          * @param errorCode Standard ICU error code. Its input value must
          *                  pass the U_SUCCESS() test, or else the function returns
          *                  immediately. Check for U_FAILURE() on output or use with
          *                  function chaining. (See User Guide for details.)
          * @stable ICU 4.8
          */
         Iterator(const UCharsTrie &trie, int32_t maxStringLength, UErrorCode &errorCode);
 
         /**
          * Destructor.
          * @stable ICU 4.8
          */
         ~Iterator();
 
         /**
          * Resets this iterator to its initial state.
          * @return *this
          * @stable ICU 4.8
          */
         Iterator &reset();
 
         /**
          * @return true if there are more elements.
          * @stable ICU 4.8
          */
         UBool hasNext() const;
 
         /**
          * Finds the next (string, value) pair if there is one.
          *
          * If the string is truncated to the maximum length and does not
          * have a real value, then the value is set to -1.
          * In this case, this "not a real value" is indistinguishable from
          * a real value of -1.
          * @param errorCode Standard ICU error code. Its input value must
          *                  pass the U_SUCCESS() test, or else the function returns
          *                  immediately. Check for U_FAILURE() on output or use with
          *                  function chaining. (See User Guide for details.)
          * @return true if there is another element.
          * @stable ICU 4.8
          */
         UBool next(UErrorCode &errorCode);
 
         /**
          * @return The string for the last successful next().
          * @stable ICU 4.8
          */
         const UnicodeString &getString() const { return str_; }
         /**
          * @return The value for the last successful next().
          * @stable ICU 4.8
          */
         int32_t getValue() const { return value_; }
 
     private:
         UBool truncateAndStop() {
             pos_=nullptr;
             value_=-1;  // no real value for str
             return true;
         }
 
         const char16_t *branchNext(const char16_t *pos, int32_t length, UErrorCode &errorCode);
 
         const char16_t *uchars_;
         const char16_t *pos_;
         const char16_t *initialPos_;
         int32_t remainingMatchLength_;
         int32_t initialRemainingMatchLength_;
         UBool skipValue_;  // Skip intermediate value which was already delivered.
 
         UnicodeString str_;
         int32_t maxLength_;
         int32_t value_;
 
         // The stack stores pairs of integers for backtracking to another
         // outbound edge of a branch node.
         // The first integer is an offset from uchars_.
         // The second integer has the str_.length() from before the node in bits 15..0,
         // and the remaining branch length in bits 31..16.
         // (We could store the remaining branch length minus 1 in bits 30..16 and not use the sign bit,
         // but the code looks more confusing that way.)
         UVector32 *stack_;
     };
 
 private:
     friend class UCharsTrieBuilder;
 
     /**
      * Constructs a UCharsTrie reader instance.
      * Unlike the public constructor which just aliases an array,
      * this constructor adopts the builder's array.
      * This constructor is only called by the builder.
      */
     UCharsTrie(char16_t *adoptUChars, const char16_t *trieUChars)
             : ownedArray_(adoptUChars), uchars_(trieUChars),
               pos_(uchars_), remainingMatchLength_(-1) {}
 
     // No assignment operator.
     UCharsTrie &operator=(const UCharsTrie &other) = delete;
 
     inline void stop() {
         pos_=nullptr;
     }
 
     // Reads a compact 32-bit integer.
     // pos is already after the leadUnit, and the lead unit has bit 15 reset.
     static inline int32_t readValue(const char16_t *pos, int32_t leadUnit) {
         int32_t value;
         if(leadUnit<kMinTwoUnitValueLead) {
             value=leadUnit;
         } else if(leadUnit<kThreeUnitValueLead) {
             value=((leadUnit-kMinTwoUnitValueLead)<<16)|*pos;
         } else {
             value=(pos[0]<<16)|pos[1];
         }
         return value;
     }
     static inline const char16_t *skipValue(const char16_t *pos, int32_t leadUnit) {
         if(leadUnit>=kMinTwoUnitValueLead) {
             if(leadUnit<kThreeUnitValueLead) {
                 ++pos;
             } else {
                 pos+=2;
             }
         }
         return pos;
     }
     static inline const char16_t *skipValue(const char16_t *pos) {
         int32_t leadUnit=*pos++;
         return skipValue(pos, leadUnit&0x7fff);
     }
 
     static inline int32_t readNodeValue(const char16_t *pos, int32_t leadUnit) {
         // U_ASSERT(kMinValueLead<=leadUnit && leadUnit<kValueIsFinal);
         int32_t value;
         if(leadUnit<kMinTwoUnitNodeValueLead) {
             value=(leadUnit>>6)-1;
         } else if(leadUnit<kThreeUnitNodeValueLead) {
             value=(((leadUnit&0x7fc0)-kMinTwoUnitNodeValueLead)<<10)|*pos;
         } else {
             value=(pos[0]<<16)|pos[1];
         }
         return value;
     }
     static inline const char16_t *skipNodeValue(const char16_t *pos, int32_t leadUnit) {
         // U_ASSERT(kMinValueLead<=leadUnit && leadUnit<kValueIsFinal);
         if(leadUnit>=kMinTwoUnitNodeValueLead) {
             if(leadUnit<kThreeUnitNodeValueLead) {
                 ++pos;
             } else {
                 pos+=2;
             }
         }
         return pos;
     }
 
     static inline const char16_t *jumpByDelta(const char16_t *pos) {
         int32_t delta=*pos++;
         if(delta>=kMinTwoUnitDeltaLead) {
             if(delta==kThreeUnitDeltaLead) {
                 delta=(pos[0]<<16)|pos[1];
                 pos+=2;
             } else {
                 delta=((delta-kMinTwoUnitDeltaLead)<<16)|*pos++;
             }
         }
         return pos+delta;
     }
 
     static const char16_t *skipDelta(const char16_t *pos) {
         int32_t delta=*pos++;
         if(delta>=kMinTwoUnitDeltaLead) {
             if(delta==kThreeUnitDeltaLead) {
                 pos+=2;
             } else {
                 ++pos;
             }
         }
         return pos;
     }
 
     static inline UStringTrieResult valueResult(int32_t node) {
         return (UStringTrieResult)(USTRINGTRIE_INTERMEDIATE_VALUE-(node>>15));
     }
 
     // Handles a branch node for both next(uchar) and next(string).
     UStringTrieResult branchNext(const char16_t *pos, int32_t length, int32_t uchar);
 
     // Requires remainingLength_<0.
     UStringTrieResult nextImpl(const char16_t *pos, int32_t uchar);
 
     // Helper functions for hasUniqueValue().
     // Recursively finds a unique value (or whether there is not a unique one)
     // from a branch.
     static const char16_t *findUniqueValueFromBranch(const char16_t *pos, int32_t length,
                                                   UBool haveUniqueValue, int32_t &uniqueValue);
     // Recursively finds a unique value (or whether there is not a unique one)
     // starting from a position on a node lead unit.
     static UBool findUniqueValue(const char16_t *pos, UBool haveUniqueValue, int32_t &uniqueValue);
 
     // Helper functions for getNextUChars().
     // getNextUChars() when pos is on a branch node.
     static void getNextBranchUChars(const char16_t *pos, int32_t length, Appendable &out);
 
     // UCharsTrie data structure
     //
     // The trie consists of a series of char16_t-serialized nodes for incremental
     // Unicode string/char16_t sequence matching. (char16_t=16-bit unsigned integer)
     // The root node is at the beginning of the trie data.
     //
     // Types of nodes are distinguished by their node lead unit ranges.
     // After each node, except a final-value node, another node follows to
     // encode match values or continue matching further units.
     //
     // Node types:
     //  - Final-value node: Stores a 32-bit integer in a compact, variable-length format.
     //    The value is for the string/char16_t sequence so far.
     //  - Match node, optionally with an intermediate value in a different compact format.
     //    The value, if present, is for the string/char16_t sequence so far.
     //
     //  Aside from the value, which uses the node lead unit's high bits:
     //
     //  - Linear-match node: Matches a number of units.
     //  - Branch node: Branches to other nodes according to the current input unit.
     //    The node unit is the length of the branch (number of units to select from)
     //    minus 1. It is followed by a sub-node:
     //    - If the length is at most kMaxBranchLinearSubNodeLength, then
     //      there are length-1 (key, value) pairs and then one more comparison unit.
     //      If one of the key units matches, then the value is either a final value for
     //      the string so far, or a "jump" delta to the next node.
     //      If the last unit matches, then matching continues with the next node.
     //      (Values have the same encoding as final-value nodes.)
     //    - If the length is greater than kMaxBranchLinearSubNodeLength, then
     //      there is one unit and one "jump" delta.
     //      If the input unit is less than the sub-node unit, then "jump" by delta to
     //      the next sub-node which will have a length of length/2.
     //      (The delta has its own compact encoding.)
     //      Otherwise, skip the "jump" delta to the next sub-node
     //      which will have a length of length-length/2.
 
     // Match-node lead unit values, after masking off intermediate-value bits:
 
     // 0000..002f: Branch node. If node!=0 then the length is node+1, otherwise
     // the length is one more than the next unit.
 
     // For a branch sub-node with at most this many entries, we drop down
     // to a linear search.
     static const int32_t kMaxBranchLinearSubNodeLength=5;
 
     // 0030..003f: Linear-match node, match 1..16 units and continue reading the next node.
     static const int32_t kMinLinearMatch=0x30;
     static const int32_t kMaxLinearMatchLength=0x10;
 
     // Match-node lead unit bits 14..6 for the optional intermediate value.
     // If these bits are 0, then there is no intermediate value.
     // Otherwise, see the *NodeValue* constants below.
     static const int32_t kMinValueLead=kMinLinearMatch+kMaxLinearMatchLength;  // 0x0040
     static const int32_t kNodeTypeMask=kMinValueLead-1;  // 0x003f
 
     // A final-value node has bit 15 set.
     static const int32_t kValueIsFinal=0x8000;
 
     // Compact value: After testing and masking off bit 15, use the following thresholds.
     static const int32_t kMaxOneUnitValue=0x3fff;
 
     static const int32_t kMinTwoUnitValueLead=kMaxOneUnitValue+1;  // 0x4000
     static const int32_t kThreeUnitValueLead=0x7fff;
 
     static const int32_t kMaxTwoUnitValue=((kThreeUnitValueLead-kMinTwoUnitValueLead)<<16)-1;  // 0x3ffeffff
 
     // Compact intermediate-value integer, lead unit shared with a branch or linear-match node.
     static const int32_t kMaxOneUnitNodeValue=0xff;
     static const int32_t kMinTwoUnitNodeValueLead=kMinValueLead+((kMaxOneUnitNodeValue+1)<<6);  // 0x4040
     static const int32_t kThreeUnitNodeValueLead=0x7fc0;
 
     static const int32_t kMaxTwoUnitNodeValue=
         ((kThreeUnitNodeValueLead-kMinTwoUnitNodeValueLead)<<10)-1;  // 0xfdffff
 
     // Compact delta integers.
     static const int32_t kMaxOneUnitDelta=0xfbff;
     static const int32_t kMinTwoUnitDeltaLead=kMaxOneUnitDelta+1;  // 0xfc00
     static const int32_t kThreeUnitDeltaLead=0xffff;
 
     static const int32_t kMaxTwoUnitDelta=((kThreeUnitDeltaLead-kMinTwoUnitDeltaLead)<<16)-1;  // 0x03feffff
 
     // For getState64():
     // The remainingMatchLength_ is -1..14=(kMaxLinearMatchLength=0x10)-2
     // so we need at least 5 bits for that.
     // We add 2 to store it as a positive value 1..16=kMaxLinearMatchLength.
     static constexpr int32_t kState64RemainingShift = 59;
     static constexpr uint64_t kState64PosMask = (UINT64_C(1) << kState64RemainingShift) - 1;
 
     char16_t *ownedArray_;
 
     // Fixed value referencing the UCharsTrie words.
     const char16_t *uchars_;
 
     // Iterator variables.
 
     // Pointer to next trie unit to read. nullptr if no more matches.
     const char16_t *pos_;
     // Remaining length of a linear-match node, minus 1. Negative if not in such a node.
     int32_t remainingMatchLength_;
 };
 
 U_NAMESPACE_END
 
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif  // __UCHARSTRIE_H__

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