EIC code displayed by LXR master/​include/​boost/​beast/​zlib/​detail/​inflate_stream.ipp	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2025-01-18 09:29:36

 //
 // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 // Official repository: https://github.com/boostorg/beast
 //
 // This is a derivative work based on Zlib, copyright below:
 /*
     Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
 
     This software is provided 'as-is', without any express or implied
     warranty.  In no event will the authors be held liable for any damages
     arising from the use of this software.
 
     Permission is granted to anyone to use this software for any purpose,
     including commercial applications, and to alter it and redistribute it
     freely, subject to the following restrictions:
 
     1. The origin of this software must not be misrepresented; you must not
        claim that you wrote the original software. If you use this software
        in a product, an acknowledgment in the product documentation would be
        appreciated but is not required.
     2. Altered source versions must be plainly marked as such, and must not be
        misrepresented as being the original software.
     3. This notice may not be removed or altered from any source distribution.
 
     Jean-loup Gailly        Mark Adler
     jloup@gzip.org          madler@alumni.caltech.edu
 
     The data format used by the zlib library is described by RFCs (Request for
     Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
     (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
 */
 
 #ifndef BOOST_BEAST_ZLIB_DETAIL_INFLATE_STREAM_IPP
 #define BOOST_BEAST_ZLIB_DETAIL_INFLATE_STREAM_IPP
 
 #include <boost/beast/zlib/detail/inflate_stream.hpp>
 #include <boost/throw_exception.hpp>
 #include <array>
 
 namespace boost {
 namespace beast {
 namespace zlib {
 namespace detail {
 
 void
 inflate_stream::
 doClear()
 {
 }
 
 void
 inflate_stream::
 doReset(int windowBits)
 {
     if(windowBits < 8 || windowBits > 15)
         BOOST_THROW_EXCEPTION(std::domain_error{
             "windowBits out of range"});
     w_.reset(windowBits);
 
     bi_.flush();
     mode_ = HEAD;
     last_ = 0;
     dmax_ = 32768U;
     lencode_ = codes_;
     distcode_ = codes_;
     next_ = codes_;
     back_ = -1;
 }
 
 void
 inflate_stream::
 doWrite(z_params& zs, Flush flush, error_code& ec)
 {
     ranges r;
     r.in.first = static_cast<
         std::uint8_t const*>(zs.next_in);
     r.in.last = r.in.first + zs.avail_in;
     r.in.next = r.in.first;
     r.out.first = static_cast<
         std::uint8_t*>(zs.next_out);
     r.out.last = r.out.first + zs.avail_out;
     r.out.next = r.out.first;
 
     auto const done =
         [&]
         {
             /*
                Return from inflate(), updating the total counts and the check value.
                If there was no progress during the inflate() call, return a buffer
                error.  Call updatewindow() to create and/or update the window state.
                Note: a memory error from inflate() is non-recoverable.
              */
 
 
             // VFALCO TODO Don't allocate update the window unless necessary
             if(/*wsize_ ||*/ (r.out.used() && mode_ < BAD &&
                     (mode_ < CHECK || flush != Flush::finish)))
                 w_.write(r.out.first, r.out.used());
 
             zs.next_in = r.in.next;
             zs.avail_in = r.in.avail();
             zs.next_out = r.out.next;
             zs.avail_out = r.out.avail();
             zs.total_in += r.in.used();
             zs.total_out += r.out.used();
             zs.data_type = bi_.size() + (last_ ? 64 : 0) +
                 (mode_ == TYPE ? 128 : 0) +
                 (mode_ == LEN_ || mode_ == COPY_ ? 256 : 0);
 
             if(((! r.in.used() && ! r.out.used()) ||
                     flush == Flush::finish) && ! ec)
             {
                 BOOST_BEAST_ASSIGN_EC(ec, error::need_buffers);
             }
         };
     auto const err =
         [&](error e)
         {
             BOOST_BEAST_ASSIGN_EC(ec, e);
             mode_ = BAD;
         };
 
     if(mode_ == TYPE)
         mode_ = TYPEDO;
 
     for(;;)
     {
         switch(mode_)
         {
         case HEAD:
             mode_ = TYPEDO;
             break;
 
         case TYPE:
             if(flush == Flush::block || flush == Flush::trees)
                 return done();
             // fall through
 
         case TYPEDO:
         {
             if(last_)
             {
                 bi_.flush_byte();
                 mode_ = CHECK;
                 break;
             }
             if(! bi_.fill(3, r.in.next, r.in.last))
                 return done();
             std::uint8_t v;
             bi_.read(v, 1);
             last_ = v != 0;
             bi_.read(v, 2);
             switch(v)
             {
             case 0:
                 // uncompressed block
                 mode_ = STORED;
                 break;
             case 1:
                 // fixed Huffman table
                 fixedTables();
                 mode_ = LEN_;             /* decode codes */
                 if(flush == Flush::trees)
                     return done();
                 break;
             case 2:
                 // dynamic Huffman table
                 mode_ = TABLE;
                 break;
 
             default:
                 return err(error::invalid_block_type);
             }
             break;
         }
 
         case STORED:
         {
             bi_.flush_byte();
             std::uint32_t v;
             if(! bi_.fill(32, r.in.next, r.in.last))
                 return done();
             bi_.peek(v, 32);
             length_ = v & 0xffff;
             if(length_ != ((v >> 16) ^ 0xffff))
                 return err(error::invalid_stored_length);
             // flush instead of read, otherwise
             // undefined right shift behavior.
             bi_.flush();
             mode_ = COPY_;
             if(flush == Flush::trees)
                 return done();
             BOOST_FALLTHROUGH;
         }
 
         case COPY_:
             mode_ = COPY;
             BOOST_FALLTHROUGH;
 
         case COPY:
         {
             auto copy = length_;
             if(copy == 0)
             {
                 mode_ = TYPE;
                 break;
             }
             copy = clamp(copy, r.in.avail());
             copy = clamp(copy, r.out.avail());
             if(copy == 0)
                 return done();
             std::memcpy(r.out.next, r.in.next, copy);
             r.in.next += copy;
             r.out.next += copy;
             length_ -= copy;
             break;
         }
 
         case TABLE:
             if(! bi_.fill(5 + 5 + 4, r.in.next, r.in.last))
                 return done();
             bi_.read(nlen_, 5);
             nlen_ += 257;
             bi_.read(ndist_, 5);
             ndist_ += 1;
             bi_.read(ncode_, 4);
             ncode_ += 4;
             if(nlen_ > 286 || ndist_ > 30)
                 return err(error::too_many_symbols);
             have_ = 0;
             mode_ = LENLENS;
             BOOST_FALLTHROUGH;
 
         case LENLENS:
         {
             static std::array<std::uint8_t, 19> constexpr order = {{
                 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}};
             while(have_ < ncode_)
             {
                 if(! bi_.fill(3, r.in.next, r.in.last))
                     return done();
                 bi_.read(lens_[order[have_]], 3);
                 ++have_;
             }
             while(have_ < order.size())
                 lens_[order[have_++]] = 0;
 
             next_ = &codes_[0];
             lencode_ = next_;
             lenbits_ = 7;
             inflate_table(build::codes, &lens_[0],
                 order.size(), &next_, &lenbits_, work_, ec);
             if(ec)
             {
                 mode_ = BAD;
                 break;
             }
             have_ = 0;
             mode_ = CODELENS;
             BOOST_FALLTHROUGH;
         }
 
         case CODELENS:
         {
             while(have_ < nlen_ + ndist_)
             {
                 std::uint16_t v;
                 if(! bi_.fill(lenbits_, r.in.next, r.in.last))
                     return done();
                 bi_.peek(v, lenbits_);
                 auto cp = &lencode_[v];
                 if(cp->val < 16)
                 {
                     bi_.drop(cp->bits);
                     lens_[have_++] = cp->val;
                 }
                 else
                 {
                     std::uint16_t len;
                     std::uint16_t copy;
                     if(cp->val == 16)
                     {
                         if(! bi_.fill(cp->bits + 2, r.in.next, r.in.last))
                             return done();
                         bi_.drop(cp->bits);
                         if(have_ == 0)
                             return err(error::invalid_bit_length_repeat);
                         bi_.read(copy, 2);
                         len = lens_[have_ - 1];
                         copy += 3;
 
                     }
                     else if(cp->val == 17)
                     {
                         if(! bi_.fill(cp->bits + 3, r.in.next, r.in.last))
                             return done();
                         bi_.drop(cp->bits);
                         bi_.read(copy, 3);
                         len = 0;
                         copy += 3;
                     }
                     else
                     {
                         if(! bi_.fill(cp->bits + 7, r.in.next, r.in.last))
                             return done();
                         bi_.drop(cp->bits);
                         bi_.read(copy, 7);
                         len = 0;
                         copy += 11;
                     }
                     if(have_ + copy > nlen_ + ndist_)
                         return err(error::invalid_bit_length_repeat);
                     std::fill(&lens_[have_], &lens_[have_ + copy], len);
                     have_ += copy;
                     copy = 0;
                 }
             }
             // handle error breaks in while
             if(mode_ == BAD)
                 break;
             // check for end-of-block code (better have one)
             if(lens_[256] == 0)
                 return err(error::missing_eob);
             /* build code tables -- note: do not change the lenbits or distbits
                values here (9 and 6) without reading the comments in inftrees.hpp
                concerning the kEnough constants, which depend on those values */
             next_ = &codes_[0];
             lencode_ = next_;
             lenbits_ = 9;
             inflate_table(build::lens, &lens_[0],
                 nlen_, &next_, &lenbits_, work_, ec);
             if(ec)
             {
                 mode_ = BAD;
                 return;
             }
             distcode_ = next_;
             distbits_ = 6;
             inflate_table(build::dists, lens_ + nlen_,
                 ndist_, &next_, &distbits_, work_, ec);
             if(ec)
             {
                 mode_ = BAD;
                 return;
             }
             mode_ = LEN_;
             if(flush == Flush::trees)
                 return done();
             BOOST_FALLTHROUGH;
         }
 
         case LEN_:
             mode_ = LEN;
             BOOST_FALLTHROUGH;
 
         case LEN:
         {
             if(r.in.avail() >= 6 && r.out.avail() >= 258)
             {
                 inflate_fast(r, ec);
                 if(ec)
                 {
                     mode_ = BAD;
                     return;
                 }
                 if(mode_ == TYPE)
                     back_ = -1;
                 break;
             }
             if(! bi_.fill(lenbits_, r.in.next, r.in.last))
                 return done();
             std::uint16_t v;
             back_ = 0;
             bi_.peek(v, lenbits_);
             auto cp = &lencode_[v];
             if(cp->op && (cp->op & 0xf0) == 0)
             {
                 auto prev = cp;
                 if(! bi_.fill(prev->bits + prev->op, r.in.next, r.in.last))
                     return done();
                 bi_.peek(v, prev->bits + prev->op);
                 cp = &lencode_[prev->val + (v >> prev->bits)];
                 bi_.drop(prev->bits + cp->bits);
                 back_ += prev->bits + cp->bits;
             }
             else
             {
                 bi_.drop(cp->bits);
                 back_ += cp->bits;
             }
             length_ = cp->val;
             if(cp->op == 0)
             {
                 mode_ = LIT;
                 break;
             }
             if(cp->op & 32)
             {
                 back_ = -1;
                 mode_ = TYPE;
                 break;
             }
             if(cp->op & 64)
                 return err(error::invalid_literal_length);
             extra_ = cp->op & 15;
             mode_ = LENEXT;
             BOOST_FALLTHROUGH;
         }
 
         case LENEXT:
             if(extra_)
             {
                 if(! bi_.fill(extra_, r.in.next, r.in.last))
                     return done();
                 std::uint16_t v;
                 bi_.read(v, extra_);
                 length_ += v;
                 back_ += extra_;
             }
             was_ = length_;
             mode_ = DIST;
             BOOST_FALLTHROUGH;
 
         case DIST:
         {
             if(! bi_.fill(distbits_, r.in.next, r.in.last))
                 return done();
             std::uint16_t v;
             bi_.peek(v, distbits_);
             auto cp = &distcode_[v];
             if((cp->op & 0xf0) == 0)
             {
                 auto prev = cp;
                 if(! bi_.fill(prev->bits + prev->op, r.in.next, r.in.last))
                     return done();
                 bi_.peek(v, prev->bits + prev->op);
                 cp = &distcode_[prev->val + (v >> prev->bits)];
                 bi_.drop(prev->bits + cp->bits);
                 back_ += prev->bits + cp->bits;
             }
             else
             {
                 bi_.drop(cp->bits);
                 back_ += cp->bits;
             }
             if(cp->op & 64)
                 return err(error::invalid_distance_code);
             offset_ = cp->val;
             extra_ = cp->op & 15;
             mode_ = DISTEXT;
             BOOST_FALLTHROUGH;
         }
 
         case DISTEXT:
             if(extra_)
             {
                 std::uint16_t v;
                 if(! bi_.fill(extra_, r.in.next, r.in.last))
                     return done();
                 bi_.read(v, extra_);
                 offset_ += v;
                 back_ += extra_;
             }
 #ifdef INFLATE_STRICT
             if(offset_ > dmax_)
                 return err(error::invalid_distance);
 #endif
             mode_ = MATCH;
             BOOST_FALLTHROUGH;
 
         case MATCH:
         {
             if(! r.out.avail())
                 return done();
             if(offset_ > r.out.used())
             {
                 // copy from window
                 auto offset = static_cast<std::uint16_t>(
                     offset_ - r.out.used());
                 if(offset > w_.size())
                     return err(error::invalid_distance);
                 auto const n = clamp(clamp(
                     length_, offset), r.out.avail());
                 w_.read(r.out.next, offset, n);
                 r.out.next += n;
                 length_ -= n;
             }
             else
             {
                 // copy from output
                 auto in = r.out.next - offset_;
                 auto n = clamp(length_, r.out.avail());
                 length_ -= n;
                 while(n--)
                     *r.out.next++ = *in++;
             }
             if(length_ == 0)
                 mode_ = LEN;
             break;
         }
 
         case LIT:
         {
             if(! r.out.avail())
                 return done();
             auto const v = static_cast<std::uint8_t>(length_);
             *r.out.next++ = v;
             mode_ = LEN;
             break;
         }
 
         case CHECK:
             mode_ = DONE;
             BOOST_FALLTHROUGH;
 
         case DONE:
         {
             BOOST_BEAST_ASSIGN_EC(ec, error::end_of_stream);
             return done();
         }
 
         case BAD:
             return done();
 
         case SYNC:
         default:
             BOOST_THROW_EXCEPTION(std::logic_error{
                 "stream error"});
         }
     }
 }
 
 //------------------------------------------------------------------------------
 
 /*  Build a set of tables to decode the provided canonical Huffman code.
     The code lengths are lens[0..codes-1].  The result starts at *table,
     whose indices are 0..2^bits-1.  work is a writable array of at least
     lens shorts, which is used as a work area.  type is the type of code
     to be generated, build::codes, build::lens, or build::dists.  On
     return, zero is success, -1 is an invalid code, and +1 means that
     kEnough isn't enough.  table on return points to the next available
     entry's address.  bits is the requested root table index bits, and
     on return it is the actual root table index bits.  It will differ if
     the request is greater than the longest code or if it is less than
     the shortest code.
 */
 void
 inflate_stream::
 inflate_table(
     build type,
     std::uint16_t* lens,
     std::size_t codes,
     code** table,
     unsigned *bits,
     std::uint16_t* work,
     error_code& ec)
 {
     unsigned len;                   // a code's length in bits
     unsigned sym;                   // index of code symbols
     unsigned min, max;              // minimum and maximum code lengths
     unsigned root;                  // number of index bits for root table
     unsigned curr;                  // number of index bits for current table
     unsigned drop;                  // code bits to drop for sub-table
     int left;                       // number of prefix codes available
     unsigned used;                  // code entries in table used
     unsigned huff;                  // Huffman code
     unsigned incr;                  // for incrementing code, index
     unsigned fill;                  // index for replicating entries
     unsigned low;                   // low bits for current root entry
     unsigned mask;                  // mask for low root bits
     code here;                      // table entry for duplication
     code *next;                     // next available space in table
     std::uint16_t const* base;      // base value table to use
     std::uint16_t const* extra;     // extra bits table to use
     unsigned match;                 // use base and extra for symbol >= match
     std::uint16_t count[15+1];      // number of codes of each length
     std::uint16_t offs[15+1];       // offsets in table for each length
 
     // Length codes 257..285 base
     static std::uint16_t constexpr lbase[31] = {
         3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 15, 17, 19, 23, 27, 31,
         35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
 
     // Length codes 257..285 extra
     static std::uint16_t constexpr lext[31] = {
         16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
         19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 77, 202};
 
     // Distance codes 0..29 base
     static std::uint16_t constexpr dbase[32] = {
         1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
         257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
         8193, 12289, 16385, 24577, 0, 0};
 
     // Distance codes 0..29 extra
     static std::uint16_t constexpr dext[32] = {
         16, 16, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22,
         23, 23, 24, 24, 25, 25, 26, 26, 27, 27,
         28, 28, 29, 29, 64, 64};
 
     /*
        Process a set of code lengths to create a canonical Huffman code.  The
        code lengths are lens[0..codes-1].  Each length corresponds to the
        symbols 0..codes-1.  The Huffman code is generated by first sorting the
        symbols by length from short to long, and retaining the symbol order
        for codes with equal lengths.  Then the code starts with all zero bits
        for the first code of the shortest length, and the codes are integer
        increments for the same length, and zeros are appended as the length
        increases.  For the deflate format, these bits are stored backwards
        from their more natural integer increment ordering, and so when the
        decoding tables are built in the large loop below, the integer codes
        are incremented backwards.
 
        This routine assumes, but does not check, that all of the entries in
        lens[] are in the range 0..15.  The caller must assure this.
        1..15 is interpreted as that code length.  zero means that that
        symbol does not occur in this code.
 
        The codes are sorted by computing a count of codes for each length,
        creating from that a table of starting indices for each length in the
        sorted table, and then entering the symbols in order in the sorted
        table.  The sorted table is work[], with that space being provided by
        the caller.
 
        The length counts are used for other purposes as well, i.e. finding
        the minimum and maximum length codes, determining if there are any
        codes at all, checking for a valid set of lengths, and looking ahead
        at length counts to determine sub-table sizes when building the
        decoding tables.
      */
 
     /* accumulate lengths for codes (assumes lens[] all in 0..15) */
     for (len = 0; len <= 15; len++)
         count[len] = 0;
     for (sym = 0; sym < codes; sym++)
         count[lens[sym]]++;
 
     /* bound code lengths, force root to be within code lengths */
     root = *bits;
     for (max = 15; max >= 1; max--)
         if (count[max] != 0)
             break;
     if (root > max)
         root = max;
     if (max == 0)
     {                     /* no symbols to code at all */
         here.op = (std::uint8_t)64;    /* invalid code marker */
         here.bits = (std::uint8_t)1;
         here.val = (std::uint16_t)0;
         *(*table)++ = here;             /* make a table to force an error */
         *(*table)++ = here;
         *bits = 1;
         return;       /* no symbols, but wait for decoding to report error */
     }
     for (min = 1; min < max; min++)
         if (count[min] != 0)
             break;
     if (root < min)
         root = min;
 
     /* check for an over-subscribed or incomplete set of lengths */
     left = 1;
     for (len = 1; len <= 15; len++)
     {
         left <<= 1;
         left -= count[len];
         if (left < 0)
         {
             BOOST_BEAST_ASSIGN_EC(ec, error::over_subscribed_length);
             return;
         }
     }
     if (left > 0 && (type == build::codes || max != 1))
     {
         BOOST_BEAST_ASSIGN_EC(ec, error::incomplete_length_set);
         return;
     }
 
     /* generate offsets into symbol table for each length for sorting */
     offs[1] = 0;
     for (len = 1; len < 15; len++)
         offs[len + 1] = offs[len] + count[len];
 
     /* sort symbols by length, by symbol order within each length */
     for (sym = 0; sym < codes; sym++)
         if (lens[sym] != 0)
             work[offs[lens[sym]]++] = (std::uint16_t)sym;
 
     /*
        Create and fill in decoding tables.  In this loop, the table being
        filled is at next and has curr index bits.  The code being used is huff
        with length len.  That code is converted to an index by dropping drop
        bits off of the bottom.  For codes where len is less than drop + curr,
        those top drop + curr - len bits are incremented through all values to
        fill the table with replicated entries.
 
        root is the number of index bits for the root table.  When len exceeds
        root, sub-tables are created pointed to by the root entry with an index
        of the low root bits of huff.  This is saved in low to check for when a
        new sub-table should be started.  drop is zero when the root table is
        being filled, and drop is root when sub-tables are being filled.
 
        When a new sub-table is needed, it is necessary to look ahead in the
        code lengths to determine what size sub-table is needed.  The length
        counts are used for this, and so count[] is decremented as codes are
        entered in the tables.
 
        used keeps track of how many table entries have been allocated from the
        provided *table space.  It is checked for build::lens and DIST tables against
        the constants kEnoughLens and kEnoughDists to guard against changes in
        the initial root table size constants.  See the comments in inftrees.hpp
        for more information.
 
        sym increments through all symbols, and the loop terminates when
        all codes of length max, i.e. all codes, have been processed.  This
        routine permits incomplete codes, so another loop after this one fills
        in the rest of the decoding tables with invalid code markers.
      */
 
     /* set up for code type */
     switch (type)
     {
     case build::codes:
         base = extra = work;    /* dummy value--not used */
         match = 20;
         break;
     case build::lens:
         base = lbase;
         extra = lext;
         match = 257;
         break;
     default:            /* build::dists */
         base = dbase;
         extra = dext;
         match = 0;
     }
 
     /* initialize state for loop */
     huff = 0;                   /* starting code */
     sym = 0;                    /* starting code symbol */
     len = min;                  /* starting code length */
     next = *table;              /* current table to fill in */
     curr = root;                /* current table index bits */
     drop = 0;                   /* current bits to drop from code for index */
     low = (unsigned)(-1);       /* trigger new sub-table when len > root */
     used = 1U << root;          /* use root table entries */
     mask = used - 1;            /* mask for comparing low */
 
     auto const not_enough = []
     {
         BOOST_THROW_EXCEPTION(std::logic_error{
             "insufficient output size when inflating tables"});
     };
 
     // check available table space
     if ((type == build::lens && used > kEnoughLens) ||
             (type == build::dists && used > kEnoughDists))
         return not_enough();
 
     /* process all codes and make table entries */
     for (;;)
     {
         /* create table entry */
         here.bits = (std::uint8_t)(len - drop);
         if (work[sym] + 1U < match)
         {
             here.op = (std::uint8_t)0;
             here.val = work[sym];
         }
         else if (work[sym] >= match)
         {
             here.op = (std::uint8_t)(extra[work[sym] - match]);
             here.val = base[work[sym] - match];
         }
         else
         {
             here.op = (std::uint8_t)(32 + 64);         /* end of block */
             here.val = 0;
         }
 
         /* replicate for those indices with low len bits equal to huff */
         incr = 1U << (len - drop);
         fill = 1U << curr;
         min = fill;                 /* save offset to next table */
         do
         {
             fill -= incr;
             next[(huff >> drop) + fill] = here;
         } while (fill != 0);
 
         /* backwards increment the len-bit code huff */
         incr = 1U << (len - 1);
         while (huff & incr)
             incr >>= 1;
         if (incr != 0)
         {
             huff &= incr - 1;
             huff += incr;
         }
         else
             huff = 0;
 
         /* go to next symbol, update count, len */
         sym++;
         if (--(count[len]) == 0)
         {
             if (len == max) break;
             len = lens[work[sym]];
         }
 
         /* create new sub-table if needed */
         if (len > root && (huff & mask) != low)
         {
             /* if first time, transition to sub-tables */
             if (drop == 0)
                 drop = root;
 
             /* increment past last table */
             next += min;            /* here min is 1 << curr */
 
             /* determine length of next table */
             curr = len - drop;
             left = (int)(1 << curr);
             while (curr + drop < max)
             {
                 left -= count[curr + drop];
                 if (left <= 0) break;
                 curr++;
                 left <<= 1;
             }
 
             /* check for enough space */
             used += 1U << curr;
             if ((type == build::lens && used > kEnoughLens) ||
                     (type == build::dists && used > kEnoughDists))
                 return not_enough();
 
             /* point entry in root table to sub-table */
             low = huff & mask;
             (*table)[low].op = (std::uint8_t)curr;
             (*table)[low].bits = (std::uint8_t)root;
             (*table)[low].val = (std::uint16_t)(next - *table);
         }
     }
 
     /* fill in remaining table entry if code is incomplete (guaranteed to have
        at most one remaining entry, since if the code is incomplete, the
        maximum code length that was allowed to get this far is one bit) */
     if (huff != 0)
     {
         here.op = 64;   // invalid code marker
         here.bits = (std::uint8_t)(len - drop);
         here.val = 0;
         next[huff] = here;
     }
 
     *table += used;
     *bits = root;
 }
 
 auto
 inflate_stream::
 get_fixed_tables() ->
     codes const&
 {
     struct fixed_codes : codes
     {
         code len_[512];
         code dist_[32];
 
         fixed_codes()
         {
             lencode = len_;
             lenbits = 9;
             distcode = dist_;
             distbits = 5;
 
             std::uint16_t lens[320];
             std::uint16_t work[288];
 
             std::fill(&lens[  0], &lens[144], std::uint16_t{8});
             std::fill(&lens[144], &lens[256], std::uint16_t{9});
             std::fill(&lens[256], &lens[280], std::uint16_t{7});
             std::fill(&lens[280], &lens[288], std::uint16_t{8});
 
             {
                 error_code ec;
                 auto next = &len_[0];
                 inflate_table(build::lens,
                     lens, 288, &next, &lenbits, work, ec);
                 if(ec)
                     BOOST_THROW_EXCEPTION(std::logic_error{ec.message()});
             }
 
             // VFALCO These fixups are from ZLib
             len_[ 99].op = 64;
             len_[227].op = 64;
             len_[355].op = 64;
             len_[483].op = 64;
 
             {
                 error_code ec;
                 auto next = &dist_[0];
                 std::fill(&lens[0], &lens[32], std::uint16_t{5});
                 inflate_table(build::dists,
                     lens, 32, &next, &distbits, work, ec);
                 if(ec)
                     BOOST_THROW_EXCEPTION(std::logic_error{ec.message()});
             }
         }
     };
 
     static fixed_codes const fc;
     return fc;
 }
 
 void
 inflate_stream::
 fixedTables()
 {
     auto const fc = get_fixed_tables();
     lencode_ = fc.lencode;
     lenbits_ = fc.lenbits;
     distcode_ = fc.distcode;
     distbits_ = fc.distbits;
 }
 
 /*
    Decode literal, length, and distance codes and write out the resulting
    literal and match bytes until either not enough input or output is
    available, an end-of-block is encountered, or a data error is encountered.
    When large enough input and output buffers are supplied to inflate(), for
    example, a 16K input buffer and a 64K output buffer, more than 95% of the
    inflate execution time is spent in this routine.
 
    Entry assumptions:
 
         state->mode_ == LEN
         zs.avail_in >= 6
         zs.avail_out >= 258
         start >= zs.avail_out
         state->bits_ < 8
 
    On return, state->mode_ is one of:
 
         LEN -- ran out of enough output space or enough available input
         TYPE -- reached end of block code, inflate() to interpret next block
         BAD -- error in block data
 
    Notes:
 
     - The maximum input bits used by a length/distance pair is 15 bits for the
       length code, 5 bits for the length extra, 15 bits for the distance code,
       and 13 bits for the distance extra.  This totals 48 bits, or six bytes.
       Therefore if zs.avail_in >= 6, then there is enough input to avoid
       checking for available input while decoding.
 
     - The maximum bytes that a single length/distance pair can output is 258
       bytes, which is the maximum length that can be coded.  inflate_fast()
       requires zs.avail_out >= 258 for each loop to avoid checking for
       output space.
 
   inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe):
    - Using bit fields for code structure
    - Different op definition to avoid & for extra bits (do & for table bits)
    - Three separate decoding do-loops for direct, window, and wnext == 0
    - Special case for distance > 1 copies to do overlapped load and store copy
    - Explicit branch predictions (based on measured branch probabilities)
    - Deferring match copy and interspersed it with decoding subsequent codes
    - Swapping literal/length else
    - Swapping window/direct else
    - Larger unrolled copy loops (three is about right)
    - Moving len -= 3 statement into middle of loop
  */
 void
 inflate_stream::
 inflate_fast(ranges& r, error_code& ec)
 {
     unsigned char const* last;  // have enough input while in < last
     unsigned char *end;         // while out < end, enough space available
     std::size_t op;             // code bits, operation, extra bits, or window position, window bytes to copy
     unsigned len;               // match length, unused bytes
     unsigned dist;              // match distance
     unsigned const lmask =
         (1U << lenbits_) - 1;   // mask for first level of length codes
     unsigned const dmask =
         (1U << distbits_) - 1;  // mask for first level of distance codes
 
     last = r.in.next + (r.in.avail() - 5);
     end = r.out.next + (r.out.avail() - 257);
 
     /* decode literals and length/distances until end-of-block or not enough
        input data or output space */
     do
     {
         if(bi_.size() < 15)
             bi_.fill_16(r.in.next);
         auto cp = &lencode_[bi_.peek_fast() & lmask];
     dolen:
         bi_.drop(cp->bits);
         op = (unsigned)(cp->op);
         if(op == 0)
         {
             // literal
             *r.out.next++ = (unsigned char)(cp->val);
         }
         else if(op & 16)
         {
             // length base
             len = (unsigned)(cp->val);
             op &= 15; // number of extra bits
             if(op)
             {
                 if(bi_.size() < op)
                     bi_.fill_8(r.in.next);
                 len += (unsigned)bi_.peek_fast() & ((1U << op) - 1);
                 bi_.drop(op);
             }
             if(bi_.size() < 15)
                 bi_.fill_16(r.in.next);
             cp = &distcode_[bi_.peek_fast() & dmask];
         dodist:
             bi_.drop(cp->bits);
             op = (unsigned)(cp->op);
             if(op & 16)
             {
                 // distance base
                 dist = (unsigned)(cp->val);
                 op &= 15; // number of extra bits
                 if(bi_.size() < op)
                 {
                     bi_.fill_8(r.in.next);
                     if(bi_.size() < op)
                         bi_.fill_8(r.in.next);
                 }
                 dist += (unsigned)bi_.peek_fast() & ((1U << op) - 1);
 #ifdef INFLATE_STRICT
                 if(dist > dmax_)
                 {
                     BOOST_BEAST_ASSIGN_EC(ec, error::invalid_distance);
                     mode_ = BAD;
                     break;
                 }
 #endif
                 bi_.drop(op);
 
                 op = r.out.used();
                 if(dist > op)
                 {
                     // copy from window
                     op = dist - op; // distance back in window
                     if(op > w_.size())
                     {
                         BOOST_BEAST_ASSIGN_EC(ec, error::invalid_distance);
                         mode_ = BAD;
                         break;
                     }
                     auto const n = clamp(len, op);
                     w_.read(r.out.next, op, n);
                     r.out.next += n;
                     len -= n;
                 }
                 if(len > 0)
                 {
                     // copy from output
                     auto in = r.out.next - dist;
                     auto n = clamp(len, r.out.avail());
                     len -= n;
                     while(n--)
                         *r.out.next++ = *in++;
                 }
             }
             else if((op & 64) == 0)
             {
                 // 2nd level distance code
                 cp = &distcode_[cp->val + (bi_.peek_fast() & ((1U << op) - 1))];
                 goto dodist;
             }
             else
             {
                 BOOST_BEAST_ASSIGN_EC(ec, error::invalid_distance_code);
                 mode_ = BAD;
                 break;
             }
         }
         else if((op & 64) == 0)
         {
             // 2nd level length code
             cp = &lencode_[cp->val + (bi_.peek_fast() & ((1U << op) - 1))];
             goto dolen;
         }
         else if(op & 32)
         {
             // end-of-block
             mode_ = TYPE;
             break;
         }
         else
         {
             BOOST_BEAST_ASSIGN_EC(ec, error::invalid_literal_length);
             mode_ = BAD;
             break;
         }
     }
     while(r.in.next < last && r.out.next < end);
 
     // return unused bytes (on entry, bits < 8, so in won't go too far back)
     bi_.rewind(r.in.next);
 }
 
 } // detail
 } // zlib
 } // beast
 } // boost
 
 #endif

This page was automatically generated by the 2.3.7 LXR engine. The LXR team