src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013-2018 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software: you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation, either version 3 of the License, or (at
   9 your option) any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20
  21 #ifdef HAVE_ZLIB
  22
  23 #include <zlib.h>
  24
  25 #include "lisp.h"
  26 #include "buffer.h"
  27
  28 #include <verify.h>
  29
  30 #ifdef WINDOWSNT
  31 # include <windows.h>
  32 # include "w32.h"
  33
  34 DEF_DLL_FN (int, inflateInit2_,
  35             (z_streamp strm, int windowBits, const char *version,
  36              int stream_size));
  37 DEF_DLL_FN (int, inflate, (z_streamp strm, int flush));
  38 DEF_DLL_FN (int, inflateEnd, (z_streamp strm));
  39
  40 static bool zlib_initialized;
  41
  42 static bool
  43 init_zlib_functions (void)
  44 {
  45   HMODULE library = w32_delayed_load (Qzlib);
  46
  47   if (!library)
  48     return false;
  49
  50   LOAD_DLL_FN (library, inflateInit2_);
  51   LOAD_DLL_FN (library, inflate);
  52   LOAD_DLL_FN (library, inflateEnd);
  53   return true;
  54 }
  55
  56 # undef inflate
  57 # undef inflateEnd
  58 # undef inflateInit2_
  59
  60 # define inflate fn_inflate
  61 # define inflateEnd fn_inflateEnd
  62 # define inflateInit2_ fn_inflateInit2_
  63
  64 #endif  /* WINDOWSNT */
  65
  66 \f
  67 struct decompress_unwind_data
  68 {
  69   ptrdiff_t old_point, start, nbytes;
  70   z_stream *stream;
  71 };
  72
  73 static void
  74 unwind_decompress (void *ddata)
  75 {
  76   struct decompress_unwind_data *data = ddata;
  77   inflateEnd (data->stream);
  78
  79   /* Delete any uncompressed data already inserted on error.  */
  80   if (data->start)
  81     del_range (data->start, data->start + data->nbytes);
  82
  83   /* Put point where it was, or if the buffer has shrunk because the
  84      compressed data is bigger than the uncompressed, at
  85      point-max.  */
  86   SET_PT (min (data->old_point, ZV));
  87 }
  88
  89 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
  90        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
  91      (void)
  92 {
  93 #ifdef WINDOWSNT
  94   Lisp_Object found = Fassq (Qzlib, Vlibrary_cache);
  95   if (CONSP (found))
  96     return XCDR (found);
  97   else
  98     {
  99       Lisp_Object status;
 100       zlib_initialized = init_zlib_functions ();
 101       status = zlib_initialized ? Qt : Qnil;
 102       Vlibrary_cache = Fcons (Fcons (Qzlib, status), Vlibrary_cache);
 103       return status;
 104     }
 105 #else
 106   return Qt;
 107 #endif
 108 }
 109
 110 DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
 111        Szlib_decompress_region,
 112        2, 2, 0,
 113        doc: /* Decompress a gzip- or zlib-compressed region.
 114 Replace the text in the region by the decompressed data.
 115 On failure, return nil and leave the data in place.
 116 This function can be called only in unibyte buffers.  */)
 117   (Lisp_Object start, Lisp_Object end)
 118 {
 119   ptrdiff_t istart, iend, pos_byte;
 120   z_stream stream;
 121   int inflate_status;
 122   struct decompress_unwind_data unwind_data;
 123   ptrdiff_t count = SPECPDL_INDEX ();
 124
 125   validate_region (&start, &end);
 126
 127   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 128     error ("This function can be called only in unibyte buffers");
 129
 130 #ifdef WINDOWSNT
 131   if (!zlib_initialized)
 132     zlib_initialized = init_zlib_functions ();
 133   if (!zlib_initialized)
 134     {
 135       message1 ("zlib library not found");
 136       return Qnil;
 137     }
 138 #endif
 139
 140   /* This is a unibyte buffer, so character positions and bytes are
 141      the same.  */
 142   istart = XINT (start);
 143   iend = XINT (end);
 144   move_gap_both (iend, iend);
 145
 146   stream.zalloc = Z_NULL;
 147   stream.zfree = Z_NULL;
 148   stream.opaque = Z_NULL;
 149   stream.avail_in = 0;
 150   stream.next_in = Z_NULL;
 151
 152   /* The magic number 32 apparently means "autodetect both the gzip and
 153      zlib formats" according to zlib.h.  */
 154   if (inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
 155     return Qnil;
 156
 157   unwind_data.start = iend;
 158   unwind_data.stream = &stream;
 159   unwind_data.old_point = PT;
 160   unwind_data.nbytes = 0;
 161   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 162
 163   /* Insert the decompressed data at the end of the compressed data.  */
 164   SET_PT (iend);
 165
 166   pos_byte = istart;
 167
 168   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 169   do
 170     {
 171       /* Maximum number of bytes that one 'inflate' call should read and write.
 172          Do not make avail_out too large, as that might unduly delay C-g.
 173          zlib requires that avail_in and avail_out not exceed UINT_MAX.  */
 174       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 175       int avail_out = 16 * 1024;
 176       int decompressed;
 177
 178       if (GAP_SIZE < avail_out)
 179         make_gap (avail_out - GAP_SIZE);
 180       stream.next_in = BYTE_POS_ADDR (pos_byte);
 181       stream.avail_in = avail_in;
 182       stream.next_out = GPT_ADDR;
 183       stream.avail_out = avail_out;
 184       inflate_status = inflate (&stream, Z_NO_FLUSH);
 185       pos_byte += avail_in - stream.avail_in;
 186       decompressed = avail_out - stream.avail_out;
 187       insert_from_gap (decompressed, decompressed, 0);
 188       unwind_data.nbytes += decompressed;
 189       maybe_quit ();
 190     }
 191   while (inflate_status == Z_OK);
 192
 193   if (inflate_status != Z_STREAM_END)
 194     return unbind_to (count, Qnil);
 195
 196   unwind_data.start = 0;
 197
 198   /* Delete the compressed data.  */
 199   del_range (istart, iend);
 200
 201   return unbind_to (count, Qt);
 202 }
 203
 204 \f
 205 /***********************************************************************
 206                             Initialization
 207  ***********************************************************************/
 208 void
 209 syms_of_decompress (void)
 210 {
 211   defsubr (&Szlib_decompress_region);
 212   defsubr (&Szlib_available_p);
 213 }
 214
 215 #endif /* HAVE_ZLIB */