src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013-2015 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
   9 (at 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 <http://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 "character.h"
  27 #include "buffer.h"
  28
  29 #include <verify.h>
  30
  31 static Lisp_Object Qzlib_dll;
  32
  33 #ifdef WINDOWSNT
  34 # include <windows.h>
  35 # include "w32.h"
  36
  37 DEF_DLL_FN (int, inflateInit2_,
  38             (z_streamp strm, int windowBits, const char *version,
  39              int stream_size));
  40 DEF_DLL_FN (int, inflate, (z_streamp strm, int flush));
  41 DEF_DLL_FN (int, inflateEnd, (z_streamp strm));
  42
  43 static bool zlib_initialized;
  44
  45 static bool
  46 init_zlib_functions (void)
  47 {
  48   HMODULE library = w32_delayed_load (Qzlib_dll);
  49
  50   if (!library)
  51     return false;
  52
  53   LOAD_DLL_FN (library, inflateInit2_);
  54   LOAD_DLL_FN (library, inflate);
  55   LOAD_DLL_FN (library, inflateEnd);
  56   return true;
  57 }
  58
  59 # undef inflate
  60 # undef inflateEnd
  61 # undef inflateInit2_
  62
  63 # define inflate fn_inflate
  64 # define inflateEnd fn_inflateEnd
  65 # define inflateInit2_ fn_inflateInit2_
  66
  67 #endif  /* WINDOWSNT */
  68
  69 \f
  70 struct decompress_unwind_data
  71 {
  72   ptrdiff_t old_point, start, nbytes;
  73   z_stream *stream;
  74 };
  75
  76 static void
  77 unwind_decompress (void *ddata)
  78 {
  79   struct decompress_unwind_data *data = ddata;
  80   inflateEnd (data->stream);
  81
  82   /* Delete any uncompressed data already inserted on error.  */
  83   if (data->start)
  84     del_range (data->start, data->start + data->nbytes);
  85
  86   /* Put point where it was, or if the buffer has shrunk because the
  87      compressed data is bigger than the uncompressed, at
  88      point-max.  */
  89   SET_PT (min (data->old_point, ZV));
  90 }
  91
  92 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
  93        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
  94      (void)
  95 {
  96 #ifdef WINDOWSNT
  97   Lisp_Object found = Fassq (Qzlib_dll, Vlibrary_cache);
  98   if (CONSP (found))
  99     return XCDR (found);
 100   else
 101     {
 102       Lisp_Object status;
 103       zlib_initialized = init_zlib_functions ();
 104       status = zlib_initialized ? Qt : Qnil;
 105       Vlibrary_cache = Fcons (Fcons (Qzlib_dll, status), Vlibrary_cache);
 106       return status;
 107     }
 108 #else
 109   return Qt;
 110 #endif
 111 }
 112
 113 DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
 114        Szlib_decompress_region,
 115        2, 2, 0,
 116        doc: /* Decompress a gzip- or zlib-compressed region.
 117 Replace the text in the region by the decompressed data.
 118 On failure, return nil and leave the data in place.
 119 This function can be called only in unibyte buffers.  */)
 120   (Lisp_Object start, Lisp_Object end)
 121 {
 122   ptrdiff_t istart, iend, pos_byte;
 123   z_stream stream;
 124   int inflate_status;
 125   struct decompress_unwind_data unwind_data;
 126   ptrdiff_t count = SPECPDL_INDEX ();
 127
 128   validate_region (&start, &end);
 129
 130   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 131     error ("This function can be called only in unibyte buffers");
 132
 133 #ifdef WINDOWSNT
 134   if (!zlib_initialized)
 135     zlib_initialized = init_zlib_functions ();
 136   if (!zlib_initialized)
 137     {
 138       message1 ("zlib library not found");
 139       return Qnil;
 140     }
 141 #endif
 142
 143   /* This is a unibyte buffer, so character positions and bytes are
 144      the same.  */
 145   istart = XINT (start);
 146   iend = XINT (end);
 147   move_gap_both (iend, iend);
 148
 149   stream.zalloc = Z_NULL;
 150   stream.zfree = Z_NULL;
 151   stream.opaque = Z_NULL;
 152   stream.avail_in = 0;
 153   stream.next_in = Z_NULL;
 154
 155   /* The magic number 32 apparently means "autodetect both the gzip and
 156      zlib formats" according to zlib.h.  */
 157   if (inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
 158     return Qnil;
 159
 160   unwind_data.start = iend;
 161   unwind_data.stream = &stream;
 162   unwind_data.old_point = PT;
 163   unwind_data.nbytes = 0;
 164   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 165
 166   /* Insert the decompressed data at the end of the compressed data.  */
 167   SET_PT (iend);
 168
 169   pos_byte = istart;
 170
 171   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 172   do
 173     {
 174       /* Maximum number of bytes that one 'inflate' call should read and write.
 175          Do not make avail_out too large, as that might unduly delay C-g.
 176          zlib requires that avail_in and avail_out not exceed UINT_MAX.  */
 177       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 178       int avail_out = 16 * 1024;
 179       int decompressed;
 180
 181       if (GAP_SIZE < avail_out)
 182         make_gap (avail_out - GAP_SIZE);
 183       stream.next_in = BYTE_POS_ADDR (pos_byte);
 184       stream.avail_in = avail_in;
 185       stream.next_out = GPT_ADDR;
 186       stream.avail_out = avail_out;
 187       inflate_status = inflate (&stream, Z_NO_FLUSH);
 188       pos_byte += avail_in - stream.avail_in;
 189       decompressed = avail_out - stream.avail_out;
 190       insert_from_gap (decompressed, decompressed, 0);
 191       unwind_data.nbytes += decompressed;
 192       QUIT;
 193     }
 194   while (inflate_status == Z_OK);
 195
 196   if (inflate_status != Z_STREAM_END)
 197     return unbind_to (count, Qnil);
 198
 199   unwind_data.start = 0;
 200
 201   /* Delete the compressed data.  */
 202   del_range (istart, iend);
 203
 204   return unbind_to (count, Qt);
 205 }
 206
 207 \f
 208 /***********************************************************************
 209                             Initialization
 210  ***********************************************************************/
 211 void
 212 syms_of_decompress (void)
 213 {
 214   DEFSYM (Qzlib_dll, "zlib");
 215   defsubr (&Szlib_decompress_region);
 216   defsubr (&Szlib_available_p);
 217 }
 218
 219 #endif /* HAVE_ZLIB */