src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013 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 static Lisp_Object Qzlib_dll;
  30
  31 #ifdef WINDOWSNT
  32 #include <windows.h>
  33 #include "w32.h"
  34
  35 /* Macro for defining functions that will be loaded from the zlib DLL.  */
  36 #define DEF_ZLIB_FN(rettype,func,args) static rettype (FAR CDECL *fn_##func)args
  37
  38 /* Macro for loading zlib functions from the library.  */
  39 #define LOAD_ZLIB_FN(lib,func) {                                        \
  40     fn_##func = (void *) GetProcAddress (lib, #func);                   \
  41     if (!fn_##func) return 0;                                           \
  42   }
  43
  44 DEF_ZLIB_FN (int, inflateInit2_,
  45              (z_streamp strm, int  windowBits, const char *version, int stream_size));
  46
  47 DEF_ZLIB_FN (int, inflate,
  48              (z_streamp strm, int flush));
  49
  50 DEF_ZLIB_FN (int, inflateEnd,
  51              (z_streamp strm));
  52
  53 static bool
  54 init_zlib_functions (void)
  55 {
  56   HMODULE library = w32_delayed_load (Qzlib_dll);
  57
  58   if (!library)
  59     {
  60       message1 ("zlib library not found");
  61       return 0;
  62     }
  63
  64   LOAD_ZLIB_FN (library, inflateInit2_);
  65   LOAD_ZLIB_FN (library, inflate);
  66   LOAD_ZLIB_FN (library, inflateEnd);
  67   return 1;
  68 }
  69
  70 #define fn_inflateInit2(strm, windowBits) \
  71         fn_inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
  72
  73 #else /* !WINDOWSNT */
  74
  75 #define fn_inflateInit2         inflateInit2
  76 #define fn_inflate              inflate
  77 #define fn_inflateEnd           inflateEnd
  78
  79 #endif  /* WINDOWSNT */
  80
  81 \f
  82 struct decompress_unwind_data
  83 {
  84   ptrdiff_t old_point, start;
  85   z_stream *stream;
  86 };
  87
  88 static void
  89 unwind_decompress (void *ddata)
  90 {
  91   struct decompress_unwind_data *data = ddata;
  92   fn_inflateEnd (data->stream);
  93
  94   /* Delete any uncompressed data already inserted and restore point.  */
  95   if (data->start)
  96     {
  97       del_range (data->start, PT);
  98       SET_PT (data->old_point);
  99     }
 100 }
 101
 102 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
 103        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
 104      (void)
 105 {
 106 #ifdef WINDOWSNT
 107   Lisp_Object found = Fassq (Qzlib_dll, Vlibrary_cache);
 108   if (CONSP (found))
 109     return XCDR (found);
 110   else
 111     {
 112       Lisp_Object status;
 113       status = init_zlib_functions () ? Qt : Qnil;
 114       Vlibrary_cache = Fcons (Fcons (Qzlib_dll, status), Vlibrary_cache);
 115       return status;
 116     }
 117 #else
 118   return Qt;
 119 #endif
 120 }
 121
 122 DEFUN ("zlib-decompress-gzipped-region", Fzlib_decompress_gzipped_region,
 123        Szlib_decompress_gzipped_region,
 124        2, 2, 0,
 125        doc: /* Decompress a gzip-compressed region.
 126 Replace the text in the region by the decompressed data.
 127 On failure, return nil and leave the data in place.
 128 This function can be called only in unibyte buffers.  */)
 129   (Lisp_Object start, Lisp_Object end)
 130 {
 131   ptrdiff_t istart, iend, pos_byte;
 132   z_stream stream;
 133   int inflate_status;
 134   struct decompress_unwind_data unwind_data;
 135   ptrdiff_t count = SPECPDL_INDEX ();
 136
 137   validate_region (&start, &end);
 138
 139   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 140     error ("This function can be called only in unibyte buffers");
 141
 142   /* This is a unibyte buffer, so character positions and bytes are
 143      the same.  */
 144   istart = XINT (start);
 145   iend = XINT (end);
 146   move_gap_both (iend, iend);
 147
 148   stream.zalloc = Z_NULL;
 149   stream.zfree = Z_NULL;
 150   stream.opaque = Z_NULL;
 151   stream.avail_in = 0;
 152   stream.next_in = Z_NULL;
 153
 154   /* This magic number apparently means "this is gzip".  */
 155   if (fn_inflateInit2 (&stream, 16 + MAX_WBITS) != Z_OK)
 156     return Qnil;
 157
 158   unwind_data.start = iend;
 159   unwind_data.stream = &stream;
 160   unwind_data.old_point = PT;
 161
 162   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 163
 164   /* Insert the decompressed data at the end of the compressed data.  */
 165   SET_PT (iend);
 166
 167   pos_byte = istart;
 168
 169   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 170   do
 171     {
 172       /* Maximum number of bytes that one 'inflate' call should read and write.
 173          zlib requires that these values not exceed UINT_MAX.
 174          Do not make avail_out too large, as that might unduly delay C-g.  */
 175       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 176       ptrdiff_t avail_out = min (1 << 14, UINT_MAX);
 177
 178       ptrdiff_t decompressed;
 179
 180       if (GAP_SIZE < avail_out)
 181         make_gap (avail_out - GAP_SIZE);
 182       stream.next_in = BYTE_POS_ADDR (pos_byte);
 183       stream.avail_in = avail_in;
 184       stream.next_out = GPT_ADDR;
 185       stream.avail_out = avail_out;
 186       inflate_status = fn_inflate (&stream, Z_NO_FLUSH);
 187       pos_byte += avail_in - stream.avail_in;
 188       decompressed = avail_out - stream.avail_out;
 189       insert_from_gap (decompressed, decompressed, 0);
 190       QUIT;
 191     }
 192   while (inflate_status == Z_OK);
 193
 194   if (inflate_status != Z_STREAM_END)
 195     return unbind_to (count, Qnil);
 196
 197   unwind_data.start = 0;
 198
 199   /* Delete the compressed data.  */
 200   del_range (istart, iend);
 201
 202   return unbind_to (count, Qt);
 203 }
 204
 205 \f
 206 /***********************************************************************
 207                             Initialization
 208  ***********************************************************************/
 209 void
 210 syms_of_decompress (void)
 211 {
 212   DEFSYM (Qzlib_dll, "zlib");
 213   defsubr (&Szlib_decompress_gzipped_region);
 214   defsubr (&Szlib_available_p);
 215 }
 216
 217 #endif /* HAVE_ZLIB */