code.delx.au - gnu-emacs/blob - 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 \f
  30 struct decompress_unwind_data
  31 {
  32   ptrdiff_t old_point, start;
  33   z_stream *stream;
  34 };
  35
  36 static void
  37 unwind_decompress (void *ddata)
  38 {
  39   struct decompress_unwind_data *data = ddata;
  40   inflateEnd (data->stream);
  41
  42   /* Delete any uncompressed data already inserted and restore point.  */
  43   if (data->start)
  44     {
  45       del_range (data->start, PT);
  46       SET_PT (data->old_point);
  47     }
  48 }
  49
  50 DEFUN ("decompress-gzipped-region", Fdecompress_gzipped_region,
  51        Sdecompress_gzipped_region,
  52        2, 2, 0,
  53        doc: /* Decompress a gzip-compressed region.
  54 Replace the text in the region by the decompressed data.
  55 On failure, return nil and leave the data in place.
  56 This function can be called only in unibyte buffers.  */)
  57   (Lisp_Object start, Lisp_Object end)
  58 {
  59   ptrdiff_t istart, iend, pos_byte;
  60   z_stream stream;
  61   int inflate_status;
  62   struct decompress_unwind_data unwind_data;
  63   ptrdiff_t count = SPECPDL_INDEX ();
  64
  65   validate_region (&start, &end);
  66
  67   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
  68     error ("This function can be called only in unibyte buffers");
  69
  70   /* This is a unibyte buffer, so character positions and bytes are
  71      the same.  */
  72   istart = XINT (start);
  73   iend = XINT (end);
  74   move_gap_both (iend, iend);
  75
  76   stream.zalloc = Z_NULL;
  77   stream.zfree = Z_NULL;
  78   stream.opaque = Z_NULL;
  79   stream.avail_in = 0;
  80   stream.next_in = Z_NULL;
  81
  82   /* This magic number apparently means "this is gzip".  */
  83   if (inflateInit2 (&stream, 16 + MAX_WBITS) != Z_OK)
  84     return Qnil;
  85
  86   unwind_data.start = iend;
  87   unwind_data.stream = &stream;
  88   unwind_data.old_point = PT;
  89
  90   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
  91
  92   /* Insert the decompressed data at the end of the compressed data.  */
  93   SET_PT (iend);
  94
  95   pos_byte = istart;
  96
  97   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
  98   do
  99     {
 100       /* Maximum number of bytes that one 'inflate' call should read and write.
 101          zlib requires that these values not exceed UINT_MAX.
 102          Do not make avail_out too large, as that might unduly delay C-g.  */
 103       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 104       ptrdiff_t avail_out = min (1 << 14, UINT_MAX);
 105
 106       ptrdiff_t decompressed;
 107
 108       if (GAP_SIZE < avail_out)
 109         make_gap (avail_out - GAP_SIZE);
 110       stream.next_in = BYTE_POS_ADDR (pos_byte);
 111       stream.avail_in = avail_in;
 112       stream.next_out = GPT_ADDR;
 113       stream.avail_out = avail_out;
 114       inflate_status = inflate (&stream, Z_NO_FLUSH);
 115       pos_byte += avail_in - stream.avail_in;
 116       decompressed = avail_out - stream.avail_out;
 117       insert_from_gap (decompressed, decompressed, 0);
 118       QUIT;
 119     }
 120   while (inflate_status == Z_OK);
 121
 122   if (inflate_status != Z_STREAM_END)
 123     return unbind_to (count, Qnil);
 124
 125   unwind_data.start = 0;
 126
 127   /* Delete the compressed data.  */
 128   del_range (istart, iend);
 129
 130   return unbind_to (count, Qt);
 131 }
 132
 133 \f
 134 /***********************************************************************
 135                             Initialization
 136  ***********************************************************************/
 137 void
 138 syms_of_decompress (void)
 139 {
 140   defsubr (&Sdecompress_gzipped_region);
 141 }
 142
 143 #endif /* HAVE_ZLIB */