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 #define BUFFER_SIZE 16384
  31
  32 struct decompress_unwind_data {
  33   ptrdiff_t old_point, start;
  34   z_stream *stream;
  35 };
  36
  37 static void
  38 unwind_decompress (void *ddata) {
  39   struct decompress_unwind_data *data = ddata;
  40   inflateEnd (data->stream);
  41   /* Delete any uncompressed data already inserted and restore
  42      point. */
  43   if (data->start) {
  44     del_range (data->start, PT);
  45     SET_PT (data->old_point);
  46   }
  47 }
  48
  49 DEFUN ("decompress-gzipped-region", Fdecompress_gzipped_region,
  50        Sdecompress_gzipped_region,
  51        2, 2, 0,
  52        doc: /* Decompress a gzip-compressed region.
  53 The text in the region will be replaced by the decompressed data.
  54 On failure, nil is returned and the data is left in place.
  55 This function can only be called in unibyte buffers.*/)
  56   (Lisp_Object start, Lisp_Object end)
  57 {
  58   ptrdiff_t istart, iend, point = PT;
  59   z_stream stream;
  60   int decompressed;
  61   char out[16384];
  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 only be called 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   /* We're inserting the decompressed data at the end of the
  87      compressed data. */
  88   SET_PT (iend);
  89
  90   stream.avail_in = iend - istart;
  91   stream.next_in = (char *) BYTE_POS_ADDR (istart);
  92
  93   unwind_data.start = iend;
  94   unwind_data.stream = &stream;
  95   unwind_data.old_point = point;
  96   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
  97
  98   immediate_quit = 1;
  99
 100   /* Run inflate() on input until the output buffer isn't full. */
 101   do {
 102     int result;
 103     stream.avail_out = BUFFER_SIZE;
 104     stream.next_out = out;
 105     result = inflate (&stream, Z_NO_FLUSH);
 106     if (result < 0) {
 107       unbind_to (count, Qnil);
 108       return Qnil;
 109     }
 110
 111     decompressed = BUFFER_SIZE - stream.avail_out;
 112     insert_1_both (out, decompressed, decompressed, 0, 0, 0);
 113     QUIT;
 114   } while (stream.avail_out == 0);
 115
 116   immediate_quit = 0;
 117
 118   unwind_data.start = 0;
 119   unbind_to (count, Qnil);
 120
 121   /* Delete the compressed data. */
 122   del_range (istart, iend);
 123
 124   return Qt;
 125 }
 126
 127 \f
 128 /***********************************************************************
 129                             Initialization
 130  ***********************************************************************/
 131 void
 132 syms_of_decompress (void)
 133 {
 134   defsubr (&Sdecompress_gzipped_region);
 135 }
 136
 137 #endif /* HAVE_ZLIB */