doc/examples/03_compress_custom.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       03_compress_custom.c
   4 /// \brief      Compress in multi-call mode using x86 BCJ and LZMA2
   5 ///
   6 /// Usage:      ./03_compress_custom < INFILE > OUTFILE
   7 ///
   8 /// Example:    ./03_compress_custom < foo > foo.xz
   9 //
  10 //  Author:     Lasse Collin
  11 //
  12 //  This file has been put into the public domain.
  13 //  You can do whatever you want with this file.
  14 //
  15 ///////////////////////////////////////////////////////////////////////////////
  16
  17 #include <stdbool.h>
  18 #include <stdlib.h>
  19 #include <stdio.h>
  20 #include <string.h>
  21 #include <errno.h>
  22 #include <lzma.h>
  23
  24
  25 static bool
  26 init_encoder(lzma_stream *strm)
  27 {
  28         // Use the default preset (6) for LZMA2.
  29         //
  30         // The lzma_options_lzma structure and the lzma_lzma_preset() function
  31         // are declared in lzma/lzma12.h (src/liblzma/api/lzma/lzma12.h in the
  32         // source package or e.g. /usr/include/lzma/lzma12.h depending on
  33         // the install prefix).
  34         lzma_options_lzma opt_lzma2;
  35         if (lzma_lzma_preset(&opt_lzma2, LZMA_PRESET_DEFAULT)) {
  36                 // It should never fail because the default preset
  37                 // (and presets 0-9 optionally with LZMA_PRESET_EXTREME)
  38                 // are supported by all stable liblzma versions.
  39                 //
  40                 // (The encoder initialization later in this function may
  41                 // still fail due to unsupported preset *if* the features
  42                 // required by the preset have been disabled at build time,
  43                 // but no-one does such things except on embedded systems.)
  44                 fprintf(stderr, "Unsupported preset, possibly a bug\n");
  45                 return false;
  46         }
  47
  48         // Now we could customize the LZMA2 options if we wanted. For example,
  49         // we could set the the dictionary size (opt_lzma2.dict_size) to
  50         // something else than the default (8 MiB) of the default preset.
  51         // See lzma/lzma12.h for details of all LZMA2 options.
  52         //
  53         // The x86 BCJ filter will try to modify the x86 instruction stream so
  54         // that LZMA2 can compress it better. The x86 BCJ filter doesn't need
  55         // any options so it will be set to NULL below.
  56         //
  57         // Construct the filter chain. The uncompressed data goes first to
  58         // the first filter in the array, in this case the x86 BCJ filter.
  59         // The array is always terminated by setting .id = LZMA_VLI_UNKNOWN.
  60         //
  61         // See lzma/filter.h for more information about the lzma_filter
  62         // structure.
  63         lzma_filter filters[] = {
  64                 { .id = LZMA_FILTER_X86, .options = NULL },
  65                 { .id = LZMA_FILTER_LZMA2, .options = &opt_lzma2 },
  66                 { .id = LZMA_VLI_UNKNOWN, .options = NULL },
  67         };
  68
  69         // Initialize the encoder using the custom filter chain.
  70         lzma_ret ret = lzma_stream_encoder(strm, filters, LZMA_CHECK_CRC64);
  71
  72         if (ret == LZMA_OK)
  73                 return true;
  74
  75         const char *msg;
  76         switch (ret) {
  77         case LZMA_MEM_ERROR:
  78                 msg = "Memory allocation failed";
  79                 break;
  80
  81         case LZMA_OPTIONS_ERROR:
  82                 // We are no longer using a plain preset so this error
  83                 // message has been edited accordingly compared to
  84                 // 01_compress_easy.c.
  85                 msg = "Specified filter chain is not supported";
  86                 break;
  87
  88         case LZMA_UNSUPPORTED_CHECK:
  89                 msg = "Specified integrity check is not supported";
  90                 break;
  91
  92         default:
  93                 msg = "Unknown error, possibly a bug";
  94                 break;
  95         }
  96
  97         fprintf(stderr, "Error initializing the encoder: %s (error code %u)\n",
  98                         msg, ret);
  99         return false;
 100 }
 101
 102
 103 // This function is identical to the one in 01_compress_easy.c.
 104 static bool
 105 compress(lzma_stream *strm, FILE *infile, FILE *outfile)
 106 {
 107         lzma_action action = LZMA_RUN;
 108
 109         uint8_t inbuf[BUFSIZ];
 110         uint8_t outbuf[BUFSIZ];
 111
 112         strm->next_in = NULL;
 113         strm->avail_in = 0;
 114         strm->next_out = outbuf;
 115         strm->avail_out = sizeof(outbuf);
 116
 117         while (true) {
 118                 if (strm->avail_in == 0 && !feof(infile)) {
 119                         strm->next_in = inbuf;
 120                         strm->avail_in = fread(inbuf, 1, sizeof(inbuf),
 121                                         infile);
 122
 123                         if (ferror(infile)) {
 124                                 fprintf(stderr, "Read error: %s\n",
 125                                                 strerror(errno));
 126                                 return false;
 127                         }
 128
 129                         if (feof(infile))
 130                                 action = LZMA_FINISH;
 131                 }
 132
 133                 lzma_ret ret = lzma_code(strm, action);
 134
 135                 if (strm->avail_out == 0 || ret == LZMA_STREAM_END) {
 136                         size_t write_size = sizeof(outbuf) - strm->avail_out;
 137
 138                         if (fwrite(outbuf, 1, write_size, outfile)
 139                                         != write_size) {
 140                                 fprintf(stderr, "Write error: %s\n",
 141                                                 strerror(errno));
 142                                 return false;
 143                         }
 144
 145                         strm->next_out = outbuf;
 146                         strm->avail_out = sizeof(outbuf);
 147                 }
 148
 149                 if (ret != LZMA_OK) {
 150                         if (ret == LZMA_STREAM_END)
 151                                 return true;
 152
 153                         const char *msg;
 154                         switch (ret) {
 155                         case LZMA_MEM_ERROR:
 156                                 msg = "Memory allocation failed";
 157                                 break;
 158
 159                         case LZMA_DATA_ERROR:
 160                                 msg = "File size limits exceeded";
 161                                 break;
 162
 163                         default:
 164                                 msg = "Unknown error, possibly a bug";
 165                                 break;
 166                         }
 167
 168                         fprintf(stderr, "Encoder error: %s (error code %u)\n",
 169                                         msg, ret);
 170                         return false;
 171                 }
 172         }
 173 }
 174
 175
 176 extern int
 177 main(void)
 178 {
 179         lzma_stream strm = LZMA_STREAM_INIT;
 180
 181         bool success = init_encoder(&strm);
 182         if (success)
 183                 success = compress(&strm, stdin, stdout);
 184
 185         lzma_end(&strm);
 186
 187         if (fclose(stdout)) {
 188                 fprintf(stderr, "Write error: %s\n", strerror(errno));
 189                 success = false;
 190         }
 191
 192         return success ? EXIT_SUCCESS : EXIT_FAILURE;
 193 }