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Viewing File: /usr/share/doc/xz/examples/03_compress_custom.c
///////////////////////////////////////////////////////////////////////////////
//
/// \file 03_compress_custom.c
/// \brief Compress in multi-call mode using x86 BCJ and LZMA2
///
/// Usage: ./03_compress_custom < INFILE > OUTFILE
///
/// Example: ./03_compress_custom < foo > foo.xz
//
// Author: Lasse Collin
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <lzma.h>
static bool
init_encoder(lzma_stream *strm)
{
// Use the default preset (6) for LZMA2.
//
// The lzma_options_lzma structure and the lzma_lzma_preset() function
// are declared in lzma/lzma12.h (src/liblzma/api/lzma/lzma12.h in the
// source package or e.g. /usr/include/lzma/lzma12.h depending on
// the install prefix).
lzma_options_lzma opt_lzma2;
if (lzma_lzma_preset(&opt_lzma2, LZMA_PRESET_DEFAULT)) {
// It should never fail because the default preset
// (and presets 0-9 optionally with LZMA_PRESET_EXTREME)
// are supported by all stable liblzma versions.
//
// (The encoder initialization later in this function may
// still fail due to unsupported preset *if* the features
// required by the preset have been disabled at build time,
// but no-one does such things except on embedded systems.)
fprintf(stderr, "Unsupported preset, possibly a bug\n");
return false;
}
// Now we could customize the LZMA2 options if we wanted. For example,
// we could set the the dictionary size (opt_lzma2.dict_size) to
// something else than the default (8 MiB) of the default preset.
// See lzma/lzma12.h for details of all LZMA2 options.
//
// The x86 BCJ filter will try to modify the x86 instruction stream so
// that LZMA2 can compress it better. The x86 BCJ filter doesn't need
// any options so it will be set to NULL below.
//
// Construct the filter chain. The uncompressed data goes first to
// the first filter in the array, in this case the x86 BCJ filter.
// The array is always terminated by setting .id = LZMA_VLI_UNKNOWN.
//
// See lzma/filter.h for more information about the lzma_filter
// structure.
lzma_filter filters[] = {
{ .id = LZMA_FILTER_X86, .options = NULL },
{ .id = LZMA_FILTER_LZMA2, .options = &opt_lzma2 },
{ .id = LZMA_VLI_UNKNOWN, .options = NULL },
};
// Initialize the encoder using the custom filter chain.
lzma_ret ret = lzma_stream_encoder(strm, filters, LZMA_CHECK_CRC64);
if (ret == LZMA_OK)
return true;
const char *msg;
switch (ret) {
case LZMA_MEM_ERROR:
msg = "Memory allocation failed";
break;
case LZMA_OPTIONS_ERROR:
// We are no longer using a plain preset so this error
// message has been edited accordingly compared to
// 01_compress_easy.c.
msg = "Specified filter chain is not supported";
break;
case LZMA_UNSUPPORTED_CHECK:
msg = "Specified integrity check is not supported";
break;
default:
msg = "Unknown error, possibly a bug";
break;
}
fprintf(stderr, "Error initializing the encoder: %s (error code %u)\n",
msg, ret);
return false;
}
// This function is identical to the one in 01_compress_easy.c.
static bool
compress(lzma_stream *strm, FILE *infile, FILE *outfile)
{
lzma_action action = LZMA_RUN;
uint8_t inbuf[BUFSIZ];
uint8_t outbuf[BUFSIZ];
strm->next_in = NULL;
strm->avail_in = 0;
strm->next_out = outbuf;
strm->avail_out = sizeof(outbuf);
while (true) {
if (strm->avail_in == 0 && !feof(infile)) {
strm->next_in = inbuf;
strm->avail_in = fread(inbuf, 1, sizeof(inbuf),
infile);
if (ferror(infile)) {
fprintf(stderr, "Read error: %s\n",
strerror(errno));
return false;
}
if (feof(infile))
action = LZMA_FINISH;
}
lzma_ret ret = lzma_code(strm, action);
if (strm->avail_out == 0 || ret == LZMA_STREAM_END) {
size_t write_size = sizeof(outbuf) - strm->avail_out;
if (fwrite(outbuf, 1, write_size, outfile)
!= write_size) {
fprintf(stderr, "Write error: %s\n",
strerror(errno));
return false;
}
strm->next_out = outbuf;
strm->avail_out = sizeof(outbuf);
}
if (ret != LZMA_OK) {
if (ret == LZMA_STREAM_END)
return true;
const char *msg;
switch (ret) {
case LZMA_MEM_ERROR:
msg = "Memory allocation failed";
break;
case LZMA_DATA_ERROR:
msg = "File size limits exceeded";
break;
default:
msg = "Unknown error, possibly a bug";
break;
}
fprintf(stderr, "Encoder error: %s (error code %u)\n",
msg, ret);
return false;
}
}
}
extern int
main(void)
{
lzma_stream strm = LZMA_STREAM_INIT;
bool success = init_encoder(&strm);
if (success)
success = compress(&strm, stdin, stdout);
lzma_end(&strm);
if (fclose(stdout)) {
fprintf(stderr, "Write error: %s\n", strerror(errno));
success = false;
}
return success ? EXIT_SUCCESS : EXIT_FAILURE;
}
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