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Diffstat (limited to 'doc/examples/03_compress_custom.c')
| -rw-r--r-- | doc/examples/03_compress_custom.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/doc/examples/03_compress_custom.c b/doc/examples/03_compress_custom.c new file mode 100644 index 0000000..40c85e3 --- /dev/null +++ b/doc/examples/03_compress_custom.c @@ -0,0 +1,193 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \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; +} |