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authorLasse Collin <lasse.collin@tukaani.org>2012-06-14 10:52:33 +0300
committerLasse Collin <lasse.collin@tukaani.org>2012-06-14 10:52:33 +0300
commit3a0c5378abefaf86aa39a62a7c9682bdb21568a1 (patch)
tree2ce6cc67b02009b36955b7d6e9b134ae1ce40821 /doc/examples/03_compress_custom.c
parentDocs: Move xz_pipe_comp.c and xz_pipe_decomp.c to doc/examples_old. (diff)
downloadxz-3a0c5378abefaf86aa39a62a7c9682bdb21568a1.tar.xz
Docs: Add new example programs.
These have more comments than the old examples and human-readable error messages. More tutorial-like examples are needed but these are a start.
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+///////////////////////////////////////////////////////////////////////////////
+//
+/// \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/lzma.h (src/liblzma/api/lzma/lzma.h in the
+ // source package or e.g. /usr/include/lzma/lzma.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/lzma.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;
+}