name : 01_compress_easy.c /////////////////////////////////////////////////////////////////////////////// // /// \file 01_compress_easy.c /// \brief Compress from stdin to stdout in multi-call mode /// /// Usage: ./01_compress_easy PRESET < INFILE > OUTFILE /// /// Example: ./01_compress_easy 6 < 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 void show_usage_and_exit(const char *argv0) { fprintf(stderr, "Usage: %s PRESET < INFILE > OUTFILE\n" "PRESET is a number 0-9 and can optionally be " "followed by `e' to indicate extreme preset\n", argv0); exit(EXIT_FAILURE); } static uint32_t get_preset(int argc, char **argv) { // One argument whose first char must be 0-9. if (argc != 2 || argv[1][0] < '0' || argv[1][0] > '9') show_usage_and_exit(argv[0]); // Calculate the preste level 0-9. uint32_t preset = argv[1][0] - '0'; // If there is a second char, it must be 'e'. It will set // the LZMA_PRESET_EXTREME flag. if (argv[1][1] != '\0') { if (argv[1][1] != 'e' || argv[1][2] != '\0') show_usage_and_exit(argv[0]); preset |= LZMA_PRESET_EXTREME; } return preset; } static bool init_encoder(lzma_stream *strm, uint32_t preset) { // Initialize the encoder using a preset. Set the integrity to check // to CRC64, which is the default in the xz command line tool. If // the .xz file needs to be decompressed with XZ Embedded, use // LZMA_CHECK_CRC32 instead. lzma_ret ret = lzma_easy_encoder(strm, preset, LZMA_CHECK_CRC64); // Return successfully if the initialization went fine. if (ret == LZMA_OK) return true; // Something went wrong. The possible errors are documented in // lzma/container.h (src/liblzma/api/lzma/container.h in the source // package or e.g. /usr/include/lzma/container.h depending on the // install prefix). const char *msg; switch (ret) { case LZMA_MEM_ERROR: msg = "Memory allocation failed"; break; case LZMA_OPTIONS_ERROR: msg = "Specified preset is not supported"; break; case LZMA_UNSUPPORTED_CHECK: msg = "Specified integrity check is not supported"; break; default: // This is most likely LZMA_PROG_ERROR indicating a bug in // this program or in liblzma. It is inconvenient to have a // separate error message for errors that should be impossible // to occur, but knowing the error code is important for // debugging. That's why it is good to print the error code // at least when there is no good error message to show. msg = "Unknown error, possibly a bug"; break; } fprintf(stderr, "Error initializing the encoder: %s (error code %u)\n", msg, ret); return false; } static bool compress(lzma_stream *strm, FILE *infile, FILE *outfile) { // This will be LZMA_RUN until the end of the input file is reached. // This tells lzma_code() when there will be no more input. lzma_action action = LZMA_RUN; // Buffers to temporarily hold uncompressed input // and compressed output. uint8_t inbuf[BUFSIZ]; uint8_t outbuf[BUFSIZ]; // Initialize the input and output pointers. Initializing next_in // and avail_in isn't really necessary when we are going to encode // just one file since LZMA_STREAM_INIT takes care of initializing // those already. But it doesn't hurt much and it will be needed // if encoding more than one file like we will in 02_decompress.c. // // While we don't care about strm->total_in or strm->total_out in this // example, it is worth noting that initializing the encoder will // always reset total_in and total_out to zero. But the encoder // initialization doesn't touch next_in, avail_in, next_out, or // avail_out. strm->next_in = NULL; strm->avail_in = 0; strm->next_out = outbuf; strm->avail_out = sizeof(outbuf); // Loop until the file has been successfully compressed or until // an error occurs. while (true) { // Fill the input buffer if it is empty. 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; } // Once the end of the input file has been reached, // we need to tell lzma_code() that no more input // will be coming and that it should finish the // encoding. if (feof(infile)) action = LZMA_FINISH; } // Tell liblzma do the actual encoding. // // This reads up to strm->avail_in bytes of input starting // from strm->next_in. avail_in will be decremented and // next_in incremented by an equal amount to match the // number of input bytes consumed. // // Up to strm->avail_out bytes of compressed output will be // written starting from strm->next_out. avail_out and next_out // will be incremented by an equal amount to match the number // of output bytes written. // // The encoder has to do internal buffering, which means that // it may take quite a bit of input before the same data is // available in compressed form in the output buffer. lzma_ret ret = lzma_code(strm, action); // If the output buffer is full or if the compression finished // successfully, write the data from the output buffer to // the output file. if (strm->avail_out == 0 || ret == LZMA_STREAM_END) { // When lzma_code() has returned LZMA_STREAM_END, // the output buffer is likely to be only partially // full. Calculate how much new data there is to // be written to the output file. 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; } // Reset next_out and avail_out. strm->next_out = outbuf; strm->avail_out = sizeof(outbuf); } // Normally the return value of lzma_code() will be LZMA_OK // until everything has been encoded. if (ret != LZMA_OK) { // Once everything has been encoded successfully, the // return value of lzma_code() will be LZMA_STREAM_END. // // It is important to check for LZMA_STREAM_END. Do not // assume that getting ret != LZMA_OK would mean that // everything has gone well. if (ret == LZMA_STREAM_END) return true; // It's not LZMA_OK nor LZMA_STREAM_END, // so it must be an error code. See lzma/base.h // (src/liblzma/api/lzma/base.h in the source package // or e.g. /usr/include/lzma/base.h depending on the // install prefix) for the list and documentation of // possible values. Most values listen in lzma_ret // enumeration aren't possible in this example. const char *msg; switch (ret) { case LZMA_MEM_ERROR: msg = "Memory allocation failed"; break; case LZMA_DATA_ERROR: // This error is returned if the compressed // or uncompressed size get near 8 EiB // (2^63 bytes) because that's where the .xz // file format size limits currently are. // That is, the possibility of this error // is mostly theoretical unless you are doing // something very unusual. // // Note that strm->total_in and strm->total_out // have nothing to do with this error. Changing // those variables won't increase or decrease // the chance of getting this error. msg = "File size limits exceeded"; break; default: // This is most likely LZMA_PROG_ERROR, but // if this program is buggy (or liblzma has // a bug), it may be e.g. LZMA_BUF_ERROR or // LZMA_OPTIONS_ERROR too. // // It is inconvenient to have a separate // error message for errors that should be // impossible to occur, but knowing the error // code is important for debugging. That's why // it is good to print the error code at least // when there is no good error message to show. msg = "Unknown error, possibly a bug"; break; } fprintf(stderr, "Encoder error: %s (error code %u)\n", msg, ret); return false; } } } extern int main(int argc, char **argv) { // Get the preset number from the command line. uint32_t preset = get_preset(argc, argv); // Initialize a lzma_stream structure. When it is allocated on stack, // it is simplest to use LZMA_STREAM_INIT macro like below. When it // is allocated on heap, using memset(strmptr, 0, sizeof(*strmptr)) // works (as long as NULL pointers are represented with zero bits // as they are on practically all computers today). lzma_stream strm = LZMA_STREAM_INIT; // Initialize the encoder. If it succeeds, compress from // stdin to stdout. bool success = init_encoder(&strm, preset); if (success) success = compress(&strm, stdin, stdout); // Free the memory allocated for the encoder. If we were encoding // multiple files, this would only need to be done after the last // file. See 02_decompress.c for handling of multiple files. // // It is OK to call lzma_end() multiple times or when it hasn't been // actually used except initialized with LZMA_STREAM_INIT. lzma_end(&strm); // Close stdout to catch possible write errors that can occur // when pending data is flushed from the stdio buffers. if (fclose(stdout)) { fprintf(stderr, "Write error: %s\n", strerror(errno)); success = false; } return success ? EXIT_SUCCESS : EXIT_FAILURE; }