/* overlap.c -- example program: overlapping (de)compression This file is part of the LZO real-time data compression library. Copyright (C) 1996-2014 Markus Franz Xaver Johannes Oberhumer All Rights Reserved. The LZO library is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The LZO library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with the LZO library; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. Markus F.X.J. Oberhumer http://www.oberhumer.com/opensource/lzo/ */ /************************************************************************* // This program shows how to do overlapping compression and // in-place decompression. // // Please study LZO.FAQ and simple.c first. **************************************************************************/ #include "lzo/lzoconf.h" #include "lzo/lzo1x.h" /* portability layer */ static const char *progname = NULL; #define WANT_LZO_MALLOC 1 #define WANT_LZO_FREAD 1 #define WANT_LZO_WILDARGV 1 #define WANT_XMALLOC 1 #include "examples/portab.h" /* Overhead (in bytes) for the in-place decompression buffer. * Most files need only 16 ! * (try 'overlap -16 file' or even 'overlap -8 file') * * Worst case (for files that are compressible by only a few bytes) * is 'in_len / 16 + 64 + 3'. See step 5a) below. * * For overlapping compression '0xbfff + in_len / 16 + 64 + 3' bytes * will be needed. See step 4a) below. */ static long opt_overhead = 0; /* assume worst case */ static unsigned long total_files = 0; static unsigned long total_in = 0; /************************************************************************* // **************************************************************************/ static int do_file(const char *in_name) { int r; FILE *fp = NULL; long l; lzo_voidp wrkmem = NULL; lzo_bytep in = NULL; lzo_uint in_len; /* uncompressed length */ lzo_bytep out = NULL; lzo_uint out_len; /* compressed length */ lzo_bytep overlap = NULL; lzo_uint overhead; lzo_uint offset; lzo_uint new_len = 0; /* * Step 1: open the input file */ fp = fopen(in_name, "rb"); if (fp == NULL) { printf("%s: %s: cannot open file\n", progname, in_name); goto next_file; } fseek(fp, 0, SEEK_END); l = ftell(fp); fseek(fp, 0, SEEK_SET); if (l <= 0) { printf("%s: %s: empty file -- skipping\n", progname, in_name); goto next_file; } in_len = (lzo_uint) l; if ((long) in_len != l || l > 256L * 1024L * 1024L) { printf("%s: %s: file is too big -- skipping\n", progname, in_name); goto next_file; } /* * Step 2: allocate compression buffers and read the file */ in = (lzo_bytep) xmalloc(in_len); out = (lzo_bytep) xmalloc(in_len + in_len / 16 + 64 + 3); wrkmem = (lzo_voidp) xmalloc(LZO1X_1_MEM_COMPRESS); in_len = (lzo_uint) lzo_fread(fp, in, in_len); fclose(fp); fp = NULL; printf("%s: %s: read %lu bytes\n", progname, in_name, (unsigned long) in_len); total_files++; total_in += (unsigned long) in_len; /* * Step 3: compress from 'in' to 'out' with LZO1X-1 */ r = lzo1x_1_compress(in, in_len, out, &out_len, wrkmem); if (r != LZO_E_OK || out_len > in_len + in_len / 16 + 64 + 3) { /* this should NEVER happen */ printf("internal error - compression failed: %d\n", r); exit(1); } printf("%-25s %8lu -> %8lu\n", "LZO1X-1:", (unsigned long) in_len, (unsigned long) out_len); /***** Step 4: overlapping compression *****/ /* * Step 4a: allocate the 'overlap' buffer for overlapping compression */ overhead = in_len > 0xbfff ? 0xbfff : in_len; overhead += in_len / 16 + 64 + 3; overlap = (lzo_bytep) xmalloc(in_len + overhead); /* * Step 4b: prepare data in 'overlap' buffer. * copy uncompressed data at the top of the overlap buffer */ /*** offset = in_len + overhead - in_len; ***/ offset = overhead; lzo_memcpy(overlap + offset, in, in_len); /* * Step 4c: do an in-place compression within the 'overlap' buffer */ r = lzo1x_1_compress(overlap + offset, in_len, overlap, &new_len, wrkmem); if (r != LZO_E_OK) { /* this should NEVER happen */ printf("in-place compression failed: %d\n", r); exit(1); } /* * Step 4d: verify overlapping compression */ if (new_len != out_len || lzo_memcmp(out, overlap, out_len) != 0) { /* As compression is non-deterministic there can be a difference * in the representation of the compressed data (but this usually * happens very seldom). So we have to verify the overlapping * compression by doing a temporary decompression. */ lzo_uint ll = in_len; lzo_bytep tmp = (lzo_bytep) xmalloc(ll); r = lzo1x_decompress_safe(overlap, new_len, tmp, &ll, NULL); if (r != LZO_E_OK || ll != in_len || lzo_memcmp(in, tmp, ll) != 0) { /* this should NEVER happen */ printf("in-place compression data error\n"); exit(1); } lzo_free(tmp); } printf(" in-place compression: %8lu -> %8lu overhead: %7lu\n", (unsigned long) in_len, (unsigned long) new_len, (unsigned long) overhead); lzo_free(overlap); overlap = NULL; /***** Step 5: in-place decompression *****/ /* * Step 5a: allocate the 'overlap' buffer for in-place decompression */ if (opt_overhead == 0 || out_len >= in_len) overhead = in_len / 16 + 64 + 3; else overhead = (lzo_uint) opt_overhead; overlap = (lzo_bytep) xmalloc(in_len + overhead); /* * Step 5b: prepare data in 'overlap' buffer. * copy compressed data at the top of the overlap buffer */ offset = in_len + overhead - out_len; lzo_memcpy(overlap + offset, out, out_len); /* * Step 5c: do an in-place decompression within the 'overlap' buffer */ new_len = in_len; r = lzo1x_decompress_safe(overlap + offset, out_len, overlap, &new_len, NULL); if (r != LZO_E_OK) { /* this may happen if overhead is too small */ printf("in-place decompression failed: %d - increase 'opt_overhead'\n", r); exit(1); } /* * Step 5d: verify decompression */ if (new_len != in_len || lzo_memcmp(in, overlap, in_len) != 0) { /* this may happen if overhead is too small */ printf("in-place decompression data error - increase 'opt_overhead'\n"); exit(1); } printf(" in-place decompression: %8lu -> %8lu overhead: %7lu\n", (unsigned long) out_len, (unsigned long) new_len, (unsigned long) overhead); lzo_free(overlap); overlap = NULL; next_file: lzo_free(overlap); lzo_free(wrkmem); lzo_free(out); lzo_free(in); if (fp) fclose(fp); return 0; } /************************************************************************* // **************************************************************************/ int __lzo_cdecl_main main(int argc, char *argv[]) { int r; int i = 1; lzo_wildargv(&argc, &argv); printf("\nLZO real-time data compression library (v%s, %s).\n", lzo_version_string(), lzo_version_date()); printf("Copyright (C) 1996-2014 Markus Franz Xaver Johannes Oberhumer\nAll Rights Reserved.\n\n"); progname = argv[0]; if (i < argc && argv[i][0] == '-') opt_overhead = atol(&argv[i++][1]); #if 1 if (opt_overhead != 0 && opt_overhead < 4) { printf("%s: invalid overhead value %ld\n", progname, opt_overhead); exit(1); } #endif if (i >= argc) { printf("usage: %s [-overhead_in_bytes] file..\n", progname); exit(1); } /* * Step 1: initialize the LZO library */ if (lzo_init() != LZO_E_OK) { printf("internal error - lzo_init() failed !!!\n"); printf("(this usually indicates a compiler bug - try recompiling\nwithout optimizations, and enable '-DLZO_DEBUG' for diagnostics)\n"); exit(1); } /* * Step 2: process files */ for (r = 0; r == 0 && i < argc; i++) r = do_file(argv[i]); printf("\nDone. Successfully processed %lu bytes in %lu files.\n", total_in, total_files); return r; } /* vim:set ts=4 sw=4 et: */