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+/* 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
+ <markus@oberhumer.com>
+ 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: */