overlap.c

lzo-1.08-src.zip 高效的压缩解压代码

/* overlap.c -- example program: overlapping (de)compression

   This file is part of the LZO real-time data compression library.

   Copyright (C) 1996-2002 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.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer
   <[e-mail]>
 */


/*************************************************************************
// This program shows how to do overlapping compression and
// in-place decompression.
//
// Please study LZO.FAQ and simple.c first.
**************************************************************************/

#include <lzo1x.h>
#include "lutil.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 / 64 + 16 + 3'. See step 5a) below.
 *
 * For overlapping compression '0xbfff + in_len / 64 + 16 + 3' bytes
 * will be needed. See step 4a) below.
 */

static lzo_uint opt_overhead = 0;	/* assume worst case */


#if 0 && defined(__GNUC__) && defined(__i386__)
/* used for test purposes only */
LZO_EXTERN_CDECL(int)
lzo1x_decompress_asm_fast ( const lzo_byte *src, lzo_uint  src_len,
                                  lzo_byte *dst, lzo_uintp dst_len,
                                  lzo_voidp wrkmem /* NOT USED */ )
                           __asm__("_lzo1x_decompress_asm_fast");
#endif


/*************************************************************************
//
**************************************************************************/

static const char *progname = NULL;

static unsigned long total_files = 0;
static unsigned long total_in = 0;


static lzo_byte *xmalloc(lzo_uint len)
{
	lzo_byte *p;

	p = (lzo_bytep) lzo_malloc(len > 0 ? len : 1);
	if (p == NULL)
	{
		printf("%s: out of memory\n", progname);
		exit(1);
	}
	return p;
}


/*************************************************************************
//
**************************************************************************/

int do_file ( const char *in_name )
{
	int r;
	FILE *f = NULL;
	long l;

	lzo_byte *wrkmem = NULL;

	lzo_byte *in = NULL;
	lzo_uint in_len;				/* uncompressed length */

	lzo_byte *out = NULL;
	lzo_uint out_len;				/* compressed length */

	lzo_byte *overlap = NULL;
	lzo_uint overhead;
	lzo_uint offset;

	lzo_uint new_len = 0;

/*
 * Step 1: open the input file
 */
 	f = fopen(in_name,"rb");
	if (f == NULL)
	{
		printf("%s: %s: cannot open file\n", progname, in_name);
		goto next_file;
	}
	fseek(f,0,SEEK_END);
	l = ftell(f);
	fseek(f,0,SEEK_SET);
	if (l <= 0)
	{
		printf("%s: %s: empty file -- skipping\n", progname, in_name);
		goto next_file;
	}
	in_len = (lzo_uint) l;

/*
 * Step 2: allocate compression buffers and read the file
 */
	in = xmalloc(in_len);
	out = xmalloc(in_len + in_len / 64 + 16 + 3);
	wrkmem = xmalloc(LZO1X_1_MEM_COMPRESS);
	in_len = lzo_fread(f,in,in_len);
	fclose(f); f = NULL;
	printf("%s: %s: read %ld bytes\n", progname, in_name, (long) in_len);

	total_files++;
	total_in += 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 / 64 + 16 + 3)
	{
		/* this should NEVER happen */
		printf("internal error - compression failed: %d\n", r);
		exit(1);
	}
	printf("%-26s %8lu -> %8lu\n", "LZO1X-1:", (long) in_len, (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 / 64 + 16 + 3;
	overlap = 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("overlapping 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 l = in_len;
		lzo_byte *tmp = xmalloc(l);
		r = lzo1x_decompress_safe(overlap,new_len,tmp,&l,NULL);
 		if (r != LZO_E_OK || l != in_len || lzo_memcmp(in,tmp,l) != 0)
		{
			/* this should NEVER happen */
			printf("overlapping compression data error\n");
			exit(1);
		}
		lzo_free(tmp);
	}

	printf("overlapping compression:   %8lu -> %8lu    overhead: %7ld\n",
			(long) in_len, (long) new_len, (long) overhead);
	lzo_free(overlap); overlap = NULL;


/***** Step 5: overlapping decompression *****/

/*
 * Step 5a: allocate the `overlap' buffer for in-place decompression
 */
 	if (opt_overhead == 0 || out_len >= in_len)
		overhead = in_len / 64 + 16 + 3;
	else
 		overhead = opt_overhead;
	overlap = 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;
#if 1
	r = lzo1x_decompress(overlap+offset,out_len,overlap,&new_len,NULL);
#else
	r = lzo1x_decompress_asm_fast(overlap+offset,out_len,overlap,&new_len,NULL);
#endif
	if (r != LZO_E_OK)
	{
		/* this may happen if overhead is too small */
		printf("overlapping 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("overlapping decompression data error - increase `opt_overhead'\n");
		exit(1);
	}
	printf("overlapping decompression: %8lu -> %8lu    overhead: %7ld\n",
			(long) out_len, (long) new_len, (long) overhead);
	lzo_free(overlap); overlap = NULL;


next_file:
	lzo_free(overlap);
	lzo_free(wrkmem);
	lzo_free(out);
	lzo_free(in);
	if (f) fclose(f);

	return 0;
}


/*************************************************************************
//
**************************************************************************/

int main(int argc, char *argv[])
{
	int r;
	int i = 1;

#if defined(__EMX__)
	_response(&argc,&argv);
	_wildcard(&argc,&argv);
#endif

	printf("\nLZO real-time data compression library (v%s, %s).\n",
	        lzo_version_string(), lzo_version_date());
	printf("Copyright (C) 1996-2002 Markus Franz Xaver Johannes Oberhumer\n\n");

	progname = argv[0];
	if (i < argc && argv[i][0] == '-')
		opt_overhead = atoi(&argv[i++][1]);
#if 1
	if (opt_overhead != 0 && opt_overhead < 8)
	{
		printf("%s: invalid overhead value %ld\n", progname, (long)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("lzo_init() failed !!!\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;
}

/*
vi:ts=4
*/