linux/lib/lz4/lz4_compress.c

/*
 * LZ4 - Fast LZ compression algorithm
 * Copyright (C) 2011-2012, Yann Collet.
 * BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)

 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * You can contact the author at :
 * - LZ4 homepage : http://fastcompression.blogspot.com/p/lz4.html
 * - LZ4 source repository : http://code.google.com/p/lz4/
 *
 *  Changed for kernel use by:
 *  Chanho Min <chanho.min@lge.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/lz4.h>
#include <asm/unaligned.h>
#include "lz4defs.h"

/*
 * LZ4_compressCtx :
 * -----------------
 * Compress 'isize' bytes from 'source' into an output buffer 'dest' of
 * maximum size 'maxOutputSize'.  * If it cannot achieve it, compression
 * will stop, and result of the function will be zero.
 * return : the number of bytes written in buffer 'dest', or 0 if the
 * compression fails
 */
static inline int lz4_compressctx(void *ctx,
		const char *source,
		char *dest,
		int isize,
		int maxoutputsize)
{
	HTYPE *hashtable = (HTYPE *)ctx;
	const u8 *ip = (u8 *)source;
#if LZ4_ARCH64
	const BYTE * const base = ip;
#else
	const int base = 0;
#endif
	const u8 *anchor = ip;
	const u8 *const iend = ip + isize;
	const u8 *const mflimit = iend - MFLIMIT;
	#define MATCHLIMIT (iend - LASTLITERALS)

	u8 *op = (u8 *) dest;
	u8 *const oend = op + maxoutputsize;
	int length;
	const int skipstrength = SKIPSTRENGTH;
	u32 forwardh;
	int lastrun;

	/* Init */
	if (isize < MINLENGTH)
		goto _last_literals;

	memset((void *)hashtable, 0, LZ4_MEM_COMPRESS);

	/* First Byte */
	hashtable[LZ4_HASH_VALUE(ip)] = ip - base;
	ip++;
	forwardh = LZ4_HASH_VALUE(ip);

	/* Main Loop */
	for (;;) {
		int findmatchattempts = (1U << skipstrength) + 3;
		const u8 *forwardip = ip;
		const u8 *ref;
		u8 *token;

		/* Find a match */
		do {
			u32 h = forwardh;
			int step = findmatchattempts++ >> skipstrength;
			ip = forwardip;
			forwardip = ip + step;

			if (unlikely(forwardip > mflimit))
				goto _last_literals;

			forwardh = LZ4_HASH_VALUE(forwardip);
			ref = base + hashtable[h];
			hashtable[h] = ip - base;
		} while ((ref < ip - MAX_DISTANCE) || (A32(ref) != A32(ip)));

		/* Catch up */
		while ((ip > anchor) && (ref > (u8 *)source) &&
			unlikely(ip[-1] == ref[-1])) {
			ip--;
			ref--;
		}

		/* Encode Literal length */
		length = (int)(ip - anchor);
		token = op++;
		/* check output limit */
		if (unlikely(op + length + (2 + 1 + LASTLITERALS) +
			(length >> 8) > oend))
			return 0;

		if (length >= (int)RUN_MASK) {
			int len;
			*token = (RUN_MASK << ML_BITS);
			len = length - RUN_MASK;
			for (; len > 254 ; len -= 255)
				*op++ = 255;
			*op++ = (u8)len;
		} else
			*token = (length << ML_BITS);

		/* Copy Literals */
		LZ4_BLINDCOPY(anchor, op, length);
_next_match:
		/* Encode Offset */
		LZ4_WRITE_LITTLEENDIAN_16(op, (u16)(ip - ref));

		/* Start Counting */
		ip += MINMATCH;
		/* MinMatch verified */
		ref += MINMATCH;
		anchor = ip;
		while (likely(ip < MATCHLIMIT - (STEPSIZE - 1))) {
			#if LZ4_ARCH64
			u64 diff = A64(ref) ^ A64(ip);
			#else
			u32 diff = A32(ref) ^ A32(ip);
			#endif
			if (!diff) {
				ip += STEPSIZE;
				ref += STEPSIZE;
				continue;
			}
			ip += LZ4_NBCOMMONBYTES(diff);
			goto _endcount;
		}
		#if LZ4_ARCH64
		if ((ip < (MATCHLIMIT - 3)) && (A32(ref) == A32(ip))) {
			ip += 4;
			ref += 4;
		}
		#endif
		if ((ip < (MATCHLIMIT - 1)) && (A16(ref) == A16(ip))) {
			ip += 2;
			ref += 2;
		}
		if ((ip < MATCHLIMIT) && (*ref == *ip))
			ip++;
_endcount:
		/* Encode MatchLength */
		length = (int)(ip - anchor);
		/* Check output limit */
		if (unlikely(op + (1 + LASTLITERALS) + (length >> 8) > oend))
			return 0;
		if (length >= (int)ML_MASK) {
			*token += ML_MASK;
			length -= ML_MASK;
			for (; length > 509 ; length -= 510) {
				*op++ = 255;
				*op++ = 255;
			}
			if (length > 254) {
				length -= 255;
				*op++ = 255;
			}
			*op++ = (u8)length;
		} else
			*token += length;

		/* Test end of chunk */
		if (ip > mflimit) {
			anchor = ip;
			break;
		}

		/* Fill table */
		hashtable[LZ4_HASH_VALUE(ip-2)] = ip - 2 - base;

		/* Test next position */
		ref = base + hashtable[LZ4_HASH_VALUE(ip)];
		hashtable[LZ4_HASH_VALUE(ip)] = ip - base;
		if ((ref > ip - (MAX_DISTANCE + 1)) && (A32(ref) == A32(ip))) {
			token = op++;
			*token = 0;
			goto _next_match;
		}

		/* Prepare next loop */
		anchor = ip++;
		forwardh = LZ4_HASH_VALUE(ip);
	}

_last_literals:
	/* Encode Last Literals */
	lastrun = (int)(iend - anchor);
	if (((char *)op - dest) + lastrun + 1
		+ ((lastrun + 255 - RUN_MASK) / 255) > (u32)maxoutputsize)
		return 0;

	if (lastrun >= (int)RUN_MASK) {
		*op++ = (RUN_MASK << ML_BITS);
		lastrun -= RUN_MASK;
		for (; lastrun > 254 ; lastrun -= 255)
			*op++ = 255;
		*op++ = (u8)lastrun;
	} else
		*op++ = (lastrun << ML_BITS);
	memcpy(op, anchor, iend - anchor);
	op += iend - anchor;

	/* End */
	return (int)(((char *)op) - dest);
}

static inline int lz4_compress64kctx(void *ctx,
		const char *source,
		char *dest,
		int isize,
		int maxoutputsize)
{
	u16 *hashtable = (u16 *)ctx;
	const u8 *ip = (u8 *) source;
	const u8 *anchor = ip;
	const u8 *const base = ip;
	const u8 *const iend = ip + isize;
	const u8 *const mflimit = iend - MFLIMIT;
	#define MATCHLIMIT (iend - LASTLITERALS)

	u8 *op = (u8 *) dest;
	u8 *const oend = op + maxoutputsize;
	int len, length;
	const int skipstrength = SKIPSTRENGTH;
	u32 forwardh;
	int lastrun;

	/* Init */
	if (isize < MINLENGTH)
		goto _last_literals;

	memset((void *)hashtable, 0, LZ4_MEM_COMPRESS);

	/* First Byte */
	ip++;
	forwardh = LZ4_HASH64K_VALUE(ip);

	/* Main Loop */
	for (;;) {
		int findmatchattempts = (1U << skipstrength) + 3;
		const u8 *forwardip = ip;
		const u8 *ref;
		u8 *token;

		/* Find a match */
		do {
			u32 h = forwardh;
			int step = findmatchattempts++ >> skipstrength;
			ip = forwardip;
			forwardip = ip + step;

			if (forwardip > mflimit)
				goto _last_literals;

			forwardh = LZ4_HASH64K_VALUE(forwardip);
			ref = base + hashtable[h];
			hashtable[h] = (u16)(ip - base);
		} while (A32(ref) != A32(ip));

		/* Catch up */
		while ((ip > anchor) && (ref > (u8 *)source)
			&& (ip[-1] == ref[-1])) {
			ip--;
			ref--;
		}

		/* Encode Literal length */
		length = (int)(ip - anchor);
		token = op++;
		/* Check output limit */
		if (unlikely(op + length + (2 + 1 + LASTLITERALS)
			+ (length >> 8) > oend))
			return 0;
		if (length >= (int)RUN_MASK) {
			*token = (RUN_MASK << ML_BITS);
			len = length - RUN_MASK;
			for (; len > 254 ; len -= 255)
				*op++ = 255;
			*op++ = (u8)len;
		} else
			*token = (length << ML_BITS);

		/* Copy Literals */
		LZ4_BLINDCOPY(anchor, op, length);

_next_match:
		/* Encode Offset */
		LZ4_WRITE_LITTLEENDIAN_16(op, (u16)(ip - ref));

		/* Start Counting */
		ip += MINMATCH;
		/* MinMatch verified */
		ref += MINMATCH;
		anchor = ip;

		while (ip < MATCHLIMIT - (STEPSIZE - 1)) {
			#if LZ4_ARCH64
			u64 diff = A64(ref) ^ A64(ip);
			#else
			u32 diff = A32(ref) ^ A32(ip);
			#endif

			if (!diff) {
				ip += STEPSIZE;
				ref += STEPSIZE;
				continue;
			}
			ip += LZ4_NBCOMMONBYTES(diff);
			goto _endcount;
		}
		#if LZ4_ARCH64
		if ((ip < (MATCHLIMIT - 3)) && (A32(ref) == A32(ip))) {
			ip += 4;
			ref += 4;
		}
		#endif
		if ((ip < (MATCHLIMIT - 1)) && (A16(ref) == A16(ip))) {
			ip += 2;
			ref += 2;
		}
		if ((ip < MATCHLIMIT) && (*ref == *ip))
			ip++;
_endcount:

		/* Encode MatchLength */
		len = (int)(ip - anchor);
		/* Check output limit */
		if (unlikely(op + (1 + LASTLITERALS) + (len >> 8) > oend))
			return 0;
		if (len >= (int)ML_MASK) {
			*token += ML_MASK;
			len -= ML_MASK;
			for (; len > 509 ; len -= 510) {
				*op++ = 255;
				*op++ = 255;
			}
			if (len > 254) {
				len -= 255;
				*op++ = 255;
			}
			*op++ = (u8)len;
		} else
			*token += len;

		/* Test end of chunk */
		if (ip > mflimit) {
			anchor = ip;
			break;
		}

		/* Fill table */
		hashtable[LZ4_HASH64K_VALUE(ip-2)] = (u16)(ip - 2 - base);

		/* Test next position */
		ref = base + hashtable[LZ4_HASH64K_VALUE(ip)];
		hashtable[LZ4_HASH64K_VALUE(ip)] = (u16)(ip - base);
		if (A32(ref) == A32(ip)) {
			token = op++;
			*token = 0;
			goto _next_match;
		}

		/* Prepare next loop */
		anchor = ip++;
		forwardh = LZ4_HASH64K_VALUE(ip);
	}

_last_literals:
	/* Encode Last Literals */
	lastrun = (int)(iend - anchor);
	if (op + lastrun + 1 + (lastrun - RUN_MASK + 255) / 255 > oend)
		return 0;
	if (lastrun >= (int)RUN_MASK) {
		*op++ = (RUN_MASK << ML_BITS);
		lastrun -= RUN_MASK;
		for (; lastrun > 254 ; lastrun -= 255)
			*op++ = 255;
		*op++ = (u8)lastrun;
	} else
		*op++ = (lastrun << ML_BITS);
	memcpy(op, anchor, iend - anchor);
	op += iend - anchor;
	/* End */
	return (int)(((char *)op) - dest);
}

int lz4_compress(const unsigned char *src, size_t src_len,
			unsigned char *dst, size_t *dst_len, void *wrkmem)
{
	int ret = -1;
	int out_len = 0;

	if (src_len < LZ4_64KLIMIT)
		out_len = lz4_compress64kctx(wrkmem, src, dst, src_len,
				lz4_compressbound(src_len));
	else
		out_len = lz4_compressctx(wrkmem, src, dst, src_len,
				lz4_compressbound(src_len));

	if (out_len < 0)
		goto exit;

	*dst_len = out_len;

	return 0;
exit:
	return ret;
}
EXPORT_SYMBOL(lz4_compress);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("LZ4 compressor");