369 lines
11 KiB
C
369 lines
11 KiB
C
/*
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* Copyright (c) 2009 Andrew Collette <andrew.collette at gmail.com>
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* http://lzfx.googlecode.com
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*
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* Implements an LZF-compatible compressor/decompressor based on the liblzf
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* codebase written by Marc Lehmann. This code is released under the BSD
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* license. License and original copyright statement follow.
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*
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*
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* Copyright (c) 2000-2008 Marc Alexander Lehmann <schmorp@schmorp.de>
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*
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* Redistribution and use in source and binary forms, with or without modifica-
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* tion, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
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* CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
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* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
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* CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
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* ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "lzfx.h"
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#define LZFX_HSIZE (1 << (LZFX_HLOG))
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#include <stdint.h>
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/* We need this for memset */
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#ifdef __cplusplus
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# include <cstring>
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#else
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# include <string.h>
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#endif
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#if __GNUC__ >= 3 && !DISABLE_EXPECT
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# define fx_expect_false(expr) __builtin_expect((expr) != 0, 0)
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# define fx_expect_true(expr) __builtin_expect((expr) != 0, 1)
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#else
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# define fx_expect_false(expr) (expr)
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# define fx_expect_true(expr) (expr)
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#endif
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typedef unsigned char u8;
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typedef const u8 *LZSTATE[LZFX_HSIZE];
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/* Define the hash function */
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#define LZFX_FRST(p) (((p[0]) << 8) | p[1])
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#define LZFX_NEXT(v,p) (((v) << 8) | p[2])
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#define LZFX_IDX(h) ((( h >> (3*8 - LZFX_HLOG)) - h ) & (LZFX_HSIZE - 1))
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/* These cannot be changed, as they are related to the compressed format. */
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#define LZFX_MAX_LIT (1 << 5)
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#define LZFX_MAX_OFF (1 << 13)
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#define LZFX_MAX_REF ((1 << 8) + (1 << 3))
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static
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int lzfx_getsize(const void* ibuf, unsigned int ilen, unsigned int *olen);
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/* Compressed format
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There are two kinds of structures in LZF/LZFX: literal runs and back
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references. The length of a literal run is encoded as L - 1, as it must
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contain at least one byte. Literals are encoded as follows:
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000LLLLL <L+1 bytes>
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Back references are encoded as follows. The smallest possible encoded
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length value is 1, as otherwise the control byte would be recognized as
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a literal run. Since at least three bytes must match for a back reference
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to be inserted, the length is encoded as L - 2 instead of L - 1. The
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offset (distance to the desired data in the output buffer) is encoded as
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o - 1, as all offsets are at least 1. The binary format is:
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LLLooooo oooooooo for backrefs of real length < 9 (1 <= L < 7)
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111ooooo LLLLLLLL oooooooo for backrefs of real length >= 9 (L > 7)
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*/
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#include <stdio.h>
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int lzfx_compress(const void *const ibuf, const unsigned int ilen,
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void *obuf, unsigned int *const olen){
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/* Hash table; an array of u8*'s which point
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to various locations in the input buffer */
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const u8 *htab[LZFX_HSIZE];
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const u8 **hslot; /* Pointer to entry in hash table */
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unsigned int hval; /* Hash value generated by macros above */
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const u8 *ref; /* Pointer to candidate match location in input */
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const u8 *ip = (const u8 *)ibuf;
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const u8 *const in_end = ip + ilen;
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u8 *op = (u8 *)obuf;
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const u8 *const out_end = (olen == NULL ? NULL : op + *olen);
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int lit; /* # of bytes in current literal run */
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#if defined (WIN32) && defined (_M_X64)
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uint64_t off; /* workaround for missing POSIX compliance */
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#else
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unsigned long off;
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#endif
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if(olen == NULL) return LZFX_EARGS;
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if(ibuf == NULL){
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if(ilen != 0) return LZFX_EARGS;
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*olen = 0;
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return 0;
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}
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if(obuf == NULL){
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if(olen != 0) return LZFX_EARGS;
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return lzfx_getsize(ibuf, ilen, olen);
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}
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memset(htab, 0, sizeof(htab));
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/* Start a literal run. Whenever we do this the output pointer is
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advanced because the current byte will hold the encoded length. */
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lit = 0; op++;
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hval = LZFX_FRST(ip);
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while(ip + 2 < in_end){ /* The NEXT macro reads 2 bytes ahead */
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hval = LZFX_NEXT(hval, ip);
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hslot = htab + LZFX_IDX(hval);
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ref = *hslot; *hslot = ip;
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if( ref < ip
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&& (off = ip - ref - 1) < LZFX_MAX_OFF
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&& ip + 4 < in_end /* Backref takes up to 3 bytes, so don't bother */
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&& ref > (u8 *)ibuf
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&& ref[0] == ip[0]
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&& ref[1] == ip[1]
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&& ref[2] == ip[2] ) {
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unsigned int len = 3; /* We already know 3 bytes match */
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const unsigned int maxlen = in_end - ip - 2 > LZFX_MAX_REF ?
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LZFX_MAX_REF : in_end - ip - 2;
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/* lit == 0: op + 3 must be < out_end (because we undo the run)
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lit != 0: op + 3 + 1 must be < out_end */
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if(fx_expect_false(op - !lit + 3 + 1 >= out_end))
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return LZFX_ESIZE;
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op [- lit - 1] = lit - 1; /* Terminate literal run */
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op -= !lit; /* Undo run if length is zero */
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/* Start checking at the fourth byte */
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while (len < maxlen && ref[len] == ip[len])
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len++;
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len -= 2; /* We encode the length as #octets - 2 */
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/* Format 1: [LLLooooo oooooooo] */
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if (len < 7) {
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*op++ = (off >> 8) + (len << 5);
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*op++ = off;
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/* Format 2: [111ooooo LLLLLLLL oooooooo] */
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} else {
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*op++ = (off >> 8) + (7 << 5);
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*op++ = len - 7;
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*op++ = off;
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}
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lit = 0; op++;
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ip += len + 1; /* ip = initial ip + #octets -1 */
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if (fx_expect_false (ip + 3 >= in_end)){
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ip++; /* Code following expects exit at bottom of loop */
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break;
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}
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hval = LZFX_FRST (ip);
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hval = LZFX_NEXT (hval, ip);
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htab[LZFX_IDX (hval)] = ip;
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ip++; /* ip = initial ip + #octets */
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} else {
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/* Keep copying literal bytes */
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if (fx_expect_false (op >= out_end)) return LZFX_ESIZE;
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lit++; *op++ = *ip++;
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if (fx_expect_false (lit == LZFX_MAX_LIT)) {
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op [- lit - 1] = lit - 1; /* stop run */
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lit = 0; op++; /* start run */
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}
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} /* if() found match in htab */
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} /* while(ip < ilen -2) */
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/* At most 3 bytes remain in input. We therefore need 4 bytes available
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in the output buffer to store them (3 data + ctrl byte).*/
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if (op + 3 > out_end) return LZFX_ESIZE;
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while (ip < in_end) {
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lit++; *op++ = *ip++;
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if (fx_expect_false (lit == LZFX_MAX_LIT)){
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op [- lit - 1] = lit - 1;
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lit = 0; op++;
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}
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}
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op [- lit - 1] = lit - 1;
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op -= !lit;
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*olen = op - (u8 *)obuf;
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return 0;
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}
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/* Decompressor */
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int lzfx_decompress(const void* ibuf, unsigned int ilen,
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void* obuf, unsigned int *olen){
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u8 const *ip = (const u8 *)ibuf;
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u8 const *const in_end = ip + ilen;
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u8 *op = (u8 *)obuf;
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u8 const *const out_end = (olen == NULL ? NULL : op + *olen);
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unsigned int remain_len = 0;
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int rc;
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if(olen == NULL) return LZFX_EARGS;
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if(ibuf == NULL){
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if(ilen != 0) return LZFX_EARGS;
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*olen = 0;
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return 0;
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}
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if(obuf == NULL){
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if(olen != 0) return LZFX_EARGS;
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return lzfx_getsize(ibuf, ilen, olen);
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}
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do {
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unsigned int ctrl = *ip++;
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/* Format 000LLLLL: a literal byte string follows, of length L+1 */
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if(ctrl < (1 << 5)) {
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ctrl++;
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if(fx_expect_false(op + ctrl > out_end)){
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--ip; /* Rewind to control byte */
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goto guess;
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}
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if(fx_expect_false(ip + ctrl > in_end)) return LZFX_ECORRUPT;
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do
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*op++ = *ip++;
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while(--ctrl);
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/* Format #1 [LLLooooo oooooooo]: backref of length L+1+2
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^^^^^ ^^^^^^^^
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A B
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#2 [111ooooo LLLLLLLL oooooooo] backref of length L+7+2
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^^^^^ ^^^^^^^^
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A B
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In both cases the location of the backref is computed from the
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remaining part of the data as follows:
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location = op - A*256 - B - 1
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*/
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} else {
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unsigned int len = (ctrl >> 5);
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u8 *ref = op - ((ctrl & 0x1f) << 8) -1;
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if(len==7) len += *ip++; /* i.e. format #2 */
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len += 2; /* len is now #octets */
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if(fx_expect_false(op + len > out_end)){
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ip -= (len >= 9) ? 2 : 1; /* Rewind to control byte */
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goto guess;
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}
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if(fx_expect_false(ip >= in_end)) return LZFX_ECORRUPT;
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ref -= *ip++;
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if(fx_expect_false(ref < (u8*)obuf)) return LZFX_ECORRUPT;
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do
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*op++ = *ref++;
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while (--len);
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}
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} while (ip < in_end);
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*olen = op - (u8 *)obuf;
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return 0;
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guess:
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rc = lzfx_getsize(ip, ilen - (ip-(u8*)ibuf), &remain_len);
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if(rc>=0) *olen = remain_len + (op - (u8*)obuf);
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return rc;
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}
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/* Guess len. No parameters may be NULL; this is not checked. */
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static
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int lzfx_getsize(const void* ibuf, unsigned int ilen, unsigned int *olen){
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u8 const *ip = (const u8 *)ibuf;
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u8 const *const in_end = ip + ilen;
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int tot_len = 0;
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while (ip < in_end) {
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unsigned int ctrl = *ip++;
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if(ctrl < (1 << 5)) {
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ctrl++;
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if(ip + ctrl > in_end)
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return LZFX_ECORRUPT;
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tot_len += ctrl;
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ip += ctrl;
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} else {
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unsigned int len = (ctrl >> 5);
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if(len==7){ /* i.e. format #2 */
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len += *ip++;
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}
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len += 2; /* len is now #octets */
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if(ip >= in_end) return LZFX_ECORRUPT;
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ip++; /* skip the ref byte */
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tot_len += len;
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}
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}
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*olen = tot_len;
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return 0;
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}
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