243 lines
6.7 KiB
C
243 lines
6.7 KiB
C
/*
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* Copyright (c) 2000-2005 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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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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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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* Alternatively, the contents of this file may be used under the terms of
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* the GNU General Public License version 2 (the "GPL"), in which case the
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* provisions of the GPL are applicable instead of the above. If you wish to
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* allow the use of your version of this file only under the terms of the
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* GPL and not to allow others to use your version of this file under the
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* BSD license, indicate your decision by deleting the provisions above and
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* replace them with the notice and other provisions required by the GPL. If
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* you do not delete the provisions above, a recipient may use your version
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* of this file under either the BSD or the GPL.
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*/
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#include "lzfP.h"
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#define HSIZE (1 << (HLOG))
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/*
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* don't play with this unless you benchmark!
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* decompression is not dependent on the hash function
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* the hashing function might seem strange, just believe me
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* it works ;)
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*/
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#ifndef FRST
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# define FRST(p) (((p[0]) << 8) | p[1])
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# define NEXT(v,p) (((v) << 8) | p[2])
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# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
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#endif
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/*
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* IDX works because it is very similar to a multiplicative hash, e.g.
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* ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
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* the latter is also quite fast on newer CPUs, and sligthly better
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*
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* the next one is also quite good, albeit slow ;)
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* (int)(cos(h & 0xffffff) * 1e6)
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*/
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#if 0
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/* original lzv-like hash function, much worse and thus slower */
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# define FRST(p) (p[0] << 5) ^ p[1]
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# define NEXT(v,p) ((v) << 5) ^ p[2]
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# define IDX(h) ((h) & (HSIZE - 1))
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#endif
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#define MAX_LIT (1 << 5)
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#define MAX_OFF (1 << 13)
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#define MAX_REF ((1 << 8) + (1 << 3))
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/*
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* compressed format
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*
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* 000LLLLL <L+1> ; literal
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* LLLooooo oooooooo ; backref L
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* 111ooooo LLLLLLLL oooooooo ; backref L+7
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*
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*/
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unsigned int
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lzf_compress (const void *const in_data, unsigned int in_len,
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void *out_data, unsigned int out_len
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#if LZF_STATE_ARG
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, LZF_STATE *htab
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#endif
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)
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{
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#if !LZF_STATE_ARG
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LZF_STATE htab;
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#endif
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const u8 **hslot;
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const u8 *ip = (const u8 *)in_data;
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u8 *op = (u8 *)out_data;
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const u8 *in_end = ip + in_len;
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u8 *out_end = op + out_len;
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const u8 *ref;
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unsigned int hval = FRST (ip);
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unsigned long off;
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int lit = 0;
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#if INIT_HTAB
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# if USE_MEMCPY
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memset (htab, 0, sizeof (htab));
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# else
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for (hslot = htab; hslot < htab + HSIZE; hslot++)
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*hslot++ = ip;
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# endif
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#endif
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for (;;)
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{
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if (ip < in_end - 2)
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{
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hval = NEXT (hval, ip);
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hslot = htab + IDX (hval);
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ref = *hslot; *hslot = ip;
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if (1
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#if INIT_HTAB && !USE_MEMCPY
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&& ref < ip /* the next test will actually take care of this, but this is faster */
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#endif
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&& (off = ip - ref - 1) < MAX_OFF
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&& ip + 4 < in_end
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&& ref > (u8 *)in_data
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#if STRICT_ALIGN
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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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#else
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&& *(u16 *)ref == *(u16 *)ip
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&& ref[2] == ip[2]
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#endif
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)
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{
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/* match found at *ref++ */
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unsigned int len = 2;
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unsigned int maxlen = in_end - ip - len;
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maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
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if (op + lit + 1 + 3 >= out_end)
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return 0;
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do
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len++;
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while (len < maxlen && ref[len] == ip[len]);
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if (lit)
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{
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*op++ = lit - 1;
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lit = -lit;
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do
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*op++ = ip[lit];
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while (++lit);
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}
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len -= 2;
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ip++;
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if (len < 7)
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{
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*op++ = (off >> 8) + (len << 5);
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}
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else
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{
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*op++ = (off >> 8) + ( 7 << 5);
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*op++ = len - 7;
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}
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*op++ = off;
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#if ULTRA_FAST || VERY_FAST
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ip += len;
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#if VERY_FAST && !ULTRA_FAST
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--ip;
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#endif
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hval = FRST (ip);
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hval = NEXT (hval, ip);
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htab[IDX (hval)] = ip;
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ip++;
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#if VERY_FAST && !ULTRA_FAST
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hval = NEXT (hval, ip);
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htab[IDX (hval)] = ip;
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ip++;
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#endif
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#else
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do
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{
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hval = NEXT (hval, ip);
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htab[IDX (hval)] = ip;
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ip++;
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}
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while (len--);
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#endif
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continue;
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}
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}
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else if (ip == in_end)
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break;
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/* one more literal byte we must copy */
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lit++;
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ip++;
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if (lit == MAX_LIT)
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{
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if (op + 1 + MAX_LIT >= out_end)
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return 0;
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*op++ = MAX_LIT - 1;
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#if USE_MEMCPY
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memcpy (op, ip - MAX_LIT, MAX_LIT);
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op += MAX_LIT;
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lit = 0;
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#else
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lit = -lit;
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do
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*op++ = ip[lit];
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while (++lit);
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#endif
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}
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}
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if (lit)
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{
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if (op + lit + 1 >= out_end)
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return 0;
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*op++ = lit - 1;
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lit = -lit;
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do
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*op++ = ip[lit];
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while (++lit);
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}
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return op - (u8 *) out_data;
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}
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