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/* |
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* Copyright (c) 2000-2012 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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* Alternatively, the contents of this file may be used under the terms of |
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* the GNU General Public License ("GPL") version 2 or any later version, |
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* in which case the provisions of the GPL are applicable instead of |
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* the above. If you wish to allow the use of your version of this file |
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* only under the terms of the GPL and not to allow others to use your |
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* version of this file under the BSD license, indicate your decision |
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* by deleting the provisions above and replace them with the notice |
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* and other provisions required by the GPL. If you do not delete the |
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* provisions above, a recipient may use your version of this file under |
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* either the BSD or the GPL. |
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*/ |
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|
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#include "lzfP.h" |
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|
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#define HASH(p) (p[0] << 6) ^ (p[1] << 3) ^ p[2] |
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|
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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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#if __GNUC__ >= 3 |
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# define expect(expr,value) __builtin_expect ((expr),(value)) |
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# define inline inline |
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#else |
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# define expect(expr,value) (expr) |
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# define inline static |
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#endif |
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|
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#define expect_false(expr) expect ((expr) != 0, 0) |
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#define expect_true(expr) expect ((expr) != 0, 1) |
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|
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/* |
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* compressed format |
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* |
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* 000LLLLL <L+1> ; literal, L+1=1..33 octets |
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* LLLooooo oooooooo ; backref L+1=1..7 octets, o+1=1..4096 offset |
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* 111ooooo LLLLLLLL oooooooo ; backref L+8 octets, o+1=1..4096 offset |
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* |
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*/ |
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|
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unsigned int |
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lzf_compress_best (const void *const in_data, unsigned int in_len, |
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void *out_data, unsigned int out_len) |
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{ |
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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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|
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const u8 *first [1 << (6+8)]; /* most recent occurance of a match */ |
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u16 prev [MAX_OFF]; /* how many bytes to go backwards for te next match */ |
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|
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int lit; |
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|
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if (!in_len || !out_len) |
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return 0; |
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|
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lit = 0; op++; /* start run */ |
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|
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lit++; *op++ = *ip++; |
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|
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while (ip < in_end - 2) |
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{ |
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int best_l = 0; |
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const u8 *best_p; |
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int e = (in_end - ip < MAX_REF ? in_end - ip : MAX_REF) - 1; |
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unsigned int res = ((unsigned int)ip) & (MAX_OFF - 1); |
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u16 hash = HASH (ip); |
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u16 diff; |
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const u8 *b = ip < (u8 *)in_data + MAX_OFF ? in_data : ip - MAX_OFF; |
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const u8 *p = first [hash]; |
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prev [res] = ip - p; /* update ptr to previous hash match */ |
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first [hash] = ip; /* first hash match is here */ |
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|
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if (p < ip) |
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while (p >= b) |
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{ |
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if (p[2] == ip[2]) /* first two bytes almost always match */ |
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if (p[best_l] == ip[best_l]) /* new match must be longer than the old one to qualify */ |
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if (p[1] == ip[1] && p[0] == ip[0]) /* just to be sure */ |
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{ |
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int l = 3; |
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|
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while (p[l] == ip[l] && l < e) |
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++l; |
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|
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if (l >= best_l) |
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{ |
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best_p = p; |
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best_l = l; |
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} |
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} |
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|
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diff = prev [((unsigned int)p) & (MAX_OFF - 1)]; |
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p = diff ? p - diff : (u8 *)diff; |
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} |
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|
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if (best_l) |
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{ |
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int len = best_l; |
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int off = ip - best_p - 1; |
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|
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if (expect_false (op + 3 + 1 >= out_end)) /* first a faster conservative test */ |
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if (op - !lit + 3 + 1 >= out_end) /* second the exact but rare test */ |
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return 0; |
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|
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op [- lit - 1] = lit - 1; /* stop run */ |
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op -= !lit; /* undo run if length is zero */ |
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|
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len -= 2; /* len is now #octets - 1 */ |
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ip++; |
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|
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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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|
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*op++ = off; |
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|
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lit = 0; op++; /* start run */ |
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|
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ip += len + 1; |
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|
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if (expect_false (ip >= in_end - 2)) |
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break; |
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|
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ip -= len + 1; |
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|
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//printf (" fill %p for %d\n", ip, len);//D |
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do |
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{ |
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u16 hash = HASH (ip); |
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res = ((unsigned int)ip) & (MAX_OFF - 1); |
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|
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p = first [hash]; |
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prev [res] = ip - p; /* update ptr to previous hash match */ |
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first [hash] = ip; /* first hash match is here */ |
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|
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ip++; |
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} |
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while (len--); |
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} |
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else |
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{ |
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/* one more literal byte we must copy */ |
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if (expect_false (op >= out_end)) |
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return 0; |
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|
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lit++; *op++ = *ip++; |
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|
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if (expect_false (lit == MAX_LIT)) |
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{ |
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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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} |
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} |
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|
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if (op + 3 > out_end) /* at most 3 bytes can be missing here */ |
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return 0; |
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|
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while (ip < in_end) |
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{ |
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lit++; *op++ = *ip++; |
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|
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if (expect_false (lit == MAX_LIT)) |
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{ |
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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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} |
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|
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op [- lit - 1] = lit - 1; /* end run */ |
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op -= !lit; /* undo run if length is zero */ |
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|
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return op - (u8 *)out_data; |
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} |
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|
