465 lines
13 KiB
C
465 lines
13 KiB
C
#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#include <stdio.h>
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#include "ldm.h"
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#include "util.h"
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#define HASH_EVERY 1
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#define LDM_MEMORY_USAGE 16
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#define LDM_HASHLOG (LDM_MEMORY_USAGE-2)
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#define LDM_HASHTABLESIZE (1 << (LDM_MEMORY_USAGE))
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#define LDM_HASHTABLESIZE_U32 ((LDM_HASHTABLESIZE) >> 2)
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#define LDM_HASH_SIZE_U32 (1 << (LDM_HASHLOG))
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#define LDM_OFFSET_SIZE 4
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#define WINDOW_SIZE (1 << 20)
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#define MAX_WINDOW_SIZE 31
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#define HASH_SIZE 4
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#define LDM_HASH_LENGTH 4
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#define MINMATCH 4
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#define ML_BITS 4
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#define ML_MASK ((1U<<ML_BITS)-1)
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#define RUN_BITS (8-ML_BITS)
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#define RUN_MASK ((1U<<RUN_BITS)-1)
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//#define LDM_ROLLING_HASH
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//#define LDM_DEBUG
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typedef uint8_t BYTE;
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typedef uint16_t U16;
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typedef uint32_t U32;
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typedef int32_t S32;
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typedef uint64_t U64;
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typedef uint32_t offset_t;
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typedef uint32_t hash_t;
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typedef signed char schar;
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typedef struct LDM_hashEntry {
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offset_t offset;
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} LDM_hashEntry;
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typedef struct LDM_compressStats {
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U32 numMatches;
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U32 totalMatchLength;
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U32 totalLiteralLength;
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U64 totalOffset;
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} LDM_compressStats;
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static void LDM_printCompressStats(const LDM_compressStats *stats) {
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printf("=====================\n");
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printf("Compression statistics\n");
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printf("Total number of matches: %u\n", stats->numMatches);
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printf("Average match length: %.1f\n", ((double)stats->totalMatchLength) /
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(double)stats->numMatches);
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printf("Average literal length: %.1f\n",
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((double)stats->totalLiteralLength) / (double)stats->numMatches);
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printf("Average offset length: %.1f\n",
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((double)stats->totalOffset) / (double)stats->numMatches);
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printf("=====================\n");
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}
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typedef struct LDM_CCtx {
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size_t isize; /* Input size */
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size_t maxOSize; /* Maximum output size */
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const BYTE *ibase; /* Base of input */
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const BYTE *ip; /* Current input position */
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const BYTE *iend; /* End of input */
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// Maximum input position such that hashing at the position does not exceed
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// end of input.
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const BYTE *ihashLimit;
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// Maximum input position such that finding a match of at least the minimum
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// match length does not exceed end of input.
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const BYTE *imatchLimit;
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const BYTE *obase; /* Base of output */
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BYTE *op; /* Output */
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const BYTE *anchor; /* Anchor to start of current (match) block */
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LDM_compressStats stats; /* Compression statistics */
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LDM_hashEntry hashTable[LDM_HASHTABLESIZE_U32];
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const BYTE *lastPosHashed; /* Last position hashed */
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hash_t lastHash; /* Hash corresponding to lastPosHashed */
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const BYTE *nextIp;
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hash_t nextHash; /* Hash corresponding to nextIp */
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unsigned step;
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} LDM_CCtx;
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#ifdef LDM_ROLLING_HASH
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/**
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* Convert a sum computed from LDM_getRollingHash to a hash value in the range
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* of the hash table.
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*/
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static hash_t LDM_sumToHash(U32 sum) {
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return sum % (LDM_HASHTABLESIZE >> 2);
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// return sum & (LDM_HASHTABLESIZE - 1);
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}
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static U32 LDM_getRollingHash(const char *data, U32 len) {
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U32 i;
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U32 s1, s2;
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const schar *buf = (const schar *)data;
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s1 = s2 = 0;
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for (i = 0; i < (len - 4); i += 4) {
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s2 += (4 * (s1 + buf[i])) + (3 * buf[i + 1]) +
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(2 * buf[i + 2]) + (buf[i + 3]);
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s1 += buf[i] + buf[i + 1] + buf[i + 2] + buf[i + 3];
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}
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for(; i < len; i++) {
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s1 += buf[i];
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s2 += s1;
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}
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return (s1 & 0xffff) + (s2 << 16);
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}
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static hash_t LDM_hashPosition(const void * const p) {
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return LDM_sumToHash(LDM_getRollingHash((const char *)p, LDM_HASH_LENGTH));
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}
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typedef struct LDM_sumStruct {
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U16 s1, s2;
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} LDM_sumStruct;
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static void LDM_getRollingHashParts(U32 sum, LDM_sumStruct *sumStruct) {
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sumStruct->s1 = sum & 0xffff;
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sumStruct->s2 = sum >> 16;
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}
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#else
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static hash_t LDM_hash(U32 sequence) {
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return ((sequence * 2654435761U) >> ((32)-LDM_HASHLOG));
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}
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static hash_t LDM_hashPosition(const void * const p) {
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return LDM_hash(LDM_read32(p));
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}
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#endif
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/*
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static hash_t LDM_hash5(U64 sequence) {
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static const U64 prime5bytes = 889523592379ULL;
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static const U64 prime8bytes = 11400714785074694791ULL;
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const U32 hashLog = LDM_HASHLOG;
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if (LDM_isLittleEndian())
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return (((sequence << 24) * prime5bytes) >> (64 - hashLog));
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else
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return (((sequence >> 24) * prime8bytes) >> (64 - hashLog));
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}
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*/
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static void LDM_putHashOfCurrentPositionFromHash(
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LDM_CCtx *cctx, hash_t hash) {
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if (((cctx->ip - cctx->ibase) & HASH_EVERY) != HASH_EVERY) {
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return;
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}
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(cctx->hashTable)[hash] = (LDM_hashEntry){ (hash_t)(cctx->ip - cctx->ibase) };
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cctx->lastPosHashed = cctx->ip;
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cctx->lastHash = hash;
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}
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static void LDM_putHashOfCurrentPosition(LDM_CCtx *cctx) {
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hash_t hash = LDM_hashPosition(cctx->ip);
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LDM_putHashOfCurrentPositionFromHash(cctx, hash);
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}
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static const BYTE *LDM_get_position_on_hash(
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hash_t h, void *tableBase, const BYTE *srcBase) {
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const LDM_hashEntry * const hashTable = (LDM_hashEntry *)tableBase;
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return hashTable[h].offset + srcBase;
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}
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static BYTE LDM_read_byte(const void *memPtr) {
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BYTE val;
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memcpy(&val, memPtr, 1);
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return val;
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}
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static unsigned LDM_count(const BYTE *pIn, const BYTE *pMatch,
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const BYTE *pInLimit) {
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const BYTE * const pStart = pIn;
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while (pIn < pInLimit - 1) {
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BYTE const diff = LDM_read_byte(pMatch) ^ LDM_read_byte(pIn);
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if (!diff) {
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pIn++;
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pMatch++;
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continue;
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}
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return (unsigned)(pIn - pStart);
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}
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return (unsigned)(pIn - pStart);
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}
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void LDM_readHeader(const void *src, size_t *compressSize,
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size_t *decompressSize) {
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const U32 *ip = (const U32 *)src;
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*compressSize = *ip++;
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*decompressSize = *ip;
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}
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static void LDM_initializeCCtx(LDM_CCtx *cctx,
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const void *src, size_t srcSize,
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void *dst, size_t maxDstSize) {
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cctx->isize = srcSize;
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cctx->maxOSize = maxDstSize;
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cctx->ibase = (const BYTE *)src;
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cctx->ip = cctx->ibase;
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cctx->iend = cctx->ibase + srcSize;
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cctx->ihashLimit = cctx->iend - HASH_SIZE;
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cctx->imatchLimit = cctx->iend - MINMATCH;
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cctx->obase = (BYTE *)dst;
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cctx->op = (BYTE *)dst;
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cctx->anchor = cctx->ibase;
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memset(&(cctx->stats), 0, sizeof(cctx->stats));
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memset(cctx->hashTable, 0, sizeof(cctx->hashTable));
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cctx->lastPosHashed = NULL;
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cctx->nextIp = NULL;
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cctx->step = 1;
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}
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static int LDM_findBestMatch(LDM_CCtx *cctx, const BYTE **match) {
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cctx->nextIp = cctx->ip;
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do {
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hash_t const h = cctx->nextHash;
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cctx->ip = cctx->nextIp;
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cctx->nextIp += cctx->step;
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if (cctx->nextIp > cctx->imatchLimit) {
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return 1;
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}
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*match = LDM_get_position_on_hash(h, cctx->hashTable, cctx->ibase);
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cctx->nextHash = LDM_hashPosition(cctx->nextIp);
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LDM_putHashOfCurrentPositionFromHash(cctx, h);
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} while (cctx->ip - *match > WINDOW_SIZE ||
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LDM_read64(*match) != LDM_read64(cctx->ip));
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return 0;
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}
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// TODO: srcSize and maxDstSize is unused
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size_t LDM_compress(const void *src, size_t srcSize,
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void *dst, size_t maxDstSize) {
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LDM_CCtx cctx;
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LDM_initializeCCtx(&cctx, src, srcSize, dst, maxDstSize);
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/* Hash the first position and put it into the hash table. */
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LDM_putHashOfCurrentPosition(&cctx);
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cctx.ip++;
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cctx.nextHash = LDM_hashPosition(cctx.ip);
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// TODO: loop condition is not accurate.
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while (1) {
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const BYTE *match;
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/**
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* Find a match.
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* If no more matches can be found (i.e. the length of the remaining input
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* is less than the minimum match length), then stop searching for matches
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* and encode the final literals.
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*/
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if (LDM_findBestMatch(&cctx, &match) != 0) {
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goto _last_literals;
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}
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cctx.stats.numMatches++;
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/**
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* Catch up: look back to extend the match backwards from the found match.
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*/
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while (cctx.ip > cctx.anchor && match > cctx.ibase &&
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cctx.ip[-1] == match[-1]) {
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cctx.ip--;
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match--;
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}
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/**
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* Write current block (literals, literal length, match offset, match
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* length) and update pointers and hashes.
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*/
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{
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unsigned const literalLength = (unsigned)(cctx.ip - cctx.anchor);
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unsigned const offset = cctx.ip - match;
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unsigned const matchLength = LDM_count(
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cctx.ip + MINMATCH, match + MINMATCH, cctx.ihashLimit);
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BYTE *token = cctx.op++;
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cctx.stats.totalLiteralLength += literalLength;
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cctx.stats.totalOffset += offset;
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cctx.stats.totalMatchLength += matchLength + MINMATCH;
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/* Encode the literal length. */
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if (literalLength >= RUN_MASK) {
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int len = (int)literalLength - RUN_MASK;
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*token = (RUN_MASK << ML_BITS);
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for (; len >= 255; len -= 255) {
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*(cctx.op)++ = 255;
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}
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*(cctx.op)++ = (BYTE)len;
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} else {
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*token = (BYTE)(literalLength << ML_BITS);
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}
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/* Encode the literals. */
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memcpy(cctx.op, cctx.anchor, literalLength);
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cctx.op += literalLength;
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/* Encode the offset. */
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LDM_write32(cctx.op, offset);
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cctx.op += LDM_OFFSET_SIZE;
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/* Encode match length */
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if (matchLength >= ML_MASK) {
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unsigned matchLengthRemaining = matchLength;
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*token += ML_MASK;
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matchLengthRemaining -= ML_MASK;
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LDM_write32(cctx.op, 0xFFFFFFFF);
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while (matchLengthRemaining >= 4*0xFF) {
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cctx.op += 4;
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LDM_write32(cctx.op, 0xffffffff);
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matchLengthRemaining -= 4*0xFF;
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}
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cctx.op += matchLengthRemaining / 255;
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*(cctx.op)++ = (BYTE)(matchLengthRemaining % 255);
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} else {
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*token += (BYTE)(matchLength);
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}
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/* Update input pointer, inserting hashes into hash table along the
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* way.
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*/
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while (cctx.ip < cctx.anchor + MINMATCH + matchLength + literalLength) {
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LDM_putHashOfCurrentPosition(&cctx);
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cctx.ip++;
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}
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}
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// Set start of next block to current input pointer.
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cctx.anchor = cctx.ip;
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LDM_putHashOfCurrentPosition(&cctx);
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cctx.nextHash = LDM_hashPosition(++cctx.ip);
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}
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_last_literals:
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/* Encode the last literals (no more matches). */
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{
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size_t const lastRun = (size_t)(cctx.iend - cctx.anchor);
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if (lastRun >= RUN_MASK) {
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size_t accumulator = lastRun - RUN_MASK;
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*(cctx.op)++ = RUN_MASK << ML_BITS;
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for(; accumulator >= 255; accumulator -= 255) {
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*(cctx.op)++ = 255;
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}
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*(cctx.op)++ = (BYTE)accumulator;
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} else {
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*(cctx.op)++ = (BYTE)(lastRun << ML_BITS);
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}
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memcpy(cctx.op, cctx.anchor, lastRun);
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cctx.op += lastRun;
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}
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LDM_printCompressStats(&cctx.stats);
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return (cctx.op - (const BYTE *)cctx.obase);
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}
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typedef struct LDM_DCtx {
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size_t compressSize;
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size_t maxDecompressSize;
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const BYTE *ibase; /* Base of input */
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const BYTE *ip; /* Current input position */
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const BYTE *iend; /* End of source */
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const BYTE *obase; /* Base of output */
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BYTE *op; /* Current output position */
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const BYTE *oend; /* End of output */
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} LDM_DCtx;
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static void LDM_initializeDCtx(LDM_DCtx *dctx,
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const void *src, size_t compressSize,
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void *dst, size_t maxDecompressSize) {
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dctx->compressSize = compressSize;
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dctx->maxDecompressSize = maxDecompressSize;
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dctx->ibase = src;
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dctx->ip = (const BYTE *)src;
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dctx->iend = dctx->ip + dctx->compressSize;
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dctx->op = dst;
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dctx->oend = dctx->op + dctx->maxDecompressSize;
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}
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size_t LDM_decompress(const void *src, size_t compressSize,
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void *dst, size_t maxDecompressSize) {
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LDM_DCtx dctx;
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LDM_initializeDCtx(&dctx, src, compressSize, dst, maxDecompressSize);
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while (dctx.ip < dctx.iend) {
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BYTE *cpy;
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const BYTE *match;
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size_t length, offset;
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/* Get the literal length. */
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unsigned const token = *(dctx.ip)++;
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if ((length = (token >> ML_BITS)) == RUN_MASK) {
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unsigned s;
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do {
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s = *(dctx.ip)++;
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length += s;
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} while (s == 255);
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}
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/* Copy literals. */
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cpy = dctx.op + length;
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memcpy(dctx.op, dctx.ip, length);
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dctx.ip += length;
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dctx.op = cpy;
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//TODO : dynamic offset size
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offset = LDM_read32(dctx.ip);
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dctx.ip += LDM_OFFSET_SIZE;
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match = dctx.op - offset;
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/* Get the match length. */
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length = token & ML_MASK;
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if (length == ML_MASK) {
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unsigned s;
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do {
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s = *(dctx.ip)++;
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length += s;
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} while (s == 255);
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}
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length += MINMATCH;
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/* Copy match. */
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cpy = dctx.op + length;
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// Inefficient for now
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while (match < cpy - offset && dctx.op < dctx.oend) {
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*(dctx.op)++ = *match++;
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}
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}
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return dctx.op - (BYTE *)dst;
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}
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