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android / platform / external / zstd / 273c17b3 / . / contrib / long_distance_matching / ldm_with_table.c
blob: c727616af08930a28e0f1013bf76254d4ffd10b2 [file] [log] [blame]
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "ldm.h"
#define LDM_HASHTABLESIZE (1 << (LDM_MEMORY_USAGE))
#define LDM_HASH_ENTRY_SIZE_LOG 3
#define LDM_HASHTABLESIZE_U32 ((LDM_HASHTABLESIZE) >> 2)
#define LDM_HASHTABLESIZE_U64 ((LDM_HASHTABLESIZE) >> 3)
// Insert every (HASH_ONLY_EVERY + 1) into the hash table.
#define HASH_ONLY_EVERY_LOG (LDM_WINDOW_SIZE_LOG-((LDM_MEMORY_USAGE) - (LDM_HASH_ENTRY_SIZE_LOG)))
#define HASH_ONLY_EVERY ((1 << HASH_ONLY_EVERY_LOG) - 1)
/* Hash table stuff. */
#define HASH_BUCKET_SIZE (1 << (HASH_BUCKET_SIZE_LOG))
#define LDM_HASHLOG ((LDM_MEMORY_USAGE)-(LDM_HASH_ENTRY_SIZE_LOG)-(HASH_BUCKET_SIZE_LOG))
#define ML_BITS 4
#define ML_MASK ((1U<<ML_BITS)-1)
#define RUN_BITS (8-ML_BITS)
#define RUN_MASK ((1U<<RUN_BITS)-1)
#define COMPUTE_STATS
#define OUTPUT_CONFIGURATION
#define CHECKSUM_CHAR_OFFSET 10
// Take first match only.
//#define ZSTD_SKIP
//#define RUN_CHECKS
/* Hash table stuff */
typedef U32 hash_t;
typedef struct LDM_hashEntry {
U32 offset;
U32 checksum;
} LDM_hashEntry;
// TODO: Memory usage
struct LDM_compressStats {
U32 windowSizeLog, hashTableSizeLog;
U32 numMatches;
U64 totalMatchLength;
U64 totalLiteralLength;
U64 totalOffset;
U32 minOffset, maxOffset;
U32 numCollisions;
U32 numHashInserts;
U32 offsetHistogram[32];
};
typedef struct LDM_hashTable LDM_hashTable;
struct LDM_CCtx {
U64 isize; /* Input size */
U64 maxOSize; /* Maximum output size */
const BYTE *ibase; /* Base of input */
const BYTE *ip; /* Current input position */
const BYTE *iend; /* End of input */
// Maximum input position such that hashing at the position does not exceed
// end of input.
const BYTE *ihashLimit;
// Maximum input position such that finding a match of at least the minimum
// match length does not exceed end of input.
const BYTE *imatchLimit;
const BYTE *obase; /* Base of output */
BYTE *op; /* Output */
const BYTE *anchor; /* Anchor to start of current (match) block */
LDM_compressStats stats; /* Compression statistics */
LDM_hashTable *hashTable;
// LDM_hashEntry hashTable[LDM_HASHTABLESIZE_U32];
const BYTE *lastPosHashed; /* Last position hashed */
hash_t lastHash; /* Hash corresponding to lastPosHashed */
U32 lastSum;
const BYTE *nextIp; // TODO: this is redundant (ip + step)
const BYTE *nextPosHashed;
hash_t nextHash; /* Hash corresponding to nextPosHashed */
U32 nextSum;
unsigned step; // ip step, should be 1.
const BYTE *lagIp;
hash_t lagHash;
U32 lagSum;
U64 numHashInserts;
// DEBUG
const BYTE *DEBUG_setNextHash;
};
struct LDM_hashTable {
U32 numBuckets; // Number of buckets
U32 numEntries; // Rename...
LDM_hashEntry *entries;
BYTE *bucketOffsets;
// Position corresponding to offset=0 in LDM_hashEntry.
};
/**
* Create a hash table that can contain size elements.
* The number of buckets is determined by size >> HASH_BUCKET_SIZE_LOG.
*/
LDM_hashTable *HASH_createTable(U32 size) {
LDM_hashTable *table = malloc(sizeof(LDM_hashTable));
table->numBuckets = size >> HASH_BUCKET_SIZE_LOG;
table->numEntries = size;
table->entries = calloc(size, sizeof(LDM_hashEntry));
table->bucketOffsets = calloc(size >> HASH_BUCKET_SIZE_LOG, sizeof(BYTE));
return table;
}
static LDM_hashEntry *getBucket(const LDM_hashTable *table, const hash_t hash) {
return table->entries + (hash << HASH_BUCKET_SIZE_LOG);
}
static unsigned ZSTD_NbCommonBytes (register size_t val) {
if (MEM_isLittleEndian()) {
if (MEM_64bits()) {
# if defined(_MSC_VER) && defined(_WIN64)
unsigned long r = 0;
_BitScanForward64( &r, (U64)val );
return (unsigned)(r>>3);
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_ctzll((U64)val) >> 3);
# else
static const int DeBruijnBytePos[64] = { 0, 0, 0, 0, 0, 1, 1, 2,
0, 3, 1, 3, 1, 4, 2, 7,
0, 2, 3, 6, 1, 5, 3, 5,
1, 3, 4, 4, 2, 5, 6, 7,
7, 0, 1, 2, 3, 3, 4, 6,
2, 6, 5, 5, 3, 4, 5, 6,
7, 1, 2, 4, 6, 4, 4, 5,
7, 2, 6, 5, 7, 6, 7, 7 };
return DeBruijnBytePos[((U64)((val & -(long long)val) * 0x0218A392CDABBD3FULL)) >> 58];
# endif
} else { /* 32 bits */
# if defined(_MSC_VER)
unsigned long r=0;
_BitScanForward( &r, (U32)val );
return (unsigned)(r>>3);
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_ctz((U32)val) >> 3);
# else
static const int DeBruijnBytePos[32] = { 0, 0, 3, 0, 3, 1, 3, 0,
3, 2, 2, 1, 3, 2, 0, 1,
3, 3, 1, 2, 2, 2, 2, 0,
3, 1, 2, 0, 1, 0, 1, 1 };
return DeBruijnBytePos[((U32)((val & -(S32)val) * 0x077CB531U)) >> 27];
# endif
}
} else { /* Big Endian CPU */
if (MEM_64bits()) {
# if defined(_MSC_VER) && defined(_WIN64)
unsigned long r = 0;
_BitScanReverse64( &r, val );
return (unsigned)(r>>3);
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_clzll(val) >> 3);
# else
unsigned r;
const unsigned n32 = sizeof(size_t)*4; /* calculate this way due to compiler complaining in 32-bits mode */
if (!(val>>n32)) { r=4; } else { r=0; val>>=n32; }
if (!(val>>16)) { r+=2; val>>=8; } else { val>>=24; }
r += (!val);
return r;
# endif
} else { /* 32 bits */
# if defined(_MSC_VER)
unsigned long r = 0;
_BitScanReverse( &r, (unsigned long)val );
return (unsigned)(r>>3);
# elif defined(__GNUC__) && (__GNUC__ >= 3)
return (__builtin_clz((U32)val) >> 3);
# else
unsigned r;
if (!(val>>16)) { r=2; val>>=8; } else { r=0; val>>=24; }
r += (!val);
return r;
# endif
} }
}
// From lib/compress/zstd_compress.c
static size_t ZSTD_count(const BYTE *pIn, const BYTE *pMatch,
const BYTE *const pInLimit) {
const BYTE * const pStart = pIn;
const BYTE * const pInLoopLimit = pInLimit - (sizeof(size_t)-1);
while (pIn < pInLoopLimit) {
size_t const diff = MEM_readST(pMatch) ^ MEM_readST(pIn);
if (!diff) {
pIn += sizeof(size_t);
pMatch += sizeof(size_t);
continue;
}
pIn += ZSTD_NbCommonBytes(diff);
return (size_t)(pIn - pStart);
}
if (MEM_64bits()) {
if ((pIn < (pInLimit - 3)) && (MEM_read32(pMatch) == MEM_read32(pIn))) {
pIn += 4;
pMatch += 4;
}
}
if ((pIn < (pInLimit - 1)) && (MEM_read16(pMatch) == MEM_read16(pIn))) {
pIn += 2;
pMatch += 2;
}
if ((pIn < pInLimit) && (*pMatch == *pIn)) {
pIn++;
}
return (size_t)(pIn - pStart);
}
/**
* Count number of bytes that match backwards before pIn and pMatch.
*
* We count only bytes where pMatch > pBaes and pIn > pAnchor.
*/
U32 countBackwardsMatch(const BYTE *pIn, const BYTE *pAnchor,
const BYTE *pMatch, const BYTE *pBase) {
U32 matchLength = 0;
while (pIn > pAnchor && pMatch > pBase && pIn[-1] == pMatch[-1]) {
pIn--;
pMatch--;
matchLength++;
}
return matchLength;
}
/**
* Returns a pointer to the entry in the hash table matching the hash and
* checksum with the "longest match length" as defined below. The forward and
* backward match lengths are written to *pForwardMatchLength and
* *pBackwardMatchLength.
*
* The match length is defined based on cctx->ip and the entry's offset.
* The forward match is computed from cctx->ip and entry->offset + cctx->ibase.
* The backward match is computed backwards from cctx->ip and
* cctx->ibase only if the forward match is longer than LDM_MIN_MATCH_LENGTH.
*
*/
LDM_hashEntry *HASH_getBestEntry(const LDM_CCtx *cctx,
const hash_t hash,
const U32 checksum,
U32 *pForwardMatchLength,
U32 *pBackwardMatchLength) {
LDM_hashTable *table = cctx->hashTable;
LDM_hashEntry *bucket = getBucket(table, hash);
LDM_hashEntry *cur = bucket;
LDM_hashEntry *bestEntry = NULL;
U32 bestMatchLength = 0;
for (; cur < bucket + HASH_BUCKET_SIZE; ++cur) {
const BYTE *pMatch = cur->offset + cctx->ibase;
// Check checksum for faster check.
if (cur->checksum == checksum &&
cctx->ip - pMatch <= LDM_WINDOW_SIZE) {
U32 forwardMatchLength = ZSTD_count(cctx->ip, pMatch, cctx->iend);
U32 backwardMatchLength, totalMatchLength;
// For speed.
if (forwardMatchLength < LDM_MIN_MATCH_LENGTH) {
continue;
}
backwardMatchLength =
countBackwardsMatch(cctx->ip, cctx->anchor,
cur->offset + cctx->ibase,
cctx->ibase);
totalMatchLength = forwardMatchLength + backwardMatchLength;
if (totalMatchLength >= bestMatchLength) {
bestMatchLength = totalMatchLength;
*pForwardMatchLength = forwardMatchLength;
*pBackwardMatchLength = backwardMatchLength;
bestEntry = cur;
#ifdef ZSTD_SKIP
return cur;
#endif
}
}
}
if (bestEntry != NULL) {
return bestEntry;
}
return NULL;
}
void HASH_insert(LDM_hashTable *table,
const hash_t hash, const LDM_hashEntry entry) {
*(getBucket(table, hash) + table->bucketOffsets[hash]) = entry;
table->bucketOffsets[hash]++;
table->bucketOffsets[hash] &= HASH_BUCKET_SIZE - 1;
}
U32 HASH_getSize(const LDM_hashTable *table) {
return table->numBuckets;
}
void HASH_destroyTable(LDM_hashTable *table) {
free(table->entries);
free(table->bucketOffsets);
free(table);
}
void HASH_outputTableOccupancy(const LDM_hashTable *table) {
U32 ctr = 0;
LDM_hashEntry *cur = table->entries;
LDM_hashEntry *end = table->entries + (table->numBuckets * HASH_BUCKET_SIZE);
for (; cur < end; ++cur) {
if (cur->offset == 0) {
ctr++;
}
}
printf("Num buckets, bucket size: %d, %d\n",
table->numBuckets, HASH_BUCKET_SIZE);
printf("Hash table size, empty slots, %% empty: %u, %u, %.3f\n",
table->numEntries, ctr,
100.0 * (double)(ctr) / table->numEntries);
}
// TODO: This can be done more efficiently (but it is not that important as it
// is only used for computing stats).
static int intLog2(U32 x) {
int ret = 0;
while (x >>= 1) {
ret++;
}
return ret;
}
// Maybe we would eventually prefer to have linear rather than
// exponential buckets.
/**
void HASH_outputTableOffsetHistogram(const LDM_CCtx *cctx) {
U32 i = 0;
int buckets[32] = { 0 };
printf("\n");
printf("Hash table histogram\n");
for (; i < HASH_getSize(cctx->hashTable); i++) {
int offset = (cctx->ip - cctx->ibase) -
HASH_getEntryFromHash(cctx->hashTable, i)->offset;
buckets[intLog2(offset)]++;
}
i = 0;
for (; i < 32; i++) {
printf("2^%*d: %10u %6.3f%%\n", 2, i,
buckets[i],
100.0 * (double) buckets[i] /
(double) HASH_getSize(cctx->hashTable));
}
printf("\n");
}
*/
void LDM_printCompressStats(const LDM_compressStats *stats) {
int i = 0;
printf("=====================\n");
printf("Compression statistics\n");
printf("Window size, hash table size (bytes): 2^%u, 2^%u\n",
stats->windowSizeLog, stats->hashTableSizeLog);
printf("num matches, total match length, %% matched: %u, %llu, %.3f\n",
stats->numMatches,
stats->totalMatchLength,
100.0 * (double)stats->totalMatchLength /
(double)(stats->totalMatchLength + stats->totalLiteralLength));
printf("avg match length: %.1f\n", ((double)stats->totalMatchLength) /
(double)stats->numMatches);
printf("avg literal length, total literalLength: %.1f, %llu\n",
((double)stats->totalLiteralLength) / (double)stats->numMatches,
stats->totalLiteralLength);
printf("avg offset length: %.1f\n",
((double)stats->totalOffset) / (double)stats->numMatches);
printf("min offset, max offset: %u, %u\n",
stats->minOffset, stats->maxOffset);
printf("\n");
printf("offset histogram: offset, num matches, %% of matches\n");
for (; i <= intLog2(stats->maxOffset); i++) {
printf("2^%*d: %10u %6.3f%%\n", 2, i,
stats->offsetHistogram[i],
100.0 * (double) stats->offsetHistogram[i] /
(double) stats->numMatches);
}
printf("\n");
printf("=====================\n");
}
int LDM_isValidMatch(const BYTE *pIn, const BYTE *pMatch) {
U32 lengthLeft = LDM_MIN_MATCH_LENGTH;
const BYTE *curIn = pIn;
const BYTE *curMatch = pMatch;
if (pIn - pMatch > LDM_WINDOW_SIZE) {
return 0;
}
for (; lengthLeft >= 4; lengthLeft -= 4) {
if (MEM_read32(curIn) != MEM_read32(curMatch)) {
return 0;
}
curIn += 4;
curMatch += 4;
}
return 1;
}
hash_t HASH_hashU32(U32 value) {
return ((value * 2654435761U) >> (32 - LDM_HASHLOG));
}
/**
* Convert a sum computed from getChecksum to a hash value in the range
* of the hash table.
*/
static hash_t checksumToHash(U32 sum) {
return HASH_hashU32(sum);
}
/**
* Computes a checksum based on rsync's checksum.
*
* a(k,l) = \sum_{i = k}^l x_i (mod M)
* b(k,l) = \sum_{i = k}^l ((l - i + 1) * x_i) (mod M)
* checksum(k,l) = a(k,l) + 2^{16} * b(k,l)
*/
static U32 getChecksum(const BYTE *buf, U32 len) {
U32 i;
U32 s1, s2;
s1 = s2 = 0;
for (i = 0; i < (len - 4); i += 4) {
s2 += (4 * (s1 + buf[i])) + (3 * buf[i + 1]) +
(2 * buf[i + 2]) + (buf[i + 3]) +
(10 * CHECKSUM_CHAR_OFFSET);
s1 += buf[i] + buf[i + 1] + buf[i + 2] + buf[i + 3] +
+ (4 * CHECKSUM_CHAR_OFFSET);
}
for(; i < len; i++) {
s1 += buf[i] + CHECKSUM_CHAR_OFFSET;
s2 += s1;
}
return (s1 & 0xffff) + (s2 << 16);
}
/**
* Update a checksum computed from getChecksum(data, len).
*
* The checksum can be updated along its ends as follows:
* a(k+1, l+1) = (a(k,l) - x_k + x_{l+1}) (mod M)
* b(k+1, l+1) = (b(k,l) - (l-k+1)*x_k + (a(k+1,l+1)) (mod M)
*
* Thus toRemove should correspond to data[0].
*/
static U32 updateChecksum(U32 sum, U32 len,
BYTE toRemove, BYTE toAdd) {
U32 s1 = (sum & 0xffff) - toRemove + toAdd;
U32 s2 = (sum >> 16) - ((toRemove + CHECKSUM_CHAR_OFFSET) * len) + s1;
return (s1 & 0xffff) + (s2 << 16);
}
/**
* Update cctx->nextSum, cctx->nextHash, and cctx->nextPosHashed
* based on cctx->lastSum and cctx->lastPosHashed.
*
* This uses a rolling hash and requires that the last position hashed
* corresponds to cctx->nextIp - step.
*/
static void setNextHash(LDM_CCtx *cctx) {
#ifdef RUN_CHECKS
U32 check;
if ((cctx->nextIp - cctx->ibase != 1) &&
(cctx->nextIp - cctx->DEBUG_setNextHash != 1)) {
printf("CHECK debug fail: %zu %zu\n", cctx->nextIp - cctx->ibase,
cctx->DEBUG_setNextHash - cctx->ibase);
}
cctx->DEBUG_setNextHash = cctx->nextIp;
#endif
// cctx->nextSum = getChecksum((const char *)cctx->nextIp, LDM_HASH_LENGTH);
cctx->nextSum = updateChecksum(
cctx->lastSum, LDM_HASH_LENGTH,
cctx->lastPosHashed[0],
cctx->lastPosHashed[LDM_HASH_LENGTH]);
cctx->nextPosHashed = cctx->nextIp;
cctx->nextHash = checksumToHash(cctx->nextSum);
#if LDM_LAG
// printf("LDM_LAG %zu\n", cctx->ip - cctx->lagIp);
if (cctx->ip - cctx->ibase > LDM_LAG) {
cctx->lagSum = updateChecksum(
cctx->lagSum, LDM_HASH_LENGTH,
cctx->lagIp[0], cctx->lagIp[LDM_HASH_LENGTH]);
cctx->lagIp++;
cctx->lagHash = checksumToHash(cctx->lagSum);
}
#endif
#ifdef RUN_CHECKS
check = getChecksum(cctx->nextIp, LDM_HASH_LENGTH);
if (check != cctx->nextSum) {
printf("CHECK: setNextHash failed %u %u\n", check, cctx->nextSum);
}
if ((cctx->nextIp - cctx->lastPosHashed) != 1) {
printf("setNextHash: nextIp != lastPosHashed + 1. %zu %zu %zu\n",
cctx->nextIp - cctx->ibase, cctx->lastPosHashed - cctx->ibase,
cctx->ip - cctx->ibase);
}
#endif
}
static void putHashOfCurrentPositionFromHash(
LDM_CCtx *cctx, hash_t hash, U32 sum) {
// Hash only every HASH_ONLY_EVERY times, based on cctx->ip.
// Note: this works only when cctx->step is 1.
if (((cctx->ip - cctx->ibase) & HASH_ONLY_EVERY) == HASH_ONLY_EVERY) {
/**
const LDM_hashEntry entry = { cctx->ip - cctx->ibase ,
MEM_read32(cctx->ip) };
*/
#if LDM_LAG
// TODO: off by 1, but whatever
if (cctx->lagIp - cctx->ibase > 0) {
const LDM_hashEntry entry = { cctx->lagIp - cctx->ibase, cctx->lagSum };
HASH_insert(cctx->hashTable, cctx->lagHash, entry);
} else {
const LDM_hashEntry entry = { cctx->ip - cctx->ibase, sum };
HASH_insert(cctx->hashTable, hash, entry);
}
#else
const LDM_hashEntry entry = { cctx->ip - cctx->ibase, sum };
HASH_insert(cctx->hashTable, hash, entry);
#endif
}
cctx->lastPosHashed = cctx->ip;
cctx->lastHash = hash;
cctx->lastSum = sum;
}
/**
* Copy over the cctx->lastHash, cctx->lastSum, and cctx->lastPosHashed
* fields from the "next" fields.
*
* This requires that cctx->ip == cctx->nextPosHashed.
*/
static void LDM_updateLastHashFromNextHash(LDM_CCtx *cctx) {
#ifdef RUN_CHECKS
if (cctx->ip != cctx->nextPosHashed) {
printf("CHECK failed: updateLastHashFromNextHash %zu\n",
cctx->ip - cctx->ibase);
}
#endif
putHashOfCurrentPositionFromHash(cctx, cctx->nextHash, cctx->nextSum);
}
/**
* Insert hash of the current position into the hash table.
*/
static void LDM_putHashOfCurrentPosition(LDM_CCtx *cctx) {
U32 sum = getChecksum(cctx->ip, LDM_HASH_LENGTH);
hash_t hash = checksumToHash(sum);
#ifdef RUN_CHECKS
if (cctx->nextPosHashed != cctx->ip && (cctx->ip != cctx->ibase)) {
printf("CHECK failed: putHashOfCurrentPosition %zu\n",
cctx->ip - cctx->ibase);
}
#endif
putHashOfCurrentPositionFromHash(cctx, hash, sum);
}
U32 LDM_countMatchLength(const BYTE *pIn, const BYTE *pMatch,
const BYTE *pInLimit) {
const BYTE * const pStart = pIn;
while (pIn < pInLimit - 1) {
BYTE const diff = (*pMatch) ^ *(pIn);
if (!diff) {
pIn++;
pMatch++;
continue;
}
return (U32)(pIn - pStart);
}
return (U32)(pIn - pStart);
}
void LDM_outputConfiguration(void) {
printf("=====================\n");
printf("Configuration\n");
printf("Window size log: %d\n", LDM_WINDOW_SIZE_LOG);
printf("Min match, hash length: %d, %d\n",
LDM_MIN_MATCH_LENGTH, LDM_HASH_LENGTH);
printf("LDM_MEMORY_USAGE: %d\n", LDM_MEMORY_USAGE);
printf("HASH_ONLY_EVERY_LOG: %d\n", HASH_ONLY_EVERY_LOG);
printf("LDM_LAG %d\n", LDM_LAG);
printf("=====================\n");
}
void LDM_readHeader(const void *src, U64 *compressedSize,
U64 *decompressedSize) {
const BYTE *ip = (const BYTE *)src;
*compressedSize = MEM_readLE64(ip);
ip += sizeof(U64);
*decompressedSize = MEM_readLE64(ip);
// ip += sizeof(U64);
}
void LDM_initializeCCtx(LDM_CCtx *cctx,
const void *src, size_t srcSize,
void *dst, size_t maxDstSize) {
cctx->isize = srcSize;
cctx->maxOSize = maxDstSize;
cctx->ibase = (const BYTE *)src;
cctx->ip = cctx->ibase;
cctx->iend = cctx->ibase + srcSize;
cctx->ihashLimit = cctx->iend - LDM_HASH_LENGTH;
cctx->imatchLimit = cctx->iend - LDM_MIN_MATCH_LENGTH;
cctx->obase = (BYTE *)dst;
cctx->op = (BYTE *)dst;
cctx->anchor = cctx->ibase;
memset(&(cctx->stats), 0, sizeof(cctx->stats));
cctx->hashTable = HASH_createTable(LDM_HASHTABLESIZE_U64);
cctx->stats.minOffset = UINT_MAX;
cctx->stats.windowSizeLog = LDM_WINDOW_SIZE_LOG;
cctx->stats.hashTableSizeLog = LDM_MEMORY_USAGE;
cctx->lastPosHashed = NULL;
cctx->step = 1; // Fixed to be 1 for now. Changing may break things.
cctx->nextIp = cctx->ip + cctx->step;
cctx->nextPosHashed = 0;
cctx->DEBUG_setNextHash = 0;
}
void LDM_destroyCCtx(LDM_CCtx *cctx) {
HASH_destroyTable(cctx->hashTable);
}
/**
* Finds the "best" match.
*
* Returns 0 if successful and 1 otherwise (i.e. no match can be found
* in the remaining input that is long enough).
*
* forwardMatchLength contains the forward length of the match.
*/
static int LDM_findBestMatch(LDM_CCtx *cctx, const BYTE **match,
U32 *forwardMatchLength, U32 *backwardMatchLength) {
LDM_hashEntry *entry = NULL;
cctx->nextIp = cctx->ip + cctx->step;
while (entry == NULL) {
hash_t h;
U32 sum;
setNextHash(cctx);
h = cctx->nextHash;
sum = cctx->nextSum;
cctx->ip = cctx->nextIp;
cctx->nextIp += cctx->step;
if (cctx->ip > cctx->imatchLimit) {
return 1;
}
entry = HASH_getBestEntry(cctx, h, sum,
forwardMatchLength, backwardMatchLength);
if (entry != NULL) {
*match = entry->offset + cctx->ibase;
}
putHashOfCurrentPositionFromHash(cctx, h, sum);
}
setNextHash(cctx);
return 0;
}
void LDM_encodeLiteralLengthAndLiterals(
LDM_CCtx *cctx, BYTE *pToken, const U32 literalLength) {
/* Encode the literal length. */
if (literalLength >= RUN_MASK) {
int len = (int)literalLength - RUN_MASK;
*pToken = (RUN_MASK << ML_BITS);
for (; len >= 255; len -= 255) {
*(cctx->op)++ = 255;
}
*(cctx->op)++ = (BYTE)len;
} else {
*pToken = (BYTE)(literalLength << ML_BITS);
}
/* Encode the literals. */
memcpy(cctx->op, cctx->anchor, literalLength);
cctx->op += literalLength;
}
void LDM_outputBlock(LDM_CCtx *cctx,
const U32 literalLength,
const U32 offset,
const U32 matchLength) {
BYTE *pToken = cctx->op++;
/* Encode the literal length and literals. */
LDM_encodeLiteralLengthAndLiterals(cctx, pToken, literalLength);
/* Encode the offset. */
MEM_write32(cctx->op, offset);
cctx->op += LDM_OFFSET_SIZE;
/* Encode the match length. */
if (matchLength >= ML_MASK) {
unsigned matchLengthRemaining = matchLength;
*pToken += ML_MASK;
matchLengthRemaining -= ML_MASK;
MEM_write32(cctx->op, 0xFFFFFFFF);
while (matchLengthRemaining >= 4*0xFF) {
cctx->op += 4;
MEM_write32(cctx->op, 0xffffffff);
matchLengthRemaining -= 4*0xFF;
}
cctx->op += matchLengthRemaining / 255;
*(cctx->op)++ = (BYTE)(matchLengthRemaining % 255);
} else {
*pToken += (BYTE)(matchLength);
}
}
// TODO: maxDstSize is unused. This function may seg fault when writing
// beyond the size of dst, as it does not check maxDstSize. Writing to
// a buffer and performing checks is a possible solution.
//
// This is based upon lz4.
size_t LDM_compress(const void *src, size_t srcSize,
void *dst, size_t maxDstSize) {
LDM_CCtx cctx;
const BYTE *match = NULL;
U32 forwardMatchLength = 0;
U32 backwardsMatchLength = 0;
LDM_initializeCCtx(&cctx, src, srcSize, dst, maxDstSize);
LDM_outputConfiguration();
/* Hash the first position and put it into the hash table. */
LDM_putHashOfCurrentPosition(&cctx);
#if LDM_LAG
cctx.lagIp = cctx.ip;
cctx.lagHash = cctx.lastHash;
cctx.lagSum = cctx.lastSum;
#endif
/**
* Find a match.
* If no more matches can be found (i.e. the length of the remaining input
* is less than the minimum match length), then stop searching for matches
* and encode the final literals.
*/
while (LDM_findBestMatch(&cctx, &match, &forwardMatchLength,
&backwardsMatchLength) == 0) {
#ifdef COMPUTE_STATS
cctx.stats.numMatches++;
#endif
cctx.ip -= backwardsMatchLength;
match -= backwardsMatchLength;
/**
* Write current block (literals, literal length, match offset, match
* length) and update pointers and hashes.
*/
{
const U32 literalLength = cctx.ip - cctx.anchor;
const U32 offset = cctx.ip - match;
const U32 matchLength = forwardMatchLength +
backwardsMatchLength -
LDM_MIN_MATCH_LENGTH;
LDM_outputBlock(&cctx, literalLength, offset, matchLength);
#ifdef COMPUTE_STATS
cctx.stats.totalLiteralLength += literalLength;
cctx.stats.totalOffset += offset;
cctx.stats.totalMatchLength += matchLength + LDM_MIN_MATCH_LENGTH;
cctx.stats.minOffset =
offset < cctx.stats.minOffset ? offset : cctx.stats.minOffset;
cctx.stats.maxOffset =
offset > cctx.stats.maxOffset ? offset : cctx.stats.maxOffset;
cctx.stats.offsetHistogram[(U32)intLog2(offset)]++;
#endif
// Move ip to end of block, inserting hashes at each position.
cctx.nextIp = cctx.ip + cctx.step;
while (cctx.ip < cctx.anchor + LDM_MIN_MATCH_LENGTH +
matchLength + literalLength) {
if (cctx.ip > cctx.lastPosHashed) {
// TODO: Simplify.
LDM_updateLastHashFromNextHash(&cctx);
setNextHash(&cctx);
}
cctx.ip++;
cctx.nextIp++;
}
}
// Set start of next block to current input pointer.
cctx.anchor = cctx.ip;
LDM_updateLastHashFromNextHash(&cctx);
}
// HASH_outputTableOffsetHistogram(&cctx);
/* Encode the last literals (no more matches). */
{
const U32 lastRun = cctx.iend - cctx.anchor;
BYTE *pToken = cctx.op++;
LDM_encodeLiteralLengthAndLiterals(&cctx, pToken, lastRun);
}
#ifdef COMPUTE_STATS
LDM_printCompressStats(&cctx.stats);
HASH_outputTableOccupancy(cctx.hashTable);
#endif
{
const size_t ret = cctx.op - cctx.obase;
LDM_destroyCCtx(&cctx);
return ret;
}
}
struct LDM_DCtx {
size_t compressedSize;
size_t maxDecompressedSize;
const BYTE *ibase; /* Base of input */
const BYTE *ip; /* Current input position */
const BYTE *iend; /* End of source */
const BYTE *obase; /* Base of output */
BYTE *op; /* Current output position */
const BYTE *oend; /* End of output */
};
void LDM_initializeDCtx(LDM_DCtx *dctx,
const void *src, size_t compressedSize,
void *dst, size_t maxDecompressedSize) {
dctx->compressedSize = compressedSize;
dctx->maxDecompressedSize = maxDecompressedSize;
dctx->ibase = src;
dctx->ip = (const BYTE *)src;
dctx->iend = dctx->ip + dctx->compressedSize;
dctx->op = dst;
dctx->oend = dctx->op + dctx->maxDecompressedSize;
}
size_t LDM_decompress(const void *src, size_t compressedSize,
void *dst, size_t maxDecompressedSize) {
LDM_DCtx dctx;
LDM_initializeDCtx(&dctx, src, compressedSize, dst, maxDecompressedSize);
while (dctx.ip < dctx.iend) {
BYTE *cpy;
const BYTE *match;
size_t length, offset;
/* Get the literal length. */
const unsigned token = *(dctx.ip)++;
if ((length = (token >> ML_BITS)) == RUN_MASK) {
unsigned s;
do {
s = *(dctx.ip)++;
length += s;
} while (s == 255);
}
/* Copy the literals. */
cpy = dctx.op + length;
memcpy(dctx.op, dctx.ip, length);
dctx.ip += length;
dctx.op = cpy;
//TODO : dynamic offset size
offset = MEM_read32(dctx.ip);
dctx.ip += LDM_OFFSET_SIZE;
match = dctx.op - offset;
/* Get the match length. */
length = token & ML_MASK;
if (length == ML_MASK) {
unsigned s;
do {
s = *(dctx.ip)++;
length += s;
} while (s == 255);
}
length += LDM_MIN_MATCH_LENGTH;
/* Copy match. */
cpy = dctx.op + length;
// Inefficient for now.
while (match < cpy - offset && dctx.op < dctx.oend) {
*(dctx.op)++ = *match++;
}
}
return dctx.op - (BYTE *)dst;
}
// TODO: implement and test hash function
void LDM_test(const BYTE *src) {
(void)src;
}