#define LDM_HASH_ENTRY_SIZE_LOG 2
#endif
+// Force the "probability" of insertion to be some value.
+// Entries are inserted into the table HASH_ONLY_EVERY + 1 times "on average".
+
//#define HASH_ONLY_EVERY_LOG 7
#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)
#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 NUM_HASH_BUCKETS_LOG ((LDM_MEMORY_USAGE)-(LDM_HASH_ENTRY_SIZE_LOG)-(HASH_BUCKET_SIZE_LOG))
#define HASH_CHAR_OFFSET 10
-// Take first match only.
+// Take the first match in the hash bucket only.
//#define ZSTD_SKIP
-//#define RUN_CHECKS
-
static const U64 prime8bytes = 11400714785074694791ULL;
// Type of the small hash used to index into the hash table.
const BYTE *lagIp;
U64 lagHash;
-
-#ifdef RUN_CHECKS
- const BYTE *DEBUG_setNextHash;
-#endif
};
struct LDM_hashTable {
* 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) {
+static LDM_hashTable *HASH_createTable(U32 size) {
LDM_hashTable *table = malloc(sizeof(LDM_hashTable));
table->numBuckets = size >> HASH_BUCKET_SIZE_LOG;
table->numEntries = size;
/**
* Count number of bytes that match backwards before pIn and pMatch.
*
- * We count only bytes where pMatch > pBaes and pIn > pAnchor.
+ * We count only bytes where pMatch > pBase and pIn > pAnchor.
*/
static size_t countBackwardsMatch(const BYTE *pIn, const BYTE *pAnchor,
const BYTE *pMatch, const BYTE *pBase) {
* 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,
- U64 *pForwardMatchLength,
- U64 *pBackwardMatchLength) {
+static LDM_hashEntry *HASH_getBestEntry(const LDM_CCtx *cctx,
+ const hash_t hash,
+ const U32 checksum,
+ U64 *pForwardMatchLength,
+ U64 *pBackwardMatchLength) {
LDM_hashTable *table = cctx->hashTable;
LDM_hashEntry *bucket = getBucket(table, hash);
LDM_hashEntry *cur = bucket;
return NULL;
}
-void HASH_insert(LDM_hashTable *table,
- const hash_t hash, const LDM_hashEntry entry) {
+/**
+ * Insert an entry into the hash table. The table uses a "circular buffer",
+ * with the oldest entry overwritten.
+ */
+static 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) {
+static void HASH_destroyTable(LDM_hashTable *table) {
free(table->entries);
free(table->bucketOffsets);
free(table);
}
-void HASH_outputTableOccupancy(const LDM_hashTable *table) {
+static 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);
// The number of buckets is repeated as a check for now.
printf("Num buckets, bucket size: %d (2^%d), %d\n",
- table->numBuckets, LDM_HASHLOG, HASH_BUCKET_SIZE);
+ table->numBuckets, NUM_HASH_BUCKETS_LOG, HASH_BUCKET_SIZE);
printf("Hash table size, empty slots, %% empty: %u, %u, %.3f\n",
table->numEntries, ctr,
100.0 * (double)(ctr) / table->numEntries);
}
/**
- * Return the upper (most significant) LDM_HASHLOG bits.
+ * Return the upper (most significant) NUM_HASH_BUCKETS_LOG bits.
*/
static hash_t getSmallHash(U64 hash) {
- return hash >> (64 - LDM_HASHLOG);
+ return hash >> (64 - NUM_HASH_BUCKETS_LOG);
}
/**
- * Return the 32 bits after the upper LDM_HASHLOG bits.
+ * Return the 32 bits after the upper NUM_HASH_BUCKETS_LOG bits.
*/
static U32 getChecksum(U64 hash) {
- return (hash >> (64 - 32 - LDM_HASHLOG)) & 0xFFFFFFFF;
+ return (hash >> (64 - 32 - NUM_HASH_BUCKETS_LOG)) & 0xFFFFFFFF;
}
#if INSERT_BY_TAG
static U32 lowerBitsFromHfHash(U64 hash) {
- // The number of bits used so far is LDM_HASHLOG + 32.
- // So there are 32 - LDM_HASHLOG bits left.
+ // The number of bits used so far is NUM_HASH_BUCKETS_LOG + 32.
+ // So there are 32 - NUM_HASH_BUCKETS_LOG bits left.
// Occasional hashing requires HASH_ONLY_EVERY_LOG bits.
// So if 32 - LDMHASHLOG < HASH_ONLY_EVERY_LOG, just return lower bits
// allowing for reuse of bits.
- if (32 - LDM_HASHLOG < HASH_ONLY_EVERY_LOG) {
+ if (32 - NUM_HASH_BUCKETS_LOG < HASH_ONLY_EVERY_LOG) {
return hash & HASH_ONLY_EVERY;
} else {
- // Otherwise shift by (32 - LDM_HASHLOG - HASH_ONLY_EVERY_LOG) bits first.
- return (hash >> (32 - LDM_HASHLOG - HASH_ONLY_EVERY_LOG)) &
+ // Otherwise shift by
+ // (32 - NUM_HASH_BUCKETS_LOG - HASH_ONLY_EVERY_LOG) bits first.
+ return (hash >> (32 - NUM_HASH_BUCKETS_LOG - HASH_ONLY_EVERY_LOG)) &
HASH_ONLY_EVERY;
}
}
* corresponds to cctx->nextIp - step.
*/
static void setNextHash(LDM_CCtx *cctx) {
-#ifdef RUN_CHECKS
- U64 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->nextHash = updateHash(
cctx->lastHash, LDM_HASH_LENGTH,
cctx->lastPosHashed[0],
cctx->lagIp++;
}
#endif
-
-#ifdef RUN_CHECKS
- check = getHash(cctx->nextIp, LDM_HASH_LENGTH);
-
- if (check != cctx->nextHash) {
- printf("CHECK: setNextHash failed %llu %llu\n", check, cctx->nextHash);
- }
-
- 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, U64 hash) {
* 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);
}
static void LDM_putHashOfCurrentPosition(LDM_CCtx *cctx) {
U64 hash = getHash(cctx->ip, LDM_HASH_LENGTH);
-#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);
}
cctx->step = 1; // Fixed to be 1 for now. Changing may break things.
cctx->nextIp = cctx->ip + cctx->step;
cctx->nextPosHashed = 0;
-
-#ifdef RUN_CHECKS
- cctx->DEBUG_setNextHash = 0;
-#endif
}
void LDM_destroyCCtx(LDM_CCtx *cctx) {
cctx.lagIp = cctx.ip;
cctx.lagHash = cctx.lastHash;
+
/**
* Find a match.
* If no more matches can be found (i.e. the length of the remaining input
+++ /dev/null
-#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_HASHTABLESIZE_U32 ((LDM_HASHTABLESIZE) >> 2)
-#define LDM_HASHTABLESIZE_U64 ((LDM_HASHTABLESIZE) >> 3)
-
-#define LDM_HASH_ENTRY_SIZE_LOG 3
-//#define HASH_ONLY_EVERY_LOG 7
-#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 CHECKSUM_CHAR_OFFSET 10
-
-// Take first match only.
-//#define ZSTD_SKIP
-
-//#define RUN_CHECKS
-
-typedef U32 hash_t;
-
-typedef struct LDM_hashEntry {
- U32 offset;
- U32 checksum;
-} LDM_hashEntry;
-
-struct LDM_compressStats {
- U32 windowSizeLog, hashTableSizeLog;
- U32 numMatches;
- U64 totalMatchLength;
- U64 totalLiteralLength;
- U64 totalOffset;
-
- U32 matchLengthHistogram[32];
-
- U32 minOffset, maxOffset;
-
- 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;
-
- 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;
- LDM_hashEntry *entries;
-
- BYTE *bucketOffsets;
-};
-
-/**
- * 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;
-}
-
-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 | match length histogram\n");
- printf("offset/ML, num matches, %% of matches | num matches, %% of matches\n");
-
- for (; i <= intLog2(stats->maxOffset); i++) {
- printf("2^%*d: %10u %6.3f%% |2^%*d: %10u %6.3f \n",
- 2, i,
- stats->offsetHistogram[i],
- 100.0 * (double) stats->offsetHistogram[i] /
- (double) stats->numMatches,
- 2, i,
- stats->matchLengthHistogram[i],
- 100.0 * (double) stats->matchLengthHistogram[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 = 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
- 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) {
-#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);
-}
-
-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 U64 literalLength) {
- /* Encode the literal length. */
- if (literalLength >= RUN_MASK) {
- U64 len = (U64)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 U64 literalLength,
- const U32 offset,
- const U64 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 U64 literalLength = cctx.ip - cctx.anchor;
- const U32 offset = cctx.ip - match;
- const U64 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)]++;
- cctx.stats.matchLengthHistogram[
- (U32)intLog2(matchLength + LDM_MIN_MATCH_LENGTH)]++;
-#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);
- }
-
- /* 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;
- }
-}
-
-void LDM_outputConfiguration(void) {
- printf("=====================\n");
- printf("Configuration\n");
- printf("LDM_WINDOW_SIZE_LOG: %d\n", LDM_WINDOW_SIZE_LOG);
- printf("LDM_MIN_MATCH_LENGTH, LDM_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("HASH_BUCKET_SIZE_LOG: %d\n", HASH_BUCKET_SIZE_LOG);
- printf("LDM_LAG %d\n", LDM_LAG);
- printf("=====================\n");
-}
-
-
-
projects / thirdparty / zstd.git / commitdiff
