#include <string.h>
#include "delta.h"
+#include "git-compat-util.h"
/* maximum hash entry list for the same hash bucket */
#define HASH_LIMIT 64
const void *src_buf;
unsigned long src_size;
unsigned int hash_mask;
- struct index_entry *hash[0];
+ struct index_entry *hash[FLEX_ARRAY];
};
struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
{
- unsigned int i, hsize, hmask, entries, *hash_count;
+ unsigned int i, hsize, hmask, entries, prev_val, *hash_count;
const unsigned char *data, *buffer = buf;
struct delta_index *index;
struct index_entry *entry, **hash;
void *mem;
+ unsigned long memsize;
if (!buf || !bufsize)
return NULL;
/* Determine index hash size. Note that indexing skips the
- first byte to allow for optimizing the rabin polynomial
+ first byte to allow for optimizing the Rabin's polynomial
initialization in create_delta(). */
entries = (bufsize - 1) / RABIN_WINDOW;
hsize = entries / 4;
- for (i = 4; (1 << i) < hsize && i < 31; i++);
+ for (i = 4; (1u << i) < hsize && i < 31; i++);
hsize = 1 << i;
hmask = hsize - 1;
/* allocate lookup index */
- mem = malloc(sizeof(*index) +
- sizeof(*hash) * hsize +
- sizeof(*entry) * entries);
+ memsize = sizeof(*index) +
+ sizeof(*hash) * hsize +
+ sizeof(*entry) * entries;
+ mem = malloc(memsize);
if (!mem)
return NULL;
index = mem;
}
/* then populate the index */
- data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW;
- while (data >= buffer) {
+ prev_val = ~0;
+ for (data = buffer + entries * RABIN_WINDOW - RABIN_WINDOW;
+ data >= buffer;
+ data -= RABIN_WINDOW) {
unsigned int val = 0;
for (i = 1; i <= RABIN_WINDOW; i++)
val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT];
- i = val & hmask;
- entry->ptr = data + RABIN_WINDOW;
- entry->val = val;
- entry->next = hash[i];
- hash[i] = entry++;
- hash_count[i]++;
- data -= RABIN_WINDOW;
+ if (val == prev_val) {
+ /* keep the lowest of consecutive identical blocks */
+ entry[-1].ptr = data + RABIN_WINDOW;
+ } else {
+ prev_val = val;
+ i = val & hmask;
+ entry->ptr = data + RABIN_WINDOW;
+ entry->val = val;
+ entry->next = hash[i];
+ hash[i] = entry++;
+ hash_count[i]++;
+ }
}
/*
* Determine a limit on the number of entries in the same hash
- * bucket. This guard us against patological data sets causing
+ * bucket. This guards us against pathological data sets causing
* really bad hash distribution with most entries in the same hash
* bucket that would bring us to O(m*n) computing costs (m and n
* corresponding to reference and target buffer sizes).
/*
* The maximum size for any opcode sequence, including the initial header
- * plus rabin window plus biggest copy.
+ * plus Rabin window plus biggest copy.
*/
#define MAX_OP_SIZE (5 + 5 + 1 + RABIN_WINDOW + 7)
const void *trg_buf, unsigned long trg_size,
unsigned long *delta_size, unsigned long max_size)
{
- unsigned int i, outpos, outsize, hash_mask, val;
+ unsigned int i, outpos, outsize, val;
int inscnt;
const unsigned char *ref_data, *ref_top, *data, *top;
unsigned char *out;
ref_data = index->src_buf;
ref_top = ref_data + index->src_size;
data = trg_buf;
- top = trg_buf + trg_size;
- hash_mask = index->hash_mask;
+ top = (const unsigned char *) trg_buf + trg_size;
outpos++;
val = 0;
struct index_entry *entry;
val ^= U[data[-RABIN_WINDOW]];
val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
- i = val & hash_mask;
+ i = val & index->hash_mask;
for (entry = index->hash[i]; entry; entry = entry->next) {
const unsigned char *ref = entry->ptr;
const unsigned char *src = data;
outsize = max_size + MAX_OP_SIZE + 1;
if (max_size && outpos > max_size)
break;
- out = realloc(out, outsize);
+ out = xrealloc(out, outsize);
if (!out) {
free(tmp);
return NULL;