undef/git-commit-vandalism
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Revert "Revert "diff-delta: produce optimal pack data""

Browse Source
This commit is contained in:
Junio C Hamano 2006-02-27 21:37:56 -08:00
parent eae3fe5e50
commit bec2a69fe4
1 changed files with 30 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

77
diff-delta.c
View File

@ -20,21 +20,11 @@
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
#include <zlib.h>
#include "delta.h" #include "delta.h"
/* block size: min = 16, max = 64k, power of 2 */
#define BLK_SIZE 16
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define GR_PRIME 0x9e370001
#define HASH(v, shift) (((unsigned int)(v) * GR_PRIME) >> (shift))
struct index { struct index {
const unsigned char *ptr; const unsigned char *ptr;
unsigned int val;
struct index *next; struct index *next;
}; };
@ -42,21 +32,21 @@ static struct index ** delta_index(const unsigned char *buf,
unsigned long bufsize, unsigned long bufsize,
unsigned int *hash_shift) unsigned int *hash_shift)
{ {
unsigned int hsize, hshift, entries, blksize, i; unsigned long hsize;
unsigned int hshift, i;
const unsigned char *data; const unsigned char *data;
struct index *entry, **hash; struct index *entry, **hash;
void *mem; void *mem;
/* determine index hash size */ /* determine index hash size */
entries = (bufsize + BLK_SIZE - 1) / BLK_SIZE; hsize = bufsize / 4;
hsize = entries / 4; for (i = 8; (1 << i) < hsize && i < 16; i++);
for (i = 4; (1 << i) < hsize && i < 16; i++);
hsize = 1 << i; hsize = 1 << i;
hshift = 32 - i; hshift = i - 8;
*hash_shift = hshift; *hash_shift = hshift;
/* allocate lookup index */ /* allocate lookup index */
mem = malloc(hsize * sizeof(*hash) + entries * sizeof(*entry)); mem = malloc(hsize * sizeof(*hash) + bufsize * sizeof(*entry));
if (!mem) if (!mem)
return NULL; return NULL;
hash = mem; hash = mem;
@ -64,17 +54,12 @@ static struct index ** delta_index(const unsigned char *buf,
memset(hash, 0, hsize * sizeof(*hash)); memset(hash, 0, hsize * sizeof(*hash));
/* then populate it */ /* then populate it */
data = buf + entries * BLK_SIZE - BLK_SIZE; data = buf + bufsize - 2;
blksize = bufsize - (data - buf); while (data > buf) {
while (data >= buf) { entry->ptr = --data;
unsigned int val = adler32(0, data, blksize); i = data[0] ^ data[1] ^ (data[2] << hshift);
i = HASH(val, hshift);
entry->ptr = data;
entry->val = val;
entry->next = hash[i]; entry->next = hash[i];
hash[i] = entry++; hash[i] = entry++;
blksize = BLK_SIZE;
data -= BLK_SIZE;
} }
return hash; return hash;
@ -141,29 +126,27 @@ void *diff_delta(void *from_buf, unsigned long from_size,
while (data < top) { while (data < top) {
unsigned int moff = 0, msize = 0; unsigned int moff = 0, msize = 0;
unsigned int blksize = MIN(top - data, BLK_SIZE); if (data + 2 < top) {
unsigned int val = adler32(0, data, blksize); i = data[0] ^ data[1] ^ (data[2] << hash_shift);
i = HASH(val, hash_shift); for (entry = hash[i]; entry; entry = entry->next) {
for (entry = hash[i]; entry; entry = entry->next) { const unsigned char *ref = entry->ptr;
const unsigned char *ref = entry->ptr; const unsigned char *src = data;
const unsigned char *src = data; unsigned int ref_size = ref_top - ref;
unsigned int ref_size = ref_top - ref; if (ref_size > top - src)
if (entry->val != val) ref_size = top - src;
continue; if (ref_size > 0x10000)
if (ref_size > top - src) ref_size = 0x10000;
ref_size = top - src; if (ref_size <= msize)
while (ref_size && *src++ == *ref) {
ref++;
ref_size--;
}
ref_size = ref - entry->ptr;
if (ref_size > msize) {
/* this is our best match so far */
moff = entry->ptr - ref_data;
msize = ref_size;
if (msize >= 0x10000) {
msize = 0x10000;
break; break;
while (ref_size && *src++ == *ref) {
ref++;
ref_size--;
}
ref_size = ref - entry->ptr;
if (msize < ref - entry->ptr) {
/* this is our best match so far */
msize = ref - entry->ptr;
moff = entry->ptr - ref_data;
} }
} }
} }