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diff-delta: big code simplification
This is much smaller and hopefully clearer code now. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Nicolas Pitre
Junio C Hamano
parent
fe474b588b
commit
8e1454b5ad
227
diff-delta.c
227
diff-delta.c
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@ -19,8 +19,9 @@
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <zlib.h>
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#include "delta.h"
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#include "zlib.h"
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/* block size: min = 16, max = 64k, power of 2 */
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@ -29,123 +30,54 @@
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#define MIN(a, b) ((a) < (b) ? (a) : (b))
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#define GR_PRIME 0x9e370001
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#define HASH(v, b) (((unsigned int)(v) * GR_PRIME) >> (32 - (b)))
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static unsigned int hashbits(unsigned int size)
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{
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unsigned int val = 1, bits = 0;
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while (val < size && bits < 32) {
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val <<= 1;
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bits++;
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}
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return bits ? bits: 1;
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}
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#define HASH(v, shift) (((unsigned int)(v) * GR_PRIME) >> (shift))
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typedef struct s_chanode {
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struct s_chanode *next;
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int icurr;
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} chanode_t;
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typedef struct s_chastore {
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int isize, nsize;
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chanode_t *ancur;
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} chastore_t;
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static void cha_init(chastore_t *cha, int isize, int icount)
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{
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cha->isize = isize;
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cha->nsize = icount * isize;
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cha->ancur = NULL;
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}
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static void *cha_alloc(chastore_t *cha)
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{
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chanode_t *ancur;
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void *data;
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ancur = cha->ancur;
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if (!ancur || ancur->icurr == cha->nsize) {
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ancur = malloc(sizeof(chanode_t) + cha->nsize);
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if (!ancur)
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return NULL;
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ancur->icurr = 0;
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ancur->next = cha->ancur;
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cha->ancur = ancur;
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}
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data = (void *)ancur + sizeof(chanode_t) + ancur->icurr;
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ancur->icurr += cha->isize;
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return data;
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}
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static void cha_free(chastore_t *cha)
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{
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chanode_t *cur = cha->ancur;
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while (cur) {
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chanode_t *tmp = cur;
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cur = cur->next;
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free(tmp);
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}
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}
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typedef struct s_bdrecord {
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struct s_bdrecord *next;
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unsigned int fp;
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struct index {
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const unsigned char *ptr;
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} bdrecord_t;
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unsigned int val;
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struct index *next;
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};
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typedef struct s_bdfile {
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chastore_t cha;
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unsigned int fphbits;
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bdrecord_t **fphash;
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} bdfile_t;
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static int delta_prepare(const unsigned char *buf, int bufsize, bdfile_t *bdf)
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static struct index ** delta_index(const unsigned char *buf,
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unsigned long bufsize,
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unsigned int *hash_shift)
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{
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unsigned int fphbits;
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int i, hsize;
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const unsigned char *data, *top;
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bdrecord_t *brec;
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bdrecord_t **fphash;
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unsigned int hsize, hshift, entries, blksize, i;
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const unsigned char *data;
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struct index *entry, **hash;
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void *mem;
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fphbits = hashbits(bufsize / BLK_SIZE + 1);
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hsize = 1 << fphbits;
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fphash = malloc(hsize * sizeof(bdrecord_t *));
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if (!fphash)
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return -1;
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for (i = 0; i < hsize; i++)
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fphash[i] = NULL;
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cha_init(&bdf->cha, sizeof(bdrecord_t), hsize / 4 + 1);
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/* determine index hash size */
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entries = (bufsize + BLK_SIZE - 1) / BLK_SIZE;
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hsize = entries / 4;
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for (i = 4; (1 << i) < hsize && i < 16; i++);
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hsize = 1 << i;
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hshift = 32 - i;
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*hash_shift = hshift;
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top = buf + bufsize;
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data = buf + (bufsize / BLK_SIZE) * BLK_SIZE;
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if (data == top)
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/* allocate lookup index */
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mem = malloc(hsize * sizeof(*hash) + entries * sizeof(*entry));
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if (!mem)
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return NULL;
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hash = mem;
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entry = mem + hsize * sizeof(*hash);
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memset(hash, 0, hsize * sizeof(*hash));
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/* then populate it */
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data = buf + entries * BLK_SIZE - BLK_SIZE;
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blksize = bufsize - (data - buf);
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while (data >= buf) {
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unsigned int val = adler32(0, data, blksize);
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i = HASH(val, hshift);
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entry->ptr = data;
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entry->val = val;
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entry->next = hash[i];
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hash[i] = entry++;
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blksize = BLK_SIZE;
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data -= BLK_SIZE;
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}
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for ( ; data >= buf; data -= BLK_SIZE) {
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brec = cha_alloc(&bdf->cha);
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if (!brec) {
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cha_free(&bdf->cha);
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free(fphash);
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return -1;
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}
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brec->fp = adler32(0, data, MIN(BLK_SIZE, top - data));
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brec->ptr = data;
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i = HASH(brec->fp, fphbits);
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brec->next = fphash[i];
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fphash[i] = brec;
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}
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bdf->fphbits = fphbits;
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bdf->fphash = fphash;
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return 0;
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}
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static void delta_cleanup(bdfile_t *bdf)
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{
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free(bdf->fphash);
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cha_free(&bdf->cha);
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return hash;
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}
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/* provide the size of the copy opcode given the block offset and size */
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@ -161,23 +93,24 @@ void *diff_delta(void *from_buf, unsigned long from_size,
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unsigned long *delta_size,
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unsigned long max_size)
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{
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unsigned int i, outpos, outsize, inscnt, csize, msize, moff;
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unsigned int fp;
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const unsigned char *ref_data, *ref_top, *data, *top, *ptr1, *ptr2;
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unsigned char *out, *orig;
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bdrecord_t *brec;
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bdfile_t bdf;
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unsigned int i, outpos, outsize, inscnt, hash_shift;
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const unsigned char *ref_data, *ref_top, *data, *top;
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unsigned char *out;
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struct index *entry, **hash;
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if (!from_size || !to_size || delta_prepare(from_buf, from_size, &bdf))
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if (!from_size || !to_size)
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return NULL;
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hash = delta_index(from_buf, from_size, &hash_shift);
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if (!hash)
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return NULL;
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outpos = 0;
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outsize = 8192;
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if (max_size && outsize >= max_size)
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outsize = max_size + MAX_OP_SIZE + 1;
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out = malloc(outsize);
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if (!out) {
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delta_cleanup(&bdf);
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free(hash);
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return NULL;
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}
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@ -205,28 +138,32 @@ void *diff_delta(void *from_buf, unsigned long from_size,
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}
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inscnt = 0;
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moff = 0;
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while (data < top) {
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msize = 0;
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fp = adler32(0, data, MIN(top - data, BLK_SIZE));
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i = HASH(fp, bdf.fphbits);
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for (brec = bdf.fphash[i]; brec; brec = brec->next) {
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if (brec->fp == fp) {
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csize = ref_top - brec->ptr;
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if (csize > top - data)
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csize = top - data;
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for (ptr1 = brec->ptr, ptr2 = data;
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csize && *ptr1 == *ptr2;
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csize--, ptr1++, ptr2++);
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csize = ptr1 - brec->ptr;
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if (csize > msize) {
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moff = brec->ptr - ref_data;
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msize = csize;
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if (msize >= 0x10000) {
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msize = 0x10000;
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break;
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}
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while (data < top) {
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unsigned int moff = 0, msize = 0;
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unsigned int blksize = MIN(top - data, BLK_SIZE);
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unsigned int val = adler32(0, data, blksize);
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i = HASH(val, hash_shift);
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for (entry = hash[i]; entry; entry = entry->next) {
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const unsigned char *ref = entry->ptr;
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const unsigned char *src = data;
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unsigned int ref_size = ref_top - ref;
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if (entry->val != val)
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continue;
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if (ref_size > top - src)
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ref_size = top - src;
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while (ref_size && *src++ == *ref) {
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ref++;
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ref_size--;
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}
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ref_size = ref - entry->ptr;
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if (ref_size > msize) {
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/* this is our best match so far */
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moff = entry->ptr - ref_data;
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msize = ref_size;
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if (msize >= 0x10000) {
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msize = 0x10000;
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break;
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}
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}
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}
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@ -241,13 +178,15 @@ void *diff_delta(void *from_buf, unsigned long from_size,
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inscnt = 0;
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}
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} else {
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unsigned char *op;
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if (inscnt) {
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out[outpos - inscnt - 1] = inscnt;
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inscnt = 0;
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}
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data += msize;
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orig = out + outpos++;
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op = out + outpos++;
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i = 0x80;
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if (moff & 0xff) { out[outpos++] = moff; i |= 0x01; }
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@ -262,7 +201,7 @@ void *diff_delta(void *from_buf, unsigned long from_size,
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msize >>= 8;
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if (msize & 0xff) { out[outpos++] = msize; i |= 0x20; }
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*orig = i;
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*op = i;
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}
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if (outpos >= outsize - MAX_OP_SIZE) {
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@ -276,7 +215,7 @@ void *diff_delta(void *from_buf, unsigned long from_size,
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out = realloc(out, outsize);
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if (!out) {
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free(tmp);
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delta_cleanup(&bdf);
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free(hash);
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return NULL;
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}
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}
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@ -285,7 +224,7 @@ void *diff_delta(void *from_buf, unsigned long from_size,
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if (inscnt)
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out[outpos - inscnt - 1] = inscnt;
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delta_cleanup(&bdf);
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free(hash);
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*delta_size = outpos;
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return out;
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}
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