Adding upstream version 1:2.47.2.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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4535 changed files with 1510258 additions and 0 deletions
236
diffcore-delta.c
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236
diffcore-delta.c
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#include "git-compat-util.h"
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#include "diffcore.h"
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/*
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* Idea here is very simple.
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*
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* Almost all data we are interested in are text, but sometimes we have
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* to deal with binary data. So we cut them into chunks delimited by
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* LF byte, or 64-byte sequence, whichever comes first, and hash them.
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*
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* For those chunks, if the source buffer has more instances of it
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* than the destination buffer, that means the difference are the
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* number of bytes not copied from source to destination. If the
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* counts are the same, everything was copied from source to
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* destination. If the destination has more, everything was copied,
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* and destination added more.
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*
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* We are doing an approximation so we do not really have to waste
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* memory by actually storing the sequence. We just hash them into
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* somewhere around 2^16 hashbuckets and count the occurrences.
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*/
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/* Wild guess at the initial hash size */
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#define INITIAL_HASH_SIZE 9
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/* We leave more room in smaller hash but do not let it
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* grow to have unused hole too much.
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*/
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#define INITIAL_FREE(sz_log2) ((1<<(sz_log2))*(sz_log2-3)/(sz_log2))
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/* A prime rather carefully chosen between 2^16..2^17, so that
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* HASHBASE < INITIAL_FREE(17). We want to keep the maximum hashtable
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* size under the current 2<<17 maximum, which can hold this many
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* different values before overflowing to hashtable of size 2<<18.
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*/
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#define HASHBASE 107927
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struct spanhash {
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unsigned int hashval;
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unsigned int cnt;
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};
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struct spanhash_top {
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int alloc_log2;
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int free;
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struct spanhash data[FLEX_ARRAY];
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};
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static struct spanhash_top *spanhash_rehash(struct spanhash_top *orig)
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{
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struct spanhash_top *new_spanhash;
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int i;
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int osz = 1 << orig->alloc_log2;
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int sz = osz << 1;
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new_spanhash = xmalloc(st_add(sizeof(*orig),
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st_mult(sizeof(struct spanhash), sz)));
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new_spanhash->alloc_log2 = orig->alloc_log2 + 1;
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new_spanhash->free = INITIAL_FREE(new_spanhash->alloc_log2);
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memset(new_spanhash->data, 0, sizeof(struct spanhash) * sz);
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for (i = 0; i < osz; i++) {
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struct spanhash *o = &(orig->data[i]);
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int bucket;
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if (!o->cnt)
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continue;
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bucket = o->hashval & (sz - 1);
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while (1) {
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struct spanhash *h = &(new_spanhash->data[bucket++]);
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if (!h->cnt) {
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h->hashval = o->hashval;
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h->cnt = o->cnt;
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new_spanhash->free--;
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break;
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}
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if (sz <= bucket)
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bucket = 0;
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}
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}
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free(orig);
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return new_spanhash;
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}
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static struct spanhash_top *add_spanhash(struct spanhash_top *top,
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unsigned int hashval, int cnt)
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{
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int bucket, lim;
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struct spanhash *h;
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lim = (1 << top->alloc_log2);
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bucket = hashval & (lim - 1);
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while (1) {
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h = &(top->data[bucket++]);
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if (!h->cnt) {
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h->hashval = hashval;
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h->cnt = cnt;
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top->free--;
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if (top->free < 0)
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return spanhash_rehash(top);
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return top;
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}
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if (h->hashval == hashval) {
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h->cnt += cnt;
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return top;
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}
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if (lim <= bucket)
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bucket = 0;
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}
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}
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static int spanhash_cmp(const void *a_, const void *b_)
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{
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const struct spanhash *a = a_;
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const struct spanhash *b = b_;
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/* A count of zero compares at the end.. */
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if (!a->cnt)
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return !b->cnt ? 0 : 1;
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if (!b->cnt)
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return -1;
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return a->hashval < b->hashval ? -1 :
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a->hashval > b->hashval ? 1 : 0;
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}
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static struct spanhash_top *hash_chars(struct repository *r,
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struct diff_filespec *one)
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{
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int i, n;
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unsigned int accum1, accum2, hashval;
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struct spanhash_top *hash;
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unsigned char *buf = one->data;
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unsigned int sz = one->size;
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int is_text = !diff_filespec_is_binary(r, one);
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i = INITIAL_HASH_SIZE;
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hash = xmalloc(st_add(sizeof(*hash),
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st_mult(sizeof(struct spanhash), (size_t)1 << i)));
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hash->alloc_log2 = i;
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hash->free = INITIAL_FREE(i);
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memset(hash->data, 0, sizeof(struct spanhash) * ((size_t)1 << i));
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n = 0;
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accum1 = accum2 = 0;
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while (sz) {
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unsigned int c = *buf++;
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unsigned int old_1 = accum1;
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sz--;
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/* Ignore CR in CRLF sequence if text */
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if (is_text && c == '\r' && sz && *buf == '\n')
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continue;
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accum1 = (accum1 << 7) ^ (accum2 >> 25);
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accum2 = (accum2 << 7) ^ (old_1 >> 25);
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accum1 += c;
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if (++n < 64 && c != '\n')
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continue;
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hashval = (accum1 + accum2 * 0x61) % HASHBASE;
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hash = add_spanhash(hash, hashval, n);
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n = 0;
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accum1 = accum2 = 0;
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}
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if (n > 0) {
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hashval = (accum1 + accum2 * 0x61) % HASHBASE;
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hash = add_spanhash(hash, hashval, n);
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}
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QSORT(hash->data, (size_t)1ul << hash->alloc_log2, spanhash_cmp);
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return hash;
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}
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int diffcore_count_changes(struct repository *r,
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struct diff_filespec *src,
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struct diff_filespec *dst,
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void **src_count_p,
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void **dst_count_p,
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unsigned long *src_copied,
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unsigned long *literal_added)
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{
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struct spanhash *s, *d;
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struct spanhash_top *src_count, *dst_count;
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unsigned long sc, la;
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src_count = dst_count = NULL;
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if (src_count_p)
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src_count = *src_count_p;
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if (!src_count) {
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src_count = hash_chars(r, src);
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if (src_count_p)
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*src_count_p = src_count;
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}
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if (dst_count_p)
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dst_count = *dst_count_p;
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if (!dst_count) {
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dst_count = hash_chars(r, dst);
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if (dst_count_p)
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*dst_count_p = dst_count;
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}
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sc = la = 0;
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s = src_count->data;
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d = dst_count->data;
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for (;;) {
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unsigned dst_cnt, src_cnt;
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if (!s->cnt)
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break; /* we checked all in src */
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while (d->cnt) {
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if (d->hashval >= s->hashval)
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break;
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la += d->cnt;
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d++;
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}
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src_cnt = s->cnt;
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dst_cnt = 0;
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if (d->cnt && d->hashval == s->hashval) {
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dst_cnt = d->cnt;
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d++;
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}
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if (src_cnt < dst_cnt) {
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la += dst_cnt - src_cnt;
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sc += src_cnt;
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}
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else
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sc += dst_cnt;
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s++;
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}
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while (d->cnt) {
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la += d->cnt;
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d++;
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}
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if (!src_count_p)
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free(src_count);
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if (!dst_count_p)
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free(dst_count);
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*src_copied = sc;
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*literal_added = la;
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return 0;
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}
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