diff options
Diffstat (limited to 'third_party/git/diffcore-delta.c')
| -rw-r--r-- | third_party/git/diffcore-delta.c | 233 |
1 files changed, 0 insertions, 233 deletions
diff --git a/third_party/git/diffcore-delta.c b/third_party/git/diffcore-delta.c deleted file mode 100644 index 5668ace60d60..000000000000 --- a/third_party/git/diffcore-delta.c +++ /dev/null @@ -1,233 +0,0 @@ -#include "cache.h" -#include "diff.h" -#include "diffcore.h" - -/* - * Idea here is very simple. - * - * Almost all data we are interested in are text, but sometimes we have - * to deal with binary data. So we cut them into chunks delimited by - * LF byte, or 64-byte sequence, whichever comes first, and hash them. - * - * For those chunks, if the source buffer has more instances of it - * than the destination buffer, that means the difference are the - * number of bytes not copied from source to destination. If the - * counts are the same, everything was copied from source to - * destination. If the destination has more, everything was copied, - * and destination added more. - * - * We are doing an approximation so we do not really have to waste - * memory by actually storing the sequence. We just hash them into - * somewhere around 2^16 hashbuckets and count the occurrences. - */ - -/* Wild guess at the initial hash size */ -#define INITIAL_HASH_SIZE 9 - -/* We leave more room in smaller hash but do not let it - * grow to have unused hole too much. - */ -#define INITIAL_FREE(sz_log2) ((1<<(sz_log2))*(sz_log2-3)/(sz_log2)) - -/* A prime rather carefully chosen between 2^16..2^17, so that - * HASHBASE < INITIAL_FREE(17). We want to keep the maximum hashtable - * size under the current 2<<17 maximum, which can hold this many - * different values before overflowing to hashtable of size 2<<18. - */ -#define HASHBASE 107927 - -struct spanhash { - unsigned int hashval; - unsigned int cnt; -}; -struct spanhash_top { - int alloc_log2; - int free; - struct spanhash data[FLEX_ARRAY]; -}; - -static struct spanhash_top *spanhash_rehash(struct spanhash_top *orig) -{ - struct spanhash_top *new_spanhash; - int i; - int osz = 1 << orig->alloc_log2; - int sz = osz << 1; - - new_spanhash = xmalloc(st_add(sizeof(*orig), - st_mult(sizeof(struct spanhash), sz))); - new_spanhash->alloc_log2 = orig->alloc_log2 + 1; - new_spanhash->free = INITIAL_FREE(new_spanhash->alloc_log2); - memset(new_spanhash->data, 0, sizeof(struct spanhash) * sz); - for (i = 0; i < osz; i++) { - struct spanhash *o = &(orig->data[i]); - int bucket; - if (!o->cnt) - continue; - bucket = o->hashval & (sz - 1); - while (1) { - struct spanhash *h = &(new_spanhash->data[bucket++]); - if (!h->cnt) { - h->hashval = o->hashval; - h->cnt = o->cnt; - new_spanhash->free--; - break; - } - if (sz <= bucket) - bucket = 0; - } - } - free(orig); - return new_spanhash; -} - -static struct spanhash_top *add_spanhash(struct spanhash_top *top, - unsigned int hashval, int cnt) -{ - int bucket, lim; - struct spanhash *h; - - lim = (1 << top->alloc_log2); - bucket = hashval & (lim - 1); - while (1) { - h = &(top->data[bucket++]); - if (!h->cnt) { - h->hashval = hashval; - h->cnt = cnt; - top->free--; - if (top->free < 0) - return spanhash_rehash(top); - return top; - } - if (h->hashval == hashval) { - h->cnt += cnt; - return top; - } - if (lim <= bucket) - bucket = 0; - } -} - -static int spanhash_cmp(const void *a_, const void *b_) -{ - const struct spanhash *a = a_; - const struct spanhash *b = b_; - - /* A count of zero compares at the end.. */ - if (!a->cnt) - return !b->cnt ? 0 : 1; - if (!b->cnt) - return -1; - return a->hashval < b->hashval ? -1 : - a->hashval > b->hashval ? 1 : 0; -} - -static struct spanhash_top *hash_chars(struct repository *r, - struct diff_filespec *one) -{ - int i, n; - unsigned int accum1, accum2, hashval; - struct spanhash_top *hash; - unsigned char *buf = one->data; - unsigned int sz = one->size; - int is_text = !diff_filespec_is_binary(r, one); - - i = INITIAL_HASH_SIZE; - hash = xmalloc(st_add(sizeof(*hash), - st_mult(sizeof(struct spanhash), 1<<i))); - hash->alloc_log2 = i; - hash->free = INITIAL_FREE(i); - memset(hash->data, 0, sizeof(struct spanhash) * (1<<i)); - - n = 0; - accum1 = accum2 = 0; - while (sz) { - unsigned int c = *buf++; - unsigned int old_1 = accum1; - sz--; - - /* Ignore CR in CRLF sequence if text */ - if (is_text && c == '\r' && sz && *buf == '\n') - continue; - - accum1 = (accum1 << 7) ^ (accum2 >> 25); - accum2 = (accum2 << 7) ^ (old_1 >> 25); - accum1 += c; - if (++n < 64 && c != '\n') - continue; - hashval = (accum1 + accum2 * 0x61) % HASHBASE; - hash = add_spanhash(hash, hashval, n); - n = 0; - accum1 = accum2 = 0; - } - QSORT(hash->data, 1ul << hash->alloc_log2, spanhash_cmp); - return hash; -} - -int diffcore_count_changes(struct repository *r, - struct diff_filespec *src, - struct diff_filespec *dst, - void **src_count_p, - void **dst_count_p, - unsigned long *src_copied, - unsigned long *literal_added) -{ - struct spanhash *s, *d; - struct spanhash_top *src_count, *dst_count; - unsigned long sc, la; - - src_count = dst_count = NULL; - if (src_count_p) - src_count = *src_count_p; - if (!src_count) { - src_count = hash_chars(r, src); - if (src_count_p) - *src_count_p = src_count; - } - if (dst_count_p) - dst_count = *dst_count_p; - if (!dst_count) { - dst_count = hash_chars(r, dst); - if (dst_count_p) - *dst_count_p = dst_count; - } - sc = la = 0; - - s = src_count->data; - d = dst_count->data; - for (;;) { - unsigned dst_cnt, src_cnt; - if (!s->cnt) - break; /* we checked all in src */ - while (d->cnt) { - if (d->hashval >= s->hashval) - break; - la += d->cnt; - d++; - } - src_cnt = s->cnt; - dst_cnt = 0; - if (d->cnt && d->hashval == s->hashval) { - dst_cnt = d->cnt; - d++; - } - if (src_cnt < dst_cnt) { - la += dst_cnt - src_cnt; - sc += src_cnt; - } - else - sc += dst_cnt; - s++; - } - while (d->cnt) { - la += d->cnt; - d++; - } - - if (!src_count_p) - free(src_count); - if (!dst_count_p) - free(dst_count); - *src_copied = sc; - *literal_added = la; - return 0; -} |