diff options
Diffstat (limited to 'diffcore-delta.c')
| -rw-r--r-- | diffcore-delta.c | 102 |
1 files changed, 61 insertions, 41 deletions
diff --git a/diffcore-delta.c b/diffcore-delta.c index 7338a40c59..7cf431d261 100644 --- a/diffcore-delta.c +++ b/diffcore-delta.c @@ -5,23 +5,20 @@ /* * Idea here is very simple. * - * We have total of (sz-N+1) N-byte overlapping sequences in buf whose - * size is sz. If the same N-byte sequence appears in both source and - * destination, we say the byte that starts that sequence is shared - * between them (i.e. copied from source to destination). + * 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 each possible N-byte sequence, 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. + * 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. - * - * The length of the sequence is arbitrarily set to 8 for now. */ /* Wild guess at the initial hash size */ @@ -49,22 +46,6 @@ struct spanhash_top { struct spanhash data[FLEX_ARRAY]; }; -static struct spanhash *spanhash_find(struct spanhash_top *top, - unsigned int hashval) -{ - int sz = 1 << top->alloc_log2; - int bucket = hashval & (sz - 1); - while (1) { - struct spanhash *h = &(top->data[bucket++]); - if (!h->cnt) - return NULL; - if (h->hashval == hashval) - return h; - if (sz <= bucket) - bucket = 0; - } -} - static struct spanhash_top *spanhash_rehash(struct spanhash_top *orig) { struct spanhash_top *new; @@ -125,11 +106,28 @@ static struct spanhash_top *add_spanhash(struct spanhash_top *top, } } -static struct spanhash_top *hash_chars(unsigned char *buf, unsigned int sz) +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 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(one); i = INITIAL_HASH_SIZE; hash = xmalloc(sizeof(*hash) + sizeof(struct spanhash) * (1<<i)); @@ -143,6 +141,11 @@ static struct spanhash_top *hash_chars(unsigned char *buf, unsigned int 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; @@ -153,18 +156,22 @@ static struct spanhash_top *hash_chars(unsigned char *buf, unsigned int sz) n = 0; accum1 = accum2 = 0; } + qsort(hash->data, + 1ul << hash->alloc_log2, + sizeof(hash->data[0]), + spanhash_cmp); return hash; } -int diffcore_count_changes(void *src, unsigned long src_size, - void *dst, unsigned long dst_size, +int diffcore_count_changes(struct diff_filespec *src, + struct diff_filespec *dst, void **src_count_p, void **dst_count_p, unsigned long delta_limit, unsigned long *src_copied, unsigned long *literal_added) { - int i, ssz; + struct spanhash *s, *d; struct spanhash_top *src_count, *dst_count; unsigned long sc, la; @@ -172,35 +179,48 @@ int diffcore_count_changes(void *src, unsigned long src_size, if (src_count_p) src_count = *src_count_p; if (!src_count) { - src_count = hash_chars(src, src_size); + src_count = hash_chars(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(dst, dst_size); + dst_count = hash_chars(dst); if (dst_count_p) *dst_count_p = dst_count; } sc = la = 0; - ssz = 1 << src_count->alloc_log2; - for (i = 0; i < ssz; i++) { - struct spanhash *s = &(src_count->data[i]); - struct spanhash *d; + s = src_count->data; + d = dst_count->data; + for (;;) { unsigned dst_cnt, src_cnt; if (!s->cnt) - continue; + break; /* we checked all in src */ + while (d->cnt) { + if (d->hashval >= s->hashval) + break; + la += d->cnt; + d++; + } src_cnt = s->cnt; - d = spanhash_find(dst_count, s->hashval); - dst_cnt = d ? d->cnt : 0; + 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) |