/*
* 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 */
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;
}
}
-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));
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;
n = 0;
accum1 = accum2 = 0;
}
+ qsort(hash->data,
+ 1ul << hash->alloc_log2,
+ sizeof(hash->data[0]),
+ spanhash_cmp);
return hash;
}
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;
if (src_count_p)
src_count = *src_count_p;
if (!src_count) {
- src_count = hash_chars(src->data, 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->data, 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;
+ d++;
+ }
src_cnt = s->cnt;
- d = spanhash_find(dst_count, s->hashval);
- dst_cnt = d ? d->cnt : 0;
+ dst_cnt = d->hashval == s->hashval ? d->cnt : 0;
if (src_cnt < dst_cnt) {
la += dst_cnt - src_cnt;
sc += src_cnt;
}
else
sc += dst_cnt;
+ s++;
}
if (!src_count_p)