summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--diff-delta.c74
1 files changed, 58 insertions, 16 deletions
diff --git a/diff-delta.c b/diff-delta.c
index 0dde2f2..7f8a60d 100644
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -115,7 +115,11 @@ static const unsigned int U[256] = {
struct index_entry {
const unsigned char *ptr;
unsigned int val;
- struct index_entry *next;
+};
+
+struct unpacked_index_entry {
+ struct index_entry entry;
+ struct unpacked_index_entry *next;
};
struct delta_index {
@@ -131,7 +135,8 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
unsigned int i, hsize, hmask, entries, prev_val, *hash_count;
const unsigned char *data, *buffer = buf;
struct delta_index *index;
- struct index_entry *entry, **hash;
+ struct unpacked_index_entry *entry, **hash;
+ struct index_entry *packed_entry, **packed_hash;
void *mem;
unsigned long memsize;
@@ -148,28 +153,21 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
hmask = hsize - 1;
/* allocate lookup index */
- memsize = sizeof(*index) +
- sizeof(*hash) * hsize +
+ memsize = sizeof(*hash) * hsize +
sizeof(*entry) * entries;
mem = malloc(memsize);
if (!mem)
return NULL;
- index = mem;
- mem = index + 1;
hash = mem;
mem = hash + hsize;
entry = mem;
- index->memsize = memsize;
- index->src_buf = buf;
- index->src_size = bufsize;
- index->hash_mask = hmask;
memset(hash, 0, hsize * sizeof(*hash));
/* allocate an array to count hash entries */
hash_count = calloc(hsize, sizeof(*hash_count));
if (!hash_count) {
- free(index);
+ free(hash);
return NULL;
}
@@ -183,12 +181,13 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
val = ((val << 8) | data[i]) ^ T[val >> RABIN_SHIFT];
if (val == prev_val) {
/* keep the lowest of consecutive identical blocks */
- entry[-1].ptr = data + RABIN_WINDOW;
+ entry[-1].entry.ptr = data + RABIN_WINDOW;
+ --entries;
} else {
prev_val = val;
i = val & hmask;
- entry->ptr = data + RABIN_WINDOW;
- entry->val = val;
+ entry->entry.ptr = data + RABIN_WINDOW;
+ entry->entry.val = val;
entry->next = hash[i];
hash[i] = entry++;
hash_count[i]++;
@@ -212,16 +211,59 @@ struct delta_index * create_delta_index(const void *buf, unsigned long bufsize)
continue;
entry = hash[i];
do {
- struct index_entry *keep = entry;
+ struct unpacked_index_entry *keep = entry;
int skip = hash_count[i] / HASH_LIMIT;
do {
+ --entries;
entry = entry->next;
} while(--skip && entry);
+ ++entries;
keep->next = entry;
} while(entry);
}
free(hash_count);
+ /* Now create the packed index in array form rather than
+ * linked lists */
+
+ memsize = sizeof(*index)
+ + sizeof(*packed_hash) * (hsize+1)
+ + sizeof(*packed_entry) * entries;
+
+ mem = malloc(memsize);
+
+ if (!mem) {
+ free(hash);
+ return NULL;
+ }
+
+ index = mem;
+ index->memsize = memsize;
+ index->src_buf = buf;
+ index->src_size = bufsize;
+ index->hash_mask = hmask;
+
+ mem = index + 1;
+ packed_hash = mem;
+ mem = packed_hash + (hsize+1);
+ packed_entry = mem;
+
+ /* Coalesce all entries belonging to one linked list into
+ * consecutive array entries */
+
+ for (i = 0; i < hsize; i++) {
+ packed_hash[i] = packed_entry;
+ for (entry = hash[i]; entry; entry = entry->next)
+ *packed_entry++ = entry->entry;
+ }
+
+ /* Sentinel value to indicate the length of the last hash
+ * bucket */
+
+ packed_hash[hsize] = packed_entry;
+ assert(packed_entry - (struct index_entry *)mem == entries);
+ free(hash);
+
return index;
}
@@ -302,7 +344,7 @@ create_delta(const struct delta_index *index,
val ^= U[data[-RABIN_WINDOW]];
val = ((val << 8) | *data) ^ T[val >> RABIN_SHIFT];
i = val & index->hash_mask;
- for (entry = index->hash[i]; entry; entry = entry->next) {
+ for (entry = index->hash[i]; entry < index->hash[i+1]; entry++) {
const unsigned char *ref = entry->ptr;
const unsigned char *src = data;
unsigned int ref_size = ref_top - ref;