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authorNicolas Pitre <nico@cam.org>2006-04-24 23:07:47 -0400
committerJunio C Hamano <junkio@cox.net>2006-04-24 22:27:33 -0700
commit08abe669c05521499149dbf84fedefb04a8fa34d (patch)
treec08d8f9f4382085c76bbb9c1f3ffa47364746775 /delta.h
parent36932eab772dc621e79d615fda425ecf87e6d74e (diff)
downloadgit-08abe669c05521499149dbf84fedefb04a8fa34d.tar.gz
split the diff-delta interface
This patch splits the diff-delta interface into index creation and delta generation. A wrapper is provided to preserve the diff-delta() call. This will allow for an optimization in pack-objects.c where the source object could be fixed and a full window of objects tentatively tried against that same source object without recomputing the source index each time. This patch only restructure things, plus a couple cleanups for good measure. There is no performance change yet. Signed-off-by: Nicolas Pitre <nico@cam.org>
Diffstat (limited to 'delta.h')
-rw-r--r--delta.h75
1 files changed, 68 insertions, 7 deletions
diff --git a/delta.h b/delta.h
index 9464f3e9b0..727ae30e9e 100644
--- a/delta.h
+++ b/delta.h
@@ -1,12 +1,73 @@
#ifndef DELTA_H
#define DELTA_H
-/* handling of delta buffers */
-extern void *diff_delta(void *from_buf, unsigned long from_size,
- void *to_buf, unsigned long to_size,
- unsigned long *delta_size, unsigned long max_size);
-extern void *patch_delta(void *src_buf, unsigned long src_size,
- void *delta_buf, unsigned long delta_size,
+/* opaque object for delta index */
+struct delta_index;
+
+/*
+ * create_delta_index: compute index data from given buffer
+ *
+ * This returns a pointer to a struct delta_index that should be passed to
+ * subsequent create_delta() calls, or to free_delta_index(). A NULL pointer
+ * is returned on failure. The given buffer must not be freed nor altered
+ * before free_delta_index() is called. The returned pointer must be freed
+ * using free_delta_index().
+ */
+extern struct delta_index *
+create_delta_index(const void *buf, unsigned long bufsize);
+
+/*
+ * free_delta_index: free the index created by create_delta_index()
+ */
+extern void free_delta_index(struct delta_index *index);
+
+/*
+ * create_delta: create a delta from given index for the given buffer
+ *
+ * This function may be called multiple times with different buffers using
+ * the same delta_index pointer. If max_delta_size is non-zero and the
+ * resulting delta is to be larger than max_delta_size then NULL is returned.
+ * On success, a non-NULL pointer to the buffer with the delta data is
+ * returned and *delta_size is updated with its size. The returned buffer
+ * must be freed by the caller.
+ */
+extern void *
+create_delta(const struct delta_index *index,
+ const void *buf, unsigned long bufsize,
+ unsigned long *delta_size, unsigned long max_delta_size);
+
+/*
+ * diff_delta: create a delta from source buffer to target buffer
+ *
+ * If max_delta_size is non-zero and the resulting delta is to be larger
+ * than max_delta_size then NULL is returned. On success, a non-NULL
+ * pointer to the buffer with the delta data is returned and *delta_size is
+ * updated with its size. The returned buffer must be freed by the caller.
+ */
+static inline void *
+diff_delta(const void *src_buf, unsigned long src_bufsize,
+ const void *trg_buf, unsigned long trg_bufsize,
+ unsigned long *delta_size, unsigned long max_delta_size)
+{
+ struct delta_index *index = create_delta_index(src_buf, src_bufsize);
+ if (index) {
+ void *delta = create_delta(index, trg_buf, trg_bufsize,
+ delta_size, max_delta_size);
+ free_delta_index(index);
+ return delta;
+ }
+ return NULL;
+}
+
+/*
+ * patch_delta: recreate target buffer given source buffer and delta data
+ *
+ * On success, a non-NULL pointer to the target buffer is returned and
+ * *trg_bufsize is updated with its size. On failure a NULL pointer is
+ * returned. The returned buffer must be freed by the caller.
+ */
+extern void *patch_delta(const void *src_buf, unsigned long src_size,
+ const void *delta_buf, unsigned long delta_size,
unsigned long *dst_size);
/* the smallest possible delta size is 4 bytes */
@@ -14,7 +75,7 @@ extern void *patch_delta(void *src_buf, unsigned long src_size,
/*
* This must be called twice on the delta data buffer, first to get the
- * expected reference buffer size, and again to get the result buffer size.
+ * expected source buffer size, and again to get the target buffer size.
*/
static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
const unsigned char *top)