git-send-email: Add --thread option
[git/aroben.git] / delta.h
blob7b3f86d85f71e47d11c40a4abbcd9d9f499a6636
1 #ifndef DELTA_H
2 #define DELTA_H
4 /* opaque object for delta index */
5 struct delta_index;
7 /*
8 * create_delta_index: compute index data from given buffer
10 * This returns a pointer to a struct delta_index that should be passed to
11 * subsequent create_delta() calls, or to free_delta_index(). A NULL pointer
12 * is returned on failure. The given buffer must not be freed nor altered
13 * before free_delta_index() is called. The returned pointer must be freed
14 * using free_delta_index().
16 extern struct delta_index *
17 create_delta_index(const void *buf, unsigned long bufsize);
20 * free_delta_index: free the index created by create_delta_index()
22 * Given pointer must be what create_delta_index() returned, or NULL.
24 extern void free_delta_index(struct delta_index *index);
27 * create_delta: create a delta from given index for the given buffer
29 * This function may be called multiple times with different buffers using
30 * the same delta_index pointer. If max_delta_size is non-zero and the
31 * resulting delta is to be larger than max_delta_size then NULL is returned.
32 * On success, a non-NULL pointer to the buffer with the delta data is
33 * returned and *delta_size is updated with its size. The returned buffer
34 * must be freed by the caller.
36 extern void *
37 create_delta(const struct delta_index *index,
38 const void *buf, unsigned long bufsize,
39 unsigned long *delta_size, unsigned long max_delta_size);
42 * diff_delta: create a delta from source buffer to target buffer
44 * If max_delta_size is non-zero and the resulting delta is to be larger
45 * than max_delta_size then NULL is returned. On success, a non-NULL
46 * pointer to the buffer with the delta data is returned and *delta_size is
47 * updated with its size. The returned buffer must be freed by the caller.
49 static inline void *
50 diff_delta(const void *src_buf, unsigned long src_bufsize,
51 const void *trg_buf, unsigned long trg_bufsize,
52 unsigned long *delta_size, unsigned long max_delta_size)
54 struct delta_index *index = create_delta_index(src_buf, src_bufsize);
55 if (index) {
56 void *delta = create_delta(index, trg_buf, trg_bufsize,
57 delta_size, max_delta_size);
58 free_delta_index(index);
59 return delta;
61 return NULL;
65 * patch_delta: recreate target buffer given source buffer and delta data
67 * On success, a non-NULL pointer to the target buffer is returned and
68 * *trg_bufsize is updated with its size. On failure a NULL pointer is
69 * returned. The returned buffer must be freed by the caller.
71 extern void *patch_delta(const void *src_buf, unsigned long src_size,
72 const void *delta_buf, unsigned long delta_size,
73 unsigned long *dst_size);
75 /* the smallest possible delta size is 4 bytes */
76 #define DELTA_SIZE_MIN 4
79 * This must be called twice on the delta data buffer, first to get the
80 * expected source buffer size, and again to get the target buffer size.
82 static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
83 const unsigned char *top)
85 const unsigned char *data = *datap;
86 unsigned char cmd;
87 unsigned long size = 0;
88 int i = 0;
89 do {
90 cmd = *data++;
91 size |= (cmd & ~0x80) << i;
92 i += 7;
93 } while (cmd & 0x80 && data < top);
94 *datap = data;
95 return size;
98 #endif