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[git/dscho.git] / delta.h
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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 * sizeof_delta_index: returns memory usage of delta index
29 * Given pointer must be what create_delta_index() returned, or NULL.
31 extern unsigned long sizeof_delta_index(struct delta_index *index);
34 * create_delta: create a delta from given index for the given buffer
36 * This function may be called multiple times with different buffers using
37 * the same delta_index pointer. If max_delta_size is non-zero and the
38 * resulting delta is to be larger than max_delta_size then NULL is returned.
39 * On success, a non-NULL pointer to the buffer with the delta data is
40 * returned and *delta_size is updated with its size. The returned buffer
41 * must be freed by the caller.
43 extern void *
44 create_delta(const struct delta_index *index,
45 const void *buf, unsigned long bufsize,
46 unsigned long *delta_size, unsigned long max_delta_size);
49 * diff_delta: create a delta from source buffer to target buffer
51 * If max_delta_size is non-zero and the resulting delta is to be larger
52 * than max_delta_size then NULL is returned. On success, a non-NULL
53 * pointer to the buffer with the delta data is returned and *delta_size is
54 * updated with its size. The returned buffer must be freed by the caller.
56 static inline void *
57 diff_delta(const void *src_buf, unsigned long src_bufsize,
58 const void *trg_buf, unsigned long trg_bufsize,
59 unsigned long *delta_size, unsigned long max_delta_size)
61 struct delta_index *index = create_delta_index(src_buf, src_bufsize);
62 if (index) {
63 void *delta = create_delta(index, trg_buf, trg_bufsize,
64 delta_size, max_delta_size);
65 free_delta_index(index);
66 return delta;
68 return NULL;
72 * patch_delta: recreate target buffer given source buffer and delta data
74 * On success, a non-NULL pointer to the target buffer is returned and
75 * *trg_bufsize is updated with its size. On failure a NULL pointer is
76 * returned. The returned buffer must be freed by the caller.
78 extern void *patch_delta(const void *src_buf, unsigned long src_size,
79 const void *delta_buf, unsigned long delta_size,
80 unsigned long *dst_size);
82 /* the smallest possible delta size is 4 bytes */
83 #define DELTA_SIZE_MIN 4
86 * This must be called twice on the delta data buffer, first to get the
87 * expected source buffer size, and again to get the target buffer size.
89 static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
90 const unsigned char *top)
92 const unsigned char *data = *datap;
93 unsigned long cmd, size = 0;
94 int i = 0;
95 do {
96 cmd = *data++;
97 size |= (cmd & 0x7f) << i;
98 i += 7;
99 } while (cmd & 0x80 && data < top);
100 *datap = data;
101 return size;
104 #endif