| #ifndef DELTA_H |
| #define DELTA_H |
| |
| /* 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() |
| * |
| * Given pointer must be what create_delta_index() returned, or NULL. |
| */ |
| 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 */ |
| #define DELTA_SIZE_MIN 4 |
| |
| /* |
| * This must be called twice on the delta data buffer, first to get the |
| * 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) |
| { |
| const unsigned char *data = *datap; |
| unsigned char cmd; |
| unsigned long size = 0; |
| int i = 0; |
| do { |
| cmd = *data++; |
| size |= (cmd & ~0x80) << i; |
| i += 7; |
| } while (cmd & 0x80 && data < top); |
| *datap = data; |
| return size; |
| } |
| |
| #endif |