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| #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 or altered | |
| * before free_delta_index() is called. The returned pointer must be freed | |
| * using free_delta_index(). | |
| */ | |
| 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. | |
| */ | |
| void free_delta_index(struct delta_index *index); | |
| /* | |
| * sizeof_delta_index: returns memory usage of delta index | |
| * | |
| * Given pointer must be what create_delta_index() returned, or NULL. | |
| */ | |
| unsigned long sizeof_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. | |
| */ | |
| 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. | |
| */ | |
| 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 long cmd, size = 0; | |
| int i = 0; | |
| do { | |
| cmd = *data++; | |
| size |= (cmd & 0x7f) << i; | |
| i += 7; | |
| } while (cmd & 0x80 && data < top); | |
| *datap = data; | |
| return size; | |
| } | |
| #endif |