1#ifndef DELTA_H 2#define DELTA_H 3 4/* opaque object for delta index */ 5struct delta_index; 6 7/* 8 * create_delta_index: compute index data from given buffer 9 * 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(). 15 */ 16extern struct delta_index * 17create_delta_index(const void *buf, unsigned long bufsize); 18 19/* 20 * free_delta_index: free the index created by create_delta_index() 21 * 22 * Given pointer must be what create_delta_index() returned, or NULL. 23 */ 24extern void free_delta_index(struct delta_index *index); 25 26/* 27 * sizeof_delta_index: returns memory usage of delta index 28 * 29 * Given pointer must be what create_delta_index() returned, or NULL. 30 */ 31extern unsigned long sizeof_delta_index(struct delta_index *index); 32 33/* 34 * create_delta: create a delta from given index for the given buffer 35 * 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. 42 */ 43extern void * 44create_delta(const struct delta_index *index, 45 const void *buf, unsigned long bufsize, 46 unsigned long *delta_size, unsigned long max_delta_size); 47 48/* 49 * diff_delta: create a delta from source buffer to target buffer 50 * 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. 55 */ 56static inline void * 57diff_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) 60{ 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; 67 } 68 return NULL; 69} 70 71/* 72 * patch_delta: recreate target buffer given source buffer and delta data 73 * 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. 77 */ 78extern 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); 81 82/* the smallest possible delta size is 4 bytes */ 83#define DELTA_SIZE_MIN 4 84 85/* 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. 88 */ 89static inline unsigned long get_delta_hdr_size(const unsigned char **datap, 90 const unsigned char *top) 91{ 92 const unsigned char *data = *datap; 93 unsigned char cmd; 94 unsigned long size = 0; 95 int i = 0; 96 do { 97 cmd = *data++; 98 size |= (cmd & ~0x80) << i; 99 i += 7; 100 } while (cmd & 0x80 && data < top); 101 *datap = data; 102 return size; 103} 104 105#endif