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Diffstat (limited to 'delta.h')
| -rw-r--r-- | delta.h | 105 |
1 files changed, 105 insertions, 0 deletions
@@ -0,0 +1,105 @@ +#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); + +/* + * sizeof_delta_index: returns memory usage of delta index + * + * Given pointer must be what create_delta_index() returned, or NULL. + */ +extern 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. + */ +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 |