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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
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