105 lines
3.4 KiB
C
105 lines
3.4 KiB
C
#ifndef DELTA_H
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#define DELTA_H
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/* opaque object for delta index */
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struct delta_index;
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/*
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* create_delta_index: compute index data from given buffer
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*
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* This returns a pointer to a struct delta_index that should be passed to
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* subsequent create_delta() calls, or to free_delta_index(). A NULL pointer
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* is returned on failure. The given buffer must not be freed or altered
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* before free_delta_index() is called. The returned pointer must be freed
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* using free_delta_index().
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*/
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extern struct delta_index *
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create_delta_index(const void *buf, unsigned long bufsize);
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/*
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* free_delta_index: free the index created by create_delta_index()
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*
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* Given pointer must be what create_delta_index() returned, or NULL.
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*/
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extern void free_delta_index(struct delta_index *index);
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/*
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* sizeof_delta_index: returns memory usage of delta index
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*
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* Given pointer must be what create_delta_index() returned, or NULL.
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*/
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extern unsigned long sizeof_delta_index(struct delta_index *index);
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/*
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* create_delta: create a delta from given index for the given buffer
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*
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* This function may be called multiple times with different buffers using
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* the same delta_index pointer. If max_delta_size is non-zero and the
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* resulting delta is to be larger than max_delta_size then NULL is returned.
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* On success, a non-NULL pointer to the buffer with the delta data is
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* returned and *delta_size is updated with its size. The returned buffer
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* must be freed by the caller.
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*/
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extern void *
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create_delta(const struct delta_index *index,
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const void *buf, unsigned long bufsize,
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unsigned long *delta_size, unsigned long max_delta_size);
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/*
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* diff_delta: create a delta from source buffer to target buffer
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*
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* If max_delta_size is non-zero and the resulting delta is to be larger
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* than max_delta_size then NULL is returned. On success, a non-NULL
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* pointer to the buffer with the delta data is returned and *delta_size is
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* updated with its size. The returned buffer must be freed by the caller.
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*/
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static inline void *
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diff_delta(const void *src_buf, unsigned long src_bufsize,
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const void *trg_buf, unsigned long trg_bufsize,
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unsigned long *delta_size, unsigned long max_delta_size)
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{
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struct delta_index *index = create_delta_index(src_buf, src_bufsize);
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if (index) {
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void *delta = create_delta(index, trg_buf, trg_bufsize,
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delta_size, max_delta_size);
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free_delta_index(index);
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return delta;
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}
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return NULL;
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}
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/*
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* patch_delta: recreate target buffer given source buffer and delta data
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*
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* On success, a non-NULL pointer to the target buffer is returned and
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* *trg_bufsize is updated with its size. On failure a NULL pointer is
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* returned. The returned buffer must be freed by the caller.
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*/
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extern void *patch_delta(const void *src_buf, unsigned long src_size,
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const void *delta_buf, unsigned long delta_size,
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unsigned long *dst_size);
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/* the smallest possible delta size is 4 bytes */
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#define DELTA_SIZE_MIN 4
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/*
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* This must be called twice on the delta data buffer, first to get the
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* expected source buffer size, and again to get the target buffer size.
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*/
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static inline unsigned long get_delta_hdr_size(const unsigned char **datap,
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const unsigned char *top)
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{
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const unsigned char *data = *datap;
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unsigned long cmd, size = 0;
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int i = 0;
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do {
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cmd = *data++;
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size |= (cmd & 0x7f) << i;
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i += 7;
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} while (cmd & 0x80 && data < top);
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*datap = data;
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return size;
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}
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#endif
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