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ff45715ce5
Avoid creating a delta index for objects with maximum depth since they are not going to be used as delta base anyway. This also reduce peak memory usage slightly as the current object's delta index is not useful until the next object in the loop is considered for deltification. This saves a bit more than 1% on CPU usage. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
99 lines
3.2 KiB
C
99 lines
3.2 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 nor 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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* 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 char cmd;
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unsigned long 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 & ~0x80) << 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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