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08abe669c0
This patch splits the diff-delta interface into index creation and delta generation. A wrapper is provided to preserve the diff-delta() call. This will allow for an optimization in pack-objects.c where the source object could be fixed and a full window of objects tentatively tried against that same source object without recomputing the source index each time. This patch only restructure things, plus a couple cleanups for good measure. There is no performance change yet. Signed-off-by: Nicolas Pitre <nico@cam.org>
89 lines
2.1 KiB
C
89 lines
2.1 KiB
C
/*
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* patch-delta.c:
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* recreate a buffer from a source and the delta produced by diff-delta.c
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*
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* (C) 2005 Nicolas Pitre <nico@cam.org>
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*
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* This code is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include "delta.h"
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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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{
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const unsigned char *data, *top;
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unsigned char *dst_buf, *out, cmd;
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unsigned long size;
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if (delta_size < DELTA_SIZE_MIN)
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return NULL;
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data = delta_buf;
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top = delta_buf + delta_size;
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/* make sure the orig file size matches what we expect */
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size = get_delta_hdr_size(&data, top);
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if (size != src_size)
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return NULL;
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/* now the result size */
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size = get_delta_hdr_size(&data, top);
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dst_buf = malloc(size + 1);
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if (!dst_buf)
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return NULL;
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dst_buf[size] = 0;
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out = dst_buf;
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while (data < top) {
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cmd = *data++;
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if (cmd & 0x80) {
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unsigned long cp_off = 0, cp_size = 0;
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if (cmd & 0x01) cp_off = *data++;
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if (cmd & 0x02) cp_off |= (*data++ << 8);
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if (cmd & 0x04) cp_off |= (*data++ << 16);
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if (cmd & 0x08) cp_off |= (*data++ << 24);
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if (cmd & 0x10) cp_size = *data++;
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if (cmd & 0x20) cp_size |= (*data++ << 8);
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if (cmd & 0x40) cp_size |= (*data++ << 16);
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if (cp_size == 0) cp_size = 0x10000;
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if (cp_off + cp_size < cp_size ||
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cp_off + cp_size > src_size ||
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cp_size > size)
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goto bad;
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memcpy(out, src_buf + cp_off, cp_size);
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out += cp_size;
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size -= cp_size;
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} else if (cmd) {
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if (cmd > size)
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goto bad;
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memcpy(out, data, cmd);
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out += cmd;
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data += cmd;
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size -= cmd;
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} else {
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/*
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* cmd == 0 is reserved for future encoding
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* extensions. In the mean time we must fail when
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* encountering them (might be data corruption).
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*/
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goto bad;
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}
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}
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/* sanity check */
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if (data != top || size != 0) {
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bad:
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free(dst_buf);
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return NULL;
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}
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*dst_size = out - dst_buf;
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return dst_buf;
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}
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