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1368f65002
The idiom (a + b < a) works fine for detecting that an unsigned integer has overflowed, but a more explicit unsigned_add_overflows(a, b) might be easier to read. Define such a macro, expanding roughly to ((a) < UINT_MAX - (b)). Because the expansion uses each argument only once outside of sizeof() expressions, it is safe to use with arguments that have side effects. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
86 lines
2.2 KiB
C
86 lines
2.2 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@fluxnic.net>
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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 "git-compat-util.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 = (const unsigned char *) 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 = xmallocz(size);
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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 |= ((unsigned) *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 (unsigned_add_overflows(cp_off, cp_size) ||
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cp_off + cp_size > src_size ||
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cp_size > size)
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break;
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memcpy(out, (char *) 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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break;
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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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error("unexpected delta opcode 0");
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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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error("delta replay has gone wild");
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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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