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85976974 JH |
1 | /* |
2 | * Copyright (C) 2005 Junio C Hamano | |
3 | * The delta-parsing part is almost straight copy of patch-delta.c | |
4 | * which is (C) 2005 Nicolas Pitre <nico@cam.org>. | |
5 | */ | |
6 | #include <stdlib.h> | |
7 | #include <string.h> | |
8 | #include <limits.h> | |
dcde55bc | 9 | #include "delta.h" |
85976974 JH |
10 | #include "count-delta.h" |
11 | ||
85976974 JH |
12 | /* |
13 | * NOTE. We do not _interpret_ delta fully. As an approximation, we | |
14 | * just count the number of bytes that are copied from the source, and | |
355e76a4 JH |
15 | * the number of literal data bytes that are inserted. |
16 | * | |
17 | * Number of bytes that are _not_ copied from the source is deletion, | |
18 | * and number of inserted literal bytes are addition, so sum of them | |
e7ad4a9c | 19 | * is the extent of damage. |
85976974 | 20 | */ |
355e76a4 JH |
21 | int count_delta(void *delta_buf, unsigned long delta_size, |
22 | unsigned long *src_copied, unsigned long *literal_added) | |
85976974 JH |
23 | { |
24 | unsigned long copied_from_source, added_literal; | |
25 | const unsigned char *data, *top; | |
26 | unsigned char cmd; | |
27 | unsigned long src_size, dst_size, out; | |
28 | ||
dcde55bc | 29 | if (delta_size < DELTA_SIZE_MIN) |
355e76a4 | 30 | return -1; |
85976974 JH |
31 | |
32 | data = delta_buf; | |
33 | top = delta_buf + delta_size; | |
34 | ||
dcde55bc NP |
35 | src_size = get_delta_hdr_size(&data); |
36 | dst_size = get_delta_hdr_size(&data); | |
85976974 JH |
37 | |
38 | added_literal = copied_from_source = out = 0; | |
39 | while (data < top) { | |
40 | cmd = *data++; | |
41 | if (cmd & 0x80) { | |
42 | unsigned long cp_off = 0, cp_size = 0; | |
43 | if (cmd & 0x01) cp_off = *data++; | |
44 | if (cmd & 0x02) cp_off |= (*data++ << 8); | |
45 | if (cmd & 0x04) cp_off |= (*data++ << 16); | |
46 | if (cmd & 0x08) cp_off |= (*data++ << 24); | |
47 | if (cmd & 0x10) cp_size = *data++; | |
48 | if (cmd & 0x20) cp_size |= (*data++ << 8); | |
91c76743 | 49 | if (cmd & 0x40) cp_size |= (*data++ << 16); |
85976974 JH |
50 | if (cp_size == 0) cp_size = 0x10000; |
51 | ||
91c76743 | 52 | copied_from_source += cp_size; |
85976974 JH |
53 | out += cp_size; |
54 | } else { | |
55 | /* write literal into dst */ | |
56 | added_literal += cmd; | |
57 | out += cmd; | |
58 | data += cmd; | |
59 | } | |
60 | } | |
61 | ||
62 | /* sanity check */ | |
63 | if (data != top || out != dst_size) | |
355e76a4 | 64 | return -1; |
85976974 JH |
65 | |
66 | /* delete size is what was _not_ copied from source. | |
67 | * edit size is that and literal additions. | |
68 | */ | |
355e76a4 JH |
69 | *src_copied = copied_from_source; |
70 | *literal_added = added_literal; | |
71 | return 0; | |
85976974 | 72 | } |