[PATCH] clean up pack index handling a bit
[git/git.git] / pack.h
1 #ifndef PACK_H
2 #define PACK_H
3
4 #include "object.h"
5
6 /*
7 * Packed object header
8 */
9 #define PACK_SIGNATURE 0x5041434b /* "PACK" */
10 #define PACK_VERSION 2
11 #define pack_version_ok(v) ((v) == htonl(2) || (v) == htonl(3))
12 struct pack_header {
13 uint32_t hdr_signature;
14 uint32_t hdr_version;
15 uint32_t hdr_entries;
16 };
17
18 /*
19 * The first four bytes of index formats later than version 1 should
20 * start with this signature, as all older git binaries would find this
21 * value illegal and abort reading the file.
22 *
23 * This is the case because the number of objects in a packfile
24 * cannot exceed 1,431,660,000 as every object would need at least
25 * 3 bytes of data and the overall packfile cannot exceed 4 GiB with
26 * version 1 of the index file due to the offsets limited to 32 bits.
27 * Clearly the signature exceeds this maximum.
28 *
29 * Very old git binaries will also compare the first 4 bytes to the
30 * next 4 bytes in the index and abort with a "non-monotonic index"
31 * error if the second 4 byte word is smaller than the first 4
32 * byte word. This would be true in the proposed future index
33 * format as idx_signature would be greater than idx_version.
34 */
35 #define PACK_IDX_SIGNATURE 0xff744f63 /* "\377tOc" */
36
37 /*
38 * Packed object index header
39 */
40 struct pack_idx_header {
41 uint32_t idx_signature;
42 uint32_t idx_version;
43 };
44
45
46 extern int verify_pack(struct packed_git *, int);
47
48 #define PH_ERROR_EOF (-1)
49 #define PH_ERROR_PACK_SIGNATURE (-2)
50 #define PH_ERROR_PROTOCOL (-3)
51 extern int read_pack_header(int fd, struct pack_header *);
52 #endif