git/pack.h

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#ifndef PACK_H
#define PACK_H
#include "object.h"
/*
* Packed object header
*/
#define PACK_SIGNATURE 0x5041434b /* "PACK" */
#define PACK_VERSION 2
#define pack_version_ok(v) ((v) == htonl(2) || (v) == htonl(3))
struct pack_header {
uint32_t hdr_signature;
uint32_t hdr_version;
uint32_t hdr_entries;
};
/*
* Packed object index header
*
* struct pack_idx_header {
* uint32_t idx_signature;
* uint32_t idx_version;
* };
*
* Note: this header isn't active yet. In future versions of git
* we may change the index file format. At that time we would start
* the first four bytes of the new index format with this signature,
* as all older git binaries would find this value illegal and abort
* reading the file.
*
* This is the case because the number of objects in a packfile
* cannot exceed 1,431,660,000 as every object would need at least
* 3 bytes of data and the overall packfile cannot exceed 4 GiB due
* to the 32 bit offsets used by the index. Clearly the signature
* exceeds this maximum.
*
* Very old git binaries will also compare the first 4 bytes to the
* next 4 bytes in the index and abort with a "non-monotonic index"
* error if the second 4 byte word is smaller than the first 4
* byte word. This would be true in the proposed future index
* format as idx_signature would be greater than idx_version.
*/
#define PACK_IDX_SIGNATURE 0xff744f63 /* "\377tOc" */
extern int verify_pack(struct packed_git *, int);
#define PH_ERROR_EOF (-1)
#define PH_ERROR_PACK_SIGNATURE (-2)
#define PH_ERROR_PROTOCOL (-3)
extern int read_pack_header(int fd, struct pack_header *);
#endif