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csum-file.h
Junio C Hamano authored
It is useful to be able to rewind a check-summed file to a certain
previous state after writing data into it using sha1write() API. The
fast-import command does this after streaming a blob data to the packfile
being generated and then noticing that the same blob has already been
written, and it does this with a private code truncate_pack() that is
commented as "Yes, this is a layering violation".
Introduce two API functions, sha1file_checkpoint(), that allows the caller
to save a state of a sha1file, and then later revert it to the saved state.
Use it to reimplement truncate_pack().
Signed-off-by: 
Junio C Hamano <gitster@pobox.com> csum-file.h 1.05 KiB
#ifndef CSUM_FILE_H
#define CSUM_FILE_H
struct progress;
/* A SHA1-protected file */
struct sha1file {
int fd;
int check_fd;
unsigned int offset;
git_SHA_CTX ctx;
off_t total;
struct progress *tp;
const char *name;
int do_crc;
uint32_t crc32;
unsigned char buffer[8192];
};
/* Checkpoint */
struct sha1file_checkpoint {
off_t offset;
git_SHA_CTX ctx;
};
extern void sha1file_checkpoint(struct sha1file *, struct sha1file_checkpoint *);
extern int sha1file_truncate(struct sha1file *, struct sha1file_checkpoint *);
/* sha1close flags */
#define CSUM_CLOSE 1
#define CSUM_FSYNC 2
extern struct sha1file *sha1fd(int fd, const char *name);
extern struct sha1file *sha1fd_check(const char *name);
extern struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp);
extern int sha1close(struct sha1file *, unsigned char *, unsigned int);
extern int sha1write(struct sha1file *, void *, unsigned int);
extern void sha1flush(struct sha1file *f);
extern void crc32_begin(struct sha1file *);
extern uint32_t crc32_end(struct sha1file *);
#endif