gitdex.h is a small, header only C library for parsing git index files (stored at .git/index in any git repository).

The binary format itself is specified in git's technical documentation

demo.c is an example program which will simply read and print out the index file.

In order to use gitdex, you must first have your file which you would like parsed stored in a buffer. Gitdex also require that you know the size of the file.

// Parses the buffer into a gitdex_t structure.
gitdex_t *index;
index = gitdex_alloc(buffer, size);

// print the first entry
gitdex_print_entry(&index->entries[0])

// free the gitdex_t structure
gitdex_free(index);

Will take a file buffer stored at src, of length size (in bytes) and return a pointer to parsed gitdex structure.

Free's the memory allocated by gitdex_alloc.

Parses a file buffer src of length size into a structure at dest.

Returns the size of the index (the size of the header plus the total size of all the entries as they were store in the original buffer).

Parses a file buffer src into a structure at dest.

Returns the length of the header (alwayas 12 bytes).

Parses an entry at src into a structure at dest.

Returns the length of the entry.

Checks to see if a file buffer at src has a valid file signature.

Returns 1 or 0 if the file is valid or not respectively.

void gitdex_print_index(gitdex_t *index)
void gitdex_print_entry(gitdex_entry_t *entry)
void gitdex_print_header(gitdex_header_t *header)

gitdex_header_t stores the first 12 bytes of the index file, which always contains the signature, version and number of entries.

typedef struct {
	char signature[4];
	uint32_t version;
	uint32_t entries;
} gitdex_header_t;

gitdex_entry_t stores a single index entry, which contains everything git knows about a single file.

typedef struct {
	uint32_t ctime_second;
	uint32_t ctime_nano;
	uint32_t mtime_second;
	uint32_t mtime_nano;
	uint32_t dev;
	uint32_t ino;
	uint32_t mode;
	uint32_t uid;
	uint32_t gid;
	uint32_t size;
	uint8_t  sha1[SHA1_SIZE];
	uint16_t flags;
	uint16_t extended;
	char name[NAME_MAX];
} gitdex_entry_t;

gitdex_t represents a whole index file consolidated into one structure, it contains the header information as well as a pointer to some arbitrary number of entries.

typedef struct {
	gitdex_header_t header;
	gitdex_entry_t  *entries;
} gitdex_t;