git/chunk-format.h

#ifndef CHUNK_FORMAT_H
#define CHUNK_FORMAT_H

#include "hash-ll.h"

struct hashfile;
struct chunkfile;

#define CHUNK_TOC_ENTRY_SIZE (sizeof(uint32_t) + sizeof(uint64_t))

/*
 * Initialize a 'struct chunkfile' for writing _or_ reading a file
 * with the chunk format.
 *
 * If writing a file, supply a non-NULL 'struct hashfile *' that will
 * be used to write.
 *
 * If reading a file, use a NULL 'struct hashfile *' and then call
 * read_table_of_contents(). Supply the memory-mapped data to the
 * pair_chunk() or read_chunk() methods, as appropriate.
 *
 * DO NOT MIX THESE MODES. Use different 'struct chunkfile' instances
 * for reading and writing.
 */
struct chunkfile *init_chunkfile(struct hashfile *f);
void free_chunkfile(struct chunkfile *cf);
int get_num_chunks(struct chunkfile *cf);
typedef int (*chunk_write_fn)(struct hashfile *f, void *data);
void add_chunk(struct chunkfile *cf,
	       uint32_t id,
	       size_t size,
	       chunk_write_fn fn);
int write_chunkfile(struct chunkfile *cf, void *data);

int read_table_of_contents(struct chunkfile *cf,
			   const unsigned char *mfile,
			   size_t mfile_size,
			   uint64_t toc_offset,
			   int toc_length);

#define CHUNK_NOT_FOUND (-2)

/*
 * Find 'chunk_id' in the given chunkfile and assign the
 * given pointer to the position in the mmap'd file where
 * that chunk begins. Likewise the "size" parameter is filled
 * with the size of the chunk.
 *
 * Returns CHUNK_NOT_FOUND if the chunk does not exist.
 */
int pair_chunk(struct chunkfile *cf,
	       uint32_t chunk_id,
	       const unsigned char **p,
	       size_t *size);

/*
 * Unsafe version of pair_chunk; it does not return the size,
 * meaning that the caller cannot possibly be careful about
 * reading out of bounds from the mapped memory.
 *
 * No new callers should use this function, and old callers should
 * be audited and migrated over to using the regular pair_chunk()
 * function.
 */
int pair_chunk_unsafe(struct chunkfile *cf,
		      uint32_t chunk_id,
		      const unsigned char **p);

typedef int (*chunk_read_fn)(const unsigned char *chunk_start,
			     size_t chunk_size, void *data);
/*
 * Find 'chunk_id' in the given chunkfile and call the
 * given chunk_read_fn method with the information for
 * that chunk.
 *
 * Returns CHUNK_NOT_FOUND if the chunk does not exist.
 */
int read_chunk(struct chunkfile *cf,
	       uint32_t chunk_id,
	       chunk_read_fn fn,
	       void *data);

uint8_t oid_version(const struct git_hash_algo *algop);

#endif