include/git2/pack.h

/*
 * Copyright (C) the libgit2 contributors. All rights reserved.
 *
 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
 */
#ifndef INCLUDE_git_pack_h__
#define INCLUDE_git_pack_h__

#include "common.h"
#include "oid.h"

/**
 * @file git2/pack.h
 * @brief Git pack management routines
 *
 * Packing objects
 * ---------------
 *
 * Creation of packfiles requires two steps:
 *
 * - First, insert all the objects you want to put into the packfile
 *   using `git_packbuilder_insert` and `git_packbuilder_insert_tree`.
 *   It's important to add the objects in recency order ("in the order
 *   that they are 'reachable' from head").
 *
 *   "ANY order will give you a working pack, ... [but it is] the thing
 *   that gives packs good locality. It keeps the objects close to the
 *   head (whether they are old or new, but they are _reachable_ from the
 *   head) at the head of the pack. So packs actually have absolutely
 *   _wonderful_ IO patterns." - Linus Torvalds
 *   git.git/Documentation/technical/pack-heuristics.txt
 *
 * - Second, use `git_packbuilder_write` or `git_packbuilder_foreach` to
 *   write the resulting packfile.
 *
 *   libgit2 will take care of the delta ordering and generation.
 *   `git_packbuilder_set_threads` can be used to adjust the number of
 *   threads used for the process.
 *
 * See tests-clar/pack/packbuilder.c for an example.
 *
 * @ingroup Git
 * @{
 */
GIT_BEGIN_DECL

/**
 * Initialize a new packbuilder
 *
 * @param out The new packbuilder object
 * @param repo The repository
 *
 * @return 0 or an error code
 */
GIT_EXTERN(int) git_packbuilder_new(git_packbuilder **out, git_repository *repo);

/**
 * Set number of threads to spawn
 *
 * By default, libgit2 won't spawn any threads at all;
 * when set to 0, libgit2 will autodetect the number of
 * CPUs.
 *
 * @param pb The packbuilder
 * @param n Number of threads to spawn
 * @return number of actual threads to be used
 */
GIT_EXTERN(unsigned int) git_packbuilder_set_threads(git_packbuilder *pb, unsigned int n);

/**
 * Insert a single object
 *
 * For an optimal pack it's mandatory to insert objects in recency order,
 * commits followed by trees and blobs.
 *
 * @param pb The packbuilder
 * @param id The oid of the commit
 * @param name The name; might be NULL
 *
 * @return 0 or an error code
 */
GIT_EXTERN(int) git_packbuilder_insert(git_packbuilder *pb, const git_oid *id, const char *name);

/**
 * Insert a root tree object
 *
 * This will add the tree as well as all referenced trees and blobs.
 *
 * @param pb The packbuilder
 * @param id The oid of the root tree
 *
 * @return 0 or an error code
 */
GIT_EXTERN(int) git_packbuilder_insert_tree(git_packbuilder *pb, const git_oid *id);

/**
 * Insert a commit object
 *
 * This will add a commit as well as the completed referenced tree.
 *
 * @param pb The packbuilder
 * @param id The oid of the commit
 *
 * @return 0 or an error code
 */
GIT_EXTERN(int) git_packbuilder_insert_commit(git_packbuilder *pb, const git_oid *id);

/**
 * Write the new pack and corresponding index file to path.
 *
 * @param pb The packbuilder
 * @param path to the directory where the packfile and index should be stored
 * @param progress_cb function to call with progress information from the indexer (optional)
 * @param progress_cb_payload payload for the progress callback (optional)
 *
 * @return 0 or an error code
 */
GIT_EXTERN(int) git_packbuilder_write(
	git_packbuilder *pb,
	const char *path,
	git_transfer_progress_callback progress_cb,
	void *progress_cb_payload);

typedef int (*git_packbuilder_foreach_cb)(void *buf, size_t size, void *payload);
/**
 * Create the new pack and pass each object to the callback
 *
 * @param pb the packbuilder
 * @param cb the callback to call with each packed object's buffer
 * @param payload the callback's data
 * @return 0 or an error code
 */
GIT_EXTERN(int) git_packbuilder_foreach(git_packbuilder *pb, git_packbuilder_foreach_cb cb, void *payload);

/**
 * Get the total number of objects the packbuilder will write out
 *
 * @param pb the packbuilder
 * @return
 */
GIT_EXTERN(uint32_t) git_packbuilder_object_count(git_packbuilder *pb);

/**
 * Get the number of objects the packbuilder has already written out
 *
 * @param pb the packbuilder
 * @return
 */
GIT_EXTERN(uint32_t) git_packbuilder_written(git_packbuilder *pb);

/**
 * Free the packbuilder and all associated data
 *
 * @param pb The packbuilder
 */
GIT_EXTERN(void) git_packbuilder_free(git_packbuilder *pb);

/** @} */
GIT_END_DECL
#endif