thodg/libgit2/src/odb_pack.c

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• Hash : f673e232
  Author :
  Date : 2018-12-27T13:47:34
  

  git_error: use new names in internal APIs and usage Move to the `git_error` name in the internal API for error-related functions.

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• src/odb_pack.c

• /*
   * 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.
   */
  
  #include "common.h"
  
  #include <zlib.h>
  #include "git2/repository.h"
  #include "git2/indexer.h"
  #include "git2/sys/odb_backend.h"
  #include "fileops.h"
  #include "hash.h"
  #include "odb.h"
  #include "delta.h"
  #include "sha1_lookup.h"
  #include "mwindow.h"
  #include "pack.h"
  
  #include "git2/odb_backend.h"
  
  /* re-freshen pack files no more than every 2 seconds */
  #define FRESHEN_FREQUENCY 2
  
  struct pack_backend {
  	git_odb_backend parent;
  	git_vector packs;
  	struct git_pack_file *last_found;
  	char *pack_folder;
  };
  
  struct pack_writepack {
  	struct git_odb_writepack parent;
  	git_indexer *indexer;
  };
  
  /**
   * The wonderful tale of a Packed Object lookup query
   * ===================================================
   *	A riveting and epic story of epicness and ASCII
   *			art, presented by yours truly,
   *				Sir Vicent of Marti
   *
   *
   *	Chapter 1: Once upon a time...
   *	Initialization of the Pack Backend
   *	--------------------------------------------------
   *
   *	# git_odb_backend_pack
   *	| Creates the pack backend structure, initializes the
   *	| callback pointers to our default read() and exist() methods,
   *	| and tries to preload all the known packfiles in the ODB.
   * |
   *	|-# packfile_load_all
   *	 | Tries to find the `pack` folder, if it exists. ODBs without
   *	 | a pack folder are ignored altogether. If there's a `pack` folder
   *	 | we run a `dirent` callback through every file in the pack folder
   *	 | to find our packfiles. The packfiles are then sorted according
   *	 | to a sorting callback.
   * 	 |
   *	 |-# packfile_load__cb
   *	 | | This callback is called from `dirent` with every single file
   *	 | | inside the pack folder. We find the packs by actually locating
   *	 | | their index (ends in ".idx"). From that index, we verify that
   *	 | | the corresponding packfile exists and is valid, and if so, we
   *	| | add it to the pack list.
   *	 | |
   *	 | |-# packfile_check
   *	 |		Make sure that there's a packfile to back this index, and store
   *	 |		some very basic information regarding the packfile itself,
   *	 |		such as the full path, the size, and the modification time.
   *	 |		We don't actually open the packfile to check for internal consistency.
   *	|
   *	|-# packfile_sort__cb
   *		Sort all the preloaded packs according to some specific criteria:
   *		we prioritize the "newer" packs because it's more likely they
   *		contain the objects we are looking for, and we prioritize local
   *		packs over remote ones.
   *
   *
   *
   *	Chapter 2: To be, or not to be...
   *	A standard packed `exist` query for an OID
   *	--------------------------------------------------
   *
   * # pack_backend__exists
   * | Check if the given SHA1 oid exists in any of the packs
   * | that have been loaded for our ODB.
   * |
   * |-# pack_entry_find
   *	| Iterate through all the packs that have been preloaded
   *	| (starting by the pack where the latest object was found)
   *	| to try to find the OID in one of them.
   *	|
   *	|-# pack_entry_find1
   *		| Check the index of an individual pack to see if the SHA1
   *		| OID can be found. If we can find the offset to that SHA1
   *		| inside of the index, that means the object is contained
   *		| inside of the packfile and we can stop searching.
   *		| Before returning, we verify that the packfile behing the
   *		| index we are searching still exists on disk.
   *		|
   *		|-# pack_entry_find_offset
   *		| | Mmap the actual index file to disk if it hasn't been opened
   *		| | yet, and run a binary search through it to find the OID.
   *		| | See <http://book.git-scm.com/7_the_packfile.html> for specifics
   *		| | on the Packfile Index format and how do we find entries in it.
   *		| |
   *		| |-# pack_index_open
   *		|	| Guess the name of the index based on the full path to the
   *		|	| packfile, open it and verify its contents. Only if the index
   *		|	| has not been opened already.
   *		|	|
   *		|	|-# pack_index_check
   *		|		Mmap the index file and do a quick run through the header
   *		|		to guess the index version (right now we support v1 and v2),
   *		|		and to verify that the size of the index makes sense.
   *		|
   *		|-# packfile_open
   *			See `packfile_open` in Chapter 3
   *
   *
   *
   *	Chapter 3: The neverending story...
   *	A standard packed `lookup` query for an OID
   *	--------------------------------------------------
   *	TODO
   *
   */
  
  
  /***********************************************************
   *
   * FORWARD DECLARATIONS
   *
   ***********************************************************/
  
  static int packfile_sort__cb(const void *a_, const void *b_);
  
  static int packfile_load__cb(void *_data, git_buf *path);
  
  static int pack_entry_find(struct git_pack_entry *e,
  	struct pack_backend *backend, const git_oid *oid);
  
  /* Can find the offset of an object given
   * a prefix of an identifier.
   * Sets GIT_EAMBIGUOUS if short oid is ambiguous.
   * This method assumes that len is between
   * GIT_OID_MINPREFIXLEN and GIT_OID_HEXSZ.
   */
  static int pack_entry_find_prefix(
  	struct git_pack_entry *e,
  	struct pack_backend *backend,
  	const git_oid *short_oid,
  	size_t len);
  
  
  
  /***********************************************************
   *
   * PACK WINDOW MANAGEMENT
   *
   ***********************************************************/
  
  static int packfile_sort__cb(const void *a_, const void *b_)
  {
  	const struct git_pack_file *a = a_;
  	const struct git_pack_file *b = b_;
  	int st;
  
  	/*
  	 * Local packs tend to contain objects specific to our
  	 * variant of the project than remote ones. In addition,
  	 * remote ones could be on a network mounted filesystem.
  	 * Favor local ones for these reasons.
  	 */
  	st = a->pack_local - b->pack_local;
  	if (st)
  		return -st;
  
  	/*
  	 * Younger packs tend to contain more recent objects,
  	 * and more recent objects tend to get accessed more
  	 * often.
  	 */
  	if (a->mtime < b->mtime)
  		return 1;
  	else if (a->mtime == b->mtime)
  		return 0;
  
  	return -1;
  }
  
  
  static int packfile_load__cb(void *data, git_buf *path)
  {
  	struct pack_backend *backend = data;
  	struct git_pack_file *pack;
  	const char *path_str = git_buf_cstr(path);
  	size_t i, cmp_len = git_buf_len(path);
  	int error;
  
  	if (cmp_len <= strlen(".idx") || git__suffixcmp(path_str, ".idx") != 0)
  		return 0; /* not an index */
  
  	cmp_len -= strlen(".idx");
  
  	for (i = 0; i < backend->packs.length; ++i) {
  		struct git_pack_file *p = git_vector_get(&backend->packs, i);
  
  		if (strncmp(p->pack_name, path_str, cmp_len) == 0)
  			return 0;
  	}
  
  	error = git_mwindow_get_pack(&pack, path->ptr);
  
  	/* ignore missing .pack file as git does */
  	if (error == GIT_ENOTFOUND) {
  		git_error_clear();
  		return 0;
  	}
  
  	if (!error)
  		error = git_vector_insert(&backend->packs, pack);
  
  	return error;
  
  }
  
  static int pack_entry_find_inner(
  	struct git_pack_entry *e,
  	struct pack_backend *backend,
  	const git_oid *oid,
  	struct git_pack_file *last_found)
  {
  	size_t i;
  
  	if (last_found &&
  		git_pack_entry_find(e, last_found, oid, GIT_OID_HEXSZ) == 0)
  		return 0;
  
  	for (i = 0; i < backend->packs.length; ++i) {
  		struct git_pack_file *p;
  
  		p = git_vector_get(&backend->packs, i);
  		if (p == last_found)
  			continue;
  
  		if (git_pack_entry_find(e, p, oid, GIT_OID_HEXSZ) == 0) {
  			backend->last_found = p;
  			return 0;
  		}
  	}
  
  	return -1;
  }
  
  static int pack_entry_find(struct git_pack_entry *e, struct pack_backend *backend, const git_oid *oid)
  {
  	struct git_pack_file *last_found = backend->last_found;
  
  	if (backend->last_found &&
  		git_pack_entry_find(e, backend->last_found, oid, GIT_OID_HEXSZ) == 0)
  		return 0;
  
  	if (!pack_entry_find_inner(e, backend, oid, last_found))
  		return 0;
  
  	return git_odb__error_notfound(
  		"failed to find pack entry", oid, GIT_OID_HEXSZ);
  }
  
  static int pack_entry_find_prefix(
  	struct git_pack_entry *e,
  	struct pack_backend *backend,
  	const git_oid *short_oid,
  	size_t len)
  {
  	int error;
  	size_t i;
  	git_oid found_full_oid = {{0}};
  	bool found = false;
  	struct git_pack_file *last_found = backend->last_found;
  
  	if (last_found) {
  		error = git_pack_entry_find(e, last_found, short_oid, len);
  		if (error == GIT_EAMBIGUOUS)
  			return error;
  		if (!error) {
  			git_oid_cpy(&found_full_oid, &e->sha1);
  			found = true;
  		}
  	}
  
  	for (i = 0; i < backend->packs.length; ++i) {
  		struct git_pack_file *p;
  
  		p = git_vector_get(&backend->packs, i);
  		if (p == last_found)
  			continue;
  
  		error = git_pack_entry_find(e, p, short_oid, len);
  		if (error == GIT_EAMBIGUOUS)
  			return error;
  		if (!error) {
  			if (found && git_oid_cmp(&e->sha1, &found_full_oid))
  				return git_odb__error_ambiguous("found multiple pack entries");
  			git_oid_cpy(&found_full_oid, &e->sha1);
  			found = true;
  			backend->last_found = p;
  		}
  	}
  
  	if (!found)
  		return git_odb__error_notfound("no matching pack entry for prefix",
  			short_oid, len);
  	else
  		return 0;
  }
  
  
  /***********************************************************
   *
   * PACKED BACKEND PUBLIC API
   *
   * Implement the git_odb_backend API calls
   *
   ***********************************************************/
  static int pack_backend__refresh(git_odb_backend *backend_)
  {
  	int error;
  	struct stat st;
  	git_buf path = GIT_BUF_INIT;
  	struct pack_backend *backend = (struct pack_backend *)backend_;
  
  	if (backend->pack_folder == NULL)
  		return 0;
  
  	if (p_stat(backend->pack_folder, &st) < 0 || !S_ISDIR(st.st_mode))
  		return git_odb__error_notfound("failed to refresh packfiles", NULL, 0);
  
  	git_buf_sets(&path, backend->pack_folder);
  
  	/* reload all packs */
  	error = git_path_direach(&path, 0, packfile_load__cb, backend);
  
  	git_buf_dispose(&path);
  	git_vector_sort(&backend->packs);
  
  	return error;
  }
  
  static int pack_backend__read_header(
  	size_t *len_p, git_object_t *type_p,
  	struct git_odb_backend *backend, const git_oid *oid)
  {
  	struct git_pack_entry e;
  	int error;
  
  	assert(len_p && type_p && backend && oid);
  
  	if ((error = pack_entry_find(&e, (struct pack_backend *)backend, oid)) < 0)
  		return error;
  
  	return git_packfile_resolve_header(len_p, type_p, e.p, e.offset);
  }
  
  static int pack_backend__freshen(
  	git_odb_backend *backend, const git_oid *oid)
  {
  	struct git_pack_entry e;
  	time_t now;
  	int error;
  
  	if ((error = pack_entry_find(&e, (struct pack_backend *)backend, oid)) < 0)
  		return error;
  
  	now = time(NULL);
  
  	if (e.p->last_freshen > now - FRESHEN_FREQUENCY)
  		return 0;
  
  	if ((error = git_futils_touch(e.p->pack_name, &now)) < 0)
  		return error;
  
  	e.p->last_freshen = now;
  	return 0;
  }
  
  static int pack_backend__read(
  	void **buffer_p, size_t *len_p, git_object_t *type_p,
  	git_odb_backend *backend, const git_oid *oid)
  {
  	struct git_pack_entry e;
  	git_rawobj raw = {NULL};
  	int error;
  
  	if ((error = pack_entry_find(&e, (struct pack_backend *)backend, oid)) < 0 ||
  		(error = git_packfile_unpack(&raw, e.p, &e.offset)) < 0)
  		return error;
  
  	*buffer_p = raw.data;
  	*len_p = raw.len;
  	*type_p = raw.type;
  
  	return 0;
  }
  
  static int pack_backend__read_prefix(
  	git_oid *out_oid,
  	void **buffer_p,
  	size_t *len_p,
  	git_object_t *type_p,
  	git_odb_backend *backend,
  	const git_oid *short_oid,
  	size_t len)
  {
  	int error = 0;
  
  	if (len < GIT_OID_MINPREFIXLEN)
  		error = git_odb__error_ambiguous("prefix length too short");
  
  	else if (len >= GIT_OID_HEXSZ) {
  		/* We can fall back to regular read method */
  		error = pack_backend__read(buffer_p, len_p, type_p, backend, short_oid);
  		if (!error)
  			git_oid_cpy(out_oid, short_oid);
  	} else {
  		struct git_pack_entry e;
  		git_rawobj raw = {NULL};
  
  		if ((error = pack_entry_find_prefix(
  				&e, (struct pack_backend *)backend, short_oid, len)) == 0 &&
  			(error = git_packfile_unpack(&raw, e.p, &e.offset)) == 0)
  		{
  			*buffer_p = raw.data;
  			*len_p = raw.len;
  			*type_p = raw.type;
  			git_oid_cpy(out_oid, &e.sha1);
  		}
  	}
  
  	return error;
  }
  
  static int pack_backend__exists(git_odb_backend *backend, const git_oid *oid)
  {
  	struct git_pack_entry e;
  	return pack_entry_find(&e, (struct pack_backend *)backend, oid) == 0;
  }
  
  static int pack_backend__exists_prefix(
  	git_oid *out, git_odb_backend *backend, const git_oid *short_id, size_t len)
  {
  	int error;
  	struct pack_backend *pb = (struct pack_backend *)backend;
  	struct git_pack_entry e = {0};
  
  	error = pack_entry_find_prefix(&e, pb, short_id, len);
  	git_oid_cpy(out, &e.sha1);
  	return error;
  }
  
  static int pack_backend__foreach(git_odb_backend *_backend, git_odb_foreach_cb cb, void *data)
  {
  	int error;
  	struct git_pack_file *p;
  	struct pack_backend *backend;
  	unsigned int i;
  
  	assert(_backend && cb);
  	backend = (struct pack_backend *)_backend;
  
  	/* Make sure we know about the packfiles */
  	if ((error = pack_backend__refresh(_backend)) < 0)
  		return error;
  
  	git_vector_foreach(&backend->packs, i, p) {
  		if ((error = git_pack_foreach_entry(p, cb, data)) != 0)
  			return error;
  	}
  
  	return 0;
  }
  
  static int pack_backend__writepack_append(struct git_odb_writepack *_writepack, const void *data, size_t size, git_transfer_progress *stats)
  {
  	struct pack_writepack *writepack = (struct pack_writepack *)_writepack;
  
  	assert(writepack);
  
  	return git_indexer_append(writepack->indexer, data, size, stats);
  }
  
  static int pack_backend__writepack_commit(struct git_odb_writepack *_writepack, git_transfer_progress *stats)
  {
  	struct pack_writepack *writepack = (struct pack_writepack *)_writepack;
  
  	assert(writepack);
  
  	return git_indexer_commit(writepack->indexer, stats);
  }
  
  static void pack_backend__writepack_free(struct git_odb_writepack *_writepack)
  {
  	struct pack_writepack *writepack = (struct pack_writepack *)_writepack;
  
  	assert(writepack);
  
  	git_indexer_free(writepack->indexer);
  	git__free(writepack);
  }
  
  static int pack_backend__writepack(struct git_odb_writepack **out,
  	git_odb_backend *_backend,
          git_odb *odb,
  	git_transfer_progress_cb progress_cb,
  	void *progress_payload)
  {
  	git_indexer_options opts = GIT_INDEXER_OPTIONS_INIT;
  	struct pack_backend *backend;
  	struct pack_writepack *writepack;
  
  	assert(out && _backend);
  
  	*out = NULL;
  
  	opts.progress_cb = progress_cb;
  	opts.progress_cb_payload = progress_payload;
  
  	backend = (struct pack_backend *)_backend;
  
  	writepack = git__calloc(1, sizeof(struct pack_writepack));
  	GIT_ERROR_CHECK_ALLOC(writepack);
  
  	if (git_indexer_new(&writepack->indexer,
  		backend->pack_folder, 0, odb, &opts) < 0) {
  		git__free(writepack);
  		return -1;
  	}
  
  	writepack->parent.backend = _backend;
  	writepack->parent.append = pack_backend__writepack_append;
  	writepack->parent.commit = pack_backend__writepack_commit;
  	writepack->parent.free = pack_backend__writepack_free;
  
  	*out = (git_odb_writepack *)writepack;
  
  	return 0;
  }
  
  static void pack_backend__free(git_odb_backend *_backend)
  {
  	struct pack_backend *backend;
  	size_t i;
  
  	assert(_backend);
  
  	backend = (struct pack_backend *)_backend;
  
  	for (i = 0; i < backend->packs.length; ++i) {
  		struct git_pack_file *p = git_vector_get(&backend->packs, i);
  		git_mwindow_put_pack(p);
  	}
  
  	git_vector_free(&backend->packs);
  	git__free(backend->pack_folder);
  	git__free(backend);
  }
  
  static int pack_backend__alloc(struct pack_backend **out, size_t initial_size)
  {
  	struct pack_backend *backend = git__calloc(1, sizeof(struct pack_backend));
  	GIT_ERROR_CHECK_ALLOC(backend);
  
  	if (git_vector_init(&backend->packs, initial_size, packfile_sort__cb) < 0) {
  		git__free(backend);
  		return -1;
  	}
  
  	backend->parent.version = GIT_ODB_BACKEND_VERSION;
  
  	backend->parent.read = &pack_backend__read;
  	backend->parent.read_prefix = &pack_backend__read_prefix;
  	backend->parent.read_header = &pack_backend__read_header;
  	backend->parent.exists = &pack_backend__exists;
  	backend->parent.exists_prefix = &pack_backend__exists_prefix;
  	backend->parent.refresh = &pack_backend__refresh;
  	backend->parent.foreach = &pack_backend__foreach;
  	backend->parent.writepack = &pack_backend__writepack;
  	backend->parent.freshen = &pack_backend__freshen;
  	backend->parent.free = &pack_backend__free;
  
  	*out = backend;
  	return 0;
  }
  
  int git_odb_backend_one_pack(git_odb_backend **backend_out, const char *idx)
  {
  	struct pack_backend *backend = NULL;
  	struct git_pack_file *packfile = NULL;
  
  	if (pack_backend__alloc(&backend, 1) < 0)
  		return -1;
  
  	if (git_mwindow_get_pack(&packfile, idx) < 0 ||
  		git_vector_insert(&backend->packs, packfile) < 0)
  	{
  		pack_backend__free((git_odb_backend *)backend);
  		return -1;
  	}
  
  	*backend_out = (git_odb_backend *)backend;
  	return 0;
  }
  
  int git_odb_backend_pack(git_odb_backend **backend_out, const char *objects_dir)
  {
  	int error = 0;
  	struct pack_backend *backend = NULL;
  	git_buf path = GIT_BUF_INIT;
  
  	if (pack_backend__alloc(&backend, 8) < 0)
  		return -1;
  
  	if (!(error = git_buf_joinpath(&path, objects_dir, "pack")) &&
  		git_path_isdir(git_buf_cstr(&path)))
  	{
  		backend->pack_folder = git_buf_detach(&path);
  		error = pack_backend__refresh((git_odb_backend *)backend);
  	}
  
  	if (error < 0) {
  		pack_backend__free((git_odb_backend *)backend);
  		backend = NULL;
  	}
  
  	*backend_out = (git_odb_backend *)backend;
  
  	git_buf_dispose(&path);
  
  	return error;
  }
  

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