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The callers immediately throw away the offset, so we don't need any logical changes in any of them. This will be useful for the indexer, as it does need to know where the compressed data ends. Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>
500 lines
15 KiB
C
500 lines
15 KiB
C
/*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License, version 2,
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* as published by the Free Software Foundation.
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*
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* In addition to the permissions in the GNU General Public License,
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* the authors give you unlimited permission to link the compiled
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* version of this file into combinations with other programs,
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* and to distribute those combinations without any restriction
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* coming from the use of this file. (The General Public License
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* restrictions do apply in other respects; for example, they cover
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* modification of the file, and distribution when not linked into
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* a combined executable.)
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*
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* This file is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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#include "common.h"
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#include "git2/zlib.h"
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#include "git2/repository.h"
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#include "git2/oid.h"
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#include "fileops.h"
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#include "hash.h"
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#include "odb.h"
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#include "delta-apply.h"
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#include "sha1_lookup.h"
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#include "mwindow.h"
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#include "pack.h"
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#include "git2/odb_backend.h"
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struct pack_backend {
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git_odb_backend parent;
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git_vector packs;
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struct git_pack_file *last_found;
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char *pack_folder;
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time_t pack_folder_mtime;
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};
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/**
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* The wonderful tale of a Packed Object lookup query
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* ===================================================
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* A riveting and epic story of epicness and ASCII
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* art, presented by yours truly,
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* Sir Vicent of Marti
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*
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*
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* Chapter 1: Once upon a time...
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* Initialization of the Pack Backend
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* --------------------------------------------------
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*
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* # git_odb_backend_pack
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* | Creates the pack backend structure, initializes the
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* | callback pointers to our default read() and exist() methods,
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* | and tries to preload all the known packfiles in the ODB.
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* |
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* |-# packfile_load_all
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* | Tries to find the `pack` folder, if it exists. ODBs without
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* | a pack folder are ignored altogether. If there's a `pack` folder
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* | we run a `dirent` callback through every file in the pack folder
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* | to find our packfiles. The packfiles are then sorted according
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* | to a sorting callback.
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* |
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* |-# packfile_load__cb
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* | | This callback is called from `dirent` with every single file
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* | | inside the pack folder. We find the packs by actually locating
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* | | their index (ends in ".idx"). From that index, we verify that
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* | | the corresponding packfile exists and is valid, and if so, we
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* | | add it to the pack list.
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* | |
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* | |-# packfile_check
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* | Make sure that there's a packfile to back this index, and store
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* | some very basic information regarding the packfile itself,
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* | such as the full path, the size, and the modification time.
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* | We don't actually open the packfile to check for internal consistency.
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* |
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* |-# packfile_sort__cb
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* Sort all the preloaded packs according to some specific criteria:
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* we prioritize the "newer" packs because it's more likely they
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* contain the objects we are looking for, and we prioritize local
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* packs over remote ones.
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*
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*
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*
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* Chapter 2: To be, or not to be...
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* A standard packed `exist` query for an OID
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* --------------------------------------------------
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*
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* # pack_backend__exists
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* | Check if the given SHA1 oid exists in any of the packs
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* | that have been loaded for our ODB.
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* |
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* |-# pack_entry_find
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* | Iterate through all the packs that have been preloaded
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* | (starting by the pack where the latest object was found)
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* | to try to find the OID in one of them.
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* |
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* |-# pack_entry_find1
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* | Check the index of an individual pack to see if the SHA1
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* | OID can be found. If we can find the offset to that SHA1
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* | inside of the index, that means the object is contained
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* | inside of the packfile and we can stop searching.
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* | Before returning, we verify that the packfile behing the
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* | index we are searching still exists on disk.
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* |
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* |-# pack_entry_find_offset
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* | | Mmap the actual index file to disk if it hasn't been opened
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* | | yet, and run a binary search through it to find the OID.
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* | | See <http://book.git-scm.com/7_the_packfile.html> for specifics
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* | | on the Packfile Index format and how do we find entries in it.
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* | |
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* | |-# pack_index_open
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* | | Guess the name of the index based on the full path to the
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* | | packfile, open it and verify its contents. Only if the index
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* | | has not been opened already.
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* | |
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* | |-# pack_index_check
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* | Mmap the index file and do a quick run through the header
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* | to guess the index version (right now we support v1 and v2),
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* | and to verify that the size of the index makes sense.
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* |
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* |-# packfile_open
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* See `packfile_open` in Chapter 3
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*
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*
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*
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* Chapter 3: The neverending story...
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* A standard packed `lookup` query for an OID
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* --------------------------------------------------
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* TODO
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*
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*/
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/***********************************************************
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*
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* FORWARD DECLARATIONS
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*
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***********************************************************/
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static void pack_window_free_all(struct pack_backend *backend, struct git_pack_file *p);
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static int pack_window_contains(git_mwindow *win, off_t offset);
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static int packfile_sort__cb(const void *a_, const void *b_);
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static int packfile_load__cb(void *_data, char *path);
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static int packfile_refresh_all(struct pack_backend *backend);
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static int pack_entry_find(struct git_pack_entry *e,
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struct pack_backend *backend, const git_oid *oid);
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/* Can find the offset of an object given
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* a prefix of an identifier.
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* Throws GIT_EAMBIGUOUSOIDPREFIX if short oid
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* is ambiguous.
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* This method assumes that len is between
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* GIT_OID_MINPREFIXLEN and GIT_OID_HEXSZ.
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*/
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static int pack_entry_find_prefix(struct git_pack_entry *e,
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struct pack_backend *backend,
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const git_oid *short_oid,
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unsigned int len);
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/***********************************************************
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*
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* PACK WINDOW MANAGEMENT
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*
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***********************************************************/
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GIT_INLINE(void) pack_window_free_all(struct pack_backend *GIT_UNUSED(backend), struct git_pack_file *p)
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{
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git_mwindow_free_all(&p->mwf);
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}
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GIT_INLINE(int) pack_window_contains(git_mwindow *win, off_t offset)
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{
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/* We must promise at least 20 bytes (one hash) after the
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* offset is available from this window, otherwise the offset
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* is not actually in this window and a different window (which
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* has that one hash excess) must be used. This is to support
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* the object header and delta base parsing routines below.
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*/
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return git_mwindow_contains(win, offset + 20);
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}
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static int packfile_sort__cb(const void *a_, const void *b_)
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{
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const struct git_pack_file *a = a_;
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const struct git_pack_file *b = b_;
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int st;
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/*
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* Local packs tend to contain objects specific to our
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* variant of the project than remote ones. In addition,
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* remote ones could be on a network mounted filesystem.
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* Favor local ones for these reasons.
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*/
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st = a->pack_local - b->pack_local;
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if (st)
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return -st;
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/*
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* Younger packs tend to contain more recent objects,
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* and more recent objects tend to get accessed more
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* often.
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*/
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if (a->mtime < b->mtime)
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return 1;
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else if (a->mtime == b->mtime)
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return 0;
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return -1;
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}
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static int packfile_load__cb(void *_data, char *path)
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{
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struct pack_backend *backend = (struct pack_backend *)_data;
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struct git_pack_file *pack;
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int error;
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size_t i;
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if (git__suffixcmp(path, ".idx") != 0)
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return GIT_SUCCESS; /* not an index */
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for (i = 0; i < backend->packs.length; ++i) {
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struct git_pack_file *p = git_vector_get(&backend->packs, i);
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if (memcmp(p->pack_name, path, strlen(path) - STRLEN(".idx")) == 0)
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return GIT_SUCCESS;
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}
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error = git_packfile_check(&pack, path);
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if (error < GIT_SUCCESS)
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return git__rethrow(error, "Failed to load packfile");
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if (git_vector_insert(&backend->packs, pack) < GIT_SUCCESS) {
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free(pack);
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return GIT_ENOMEM;
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}
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return GIT_SUCCESS;
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}
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static int packfile_refresh_all(struct pack_backend *backend)
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{
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int error;
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struct stat st;
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if (backend->pack_folder == NULL)
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return GIT_SUCCESS;
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if (p_stat(backend->pack_folder, &st) < 0 || !S_ISDIR(st.st_mode))
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return git__throw(GIT_ENOTFOUND, "Failed to refresh packfiles. Backend not found");
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if (st.st_mtime != backend->pack_folder_mtime) {
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char path[GIT_PATH_MAX];
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strcpy(path, backend->pack_folder);
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/* reload all packs */
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error = git_futils_direach(path, GIT_PATH_MAX, packfile_load__cb, (void *)backend);
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if (error < GIT_SUCCESS)
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return git__rethrow(error, "Failed to refresh packfiles");
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git_vector_sort(&backend->packs);
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backend->pack_folder_mtime = st.st_mtime;
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}
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return GIT_SUCCESS;
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}
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static int pack_entry_find(struct git_pack_entry *e, struct pack_backend *backend, const git_oid *oid)
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{
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int error;
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size_t i;
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if ((error = packfile_refresh_all(backend)) < GIT_SUCCESS)
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return git__rethrow(error, "Failed to find pack entry");
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if (backend->last_found &&
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git_pack_entry_find(e, backend->last_found, oid, GIT_OID_HEXSZ) == GIT_SUCCESS)
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return GIT_SUCCESS;
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for (i = 0; i < backend->packs.length; ++i) {
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struct git_pack_file *p;
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p = git_vector_get(&backend->packs, i);
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if (p == backend->last_found)
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continue;
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if (git_pack_entry_find(e, p, oid, GIT_OID_HEXSZ) == GIT_SUCCESS) {
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backend->last_found = p;
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return GIT_SUCCESS;
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}
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}
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return git__throw(GIT_ENOTFOUND, "Failed to find pack entry");
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}
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static int pack_entry_find_prefix(
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struct git_pack_entry *e,
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struct pack_backend *backend,
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const git_oid *short_oid,
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unsigned int len)
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{
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int error;
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size_t i;
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unsigned found = 0;
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if ((error = packfile_refresh_all(backend)) < GIT_SUCCESS)
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return git__rethrow(error, "Failed to find pack entry");
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if (backend->last_found) {
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error = git_pack_entry_find(e, backend->last_found, short_oid, len);
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if (error == GIT_EAMBIGUOUSOIDPREFIX) {
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return git__rethrow(error, "Failed to find pack entry. Ambiguous sha1 prefix");
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} else if (error == GIT_SUCCESS) {
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found = 1;
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}
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}
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for (i = 0; i < backend->packs.length; ++i) {
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struct git_pack_file *p;
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p = git_vector_get(&backend->packs, i);
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if (p == backend->last_found)
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continue;
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error = git_pack_entry_find(e, p, short_oid, len);
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if (error == GIT_EAMBIGUOUSOIDPREFIX) {
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return git__rethrow(error, "Failed to find pack entry. Ambiguous sha1 prefix");
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} else if (error == GIT_SUCCESS) {
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found++;
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if (found > 1)
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break;
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backend->last_found = p;
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}
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}
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if (!found) {
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return git__rethrow(GIT_ENOTFOUND, "Failed to find pack entry");
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} else if (found > 1) {
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return git__rethrow(GIT_EAMBIGUOUSOIDPREFIX, "Failed to find pack entry. Ambiguous sha1 prefix");
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} else {
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return GIT_SUCCESS;
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}
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}
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/***********************************************************
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*
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* PACKED BACKEND PUBLIC API
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*
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* Implement the git_odb_backend API calls
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*
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***********************************************************/
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/*
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int pack_backend__read_header(git_rawobj *obj, git_odb_backend *backend, const git_oid *oid)
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{
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pack_location location;
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assert(obj && backend && oid);
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if (locate_packfile(&location, (struct pack_backend *)backend, oid) < 0)
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return GIT_ENOTFOUND;
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return read_header_packed(obj, &location);
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}
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*/
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int pack_backend__read(void **buffer_p, size_t *len_p, git_otype *type_p, git_odb_backend *backend, const git_oid *oid)
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{
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struct git_pack_entry e;
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git_rawobj raw;
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int error;
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if ((error = pack_entry_find(&e, (struct pack_backend *)backend, oid)) < GIT_SUCCESS)
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return git__rethrow(error, "Failed to read pack backend");
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if ((error = git_packfile_unpack(&raw, e.p, &e.offset)) < GIT_SUCCESS)
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return git__rethrow(error, "Failed to read pack backend");
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*buffer_p = raw.data;
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*len_p = raw.len;
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*type_p = raw.type;
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return GIT_SUCCESS;
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}
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int pack_backend__read_prefix(
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git_oid *out_oid,
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void **buffer_p,
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size_t *len_p,
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git_otype *type_p,
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git_odb_backend *backend,
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const git_oid *short_oid,
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unsigned int len)
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{
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if (len < GIT_OID_MINPREFIXLEN)
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return git__throw(GIT_EAMBIGUOUSOIDPREFIX, "Failed to read pack backend. Prefix length is lower than %d.", GIT_OID_MINPREFIXLEN);
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if (len >= GIT_OID_HEXSZ) {
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/* We can fall back to regular read method */
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int error = pack_backend__read(buffer_p, len_p, type_p, backend, short_oid);
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if (error == GIT_SUCCESS)
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git_oid_cpy(out_oid, short_oid);
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return error;
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} else {
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struct git_pack_entry e;
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git_rawobj raw;
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int error;
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if ((error = pack_entry_find_prefix(&e, (struct pack_backend *)backend, short_oid, len)) < GIT_SUCCESS)
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return git__rethrow(error, "Failed to read pack backend");
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if ((error = git_packfile_unpack(&raw, e.p, &e.offset)) < GIT_SUCCESS)
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return git__rethrow(error, "Failed to read pack backend");
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*buffer_p = raw.data;
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*len_p = raw.len;
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*type_p = raw.type;
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git_oid_cpy(out_oid, &e.sha1);
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}
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return GIT_SUCCESS;
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}
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int pack_backend__exists(git_odb_backend *backend, const git_oid *oid)
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{
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struct git_pack_entry e;
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return pack_entry_find(&e, (struct pack_backend *)backend, oid) == GIT_SUCCESS;
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}
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void pack_backend__free(git_odb_backend *_backend)
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{
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struct pack_backend *backend;
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size_t i;
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assert(_backend);
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backend = (struct pack_backend *)_backend;
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for (i = 0; i < backend->packs.length; ++i) {
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struct git_pack_file *p = git_vector_get(&backend->packs, i);
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packfile_free(p);
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}
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git_vector_free(&backend->packs);
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free(backend->pack_folder);
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free(backend);
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}
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int git_odb_backend_pack(git_odb_backend **backend_out, const char *objects_dir)
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{
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struct pack_backend *backend;
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char path[GIT_PATH_MAX];
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backend = git__calloc(1, sizeof(struct pack_backend));
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if (backend == NULL)
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return GIT_ENOMEM;
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if (git_vector_init(&backend->packs, 8, packfile_sort__cb) < GIT_SUCCESS) {
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free(backend);
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return GIT_ENOMEM;
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}
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git_path_join(path, objects_dir, "pack");
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if (git_futils_isdir(path) == GIT_SUCCESS) {
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backend->pack_folder = git__strdup(path);
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backend->pack_folder_mtime = 0;
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if (backend->pack_folder == NULL) {
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free(backend);
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return GIT_ENOMEM;
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}
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}
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backend->parent.read = &pack_backend__read;
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backend->parent.read_prefix = &pack_backend__read_prefix;
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backend->parent.read_header = NULL;
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backend->parent.exists = &pack_backend__exists;
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backend->parent.free = &pack_backend__free;
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*backend_out = (git_odb_backend *)backend;
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return GIT_SUCCESS;
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}
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