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Diffstat (limited to 'src/libgit2/commit_graph.h')
-rw-r--r-- | src/libgit2/commit_graph.h | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/src/libgit2/commit_graph.h b/src/libgit2/commit_graph.h new file mode 100644 index 000000000..b78ab8177 --- /dev/null +++ b/src/libgit2/commit_graph.h @@ -0,0 +1,169 @@ +/* + * 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_commit_graph_h__ +#define INCLUDE_commit_graph_h__ + +#include "common.h" + +#include "git2/types.h" +#include "git2/sys/commit_graph.h" + +#include "map.h" +#include "vector.h" +#include "oid.h" +#include "hash.h" + +/** + * A commit-graph file. + * + * This file contains metadata about commits, particularly the generation + * number for each one. This can help speed up graph operations without + * requiring a full graph traversal. + * + * Support for this feature was added in git 2.19. + */ +typedef struct git_commit_graph_file { + git_map graph_map; + + /* The OID Fanout table. */ + const uint32_t *oid_fanout; + /* The total number of commits in the graph. */ + uint32_t num_commits; + + /* The OID Lookup table. */ + unsigned char *oid_lookup; + + /* + * The Commit Data table. Each entry contains the OID of the commit followed + * by two 8-byte fields in network byte order: + * - The indices of the first two parents (32 bits each). + * - The generation number (first 30 bits) and commit time in seconds since + * UNIX epoch (34 bits). + */ + const unsigned char *commit_data; + + /* + * The Extra Edge List table. Each 4-byte entry is a network byte order index + * of one of the i-th (i > 0) parents of commits in the `commit_data` table, + * when the commit has more than 2 parents. + */ + const unsigned char *extra_edge_list; + /* The number of entries in the Extra Edge List table. Each entry is 4 bytes wide. */ + size_t num_extra_edge_list; + + /* The trailer of the file. Contains the SHA1-checksum of the whole file. */ + unsigned char checksum[GIT_HASH_SHA1_SIZE]; +} git_commit_graph_file; + +/** + * An entry in the commit-graph file. Provides a subset of the information that + * can be obtained from the commit header. + */ +typedef struct git_commit_graph_entry { + /* The generation number of the commit within the graph */ + size_t generation; + + /* Time in seconds from UNIX epoch. */ + git_time_t commit_time; + + /* The number of parents of the commit. */ + size_t parent_count; + + /* + * The indices of the parent commits within the Commit Data table. The value + * of `GIT_COMMIT_GRAPH_MISSING_PARENT` indicates that no parent is in that + * position. + */ + size_t parent_indices[2]; + + /* The index within the Extra Edge List of any parent after the first two. */ + size_t extra_parents_index; + + /* The SHA-1 hash of the root tree of the commit. */ + git_oid tree_oid; + + /* The SHA-1 hash of the requested commit. */ + git_oid sha1; +} git_commit_graph_entry; + +/* A wrapper for git_commit_graph_file to enable lazy loading in the ODB. */ +struct git_commit_graph { + /* The path to the commit-graph file. Something like ".git/objects/info/commit-graph". */ + git_str filename; + + /* The underlying commit-graph file. */ + git_commit_graph_file *file; + + /* Whether the commit-graph file was already checked for validity. */ + bool checked; +}; + +/** Create a new commit-graph, optionally opening the underlying file. */ +int git_commit_graph_new(git_commit_graph **cgraph_out, const char *objects_dir, bool open_file); + +/** Open and validate a commit-graph file. */ +int git_commit_graph_file_open(git_commit_graph_file **file_out, const char *path); + +/* + * Attempt to get the git_commit_graph's commit-graph file. This object is + * still owned by the git_commit_graph. If the repository does not contain a commit graph, + * it will return GIT_ENOTFOUND. + * + * This function is not thread-safe. + */ +int git_commit_graph_get_file(git_commit_graph_file **file_out, git_commit_graph *cgraph); + +/* Marks the commit-graph file as needing a refresh. */ +void git_commit_graph_refresh(git_commit_graph *cgraph); + +/* + * A writer for `commit-graph` files. + */ +struct git_commit_graph_writer { + /* + * The path of the `objects/info` directory where the `commit-graph` will be + * stored. + */ + git_str objects_info_dir; + + /* The list of packed commits. */ + git_vector commits; +}; + +int git_commit_graph__writer_dump( + git_str *cgraph, + git_commit_graph_writer *w, + git_commit_graph_writer_options *opts); + +/* + * Returns whether the git_commit_graph_file needs to be reloaded since the + * contents of the commit-graph file have changed on disk. + */ +bool git_commit_graph_file_needs_refresh( + const git_commit_graph_file *file, const char *path); + +int git_commit_graph_entry_find( + git_commit_graph_entry *e, + const git_commit_graph_file *file, + const git_oid *short_oid, + size_t len); +int git_commit_graph_entry_parent( + git_commit_graph_entry *parent, + const git_commit_graph_file *file, + const git_commit_graph_entry *entry, + size_t n); +int git_commit_graph_file_close(git_commit_graph_file *cgraph); +void git_commit_graph_file_free(git_commit_graph_file *cgraph); + +/* This is exposed for use in the fuzzers. */ +int git_commit_graph_file_parse( + git_commit_graph_file *file, + const unsigned char *data, + size_t size); + +#endif |