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diff --git a/include/git2/odb.h b/include/git2/odb.h
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+++ b/include/git2/odb.h
@@ -0,0 +1,654 @@
+/*
+ * 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_odb_h__
+#define INCLUDE_git_odb_h__
+
+#include "common.h"
+#include "types.h"
+#include "oid.h"
+#include "oidarray.h"
+#include "indexer.h"
+
+/**
+ * @file git2/odb.h
+ * @brief Git object database routines
+ * @defgroup git_odb Git object database routines
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/** Flags controlling the behavior of ODB lookup operations */
+typedef enum {
+	/**
+	 * Don't call `git_odb_refresh` if the lookup fails. Useful when doing
+	 * a batch of lookup operations for objects that may legitimately not
+	 * exist. When using this flag, you may wish to manually call
+	 * `git_odb_refresh` before processing a batch of objects.
+	 */
+	GIT_ODB_LOOKUP_NO_REFRESH = (1 << 0)
+} git_odb_lookup_flags_t;
+
+/**
+ * Function type for callbacks from git_odb_foreach.
+ */
+typedef int GIT_CALLBACK(git_odb_foreach_cb)(const git_oid *id, void *payload);
+
+/** Options for configuring a loose object backend. */
+typedef struct {
+	unsigned int version; /**< version for the struct */
+
+	/**
+	 * Type of object IDs to use for this object database, or
+	 * 0 for default (currently SHA1).
+	 */
+	git_oid_t oid_type;
+} git_odb_options;
+
+/* The current version of the diff options structure */
+#define GIT_ODB_OPTIONS_VERSION 1
+
+/* Stack initializer for odb options.  Alternatively use
+ * `git_odb_options_init` programmatic initialization.
+ */
+#define GIT_ODB_OPTIONS_INIT { GIT_ODB_OPTIONS_VERSION }
+
+/**
+ * Create a new object database with no backends.
+ *
+ * Before the ODB can be used for read/writing, a custom database
+ * backend must be manually added using `git_odb_add_backend()`
+ *
+ * @param out location to store the database pointer, if opened.
+ *			Set to NULL if the open failed.
+ * @param opts the options for this object database or NULL for defaults
+ * @return 0 or an error code
+ */
+#ifdef GIT_EXPERIMENTAL_SHA256
+GIT_EXTERN(int) git_odb_new(git_odb **out, const git_odb_options *opts);
+#else
+GIT_EXTERN(int) git_odb_new(git_odb **out);
+#endif
+
+/**
+ * Create a new object database and automatically add
+ * the two default backends:
+ *
+ *	- git_odb_backend_loose: read and write loose object files
+ *		from disk, assuming `objects_dir` as the Objects folder
+ *
+ *	- git_odb_backend_pack: read objects from packfiles,
+ *		assuming `objects_dir` as the Objects folder which
+ *		contains a 'pack/' folder with the corresponding data
+ *
+ * @param out location to store the database pointer, if opened.
+ *			Set to NULL if the open failed.
+ * @param objects_dir path of the backends' "objects" directory.
+ * @param opts the options for this object database or NULL for defaults
+ * @return 0 or an error code
+ */
+#ifdef GIT_EXPERIMENTAL_SHA256
+GIT_EXTERN(int) git_odb_open(
+	git_odb **out,
+	const char *objects_dir,
+	const git_odb_options *opts);
+#else
+GIT_EXTERN(int) git_odb_open(git_odb **out, const char *objects_dir);
+#endif
+
+/**
+ * Add an on-disk alternate to an existing Object DB.
+ *
+ * Note that the added path must point to an `objects`, not
+ * to a full repository, to use it as an alternate store.
+ *
+ * Alternate backends are always checked for objects *after*
+ * all the main backends have been exhausted.
+ *
+ * Writing is disabled on alternate backends.
+ *
+ * @param odb database to add the backend to
+ * @param path path to the objects folder for the alternate
+ * @return 0 on success, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_add_disk_alternate(git_odb *odb, const char *path);
+
+/**
+ * Close an open object database.
+ *
+ * @param db database pointer to close. If NULL no action is taken.
+ */
+GIT_EXTERN(void) git_odb_free(git_odb *db);
+
+/**
+ * Read an object from the database.
+ *
+ * This method queries all available ODB backends
+ * trying to read the given OID.
+ *
+ * The returned object is reference counted and
+ * internally cached, so it should be closed
+ * by the user once it's no longer in use.
+ *
+ * @param out pointer where to store the read object
+ * @param db database to search for the object in.
+ * @param id identity of the object to read.
+ * @return 0 if the object was read, GIT_ENOTFOUND if the object is
+ *         not in the database.
+ */
+GIT_EXTERN(int) git_odb_read(git_odb_object **out, git_odb *db, const git_oid *id);
+
+/**
+ * Read an object from the database, given a prefix
+ * of its identifier.
+ *
+ * This method queries all available ODB backends
+ * trying to match the 'len' first hexadecimal
+ * characters of the 'short_id'.
+ * The remaining (GIT_OID_SHA1_HEXSIZE-len)*4 bits of
+ * 'short_id' must be 0s.
+ * 'len' must be at least GIT_OID_MINPREFIXLEN,
+ * and the prefix must be long enough to identify
+ * a unique object in all the backends; the
+ * method will fail otherwise.
+ *
+ * The returned object is reference counted and
+ * internally cached, so it should be closed
+ * by the user once it's no longer in use.
+ *
+ * @param out pointer where to store the read object
+ * @param db database to search for the object in.
+ * @param short_id a prefix of the id of the object to read.
+ * @param len the length of the prefix
+ * @return 0 if the object was read, GIT_ENOTFOUND if the object is not in the
+ *         database. GIT_EAMBIGUOUS if the prefix is ambiguous
+ *         (several objects match the prefix)
+ */
+GIT_EXTERN(int) git_odb_read_prefix(git_odb_object **out, git_odb *db, const git_oid *short_id, size_t len);
+
+/**
+ * Read the header of an object from the database, without
+ * reading its full contents.
+ *
+ * The header includes the length and the type of an object.
+ *
+ * Note that most backends do not support reading only the header
+ * of an object, so the whole object will be read and then the
+ * header will be returned.
+ *
+ * @param len_out pointer where to store the length
+ * @param type_out pointer where to store the type
+ * @param db database to search for the object in.
+ * @param id identity of the object to read.
+ * @return 0 if the object was read, GIT_ENOTFOUND if the object is not
+ *         in the database.
+ */
+GIT_EXTERN(int) git_odb_read_header(size_t *len_out, git_object_t *type_out, git_odb *db, const git_oid *id);
+
+/**
+ * Determine if the given object can be found in the object database.
+ *
+ * @param db database to be searched for the given object.
+ * @param id the object to search for.
+ * @return 1 if the object was found, 0 otherwise
+ */
+GIT_EXTERN(int) git_odb_exists(git_odb *db, const git_oid *id);
+
+/**
+ * Determine if the given object can be found in the object database, with
+ * extended options.
+ *
+ * @param db database to be searched for the given object.
+ * @param id the object to search for.
+ * @param flags flags affecting the lookup (see `git_odb_lookup_flags_t`)
+ * @return 1 if the object was found, 0 otherwise
+ */
+GIT_EXTERN(int) git_odb_exists_ext(git_odb *db, const git_oid *id, unsigned int flags);
+
+/**
+ * Determine if an object can be found in the object database by an
+ * abbreviated object ID.
+ *
+ * @param out The full OID of the found object if just one is found.
+ * @param db The database to be searched for the given object.
+ * @param short_id A prefix of the id of the object to read.
+ * @param len The length of the prefix.
+ * @return 0 if found, GIT_ENOTFOUND if not found, GIT_EAMBIGUOUS if multiple
+ *         matches were found, other value < 0 if there was a read error.
+ */
+GIT_EXTERN(int) git_odb_exists_prefix(
+	git_oid *out, git_odb *db, const git_oid *short_id, size_t len);
+
+/**
+ * The information about object IDs to query in `git_odb_expand_ids`,
+ * which will be populated upon return.
+ */
+typedef struct git_odb_expand_id {
+	/** The object ID to expand */
+	git_oid id;
+
+	/**
+	 * The length of the object ID (in nibbles, or packets of 4 bits; the
+	 * number of hex characters)
+	 * */
+	unsigned short length;
+
+	/**
+	 * The (optional) type of the object to search for; leave as `0` or set
+	 * to `GIT_OBJECT_ANY` to query for any object matching the ID.
+	 */
+	git_object_t type;
+} git_odb_expand_id;
+
+/**
+ * Determine if one or more objects can be found in the object database
+ * by their abbreviated object ID and type.
+ *
+ * The given array will be updated in place: for each abbreviated ID that is
+ * unique in the database, and of the given type (if specified),
+ * the full object ID, object ID length (`GIT_OID_SHA1_HEXSIZE`) and type will be
+ * written back to the array. For IDs that are not found (or are ambiguous),
+ * the array entry will be zeroed.
+ *
+ * Note that since this function operates on multiple objects, the
+ * underlying database will not be asked to be reloaded if an object is
+ * not found (which is unlike other object database operations.)
+ *
+ * @param db The database to be searched for the given objects.
+ * @param ids An array of short object IDs to search for
+ * @param count The length of the `ids` array
+ * @return 0 on success or an error code on failure
+ */
+GIT_EXTERN(int) git_odb_expand_ids(
+	git_odb *db,
+	git_odb_expand_id *ids,
+	size_t count);
+
+/**
+ * Refresh the object database to load newly added files.
+ *
+ * If the object databases have changed on disk while the library
+ * is running, this function will force a reload of the underlying
+ * indexes.
+ *
+ * Use this function when you're confident that an external
+ * application has tampered with the ODB.
+ *
+ * NOTE that it is not necessary to call this function at all. The
+ * library will automatically attempt to refresh the ODB
+ * when a lookup fails, to see if the looked up object exists
+ * on disk but hasn't been loaded yet.
+ *
+ * @param db database to refresh
+ * @return 0 on success, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_refresh(struct git_odb *db);
+
+/**
+ * List all objects available in the database
+ *
+ * The callback will be called for each object available in the
+ * database. Note that the objects are likely to be returned in the index
+ * order, which would make accessing the objects in that order inefficient.
+ * Return a non-zero value from the callback to stop looping.
+ *
+ * @param db database to use
+ * @param cb the callback to call for each object
+ * @param payload data to pass to the callback
+ * @return 0 on success, non-zero callback return value, or error code
+ */
+GIT_EXTERN(int) git_odb_foreach(git_odb *db, git_odb_foreach_cb cb, void *payload);
+
+/**
+ * Write an object directly into the ODB
+ *
+ * This method writes a full object straight into the ODB.
+ * For most cases, it is preferred to write objects through a write
+ * stream, which is both faster and less memory intensive, specially
+ * for big objects.
+ *
+ * This method is provided for compatibility with custom backends
+ * which are not able to support streaming writes
+ *
+ * @param out pointer to store the OID result of the write
+ * @param odb object database where to store the object
+ * @param data buffer with the data to store
+ * @param len size of the buffer
+ * @param type type of the data to store
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_odb_write(git_oid *out, git_odb *odb, const void *data, size_t len, git_object_t type);
+
+/**
+ * Open a stream to write an object into the ODB
+ *
+ * The type and final length of the object must be specified
+ * when opening the stream.
+ *
+ * The returned stream will be of type `GIT_STREAM_WRONLY`, and it
+ * won't be effective until `git_odb_stream_finalize_write` is called
+ * and returns without an error
+ *
+ * The stream must always be freed when done with `git_odb_stream_free` or
+ * will leak memory.
+ *
+ * @see git_odb_stream
+ *
+ * @param out pointer where to store the stream
+ * @param db object database where the stream will write
+ * @param size final size of the object that will be written
+ * @param type type of the object that will be written
+ * @return 0 if the stream was created; error code otherwise
+ */
+GIT_EXTERN(int) git_odb_open_wstream(git_odb_stream **out, git_odb *db, git_object_size_t size, git_object_t type);
+
+/**
+ * Write to an odb stream
+ *
+ * This method will fail if the total number of received bytes exceeds the
+ * size declared with `git_odb_open_wstream()`
+ *
+ * @param stream the stream
+ * @param buffer the data to write
+ * @param len the buffer's length
+ * @return 0 if the write succeeded, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_stream_write(git_odb_stream *stream, const char *buffer, size_t len);
+
+/**
+ * Finish writing to an odb stream
+ *
+ * The object will take its final name and will be available to the
+ * odb.
+ *
+ * This method will fail if the total number of received bytes
+ * differs from the size declared with `git_odb_open_wstream()`
+ *
+ * @param out pointer to store the resulting object's id
+ * @param stream the stream
+ * @return 0 on success, an error code otherwise
+ */
+GIT_EXTERN(int) git_odb_stream_finalize_write(git_oid *out, git_odb_stream *stream);
+
+/**
+ * Read from an odb stream
+ *
+ * Most backends don't implement streaming reads
+ *
+ * @param stream the stream
+ * @param buffer a user-allocated buffer to store the data in.
+ * @param len the buffer's length
+ * @return 0 if the read succeeded, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_stream_read(git_odb_stream *stream, char *buffer, size_t len);
+
+/**
+ * Free an odb stream
+ *
+ * @param stream the stream to free
+ */
+GIT_EXTERN(void) git_odb_stream_free(git_odb_stream *stream);
+
+/**
+ * Open a stream to read an object from the ODB
+ *
+ * Note that most backends do *not* support streaming reads
+ * because they store their objects as compressed/delta'ed blobs.
+ *
+ * It's recommended to use `git_odb_read` instead, which is
+ * assured to work on all backends.
+ *
+ * The returned stream will be of type `GIT_STREAM_RDONLY` and
+ * will have the following methods:
+ *
+ *		- stream->read: read `n` bytes from the stream
+ *		- stream->free: free the stream
+ *
+ * The stream must always be free'd or will leak memory.
+ *
+ * @see git_odb_stream
+ *
+ * @param out pointer where to store the stream
+ * @param len pointer where to store the length of the object
+ * @param type pointer where to store the type of the object
+ * @param db object database where the stream will read from
+ * @param oid oid of the object the stream will read from
+ * @return 0 if the stream was created, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_open_rstream(
+	git_odb_stream **out,
+	size_t *len,
+	git_object_t *type,
+	git_odb *db,
+	const git_oid *oid);
+
+/**
+ * Open a stream for writing a pack file to the ODB.
+ *
+ * If the ODB layer understands pack files, then the given
+ * packfile will likely be streamed directly to disk (and a
+ * corresponding index created).  If the ODB layer does not
+ * understand pack files, the objects will be stored in whatever
+ * format the ODB layer uses.
+ *
+ * @see git_odb_writepack
+ *
+ * @param out pointer to the writepack functions
+ * @param db object database where the stream will read from
+ * @param progress_cb function to call with progress information.
+ * Be aware that this is called inline with network and indexing operations,
+ * so performance may be affected.
+ * @param progress_payload payload for the progress callback
+ * @return 0 or an error code.
+ */
+GIT_EXTERN(int) git_odb_write_pack(
+	git_odb_writepack **out,
+	git_odb *db,
+	git_indexer_progress_cb progress_cb,
+	void *progress_payload);
+
+/**
+ * Write a `multi-pack-index` file from all the `.pack` files in the ODB.
+ *
+ * If the ODB layer understands pack files, then this will create a file called
+ * `multi-pack-index` next to the `.pack` and `.idx` files, which will contain
+ * an index of all objects stored in `.pack` files. This will allow for
+ * O(log n) lookup for n objects (regardless of how many packfiles there
+ * exist).
+ *
+ * @param db object database where the `multi-pack-index` file will be written.
+ * @return 0 or an error code.
+ */
+GIT_EXTERN(int) git_odb_write_multi_pack_index(
+	git_odb *db);
+
+/**
+ * Determine the object-ID (sha1 or sha256 hash) of a data buffer
+ *
+ * The resulting OID will be the identifier for the data buffer as if
+ * the data buffer it were to written to the ODB.
+ *
+ * @param out the resulting object-ID.
+ * @param data data to hash
+ * @param len size of the data
+ * @param object_type of the data to hash
+ * @param oid_type the oid type to hash to
+ * @return 0 or an error code
+ */
+#ifdef GIT_EXPERIMENTAL_SHA256
+GIT_EXTERN(int) git_odb_hash(
+	git_oid *out,
+	const void *data,
+	size_t len,
+	git_object_t object_type,
+	git_oid_t oid_type);
+#else
+GIT_EXTERN(int) git_odb_hash(git_oid *out, const void *data, size_t len, git_object_t type);
+#endif
+
+/**
+ * Read a file from disk and fill a git_oid with the object id
+ * that the file would have if it were written to the Object
+ * Database as an object of the given type (w/o applying filters).
+ * Similar functionality to git.git's `git hash-object` without
+ * the `-w` flag, however, with the --no-filters flag.
+ * If you need filters, see git_repository_hashfile.
+ *
+ * @param out oid structure the result is written into.
+ * @param path file to read and determine object id for
+ * @param object_type of the data to hash
+ * @param oid_type the oid type to hash to
+ * @return 0 or an error code
+ */
+#ifdef GIT_EXPERIMENTAL_SHA256
+GIT_EXTERN(int) git_odb_hashfile(
+	git_oid *out,
+	const char *path,
+	git_object_t object_type,
+	git_oid_t oid_type);
+#else
+GIT_EXTERN(int) git_odb_hashfile(git_oid *out, const char *path, git_object_t type);
+#endif
+
+/**
+ * Create a copy of an odb_object
+ *
+ * The returned copy must be manually freed with `git_odb_object_free`.
+ * Note that because of an implementation detail, the returned copy will be
+ * the same pointer as `source`: the object is internally refcounted, so the
+ * copy still needs to be freed twice.
+ *
+ * @param dest pointer where to store the copy
+ * @param source object to copy
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_odb_object_dup(git_odb_object **dest, git_odb_object *source);
+
+/**
+ * Close an ODB object
+ *
+ * This method must always be called once a `git_odb_object` is no
+ * longer needed, otherwise memory will leak.
+ *
+ * @param object object to close
+ */
+GIT_EXTERN(void) git_odb_object_free(git_odb_object *object);
+
+/**
+ * Return the OID of an ODB object
+ *
+ * This is the OID from which the object was read from
+ *
+ * @param object the object
+ * @return a pointer to the OID
+ */
+GIT_EXTERN(const git_oid *) git_odb_object_id(git_odb_object *object);
+
+/**
+ * Return the data of an ODB object
+ *
+ * This is the uncompressed, raw data as read from the ODB,
+ * without the leading header.
+ *
+ * This pointer is owned by the object and shall not be free'd.
+ *
+ * @param object the object
+ * @return a pointer to the data
+ */
+GIT_EXTERN(const void *) git_odb_object_data(git_odb_object *object);
+
+/**
+ * Return the size of an ODB object
+ *
+ * This is the real size of the `data` buffer, not the
+ * actual size of the object.
+ *
+ * @param object the object
+ * @return the size
+ */
+GIT_EXTERN(size_t) git_odb_object_size(git_odb_object *object);
+
+/**
+ * Return the type of an ODB object
+ *
+ * @param object the object
+ * @return the type
+ */
+GIT_EXTERN(git_object_t) git_odb_object_type(git_odb_object *object);
+
+/**
+ * Add a custom backend to an existing Object DB
+ *
+ * The backends are checked in relative ordering, based on the
+ * value of the `priority` parameter.
+ *
+ * Read <sys/odb_backend.h> for more information.
+ *
+ * @param odb database to add the backend to
+ * @param backend pointer to a git_odb_backend instance
+ * @param priority Value for ordering the backends queue
+ * @return 0 on success, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_add_backend(git_odb *odb, git_odb_backend *backend, int priority);
+
+/**
+ * Add a custom backend to an existing Object DB; this
+ * backend will work as an alternate.
+ *
+ * Alternate backends are always checked for objects *after*
+ * all the main backends have been exhausted.
+ *
+ * The backends are checked in relative ordering, based on the
+ * value of the `priority` parameter.
+ *
+ * Writing is disabled on alternate backends.
+ *
+ * Read <sys/odb_backend.h> for more information.
+ *
+ * @param odb database to add the backend to
+ * @param backend pointer to a git_odb_backend instance
+ * @param priority Value for ordering the backends queue
+ * @return 0 on success, error code otherwise
+ */
+GIT_EXTERN(int) git_odb_add_alternate(git_odb *odb, git_odb_backend *backend, int priority);
+
+/**
+ * Get the number of ODB backend objects
+ *
+ * @param odb object database
+ * @return number of backends in the ODB
+ */
+GIT_EXTERN(size_t) git_odb_num_backends(git_odb *odb);
+
+/**
+ * Lookup an ODB backend object by index
+ *
+ * @param out output pointer to ODB backend at pos
+ * @param odb object database
+ * @param pos index into object database backend list
+ * @return 0 on success, GIT_ENOTFOUND if pos is invalid, other errors < 0
+ */
+GIT_EXTERN(int) git_odb_get_backend(git_odb_backend **out, git_odb *odb, size_t pos);
+
+/**
+ * Set the git commit-graph for the ODB.
+ *
+ * After a successful call, the ownership of the cgraph parameter will be
+ * transferred to libgit2, and the caller should not free it.
+ *
+ * The commit-graph can also be unset by explicitly passing NULL as the cgraph
+ * parameter.
+ *
+ * @param odb object database
+ * @param cgraph the git commit-graph
+ * @return 0 on success; error code otherwise
+ */
+GIT_EXTERN(int) git_odb_set_commit_graph(git_odb *odb, git_commit_graph *cgraph);
+
+/** @} */
+GIT_END_DECL
+#endif