thodg/libgit2/include/git2/sys/odb_backend.h

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• Hash : 97f9a5f0
  Author :
  Date : 2017-12-17T01:12:49
  

  odb: provide length and type with streaming read The streaming read functionality should provide the length and the type of the object, like the normal read functionality does.

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• include/git2/sys/odb_backend.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_sys_git_odb_backend_h__
  #define INCLUDE_sys_git_odb_backend_h__
  
  #include "git2/common.h"
  #include "git2/types.h"
  #include "git2/oid.h"
  #include "git2/odb.h"
  
  /**
   * @file git2/sys/backend.h
   * @brief Git custom backend implementors functions
   * @defgroup git_backend Git custom backend APIs
   * @ingroup Git
   * @{
   */
  GIT_BEGIN_DECL
  
  /**
   * An instance for a custom backend
   */
  struct git_odb_backend {
  	unsigned int version;
  	git_odb *odb;
  
  	/* read and read_prefix each return to libgit2 a buffer which
  	 * will be freed later. The buffer should be allocated using
  	 * the function git_odb_backend_malloc to ensure that it can
  	 * be safely freed later. */
  	int (* read)(
  		void **, size_t *, git_otype *, git_odb_backend *, const git_oid *);
  
  	/* To find a unique object given a prefix of its oid.  The oid given
  	 * must be so that the remaining (GIT_OID_HEXSZ - len)*4 bits are 0s.
  	 */
  	int (* read_prefix)(
  		git_oid *, void **, size_t *, git_otype *,
  		git_odb_backend *, const git_oid *, size_t);
  
  	int (* read_header)(
  		size_t *, git_otype *, git_odb_backend *, const git_oid *);
  
  	/**
  	 * Write an object into the backend. The id of the object has
  	 * already been calculated and is passed in.
  	 */
  	int (* write)(
  		git_odb_backend *, const git_oid *, const void *, size_t, git_otype);
  
  	int (* writestream)(
  		git_odb_stream **, git_odb_backend *, git_off_t, git_otype);
  
  	int (* readstream)(
  		git_odb_stream **, size_t *, git_otype *,
  		git_odb_backend *, const git_oid *);
  
  	int (* exists)(
  		git_odb_backend *, const git_oid *);
  
  	int (* exists_prefix)(
  		git_oid *, git_odb_backend *, const git_oid *, size_t);
  
  	/**
  	 * If the backend implements a refreshing mechanism, it should be exposed
  	 * through this endpoint. Each call to `git_odb_refresh()` will invoke it.
  	 *
  	 * However, the backend implementation should try to stay up-to-date as much
  	 * as possible by itself as libgit2 will not automatically invoke
  	 * `git_odb_refresh()`. For instance, a potential strategy for the backend
  	 * implementation to achieve this could be to internally invoke this
  	 * endpoint on failed lookups (ie. `exists()`, `read()`, `read_header()`).
  	 */
  	int (* refresh)(git_odb_backend *);
  
  	int (* foreach)(
  		git_odb_backend *, git_odb_foreach_cb cb, void *payload);
  
  	int (* writepack)(
  		git_odb_writepack **, git_odb_backend *, git_odb *odb,
  		git_transfer_progress_cb progress_cb, void *progress_payload);
  
  	/**
  	 * "Freshens" an already existing object, updating its last-used
  	 * time.  This occurs when `git_odb_write` was called, but the
  	 * object already existed (and will not be re-written).  The
  	 * underlying implementation may want to update last-used timestamps.
  	 *
  	 * If callers implement this, they should return `0` if the object
  	 * exists and was freshened, and non-zero otherwise.
  	 */
  	int (* freshen)(git_odb_backend *, const git_oid *);
  
  	/**
  	 * Frees any resources held by the odb (including the `git_odb_backend`
  	 * itself). An odb backend implementation must provide this function.
  	 */
  	void (* free)(git_odb_backend *);
  };
  
  #define GIT_ODB_BACKEND_VERSION 1
  #define GIT_ODB_BACKEND_INIT {GIT_ODB_BACKEND_VERSION}
  
  /**
   * Initializes a `git_odb_backend` with default values. Equivalent to
   * creating an instance with GIT_ODB_BACKEND_INIT.
   *
   * @param backend the `git_odb_backend` struct to initialize.
   * @param version Version the struct; pass `GIT_ODB_BACKEND_VERSION`
   * @return Zero on success; -1 on failure.
   */
  GIT_EXTERN(int) git_odb_init_backend(
  	git_odb_backend *backend,
  	unsigned int version);
  
  GIT_EXTERN(void *) git_odb_backend_malloc(git_odb_backend *backend, size_t len);
  
  GIT_END_DECL
  
  #endif
  

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