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8f09a98e18
When writing an object, we calculate its OID and see if it exists in the object database. If it does, we need to freshen the file that contains it.
124 lines
3.8 KiB
C
124 lines
3.8 KiB
C
/*
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* Copyright (C) the libgit2 contributors. All rights reserved.
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*
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* This file is part of libgit2, distributed under the GNU GPL v2 with
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* a Linking Exception. For full terms see the included COPYING file.
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*/
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#ifndef INCLUDE_sys_git_odb_backend_h__
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#define INCLUDE_sys_git_odb_backend_h__
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#include "git2/common.h"
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#include "git2/types.h"
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#include "git2/oid.h"
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#include "git2/odb.h"
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/**
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* @file git2/sys/backend.h
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* @brief Git custom backend implementors functions
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* @defgroup git_backend Git custom backend APIs
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* @ingroup Git
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* @{
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*/
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GIT_BEGIN_DECL
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/**
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* An instance for a custom backend
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*/
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struct git_odb_backend {
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unsigned int version;
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git_odb *odb;
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/* read and read_prefix each return to libgit2 a buffer which
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* will be freed later. The buffer should be allocated using
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* the function git_odb_backend_malloc to ensure that it can
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* be safely freed later. */
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int (* read)(
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void **, size_t *, git_otype *, git_odb_backend *, const git_oid *);
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/* To find a unique object given a prefix of its oid. The oid given
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* must be so that the remaining (GIT_OID_HEXSZ - len)*4 bits are 0s.
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*/
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int (* read_prefix)(
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git_oid *, void **, size_t *, git_otype *,
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git_odb_backend *, const git_oid *, size_t);
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int (* read_header)(
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size_t *, git_otype *, git_odb_backend *, const git_oid *);
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/**
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* Write an object into the backend. The id of the object has
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* already been calculated and is passed in.
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*/
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int (* write)(
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git_odb_backend *, const git_oid *, const void *, size_t, git_otype);
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int (* writestream)(
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git_odb_stream **, git_odb_backend *, git_off_t, git_otype);
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int (* readstream)(
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git_odb_stream **, git_odb_backend *, const git_oid *);
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int (* exists)(
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git_odb_backend *, const git_oid *);
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int (* exists_prefix)(
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git_oid *, git_odb_backend *, const git_oid *, size_t);
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/**
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* If the backend implements a refreshing mechanism, it should be exposed
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* through this endpoint. Each call to `git_odb_refresh()` will invoke it.
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*
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* However, the backend implementation should try to stay up-to-date as much
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* as possible by itself as libgit2 will not automatically invoke
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* `git_odb_refresh()`. For instance, a potential strategy for the backend
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* implementation to achieve this could be to internally invoke this
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* endpoint on failed lookups (ie. `exists()`, `read()`, `read_header()`).
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*/
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int (* refresh)(git_odb_backend *);
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int (* foreach)(
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git_odb_backend *, git_odb_foreach_cb cb, void *payload);
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int (* writepack)(
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git_odb_writepack **, git_odb_backend *, git_odb *odb,
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git_transfer_progress_cb progress_cb, void *progress_payload);
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/**
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* "Freshens" an already existing object, updating its last-used
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* time. This occurs when `git_odb_write` was called, but the
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* object already existed (and will not be re-written). The
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* underlying implementation may want to update last-used timestamps.
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*
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* If callers implement this, they should return `0` if the object
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* exists and was freshened, and non-zero otherwise.
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*/
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int (* freshen)(git_odb_backend *, const git_oid *);
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/**
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* Frees any resources held by the odb (including the `git_odb_backend`
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* itself). An odb backend implementation must provide this function.
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*/
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void (* free)(git_odb_backend *);
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};
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#define GIT_ODB_BACKEND_VERSION 1
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#define GIT_ODB_BACKEND_INIT {GIT_ODB_BACKEND_VERSION}
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/**
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* Initializes a `git_odb_backend` with default values. Equivalent to
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* creating an instance with GIT_ODB_BACKEND_INIT.
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*
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* @param backend the `git_odb_backend` struct to initialize.
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* @param version Version the struct; pass `GIT_ODB_BACKEND_VERSION`
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* @return Zero on success; -1 on failure.
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*/
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GIT_EXTERN(int) git_odb_init_backend(
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git_odb_backend *backend,
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unsigned int version);
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GIT_EXTERN(void *) git_odb_backend_malloc(git_odb_backend *backend, size_t len);
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GIT_END_DECL
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#endif
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