1 /* 2 * Copyright (C) the libgit2 contributors. All rights reserved. 3 * 4 * This file is part of libgit2, distributed under the GNU GPL v2 with 5 * a Linking Exception. For full terms see the included COPYING file. 6 */ 7 #ifndef INCLUDE_sys_git_odb_backend_h__ 8 #define INCLUDE_sys_git_odb_backend_h__ 9 10 #include "git2/common.h" 11 #include "git2/types.h" 12 #include "git2/oid.h" 13 #include "git2/odb.h" 14 15 /** 16 * @file git2/sys/backend.h 17 * @brief Git custom backend implementors functions 18 * @defgroup git_backend Git custom backend APIs 19 * @ingroup Git 20 * @{ 21 */ 22 GIT_BEGIN_DECL 23 24 /** 25 * An instance for a custom backend 26 */ 27 struct git_odb_backend { 28 unsigned int version; 29 git_odb *odb; 30 31 /* read and read_prefix each return to libgit2 a buffer which 32 * will be freed later. The buffer should be allocated using 33 * the function git_odb_backend_data_alloc to ensure that libgit2 34 * can safely free it later. */ 35 int GIT_CALLBACK(read)( 36 void **, size_t *, git_object_t *, git_odb_backend *, const git_oid *); 37 38 /* To find a unique object given a prefix of its oid. The oid given 39 * must be so that the remaining (GIT_OID_HEXSZ - len)*4 bits are 0s. 40 */ 41 int GIT_CALLBACK(read_prefix)( 42 git_oid *, void **, size_t *, git_object_t *, 43 git_odb_backend *, const git_oid *, size_t); 44 45 int GIT_CALLBACK(read_header)( 46 size_t *, git_object_t *, git_odb_backend *, const git_oid *); 47 48 /** 49 * Write an object into the backend. The id of the object has 50 * already been calculated and is passed in. 51 */ 52 int GIT_CALLBACK(write)( 53 git_odb_backend *, const git_oid *, const void *, size_t, git_object_t); 54 55 int GIT_CALLBACK(writestream)( 56 git_odb_stream **, git_odb_backend *, git_object_size_t, git_object_t); 57 58 int GIT_CALLBACK(readstream)( 59 git_odb_stream **, size_t *, git_object_t *, 60 git_odb_backend *, const git_oid *); 61 62 int GIT_CALLBACK(exists)( 63 git_odb_backend *, const git_oid *); 64 65 int GIT_CALLBACK(exists_prefix)( 66 git_oid *, git_odb_backend *, const git_oid *, size_t); 67 68 /** 69 * If the backend implements a refreshing mechanism, it should be exposed 70 * through this endpoint. Each call to `git_odb_refresh()` will invoke it. 71 * 72 * However, the backend implementation should try to stay up-to-date as much 73 * as possible by itself as libgit2 will not automatically invoke 74 * `git_odb_refresh()`. For instance, a potential strategy for the backend 75 * implementation to achieve this could be to internally invoke this 76 * endpoint on failed lookups (ie. `exists()`, `read()`, `read_header()`). 77 */ 78 int GIT_CALLBACK(refresh)(git_odb_backend *); 79 80 int GIT_CALLBACK(foreach)( 81 git_odb_backend *, git_odb_foreach_cb cb, void *payload); 82 83 int GIT_CALLBACK(writepack)( 84 git_odb_writepack **, git_odb_backend *, git_odb *odb, 85 git_indexer_progress_cb progress_cb, void *progress_payload); 86 87 /** 88 * "Freshens" an already existing object, updating its last-used 89 * time. This occurs when `git_odb_write` was called, but the 90 * object already existed (and will not be re-written). The 91 * underlying implementation may want to update last-used timestamps. 92 * 93 * If callers implement this, they should return `0` if the object 94 * exists and was freshened, and non-zero otherwise. 95 */ 96 int GIT_CALLBACK(freshen)(git_odb_backend *, const git_oid *); 97 98 /** 99 * Frees any resources held by the odb (including the `git_odb_backend` 100 * itself). An odb backend implementation must provide this function. 101 */ 102 void GIT_CALLBACK(free)(git_odb_backend *); 103 }; 104 105 #define GIT_ODB_BACKEND_VERSION 1 106 #define GIT_ODB_BACKEND_INIT {GIT_ODB_BACKEND_VERSION} 107 108 /** 109 * Initializes a `git_odb_backend` with default values. Equivalent to 110 * creating an instance with GIT_ODB_BACKEND_INIT. 111 * 112 * @param backend the `git_odb_backend` struct to initialize. 113 * @param version Version the struct; pass `GIT_ODB_BACKEND_VERSION` 114 * @return Zero on success; -1 on failure. 115 */ 116 GIT_EXTERN(int) git_odb_init_backend( 117 git_odb_backend *backend, 118 unsigned int version); 119 120 /** 121 * Allocate data for an ODB object. Custom ODB backends may use this 122 * to provide data back to the ODB from their read function. This 123 * memory should not be freed once it is returned to libgit2. If a 124 * custom ODB uses this function but encounters an error and does not 125 * return this data to libgit2, then they should use the corresponding 126 * git_odb_backend_data_free function. 127 * 128 * @param backend the ODB backend that is allocating this memory 129 * @param len the number of bytes to allocate 130 * @return the allocated buffer on success or NULL if out of memory 131 */ 132 GIT_EXTERN(void *) git_odb_backend_data_alloc(git_odb_backend *backend, size_t len); 133 134 /** 135 * Frees custom allocated ODB data. This should only be called when 136 * memory allocated using git_odb_backend_data_alloc is not returned 137 * to libgit2 because the backend encountered an error in the read 138 * function after allocation and did not return this data to libgit2. 139 * 140 * @param backend the ODB backend that is freeing this memory 141 * @param data the buffer to free 142 */ 143 GIT_EXTERN(void) git_odb_backend_data_free(git_odb_backend *backend, void *data); 144 145 146 /* 147 * Users can avoid deprecated functions by defining `GIT_DEPRECATE_HARD`. 148 */ 149 #ifndef GIT_DEPRECATE_HARD 150 151 /** 152 * Allocate memory for an ODB object from a custom backend. This is 153 * an alias of `git_odb_backend_data_alloc` and is preserved for 154 * backward compatibility. 155 * 156 * This function is deprecated, but there is no plan to remove this 157 * function at this time. 158 * 159 * @deprecated git_odb_backend_data_alloc 160 * @see git_odb_backend_data_alloc 161 */ 162 GIT_EXTERN(void *) git_odb_backend_malloc(git_odb_backend *backend, size_t len); 163 164 #endif 165 166 GIT_END_DECL 167 168 #endif 169
