libbson は、ObjectID を生成する簡単な方法を提供します。 要件に応じて、シングルスレッドまたはマルチスレッドで使用できます。
The bson_oid_t structure represents an ObjectID in MongoDB. It is a 96-bit identifier.
構成
4バイト : ビッグエンディアン形式の UNIX タイムスタンプ。
5バイト : ランダム数。
3バイト : ビッグエンディアンの
rand()から増加する24ビットの単調なカウンター。
オブジェクト ID のソート
The typical way to sort in C is using qsort(). Therefore, Libbson provides a qsort() compatible callback function named bson_oid_compare. It returns less than 1, greater than 1, or 0 depending on the equality of two bson_oid_t structures.
オブジェクト ID の比較
If you simply want to compare two bson_oid_t structures for equality, use bson_oid_equal.
生成
To generate a bson_oid_t, you may use the following.
bson_oid_t oid; bson_oid_init (&oid, NULL);
ObjectId解析
You can also parse a string containing a bson_oid_t. The input string MUST be 24 characters or more in length.
bson_oid_t oid; bson_oid_init_from_string (&oid, "123456789012345678901234");
bson_oid_t oid; bson_oid_init_from_string_unsafe (&oid, "123456789012345678901234");
オブジェクト ID のハッシュ
If you need to store items in a hashtable, you may want to use the bson_oid_t as the key. Libbson provides a hash function for just this purpose. It is based on DJB hash.
unsigned hash; hash = bson_oid_hash (oid);
ObjectId作成時間の取得
You can easily fetch the time that a bson_oid_t was generated using bson_oid_get_time_t.
time_t t; t = bson_oid_get_time_t (oid); printf ("The OID was generated at %u\n", (unsigned) t);