Support encoding and decoding of object ids

Make ObjectId usable within struct that implement encodable and
decodable. Serializes to and from hex string.

Author: thijsc

src/oid.rs

@@ -5,7 +5,8 @@ use crypto::md5::Md5;
 
 use byteorder::{ByteOrder, BigEndian, LittleEndian};
 use rand::{Rng, OsRng};
-use rustc_serialize::hex::{self, FromHex};
+use rustc_serialize::hex::{self, FromHex, ToHex};
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use time;
 
 use std::{fmt, io, error, result};
@@ -145,6 +146,11 @@ impl ObjectId {
         self.id
     }
 
+    /// Returns a 12-byte (24-char) hexadecimal string
+    pub fn to_string(&self) -> String {
+        self.id.to_hex()
+    }
+
     /// Retrieves the timestamp (seconds since epoch) from an ObjectId.
     pub fn timestamp(&self) -> u32 {
         BigEndian::read_u32(&self.id)
@@ -265,6 +271,19 @@ impl ObjectId {
     }
 }
 
+impl Decodable for ObjectId {
+    fn decode<D: Decoder>(d: &mut D) -> result::Result<Self, D::Error> {
+        let str = try!(d.read_str());
+        Ok(ObjectId::with_string(&str).unwrap())
+    }
+}
+
+impl Encodable for ObjectId {
+    fn encode<S: Encoder>(&self, s: &mut S) -> result::Result<(), S::Error> {
+        s.emit_str(&self.to_string())
+    }
+}
+
 #[test]
 fn pid_generation() {
     let pid = unsafe { libc::getpid() as u16 };

tests/modules/oid.rs

@@ -1,5 +1,6 @@
 use bson::oid::ObjectId;
 use rustc_serialize::hex::ToHex;
+use rustc_serialize::json;
 
 #[test]
 fn deserialize() {
@@ -63,6 +64,7 @@ fn byte_string_oid() {
                            0x83u8, 0x2Bu8, 0x21u8, 0x8Eu8];
 
     assert_eq!(bytes, oid.bytes());
+    assert_eq!(s, oid.to_string());
 }
 
 #[test]
@@ -96,3 +98,21 @@ fn increasing() {
     let oid2 = oid2_res.unwrap();
     assert!(oid1 < oid2);
 }
+
+#[derive(RustcEncodable,RustcDecodable,PartialEq,Debug)]
+struct StructWithObjectId {
+    id: ObjectId
+}
+
+#[test]
+fn use_in_rustc_serialize() {
+    let s = "541b1a00e8a23afa832b218e";
+    let s = StructWithObjectId {
+        id: ObjectId::with_string(s).unwrap()
+    };
+    let encoded = json::encode(&s).unwrap();
+    assert_eq!("{\"id\":\"541b1a00e8a23afa832b218e\"}", encoded);
+
+    let decoded: StructWithObjectId = json::decode(&encoded).unwrap();
+    assert_eq!(s, decoded);
+}