fix char serialization and deserialization

src/serde/reader.rs

@@ -289,7 +289,6 @@ impl<'a, R: Read> serde::Deserializer for Deserializer<'a, R> {
             None => Err(error)
         });
 
-        try!(self.read_bytes(res.len_utf8() as u64));
         visitor.visit_char(res)
     }
 

src/serde/writer.rs

@@ -141,6 +141,10 @@ impl<'a, W: Write> serde::Serializer for Serializer<'a, W> {
         self.writer.write_all(v.as_bytes()).map_err(SerializeError::IoError)
     }
 
+    fn serialize_char(&mut self, c: char) -> SerializeResult<()> {
+        self.writer.write_all(encode_utf8(c).as_slice()).map_err(SerializeError::IoError)
+    }
+
     fn serialize_none(&mut self) -> SerializeResult<()> {
         self.writer.write_u8(0).map_err(wrap_io)
     }
@@ -352,6 +356,10 @@ impl serde::Serializer for SizeChecker {
         self.add_raw(v.len())
     }
 
+    fn serialize_char(&mut self, c: char) -> SerializeResult<()> {
+        self.add_raw(encode_utf8(c).as_slice().len())
+    }
+
     fn serialize_none(&mut self) -> SerializeResult<()> {
         self.add_value(0 as u8)
     }
@@ -464,3 +472,47 @@ impl serde::Serializer for SizeChecker {
         Ok(())
     }
 }
+
+const TAG_CONT: u8    = 0b1000_0000;
+const TAG_TWO_B: u8   = 0b1100_0000;
+const TAG_THREE_B: u8 = 0b1110_0000;
+const TAG_FOUR_B: u8  = 0b1111_0000;
+const MAX_ONE_B: u32   =     0x80;
+const MAX_TWO_B: u32   =    0x800;
+const MAX_THREE_B: u32 =  0x10000;
+
+fn encode_utf8(c: char) -> EncodeUtf8 {
+    let code = c as u32;
+    let mut buf = [0; 4];
+    let pos = if code < MAX_ONE_B {
+        buf[3] = code as u8;
+        3
+    } else if code < MAX_TWO_B {
+        buf[2] = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
+        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
+        2
+    } else if code < MAX_THREE_B {
+        buf[1] = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
+        buf[2] = (code >>  6 & 0x3F) as u8 | TAG_CONT;
+        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
+        1
+    } else {
+        buf[0] = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
+        buf[1] = (code >> 12 & 0x3F) as u8 | TAG_CONT;
+        buf[2] = (code >>  6 & 0x3F) as u8 | TAG_CONT;
+        buf[3] = (code & 0x3F) as u8 | TAG_CONT;
+        0
+    };
+    EncodeUtf8 { buf: buf, pos: pos }
+}
+
+struct EncodeUtf8 {
+    buf: [u8; 4],
+    pos: usize,
+}
+
+impl EncodeUtf8 {
+    fn as_slice(&self) -> &[u8] {
+        &self.buf[self.pos..]
+    }
+}

tests/test.rs

@@ -290,6 +290,16 @@ fn too_big_deserialize() {
     assert!(deserialized.is_ok());
 }
 
+#[test]
+fn char_serialization() {
+    let chars = "Aa\0☺♪";
+    for c in chars.chars() {
+        let encoded = serialize(&c, Bounded(4)).expect("serializing char failed");
+        let decoded: char = deserialize(&encoded).expect("deserializing failed");
+        assert_eq!(decoded, c);
+    }
+}
+
 #[test]
 fn too_big_char_decode() {
     let encoded = vec![0x41];