serialize::json::Encoder emit_char serializes extra nulls

[emk]

The following code snippet:

extern crate serialize;

fn main() {
    let s = serialize::json::encode(&'c');
    println!("Encoded: {}, bytes: {}", s, s.as_bytes());
    assert_eq!("\"c\"", s.as_slice());
}

Produces the following output:

Encoded: "c", bytes: [34, 99, 0, 0, 0, 34]
task '<main>' panicked at 'assertion failed: `(left == right) && (right == left)` (left: `"c"`, right: `"c"`)', <anon>:6
playpen: application terminated with error code 101

The serialized string should be [34, 99, 34], and not [34, 99, 0, 0, 0, 34].

[lifthrasiir]

fn escape_char(writer: &mut io::Writer, v: char) -> Result<(), io::IoError> {
    let mut buf = [0, .. 4];
    v.encode_utf8(&mut buf);
    escape_bytes(writer, &mut buf)
}

Ugh, this should be:

fn escape_char(writer: &mut io::Writer, v: char) -> Result<(), io::IoError> {
    let mut buf = [0, .. 4];
    let sz = v.encode_utf8(&mut buf).unwrap();
    escape_bytes(writer, buf[mut ..sz])
}

[emk]

I didn't see that @lifthrasiir had prepared a pull request, so I made a patch of my own. Oh well, it was a nice learning experience, and it helps prepare me to work on some of the stranger issues with Encode/Decode, so it's all good. :-)

@lifthrasiir's patch looks good.