Remove librbml and the RBML-tagged auto-encoder/decoder.

4 files changed, 831 insertions, 63 deletions

diff --git a/src/libserialize/leb128.rs b/src/libserialize/leb128.rs
new file mode 100644
index 00000000000..0c5356c0222
--- /dev/null
+++ b/src/libserialize/leb128.rs
@@ -0,0 +1,151 @@
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[inline]
+pub fn write_to_vec(vec: &mut Vec<u8>, position: &mut usize, byte: u8) {
+    if *position == vec.len() {
+        vec.push(byte);
+    } else {
+        vec[*position] = byte;
+    }
+
+    *position += 1;
+}
+
+pub fn write_unsigned_leb128(out: &mut Vec<u8>, start_position: usize, mut value: u64) -> usize {
+    let mut position = start_position;
+    loop {
+        let mut byte = (value & 0x7F) as u8;
+        value >>= 7;
+        if value != 0 {
+            byte |= 0x80;
+        }
+
+        write_to_vec(out, &mut position, byte);
+
+        if value == 0 {
+            break;
+        }
+    }
+
+    return position - start_position;
+}
+
+pub fn read_unsigned_leb128(data: &[u8], start_position: usize) -> (u64, usize) {
+    let mut result = 0;
+    let mut shift = 0;
+    let mut position = start_position;
+    loop {
+        let byte = data[position];
+        position += 1;
+        result |= ((byte & 0x7F) as u64) << shift;
+        if (byte & 0x80) == 0 {
+            break;
+        }
+        shift += 7;
+    }
+
+    (result, position - start_position)
+}
+
+
+pub fn write_signed_leb128(out: &mut Vec<u8>, start_position: usize, mut value: i64) -> usize {
+    let mut position = start_position;
+
+    loop {
+        let mut byte = (value as u8) & 0x7f;
+        value >>= 7;
+        let more = !((((value == 0) && ((byte & 0x40) == 0)) ||
+                      ((value == -1) && ((byte & 0x40) != 0))));
+        if more {
+            byte |= 0x80; // Mark this byte to show that more bytes will follow.
+        }
+
+        write_to_vec(out, &mut position, byte);
+
+        if !more {
+            break;
+        }
+    }
+
+    return position - start_position;
+}
+
+pub fn read_signed_leb128(data: &[u8], start_position: usize) -> (i64, usize) {
+    let mut result = 0;
+    let mut shift = 0;
+    let mut position = start_position;
+    let mut byte;
+
+    loop {
+        byte = data[position];
+        position += 1;
+        result |= ((byte & 0x7F) as i64) << shift;
+        shift += 7;
+
+        if (byte & 0x80) == 0 {
+            break;
+        }
+    }
+
+    if (shift < 64) && ((byte & 0x40) != 0) {
+        // sign extend
+        result |= -(1i64 << shift);
+    }
+
+    (result, position - start_position)
+}
+
+#[test]
+fn test_unsigned_leb128() {
+    let mut stream = Vec::with_capacity(10000);
+
+    for x in 0..62 {
+        let pos = stream.len();
+        let bytes_written = write_unsigned_leb128(&mut stream, pos, 3 << x);
+        assert_eq!(stream.len(), pos + bytes_written);
+    }
+
+    let mut position = 0;
+    for x in 0..62 {
+        let expected = 3 << x;
+        let (actual, bytes_read) = read_unsigned_leb128(&stream, position);
+        assert_eq!(expected, actual);
+        position += bytes_read;
+    }
+    assert_eq!(stream.len(), position);
+}
+
+#[test]
+fn test_signed_leb128() {
+    let mut values = Vec::new();
+
+    let mut i = -500;
+    while i < 500 {
+        values.push(i * 123457i64);
+        i += 1;
+    }
+
+    let mut stream = Vec::new();
+
+    for &x in &values {
+        let pos = stream.len();
+        let bytes_written = write_signed_leb128(&mut stream, pos, x);
+        assert_eq!(stream.len(), pos + bytes_written);
+    }
+
+    let mut pos = 0;
+    for &x in &values {
+        let (value, bytes_read) = read_signed_leb128(&mut stream, pos);
+        pos += bytes_read;
+        assert_eq!(x, value);
+    }
+    assert_eq!(pos, stream.len());
+}
diff --git a/src/libserialize/lib.rs b/src/libserialize/lib.rs
index 7082ee5d292..7cb02e2412c 100644
--- a/src/libserialize/lib.rs
+++ b/src/libserialize/lib.rs
@@ -56,6 +56,9 @@ mod collection_impls;
 pub mod hex;
 pub mod json;
 
+pub mod opaque;
+pub mod leb128;
+
 mod rustc_serialize {
     pub use serialize::*;
 }
diff --git a/src/libserialize/opaque.rs b/src/libserialize/opaque.rs
new file mode 100644
index 00000000000..e97834f63ce
--- /dev/null
+++ b/src/libserialize/opaque.rs
@@ -0,0 +1,546 @@
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use leb128::{read_signed_leb128, read_unsigned_leb128, write_signed_leb128, write_unsigned_leb128};
+use std::io::{self, Write};
+use serialize;
+
+// -----------------------------------------------------------------------------
+// Encoder
+// -----------------------------------------------------------------------------
+
+pub type EncodeResult = io::Result<()>;
+
+pub struct Encoder<'a> {
+    pub cursor: &'a mut io::Cursor<Vec<u8>>,
+}
+
+impl<'a> Encoder<'a> {
+    pub fn new(cursor: &'a mut io::Cursor<Vec<u8>>) -> Encoder<'a> {
+        Encoder { cursor: cursor }
+    }
+}
+
+
+macro_rules! write_uleb128 {
+    ($enc:expr, $value:expr) => {{
+        let pos = $enc.cursor.position() as usize;
+        let bytes_written = write_unsigned_leb128($enc.cursor.get_mut(), pos, $value as u64);
+        $enc.cursor.set_position((pos + bytes_written) as u64);
+        Ok(())
+    }}
+}
+
+macro_rules! write_sleb128 {
+    ($enc:expr, $value:expr) => {{
+        let pos = $enc.cursor.position() as usize;
+        let bytes_written = write_signed_leb128($enc.cursor.get_mut(), pos, $value as i64);
+        $enc.cursor.set_position((pos + bytes_written) as u64);
+        Ok(())
+    }}
+}
+
+impl<'a> serialize::Encoder for Encoder<'a> {
+    type Error = io::Error;
+
+    fn emit_nil(&mut self) -> EncodeResult {
+        Ok(())
+    }
+
+    fn emit_usize(&mut self, v: usize) -> EncodeResult {
+        write_uleb128!(self, v)
+    }
+
+    fn emit_u64(&mut self, v: u64) -> EncodeResult {
+        write_uleb128!(self, v)
+    }
+
+    fn emit_u32(&mut self, v: u32) -> EncodeResult {
+        write_uleb128!(self, v)
+    }
+
+    fn emit_u16(&mut self, v: u16) -> EncodeResult {
+        write_uleb128!(self, v)
+    }
+
+    fn emit_u8(&mut self, v: u8) -> EncodeResult {
+        let _ = self.cursor.write_all(&[v]);
+        Ok(())
+    }
+
+    fn emit_isize(&mut self, v: isize) -> EncodeResult {
+        write_sleb128!(self, v)
+    }
+
+    fn emit_i64(&mut self, v: i64) -> EncodeResult {
+        write_sleb128!(self, v)
+    }
+
+    fn emit_i32(&mut self, v: i32) -> EncodeResult {
+        write_sleb128!(self, v)
+    }
+
+    fn emit_i16(&mut self, v: i16) -> EncodeResult {
+        write_sleb128!(self, v)
+    }
+
+    fn emit_i8(&mut self, v: i8) -> EncodeResult {
+        let as_u8: u8 = unsafe { ::std::mem::transmute(v) };
+        let _ = self.cursor.write_all(&[as_u8]);
+        Ok(())
+    }
+
+    fn emit_bool(&mut self, v: bool) -> EncodeResult {
+        self.emit_u8(if v {
+            1
+        } else {
+            0
+        })
+    }
+
+    fn emit_f64(&mut self, v: f64) -> EncodeResult {
+        let as_u64: u64 = unsafe { ::std::mem::transmute(v) };
+        self.emit_u64(as_u64)
+    }
+
+    fn emit_f32(&mut self, v: f32) -> EncodeResult {
+        let as_u32: u32 = unsafe { ::std::mem::transmute(v) };
+        self.emit_u32(as_u32)
+    }
+
+    fn emit_char(&mut self, v: char) -> EncodeResult {
+        self.emit_u32(v as u32)
+    }
+
+    fn emit_str(&mut self, v: &str) -> EncodeResult {
+        self.emit_usize(v.len())?;
+        let _ = self.cursor.write_all(v.as_bytes());
+        Ok(())
+    }
+}
+
+impl<'a> Encoder<'a> {
+    pub fn position(&self) -> usize {
+        self.cursor.position() as usize
+    }
+}
+
+// -----------------------------------------------------------------------------
+// Decoder
+// -----------------------------------------------------------------------------
+
+pub struct Decoder<'a> {
+    pub data: &'a [u8],
+    position: usize,
+}
+
+impl<'a> Decoder<'a> {
+    pub fn new(data: &'a [u8], position: usize) -> Decoder<'a> {
+        Decoder {
+            data: data,
+            position: position,
+        }
+    }
+
+    pub fn position(&self) -> usize {
+        self.position
+    }
+
+    pub fn advance(&mut self, bytes: usize) {
+        self.position += bytes;
+    }
+}
+
+macro_rules! read_uleb128 {
+    ($dec:expr, $t:ty) => ({
+        let (value, bytes_read) = read_unsigned_leb128($dec.data, $dec.position);
+        $dec.position += bytes_read;
+        Ok(value as $t)
+    })
+}
+
+macro_rules! read_sleb128 {
+    ($dec:expr, $t:ty) => ({
+        let (value, bytes_read) = read_signed_leb128($dec.data, $dec.position);
+        $dec.position += bytes_read;
+        Ok(value as $t)
+    })
+}
+
+
+impl<'a> serialize::Decoder for Decoder<'a> {
+    type Error = String;
+
+    fn read_nil(&mut self) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn read_u64(&mut self) -> Result<u64, Self::Error> {
+        read_uleb128!(self, u64)
+    }
+
+    fn read_u32(&mut self) -> Result<u32, Self::Error> {
+        read_uleb128!(self, u32)
+    }
+
+    fn read_u16(&mut self) -> Result<u16, Self::Error> {
+        read_uleb128!(self, u16)
+    }
+
+    fn read_u8(&mut self) -> Result<u8, Self::Error> {
+        let value = self.data[self.position];
+        self.position += 1;
+        Ok(value)
+    }
+
+    fn read_usize(&mut self) -> Result<usize, Self::Error> {
+        read_uleb128!(self, usize)
+    }
+
+    fn read_i64(&mut self) -> Result<i64, Self::Error> {
+        read_sleb128!(self, i64)
+    }
+
+    fn read_i32(&mut self) -> Result<i32, Self::Error> {
+        read_sleb128!(self, i32)
+    }
+
+    fn read_i16(&mut self) -> Result<i16, Self::Error> {
+        read_sleb128!(self, i16)
+    }
+
+    fn read_i8(&mut self) -> Result<i8, Self::Error> {
+        let as_u8 = self.data[self.position];
+        self.position += 1;
+        unsafe { Ok(::std::mem::transmute(as_u8)) }
+    }
+
+    fn read_isize(&mut self) -> Result<isize, Self::Error> {
+        read_sleb128!(self, isize)
+    }
+
+    fn read_bool(&mut self) -> Result<bool, Self::Error> {
+        let value = self.read_u8()?;
+        Ok(value != 0)
+    }
+
+    fn read_f64(&mut self) -> Result<f64, Self::Error> {
+        let bits = self.read_u64()?;
+        Ok(unsafe { ::std::mem::transmute(bits) })
+    }
+
+    fn read_f32(&mut self) -> Result<f32, Self::Error> {
+        let bits = self.read_u32()?;
+        Ok(unsafe { ::std::mem::transmute(bits) })
+    }
+
+    fn read_char(&mut self) -> Result<char, Self::Error> {
+        let bits = self.read_u32()?;
+        Ok(::std::char::from_u32(bits).unwrap())
+    }
+
+    fn read_str(&mut self) -> Result<String, Self::Error> {
+        let len = self.read_usize()?;
+        let s = ::std::str::from_utf8(&self.data[self.position..self.position + len]).unwrap();
+        self.position += len;
+        Ok(s.to_string())
+    }
+
+    fn error(&mut self, err: &str) -> Self::Error {
+        err.to_string()
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use serialize::{Encodable, Decodable};
+    use std::io::Cursor;
+    use std::fmt::Debug;
+    use super::{Encoder, Decoder};
+
+    #[derive(PartialEq, Clone, Debug, RustcEncodable, RustcDecodable)]
+    struct Struct {
+        a: (),
+        b: u8,
+        c: u16,
+        d: u32,
+        e: u64,
+        f: usize,
+
+        g: i8,
+        h: i16,
+        i: i32,
+        j: i64,
+        k: isize,
+
+        l: char,
+        m: String,
+        n: f32,
+        o: f64,
+        p: bool,
+        q: Option<u32>,
+    }
+
+
+    fn check_round_trip<T: Encodable + Decodable + PartialEq + Debug>(values: Vec<T>) {
+        let mut cursor = Cursor::new(Vec::new());
+
+        for value in &values {
+            let mut encoder = Encoder::new(&mut cursor);
+            Encodable::encode(&value, &mut encoder).unwrap();
+        }
+
+        let data = cursor.into_inner();
+        let mut decoder = Decoder::new(&data[..], 0);
+
+        for value in values {
+            let decoded = Decodable::decode(&mut decoder).unwrap();
+            assert_eq!(value, decoded);
+        }
+    }
+
+    #[test]
+    fn test_unit() {
+        check_round_trip(vec![(), (), (), ()]);
+    }
+
+    #[test]
+    fn test_u8() {
+        let mut vec = vec![];
+        for i in ::std::u8::MIN..::std::u8::MAX {
+            vec.push(i);
+        }
+        check_round_trip(vec);
+    }
+
+    #[test]
+    fn test_u16() {
+        for i in ::std::u16::MIN..::std::u16::MAX {
+            check_round_trip(vec![1, 2, 3, i, i, i]);
+        }
+    }
+
+    #[test]
+    fn test_u32() {
+        check_round_trip(vec![1, 2, 3, ::std::u32::MIN, 0, 1, ::std::u32::MAX, 2, 1]);
+    }
+
+    #[test]
+    fn test_u64() {
+        check_round_trip(vec![1, 2, 3, ::std::u64::MIN, 0, 1, ::std::u64::MAX, 2, 1]);
+    }
+
+    #[test]
+    fn test_usize() {
+        check_round_trip(vec![1, 2, 3, ::std::usize::MIN, 0, 1, ::std::usize::MAX, 2, 1]);
+    }
+
+    #[test]
+    fn test_i8() {
+        let mut vec = vec![];
+        for i in ::std::i8::MIN..::std::i8::MAX {
+            vec.push(i);
+        }
+        check_round_trip(vec);
+    }
+
+    #[test]
+    fn test_i16() {
+        for i in ::std::i16::MIN..::std::i16::MAX {
+            check_round_trip(vec![-1, 2, -3, i, i, i, 2]);
+        }
+    }
+
+    #[test]
+    fn test_i32() {
+        check_round_trip(vec![-1, 2, -3, ::std::i32::MIN, 0, 1, ::std::i32::MAX, 2, 1]);
+    }
+
+    #[test]
+    fn test_i64() {
+        check_round_trip(vec![-1, 2, -3, ::std::i64::MIN, 0, 1, ::std::i64::MAX, 2, 1]);
+    }
+
+    #[test]
+    fn test_isize() {
+        check_round_trip(vec![-1, 2, -3, ::std::isize::MIN, 0, 1, ::std::isize::MAX, 2, 1]);
+    }
+
+    #[test]
+    fn test_bool() {
+        check_round_trip(vec![false, true, true, false, false]);
+    }
+
+    #[test]
+    fn test_f32() {
+        let mut vec = vec![];
+        for i in -100..100 {
+            vec.push((i as f32) / 3.0);
+        }
+        check_round_trip(vec);
+    }
+
+    #[test]
+    fn test_f64() {
+        let mut vec = vec![];
+        for i in -100..100 {
+            vec.push((i as f64) / 3.0);
+        }
+        check_round_trip(vec);
+    }
+
+    #[test]
+    fn test_char() {
+        let vec = vec!['a', 'b', 'c', 'd', 'A', 'X', ' ', '#', 'Ö', 'Ä', 'µ', '€'];
+        check_round_trip(vec);
+    }
+
+    #[test]
+    fn test_string() {
+        let vec = vec!["abcbuÖeiovÄnameÜavmpßvmea€µsbpnvapeapmaebn".to_string(),
+                       "abcbuÖganeiovÄnameÜavmpßvmea€µsbpnvapeapmaebn".to_string(),
+                       "abcbuÖganeiovÄnameÜavmpßvmea€µsbpapmaebn".to_string(),
+                       "abcbuÖganeiovÄnameÜavmpßvmeabpnvapeapmaebn".to_string(),
+                       "abcbuÖganeiÄnameÜavmpßvmea€µsbpnvapeapmaebn".to_string(),
+                       "abcbuÖganeiovÄnameÜavmpßvmea€µsbpmaebn".to_string(),
+                       "abcbuÖganeiovÄnameÜavmpßvmea€µnvapeapmaebn".to_string()];
+
+        check_round_trip(vec);
+    }
+
+    #[test]
+    fn test_option() {
+        check_round_trip(vec![Some(-1i8)]);
+        check_round_trip(vec![Some(-2i16)]);
+        check_round_trip(vec![Some(-3i32)]);
+        check_round_trip(vec![Some(-4i64)]);
+        check_round_trip(vec![Some(-5isize)]);
+
+        let none_i8: Option<i8> = None;
+        check_round_trip(vec![none_i8]);
+
+        let none_i16: Option<i16> = None;
+        check_round_trip(vec![none_i16]);
+
+        let none_i32: Option<i32> = None;
+        check_round_trip(vec![none_i32]);
+
+        let none_i64: Option<i64> = None;
+        check_round_trip(vec![none_i64]);
+
+        let none_isize: Option<isize> = None;
+        check_round_trip(vec![none_isize]);
+    }
+
+    #[test]
+    fn test_struct() {
+        check_round_trip(vec![Struct {
+                                  a: (),
+                                  b: 10,
+                                  c: 11,
+                                  d: 12,
+                                  e: 13,
+                                  f: 14,
+
+                                  g: 15,
+                                  h: 16,
+                                  i: 17,
+                                  j: 18,
+                                  k: 19,
+
+                                  l: 'x',
+                                  m: "abc".to_string(),
+                                  n: 20.5,
+                                  o: 21.5,
+                                  p: false,
+                                  q: None,
+                              }]);
+
+        check_round_trip(vec![Struct {
+                                  a: (),
+                                  b: 101,
+                                  c: 111,
+                                  d: 121,
+                                  e: 131,
+                                  f: 141,
+
+                                  g: -15,
+                                  h: -16,
+                                  i: -17,
+                                  j: -18,
+                                  k: -19,
+
+                                  l: 'y',
+                                  m: "def".to_string(),
+                                  n: -20.5,
+                                  o: -21.5,
+                                  p: true,
+                                  q: Some(1234567),
+                              }]);
+    }
+
+    #[derive(PartialEq, Clone, Debug, RustcEncodable, RustcDecodable)]
+    enum Enum {
+        Variant1,
+        Variant2(usize, f32),
+        Variant3 {
+            a: i32,
+            b: char,
+            c: bool,
+        },
+    }
+
+    #[test]
+    fn test_enum() {
+        check_round_trip(vec![Enum::Variant1,
+                              Enum::Variant2(1, 2.5),
+                              Enum::Variant3 {
+                                  a: 3,
+                                  b: 'b',
+                                  c: false,
+                              },
+                              Enum::Variant3 {
+                                  a: -4,
+                                  b: 'f',
+                                  c: true,
+                              }]);
+    }
+
+    #[test]
+    fn test_sequence() {
+        let mut vec = vec![];
+        for i in -100i64..100i64 {
+            vec.push(i * 100000);
+        }
+
+        check_round_trip(vec![vec]);
+    }
+
+    #[test]
+    fn test_hash_map() {
+        use std::collections::HashMap;
+        let mut map = HashMap::new();
+        for i in -100i64..100i64 {
+            map.insert(i * 100000, i * 10000);
+        }
+
+        check_round_trip(vec![map]);
+    }
+
+    #[test]
+    fn test_tuples() {
+        check_round_trip(vec![('x', (), false, 0.5f32)]);
+        check_round_trip(vec![(9i8, 10u16, 1.5f64)]);
+        check_round_trip(vec![(-12i16, 11u8, 12usize)]);
+        check_round_trip(vec![(1234567isize, 100000000000000u64, 99999999999999i64)]);
+        check_round_trip(vec![(String::new(), "some string".to_string())]);
+    }
+}
diff --git a/src/libserialize/serialize.rs b/src/libserialize/serialize.rs
index ba6eefe82bb..88f6c12e980 100644
--- a/src/libserialize/serialize.rs
+++ b/src/libserialize/serialize.rs
@@ -42,66 +42,99 @@ pub trait Encoder {
     fn emit_str(&mut self, v: &str) -> Result<(), Self::Error>;
 
     // Compound types:
-    fn emit_enum<F>(&mut self, name: &str, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+    fn emit_enum<F>(&mut self, _name: &str, f: F) -> Result<(), Self::Error>
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
 
-    fn emit_enum_variant<F>(&mut self, v_name: &str,
+    fn emit_enum_variant<F>(&mut self, _v_name: &str,
                             v_id: usize,
-                            len: usize,
+                            _len: usize,
                             f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_enum_variant_arg<F>(&mut self, a_idx: usize, f: F)
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_usize(v_id)?;
+        f(self)
+    }
+    fn emit_enum_variant_arg<F>(&mut self, _a_idx: usize, f: F)
                                 -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
 
     fn emit_enum_struct_variant<F>(&mut self, v_name: &str,
                                    v_id: usize,
                                    len: usize,
                                    f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_enum_variant(v_name, v_id, len, f)
+    }
     fn emit_enum_struct_variant_field<F>(&mut self,
-                                         f_name: &str,
+                                         _f_name: &str,
                                          f_idx: usize,
                                          f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_enum_variant_arg(f_idx, f)
+    }
 
-    fn emit_struct<F>(&mut self, name: &str, len: usize, f: F)
+    fn emit_struct<F>(&mut self, _name: &str, _len: usize, f: F)
                       -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_struct_field<F>(&mut self, f_name: &str, f_idx: usize, f: F)
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
+    fn emit_struct_field<F>(&mut self, _f_name: &str, _f_idx: usize, f: F)
                             -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
 
-    fn emit_tuple<F>(&mut self, len: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_tuple_arg<F>(&mut self, idx: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+    fn emit_tuple<F>(&mut self, _len: usize, f: F) -> Result<(), Self::Error>
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
+    fn emit_tuple_arg<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
 
-    fn emit_tuple_struct<F>(&mut self, name: &str, len: usize, f: F)
+    fn emit_tuple_struct<F>(&mut self, _name: &str, len: usize, f: F)
                             -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_tuple(len, f)
+    }
     fn emit_tuple_struct_arg<F>(&mut self, f_idx: usize, f: F)
                                 -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_tuple_arg(f_idx, f)
+    }
 
     // Specialized types:
     fn emit_option<F>(&mut self, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_option_none(&mut self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_enum("Option", f)
+    }
+    fn emit_option_none(&mut self) -> Result<(), Self::Error> {
+        self.emit_enum_variant("None", 0, 0, |_| Ok(()))
+    }
     fn emit_option_some<F>(&mut self, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+
+        self.emit_enum_variant("Some", 1, 1, f)
+    }
 
     fn emit_seq<F>(&mut self, len: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_seq_elt<F>(&mut self, idx: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_usize(len)?;
+        f(self)
+    }
+    fn emit_seq_elt<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
 
     fn emit_map<F>(&mut self, len: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_map_elt_key<F>(&mut self, idx: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
-    fn emit_map_elt_val<F>(&mut self, idx: usize, f: F) -> Result<(), Self::Error>
-        where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error>
+    {
+        self.emit_usize(len)?;
+        f(self)
+    }
+    fn emit_map_elt_key<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
+    fn emit_map_elt_val<F>(&mut self, _idx: usize, f: F) -> Result<(), Self::Error>
+        where F: FnOnce(&mut Self) -> Result<(), Self::Error> { f(self) }
 }
 
 pub trait Decoder {
@@ -126,66 +159,101 @@ pub trait Decoder {
     fn read_str(&mut self) -> Result<String, Self::Error>;
 
     // Compound types:
-    fn read_enum<T, F>(&mut self, name: &str, f: F) -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+    fn read_enum<T, F>(&mut self, _name: &str, f: F) -> Result<T, Self::Error>
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
 
-    fn read_enum_variant<T, F>(&mut self, names: &[&str], f: F)
+    fn read_enum_variant<T, F>(&mut self, _names: &[&str], mut f: F)
                                -> Result<T, Self::Error>
-        where F: FnMut(&mut Self, usize) -> Result<T, Self::Error>;
-    fn read_enum_variant_arg<T, F>(&mut self, a_idx: usize, f: F)
+        where F: FnMut(&mut Self, usize) -> Result<T, Self::Error>
+    {
+        let disr = self.read_usize()?;
+        f(self, disr)
+    }
+    fn read_enum_variant_arg<T, F>(&mut self, _a_idx: usize, f: F)
                                    -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
 
     fn read_enum_struct_variant<T, F>(&mut self, names: &[&str], f: F)
                                       -> Result<T, Self::Error>
-        where F: FnMut(&mut Self, usize) -> Result<T, Self::Error>;
+        where F: FnMut(&mut Self, usize) -> Result<T, Self::Error>
+    {
+        self.read_enum_variant(names, f)
+    }
     fn read_enum_struct_variant_field<T, F>(&mut self,
-                                            &f_name: &str,
+                                            _f_name: &str,
                                             f_idx: usize,
                                             f: F)
                                             -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error>
+    {
+        self.read_enum_variant_arg(f_idx, f)
+    }
 
-    fn read_struct<T, F>(&mut self, s_name: &str, len: usize, f: F)
+    fn read_struct<T, F>(&mut self, _s_name: &str, _len: usize, f: F)
                          -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
     fn read_struct_field<T, F>(&mut self,
-                               f_name: &str,
-                               f_idx: usize,
+                               _f_name: &str,
+                               _f_idx: usize,
                                f: F)
                                -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
 
-    fn read_tuple<T, F>(&mut self, len: usize, f: F) -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
-    fn read_tuple_arg<T, F>(&mut self, a_idx: usize, f: F)
+    fn read_tuple<T, F>(&mut self, _len: usize, f: F) -> Result<T, Self::Error>
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
+    fn read_tuple_arg<T, F>(&mut self, _a_idx: usize, f: F)
                             -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
 
-    fn read_tuple_struct<T, F>(&mut self, s_name: &str, len: usize, f: F)
+    fn read_tuple_struct<T, F>(&mut self, _s_name: &str, len: usize, f: F)
                                -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error>
+    {
+        self.read_tuple(len, f)
+    }
     fn read_tuple_struct_arg<T, F>(&mut self, a_idx: usize, f: F)
                                    -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error>
+    {
+        self.read_tuple_arg(a_idx, f)
+    }
 
     // Specialized types:
-    fn read_option<T, F>(&mut self, f: F) -> Result<T, Self::Error>
-        where F: FnMut(&mut Self, bool) -> Result<T, Self::Error>;
+    fn read_option<T, F>(&mut self, mut f: F) -> Result<T, Self::Error>
+        where F: FnMut(&mut Self, bool) -> Result<T, Self::Error>
+    {
+        self.read_enum("Option", move |this| {
+            this.read_enum_variant(&["None", "Some"], move |this, idx| {
+                match idx {
+                    0 => f(this, false),
+                    1 => f(this, true),
+                    _ => Err(this.error("read_option: expected 0 for None or 1 for Some")),
+                }
+            })
+        })
+    }
 
     fn read_seq<T, F>(&mut self, f: F) -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self, usize) -> Result<T, Self::Error>;
-    fn read_seq_elt<T, F>(&mut self, idx: usize, f: F) -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self, usize) -> Result<T, Self::Error>
+    {
+        let len = self.read_usize()?;
+        f(self, len)
+    }
+    fn read_seq_elt<T, F>(&mut self, _idx: usize, f: F) -> Result<T, Self::Error>
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
 
     fn read_map<T, F>(&mut self, f: F) -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self, usize) -> Result<T, Self::Error>;
-    fn read_map_elt_key<T, F>(&mut self, idx: usize, f: F)
+        where F: FnOnce(&mut Self, usize) -> Result<T, Self::Error>
+    {
+        let len = self.read_usize()?;
+        f(self, len)
+    }
+    fn read_map_elt_key<T, F>(&mut self, _idx: usize, f: F)
                               -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
-    fn read_map_elt_val<T, F>(&mut self, idx: usize, f: F)
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
+    fn read_map_elt_val<T, F>(&mut self, _idx: usize, f: F)
                               -> Result<T, Self::Error>
-        where F: FnOnce(&mut Self) -> Result<T, Self::Error>;
+        where F: FnOnce(&mut Self) -> Result<T, Self::Error> { f(self) }
 
     // Failure
     fn error(&mut self, err: &str) -> Self::Error;