src/libserialize/serialize.rs - third_party/rust - Git at Google

 // Copyright 2012-2014 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.

 //! Support code for encoding and decoding types.

 /*
 Core encoding and decoding interfaces.
 */

 use std::path;
 use std::rc::Rc;
 use std::gc::{Gc, GC};

 pub trait Encoder<E> {
     // Primitive types:
     fn emit_nil(&mut self) -> Result<(), E>;
     fn emit_uint(&mut self, v: uint) -> Result<(), E>;
     fn emit_u64(&mut self, v: u64) -> Result<(), E>;
     fn emit_u32(&mut self, v: u32) -> Result<(), E>;
     fn emit_u16(&mut self, v: u16) -> Result<(), E>;
     fn emit_u8(&mut self, v: u8) -> Result<(), E>;
     fn emit_int(&mut self, v: int) -> Result<(), E>;
     fn emit_i64(&mut self, v: i64) -> Result<(), E>;
     fn emit_i32(&mut self, v: i32) -> Result<(), E>;
     fn emit_i16(&mut self, v: i16) -> Result<(), E>;
     fn emit_i8(&mut self, v: i8) -> Result<(), E>;
     fn emit_bool(&mut self, v: bool) -> Result<(), E>;
     fn emit_f64(&mut self, v: f64) -> Result<(), E>;
     fn emit_f32(&mut self, v: f32) -> Result<(), E>;
     fn emit_char(&mut self, v: char) -> Result<(), E>;
     fn emit_str(&mut self, v: &str) -> Result<(), E>;

     // Compound types:
     fn emit_enum(&mut self, name: &str, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_enum_variant(&mut self,
                          v_name: &str,
                          v_id: uint,
                          len: uint,
                          f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_enum_variant_arg(&mut self,
                              a_idx: uint,
                              f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_enum_struct_variant(&mut self,
                                 v_name: &str,
                                 v_id: uint,
                                 len: uint,
                                 f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_enum_struct_variant_field(&mut self,
                                       f_name: &str,
                                       f_idx: uint,
                                       f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_struct(&mut self,
                    name: &str,
                    len: uint,
                    f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_struct_field(&mut self,
                          f_name: &str,
                          f_idx: uint,
                          f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_tuple(&mut self, len: uint, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_tuple_arg(&mut self, idx: uint, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_tuple_struct(&mut self,
                          name: &str,
                          len: uint,
                          f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_tuple_struct_arg(&mut self,
                              f_idx: uint,
                              f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     // Specialized types:
     fn emit_option(&mut self, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_option_none(&mut self) -> Result<(), E>;
     fn emit_option_some(&mut self, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_seq(&mut self, len: uint, f: |this: &mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_seq_elt(&mut self, idx: uint, f: |this: &mut Self| -> Result<(), E>) -> Result<(), E>;

     fn emit_map(&mut self, len: uint, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_map_elt_key(&mut self, idx: uint, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
     fn emit_map_elt_val(&mut self, idx: uint, f: |&mut Self| -> Result<(), E>) -> Result<(), E>;
 }

 pub trait Decoder<E> {
     // Primitive types:
     fn read_nil(&mut self) -> Result<(), E>;
     fn read_uint(&mut self) -> Result<uint, E>;
     fn read_u64(&mut self) -> Result<u64, E>;
     fn read_u32(&mut self) -> Result<u32, E>;
     fn read_u16(&mut self) -> Result<u16, E>;
     fn read_u8(&mut self) -> Result<u8, E>;
     fn read_int(&mut self) -> Result<int, E>;
     fn read_i64(&mut self) -> Result<i64, E>;
     fn read_i32(&mut self) -> Result<i32, E>;
     fn read_i16(&mut self) -> Result<i16, E>;
     fn read_i8(&mut self) -> Result<i8, E>;
     fn read_bool(&mut self) -> Result<bool, E>;
     fn read_f64(&mut self) -> Result<f64, E>;
     fn read_f32(&mut self) -> Result<f32, E>;
     fn read_char(&mut self) -> Result<char, E>;
     fn read_str(&mut self) -> Result<String, E>;

     // Compound types:
     fn read_enum<T>(&mut self, name: &str, f: |&mut Self| -> Result<T, E>) -> Result<T, E>;

     fn read_enum_variant<T>(&mut self,
                             names: &[&str],
                             f: |&mut Self, uint| -> Result<T, E>)
                             -> Result<T, E>;
     fn read_enum_variant_arg<T>(&mut self,
                                 a_idx: uint,
                                 f: |&mut Self| -> Result<T, E>)
                                 -> Result<T, E>;

     fn read_enum_struct_variant<T>(&mut self,
                                    names: &[&str],
                                    f: |&mut Self, uint| -> Result<T, E>)
                                    -> Result<T, E>;
     fn read_enum_struct_variant_field<T>(&mut self,
                                          &f_name: &str,
                                          f_idx: uint,
                                          f: |&mut Self| -> Result<T, E>)
                                          -> Result<T, E>;

     fn read_struct<T>(&mut self, s_name: &str, len: uint, f: |&mut Self| -> Result<T, E>)
                       -> Result<T, E>;
     fn read_struct_field<T>(&mut self,
                             f_name: &str,
                             f_idx: uint,
                             f: |&mut Self| -> Result<T, E>)
                             -> Result<T, E>;

     fn read_tuple<T>(&mut self, f: |&mut Self, uint| -> Result<T, E>) -> Result<T, E>;
     fn read_tuple_arg<T>(&mut self, a_idx: uint, f: |&mut Self| -> Result<T, E>) -> Result<T, E>;

     fn read_tuple_struct<T>(&mut self,
                             s_name: &str,
                             f: |&mut Self, uint| -> Result<T, E>)
                             -> Result<T, E>;
     fn read_tuple_struct_arg<T>(&mut self,
                                 a_idx: uint,
                                 f: |&mut Self| -> Result<T, E>)
                                 -> Result<T, E>;

     // Specialized types:
     fn read_option<T>(&mut self, f: |&mut Self, bool| -> Result<T, E>) -> Result<T, E>;

     fn read_seq<T>(&mut self, f: |&mut Self, uint| -> Result<T, E>) -> Result<T, E>;
     fn read_seq_elt<T>(&mut self, idx: uint, f: |&mut Self| -> Result<T, E>) -> Result<T, E>;

     fn read_map<T>(&mut self, f: |&mut Self, uint| -> Result<T, E>) -> Result<T, E>;
     fn read_map_elt_key<T>(&mut self, idx: uint, f: |&mut Self| -> Result<T, E>) -> Result<T, E>;
     fn read_map_elt_val<T>(&mut self, idx: uint, f: |&mut Self| -> Result<T, E>) -> Result<T, E>;
 }

 pub trait Encodable<S:Encoder<E>, E> {
     fn encode(&self, s: &mut S) -> Result<(), E>;
 }

 pub trait Decodable<D:Decoder<E>, E> {
     fn decode(d: &mut D) -> Result<Self, E>;
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for uint {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_uint(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for uint {
     fn decode(d: &mut D) -> Result<uint, E> {
         d.read_uint()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for u8 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_u8(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for u8 {
     fn decode(d: &mut D) -> Result<u8, E> {
         d.read_u8()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for u16 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_u16(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for u16 {
     fn decode(d: &mut D) -> Result<u16, E> {
         d.read_u16()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for u32 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_u32(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for u32 {
     fn decode(d: &mut D) -> Result<u32, E> {
         d.read_u32()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for u64 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_u64(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for u64 {
     fn decode(d: &mut D) -> Result<u64, E> {
         d.read_u64()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for int {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_int(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for int {
     fn decode(d: &mut D) -> Result<int, E> {
         d.read_int()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for i8 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_i8(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for i8 {
     fn decode(d: &mut D) -> Result<i8, E> {
         d.read_i8()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for i16 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_i16(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for i16 {
     fn decode(d: &mut D) -> Result<i16, E> {
         d.read_i16()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for i32 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_i32(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for i32 {
     fn decode(d: &mut D) -> Result<i32, E> {
         d.read_i32()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for i64 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_i64(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for i64 {
     fn decode(d: &mut D) -> Result<i64, E> {
         d.read_i64()
     }
 }

 impl<'a, E, S:Encoder<E>> Encodable<S, E> for &'a str {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_str(*self)
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for String {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_str(self.as_slice())
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for String {
     fn decode(d: &mut D) -> Result<String, E> {
         Ok(String::from_str(try!(d.read_str()).as_slice()))
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for f32 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_f32(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for f32 {
     fn decode(d: &mut D) -> Result<f32, E> {
         d.read_f32()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for f64 {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_f64(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for f64 {
     fn decode(d: &mut D) -> Result<f64, E> {
         d.read_f64()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for bool {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_bool(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for bool {
     fn decode(d: &mut D) -> Result<bool, E> {
         d.read_bool()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for char {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_char(*self)
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for char {
     fn decode(d: &mut D) -> Result<char, E> {
         d.read_char()
     }
 }

 impl<E, S:Encoder<E>> Encodable<S, E> for () {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_nil()
     }
 }

 impl<E, D:Decoder<E>> Decodable<D, E> for () {
     fn decode(d: &mut D) -> Result<(), E> {
         d.read_nil()
     }
 }

 impl<'a, E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for &'a T {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         (**self).encode(s)
     }
 }

 impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Box<T> {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         (**self).encode(s)
     }
 }

 impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Box<T> {
     fn decode(d: &mut D) -> Result<Box<T>, E> {
         Ok(box try!(Decodable::decode(d)))
     }
 }

 impl<E, S:Encoder<E>,T:'static + Encodable<S, E>> Encodable<S, E> for Gc<T> {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         (**self).encode(s)
     }
 }

 impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Rc<T> {
     #[inline]
     fn encode(&self, s: &mut S) -> Result<(), E> {
         (**self).encode(s)
     }
 }

 impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Rc<T> {
     #[inline]
     fn decode(d: &mut D) -> Result<Rc<T>, E> {
         Ok(Rc::new(try!(Decodable::decode(d))))
     }
 }

 impl<E, D:Decoder<E>,T:Decodable<D, E> + 'static> Decodable<D, E> for Gc<T> {
     fn decode(d: &mut D) -> Result<Gc<T>, E> {
         Ok(box(GC) try!(Decodable::decode(d)))
     }
 }

 impl<'a, E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for &'a [T] {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_seq(self.len(), |s| {
             for (i, e) in self.iter().enumerate() {
                 try!(s.emit_seq_elt(i, |s| e.encode(s)))
             }
             Ok(())
         })
     }
 }

 impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Vec<T> {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_seq(self.len(), |s| {
             for (i, e) in self.iter().enumerate() {
                 try!(s.emit_seq_elt(i, |s| e.encode(s)))
             }
             Ok(())
         })
     }
 }

 impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Vec<T> {
     fn decode(d: &mut D) -> Result<Vec<T>, E> {
         d.read_seq(|d, len| {
             let mut v = Vec::with_capacity(len);
             for i in range(0, len) {
                 v.push(try!(d.read_seq_elt(i, |d| Decodable::decode(d))));
             }
             Ok(v)
         })
     }
 }

 impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Option<T> {
     fn encode(&self, s: &mut S) -> Result<(), E> {
         s.emit_option(|s| {
             match *self {
                 None => s.emit_option_none(),
                 Some(ref v) => s.emit_option_some(|s| v.encode(s)),
             }
         })
     }
 }

 impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Option<T> {
     fn decode(d: &mut D) -> Result<Option<T>, E> {
         d.read_option(|d, b| {
             if b {
                 Ok(Some(try!(Decodable::decode(d))))
             } else {
                 Ok(None)
             }
         })
     }
 }

 macro_rules! peel(($name:ident, $($other:ident,)*) => (tuple!($($other,)*)))

 macro_rules! tuple (
     () => ();
     ( $($name:ident,)+ ) => (
         impl<E, D:Decoder<E>,$($name:Decodable<D, E>),*> Decodable<D,E> for ($($name,)*) {
             #[allow(uppercase_variables)]
             fn decode(d: &mut D) -> Result<($($name,)*), E> {
                 d.read_tuple(|d, amt| {
                     let mut i = 0;
                     let ret = ($(try!(d.read_tuple_arg({ i+=1; i-1 }, |d| -> Result<$name,E> {
                         Decodable::decode(d)
                     })),)*);
                     assert!(amt == i,
                             "expected tuple of length `{}`, found tuple \
                              of length `{}`", i, amt);
                     return Ok(ret);
                 })
             }
         }
         impl<E, S:Encoder<E>,$($name:Encodable<S, E>),*> Encodable<S, E> for ($($name,)*) {
             #[allow(uppercase_variables)]
             fn encode(&self, s: &mut S) -> Result<(), E> {
                 let ($(ref $name,)*) = *self;
                 let mut n = 0;
                 $(let $name = $name; n += 1;)*
                 s.emit_tuple(n, |s| {
                     let mut i = 0;
                     $(try!(s.emit_seq_elt({ i+=1; i-1 }, |s| $name.encode(s)));)*
                     Ok(())
                 })
             }
         }
         peel!($($name,)*)
     )
 )

 tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }

 impl<E, S: Encoder<E>> Encodable<S, E> for path::posix::Path {
     fn encode(&self, e: &mut S) -> Result<(), E> {
         self.as_vec().encode(e)
     }
 }

 impl<E, D: Decoder<E>> Decodable<D, E> for path::posix::Path {
     fn decode(d: &mut D) -> Result<path::posix::Path, E> {
         let bytes: Vec<u8> = try!(Decodable::decode(d));
         Ok(path::posix::Path::new(bytes))
     }
 }

 impl<E, S: Encoder<E>> Encodable<S, E> for path::windows::Path {
     fn encode(&self, e: &mut S) -> Result<(), E> {
         self.as_vec().encode(e)
     }
 }

 impl<E, D: Decoder<E>> Decodable<D, E> for path::windows::Path {
     fn decode(d: &mut D) -> Result<path::windows::Path, E> {
         let bytes: Vec<u8> = try!(Decodable::decode(d));
         Ok(path::windows::Path::new(bytes))
     }
 }

 // ___________________________________________________________________________
 // Helper routines
 //
 // In some cases, these should eventually be coded as traits.

 pub trait EncoderHelpers<E> {
     fn emit_from_vec<T>(&mut self,
                         v: &[T],
                         f: |&mut Self, v: &T| -> Result<(), E>) -> Result<(), E>;
 }

 impl<E, S:Encoder<E>> EncoderHelpers<E> for S {
     fn emit_from_vec<T>(&mut self, v: &[T], f: |&mut S, &T| -> Result<(), E>) -> Result<(), E> {
         self.emit_seq(v.len(), |this| {
             for (i, e) in v.iter().enumerate() {
                 try!(this.emit_seq_elt(i, |this| {
                     f(this, e)
                 }));
             }
             Ok(())
         })
     }
 }

 pub trait DecoderHelpers<E> {
     fn read_to_vec<T>(&mut self, f: |&mut Self| -> Result<T, E>) -> Result<Vec<T>, E>;
 }

 impl<E, D:Decoder<E>> DecoderHelpers<E> for D {
     fn read_to_vec<T>(&mut self, f: |&mut D| -> Result<T, E>) -> Result<Vec<T>, E> {
         self.read_seq(|this, len| {
             let mut v = Vec::with_capacity(len);
             for i in range(0, len) {
                 v.push(try!(this.read_seq_elt(i, |this| f(this))));
             }
             Ok(v)
         })
     }
 }
	// Copyright 2012-2014 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.

	//! Support code for encoding and decoding types.

	/*
	Core encoding and decoding interfaces.
	*/

	use std::path;
	use std::rc::Rc;
	use std::gc::{Gc, GC};

	pub trait Encoder<E> {
	// Primitive types:
	fn emit_nil(&mut self) -> Result<(), E>;
	fn emit_uint(&mut self, v: uint) -> Result<(), E>;
	fn emit_u64(&mut self, v: u64) -> Result<(), E>;
	fn emit_u32(&mut self, v: u32) -> Result<(), E>;
	fn emit_u16(&mut self, v: u16) -> Result<(), E>;
	fn emit_u8(&mut self, v: u8) -> Result<(), E>;
	fn emit_int(&mut self, v: int) -> Result<(), E>;
	fn emit_i64(&mut self, v: i64) -> Result<(), E>;
	fn emit_i32(&mut self, v: i32) -> Result<(), E>;
	fn emit_i16(&mut self, v: i16) -> Result<(), E>;
	fn emit_i8(&mut self, v: i8) -> Result<(), E>;
	fn emit_bool(&mut self, v: bool) -> Result<(), E>;
	fn emit_f64(&mut self, v: f64) -> Result<(), E>;
	fn emit_f32(&mut self, v: f32) -> Result<(), E>;
	fn emit_char(&mut self, v: char) -> Result<(), E>;
	fn emit_str(&mut self, v: &str) -> Result<(), E>;

	// Compound types:
	fn emit_enum(&mut self, name: &str, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_enum_variant(&mut self,
	v_name: &str,
	v_id: uint,
	len: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_enum_variant_arg(&mut self,
	a_idx: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_enum_struct_variant(&mut self,
	v_name: &str,
	v_id: uint,
	len: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_enum_struct_variant_field(&mut self,
	f_name: &str,
	f_idx: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_struct(&mut self,
	name: &str,
	len: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_struct_field(&mut self,
	f_name: &str,
	f_idx: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_tuple(&mut self, len: uint, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_tuple_arg(&mut self, idx: uint, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_tuple_struct(&mut self,
	name: &str,
	len: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_tuple_struct_arg(&mut self,
	f_idx: uint,
	f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	// Specialized types:
	fn emit_option(&mut self, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_option_none(&mut self) -> Result<(), E>;
	fn emit_option_some(&mut self, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_seq(&mut self, len: uint, f: \|this: &mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_seq_elt(&mut self, idx: uint, f: \|this: &mut Self\| -> Result<(), E>) -> Result<(), E>;

	fn emit_map(&mut self, len: uint, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_map_elt_key(&mut self, idx: uint, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	fn emit_map_elt_val(&mut self, idx: uint, f: \|&mut Self\| -> Result<(), E>) -> Result<(), E>;
	}

	pub trait Decoder<E> {
	// Primitive types:
	fn read_nil(&mut self) -> Result<(), E>;
	fn read_uint(&mut self) -> Result<uint, E>;
	fn read_u64(&mut self) -> Result<u64, E>;
	fn read_u32(&mut self) -> Result<u32, E>;
	fn read_u16(&mut self) -> Result<u16, E>;
	fn read_u8(&mut self) -> Result<u8, E>;
	fn read_int(&mut self) -> Result<int, E>;
	fn read_i64(&mut self) -> Result<i64, E>;
	fn read_i32(&mut self) -> Result<i32, E>;
	fn read_i16(&mut self) -> Result<i16, E>;
	fn read_i8(&mut self) -> Result<i8, E>;
	fn read_bool(&mut self) -> Result<bool, E>;
	fn read_f64(&mut self) -> Result<f64, E>;
	fn read_f32(&mut self) -> Result<f32, E>;
	fn read_char(&mut self) -> Result<char, E>;
	fn read_str(&mut self) -> Result<String, E>;

	// Compound types:
	fn read_enum<T>(&mut self, name: &str, f: \|&mut Self\| -> Result<T, E>) -> Result<T, E>;

	fn read_enum_variant<T>(&mut self,
	names: &[&str],
	f: \|&mut Self, uint\| -> Result<T, E>)
	-> Result<T, E>;
	fn read_enum_variant_arg<T>(&mut self,
	a_idx: uint,
	f: \|&mut Self\| -> Result<T, E>)
	-> Result<T, E>;

	fn read_enum_struct_variant<T>(&mut self,
	names: &[&str],
	f: \|&mut Self, uint\| -> Result<T, E>)
	-> Result<T, E>;
	fn read_enum_struct_variant_field<T>(&mut self,
	&f_name: &str,
	f_idx: uint,
	f: \|&mut Self\| -> Result<T, E>)
	-> Result<T, E>;

	fn read_struct<T>(&mut self, s_name: &str, len: uint, f: \|&mut Self\| -> Result<T, E>)
	-> Result<T, E>;
	fn read_struct_field<T>(&mut self,
	f_name: &str,
	f_idx: uint,
	f: \|&mut Self\| -> Result<T, E>)
	-> Result<T, E>;

	fn read_tuple<T>(&mut self, f: \|&mut Self, uint\| -> Result<T, E>) -> Result<T, E>;
	fn read_tuple_arg<T>(&mut self, a_idx: uint, f: \|&mut Self\| -> Result<T, E>) -> Result<T, E>;

	fn read_tuple_struct<T>(&mut self,
	s_name: &str,
	f: \|&mut Self, uint\| -> Result<T, E>)
	-> Result<T, E>;
	fn read_tuple_struct_arg<T>(&mut self,
	a_idx: uint,
	f: \|&mut Self\| -> Result<T, E>)
	-> Result<T, E>;

	// Specialized types:
	fn read_option<T>(&mut self, f: \|&mut Self, bool\| -> Result<T, E>) -> Result<T, E>;

	fn read_seq<T>(&mut self, f: \|&mut Self, uint\| -> Result<T, E>) -> Result<T, E>;
	fn read_seq_elt<T>(&mut self, idx: uint, f: \|&mut Self\| -> Result<T, E>) -> Result<T, E>;

	fn read_map<T>(&mut self, f: \|&mut Self, uint\| -> Result<T, E>) -> Result<T, E>;
	fn read_map_elt_key<T>(&mut self, idx: uint, f: \|&mut Self\| -> Result<T, E>) -> Result<T, E>;
	fn read_map_elt_val<T>(&mut self, idx: uint, f: \|&mut Self\| -> Result<T, E>) -> Result<T, E>;
	}

	pub trait Encodable<S:Encoder<E>, E> {
	fn encode(&self, s: &mut S) -> Result<(), E>;
	}

	pub trait Decodable<D:Decoder<E>, E> {
	fn decode(d: &mut D) -> Result<Self, E>;
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for uint {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_uint(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for uint {
	fn decode(d: &mut D) -> Result<uint, E> {
	d.read_uint()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for u8 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_u8(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for u8 {
	fn decode(d: &mut D) -> Result<u8, E> {
	d.read_u8()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for u16 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_u16(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for u16 {
	fn decode(d: &mut D) -> Result<u16, E> {
	d.read_u16()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for u32 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_u32(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for u32 {
	fn decode(d: &mut D) -> Result<u32, E> {
	d.read_u32()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for u64 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_u64(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for u64 {
	fn decode(d: &mut D) -> Result<u64, E> {
	d.read_u64()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for int {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_int(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for int {
	fn decode(d: &mut D) -> Result<int, E> {
	d.read_int()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for i8 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_i8(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for i8 {
	fn decode(d: &mut D) -> Result<i8, E> {
	d.read_i8()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for i16 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_i16(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for i16 {
	fn decode(d: &mut D) -> Result<i16, E> {
	d.read_i16()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for i32 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_i32(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for i32 {
	fn decode(d: &mut D) -> Result<i32, E> {
	d.read_i32()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for i64 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_i64(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for i64 {
	fn decode(d: &mut D) -> Result<i64, E> {
	d.read_i64()
	}
	}

	impl<'a, E, S:Encoder<E>> Encodable<S, E> for &'a str {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_str(*self)
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for String {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_str(self.as_slice())
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for String {
	fn decode(d: &mut D) -> Result<String, E> {
	Ok(String::from_str(try!(d.read_str()).as_slice()))
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for f32 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_f32(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for f32 {
	fn decode(d: &mut D) -> Result<f32, E> {
	d.read_f32()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for f64 {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_f64(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for f64 {
	fn decode(d: &mut D) -> Result<f64, E> {
	d.read_f64()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for bool {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_bool(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for bool {
	fn decode(d: &mut D) -> Result<bool, E> {
	d.read_bool()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for char {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_char(*self)
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for char {
	fn decode(d: &mut D) -> Result<char, E> {
	d.read_char()
	}
	}

	impl<E, S:Encoder<E>> Encodable<S, E> for () {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_nil()
	}
	}

	impl<E, D:Decoder<E>> Decodable<D, E> for () {
	fn decode(d: &mut D) -> Result<(), E> {
	d.read_nil()
	}
	}

	impl<'a, E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for &'a T {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	(**self).encode(s)
	}
	}

	impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Box<T> {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	(**self).encode(s)
	}
	}

	impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Box<T> {
	fn decode(d: &mut D) -> Result<Box<T>, E> {
	Ok(box try!(Decodable::decode(d)))
	}
	}

	impl<E, S:Encoder<E>,T:'static + Encodable<S, E>> Encodable<S, E> for Gc<T> {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	(**self).encode(s)
	}
	}

	impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Rc<T> {
	#[inline]
	fn encode(&self, s: &mut S) -> Result<(), E> {
	(**self).encode(s)
	}
	}

	impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Rc<T> {
	#[inline]
	fn decode(d: &mut D) -> Result<Rc<T>, E> {
	Ok(Rc::new(try!(Decodable::decode(d))))
	}
	}

	impl<E, D:Decoder<E>,T:Decodable<D, E> + 'static> Decodable<D, E> for Gc<T> {
	fn decode(d: &mut D) -> Result<Gc<T>, E> {
	Ok(box(GC) try!(Decodable::decode(d)))
	}
	}

	impl<'a, E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for &'a [T] {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_seq(self.len(), \|s\| {
	for (i, e) in self.iter().enumerate() {
	try!(s.emit_seq_elt(i, \|s\| e.encode(s)))
	}
	Ok(())
	})
	}
	}

	impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Vec<T> {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_seq(self.len(), \|s\| {
	for (i, e) in self.iter().enumerate() {
	try!(s.emit_seq_elt(i, \|s\| e.encode(s)))
	}
	Ok(())
	})
	}
	}

	impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Vec<T> {
	fn decode(d: &mut D) -> Result<Vec<T>, E> {
	d.read_seq(\|d, len\| {
	let mut v = Vec::with_capacity(len);
	for i in range(0, len) {
	v.push(try!(d.read_seq_elt(i, \|d\| Decodable::decode(d))));
	}
	Ok(v)
	})
	}
	}

	impl<E, S:Encoder<E>,T:Encodable<S, E>> Encodable<S, E> for Option<T> {
	fn encode(&self, s: &mut S) -> Result<(), E> {
	s.emit_option(\|s\| {
	match *self {
	None => s.emit_option_none(),
	Some(ref v) => s.emit_option_some(\|s\| v.encode(s)),
	}
	})
	}
	}

	impl<E, D:Decoder<E>,T:Decodable<D, E>> Decodable<D, E> for Option<T> {
	fn decode(d: &mut D) -> Result<Option<T>, E> {
	d.read_option(\|d, b\| {
	if b {
	Ok(Some(try!(Decodable::decode(d))))
	} else {
	Ok(None)
	}
	})
	}
	}

	macro_rules! peel(($name:ident, $($other:ident,)) => (tuple!($($other,))))

	macro_rules! tuple (
	() => ();
	( $($name:ident,)+ ) => (
	impl<E, D:Decoder<E>,$($name:Decodable<D, E>),> Decodable<D,E> for ($($name,)) {
	#[allow(uppercase_variables)]
	fn decode(d: &mut D) -> Result<($($name,)*), E> {
	d.read_tuple(\|d, amt\| {
	let mut i = 0;
	let ret = ($(try!(d.read_tuple_arg({ i+=1; i-1 }, \|d\| -> Result<$name,E> {
	Decodable::decode(d)
	})),)*);
	assert!(amt == i,
	"expected tuple of length `{}`, found tuple \
	of length `{}`", i, amt);
	return Ok(ret);
	})
	}
	}
	impl<E, S:Encoder<E>,$($name:Encodable<S, E>),> Encodable<S, E> for ($($name,)) {
	#[allow(uppercase_variables)]
	fn encode(&self, s: &mut S) -> Result<(), E> {
	let ($(ref $name,)) = self;
	let mut n = 0;
	$(let $name = $name; n += 1;)*
	s.emit_tuple(n, \|s\| {
	let mut i = 0;
	$(try!(s.emit_seq_elt({ i+=1; i-1 }, \|s\| $name.encode(s)));)*
	Ok(())
	})
	}
	}
	peel!($($name,)*)
	)
	)

	tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }

	impl<E, S: Encoder<E>> Encodable<S, E> for path::posix::Path {
	fn encode(&self, e: &mut S) -> Result<(), E> {
	self.as_vec().encode(e)
	}
	}

	impl<E, D: Decoder<E>> Decodable<D, E> for path::posix::Path {
	fn decode(d: &mut D) -> Result<path::posix::Path, E> {
	let bytes: Vec<u8> = try!(Decodable::decode(d));
	Ok(path::posix::Path::new(bytes))
	}
	}

	impl<E, S: Encoder<E>> Encodable<S, E> for path::windows::Path {
	fn encode(&self, e: &mut S) -> Result<(), E> {
	self.as_vec().encode(e)
	}
	}

	impl<E, D: Decoder<E>> Decodable<D, E> for path::windows::Path {
	fn decode(d: &mut D) -> Result<path::windows::Path, E> {
	let bytes: Vec<u8> = try!(Decodable::decode(d));
	Ok(path::windows::Path::new(bytes))
	}
	}

	// ___________________________________________________________________________
	// Helper routines
	//
	// In some cases, these should eventually be coded as traits.

	pub trait EncoderHelpers<E> {
	fn emit_from_vec<T>(&mut self,
	v: &[T],
	f: \|&mut Self, v: &T\| -> Result<(), E>) -> Result<(), E>;
	}

	impl<E, S:Encoder<E>> EncoderHelpers<E> for S {
	fn emit_from_vec<T>(&mut self, v: &[T], f: \|&mut S, &T\| -> Result<(), E>) -> Result<(), E> {
	self.emit_seq(v.len(), \|this\| {
	for (i, e) in v.iter().enumerate() {
	try!(this.emit_seq_elt(i, \|this\| {
	f(this, e)
	}));
	}
	Ok(())
	})
	}
	}

	pub trait DecoderHelpers<E> {
	fn read_to_vec<T>(&mut self, f: \|&mut Self\| -> Result<T, E>) -> Result<Vec<T>, E>;
	}

	impl<E, D:Decoder<E>> DecoderHelpers<E> for D {
	fn read_to_vec<T>(&mut self, f: \|&mut D\| -> Result<T, E>) -> Result<Vec<T>, E> {
	self.read_seq(\|this, len\| {
	let mut v = Vec::with_capacity(len);
	for i in range(0, len) {
	v.push(try!(this.read_seq_elt(i, \|this\| f(this))));
	}
	Ok(v)
	})
	}
	}