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::cell::{Cell, RefCell};
 use std::sync::Arc;

 pub trait Encoder {
     type Error;

     // Primitive types:
     fn emit_nil(&mut self) -> Result<(), Self::Error>;
     fn emit_uint(&mut self, v: usize) -> Result<(), Self::Error>;
     fn emit_u64(&mut self, v: u64) -> Result<(), Self::Error>;
     fn emit_u32(&mut self, v: u32) -> Result<(), Self::Error>;
     fn emit_u16(&mut self, v: u16) -> Result<(), Self::Error>;
     fn emit_u8(&mut self, v: u8) -> Result<(), Self::Error>;
     fn emit_int(&mut self, v: isize) -> Result<(), Self::Error>;
     fn emit_i64(&mut self, v: i64) -> Result<(), Self::Error>;
     fn emit_i32(&mut self, v: i32) -> Result<(), Self::Error>;
     fn emit_i16(&mut self, v: i16) -> Result<(), Self::Error>;
     fn emit_i8(&mut self, v: i8) -> Result<(), Self::Error>;
     fn emit_bool(&mut self, v: bool) -> Result<(), Self::Error>;
     fn emit_f64(&mut self, v: f64) -> Result<(), Self::Error>;
     fn emit_f32(&mut self, v: f32) -> Result<(), Self::Error>;
     fn emit_char(&mut self, v: char) -> Result<(), Self::Error>;
     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_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>;
     fn emit_enum_variant_arg<F>(&mut self, a_idx: usize, f: F)
                                 -> Result<(), Self::Error>
         where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

     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>;
     fn emit_enum_struct_variant_field<F>(&mut self,
                                          f_name: &str,
                                          f_idx: usize,
                                          f: F) -> Result<(), Self::Error>
         where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

     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)
                             -> 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>;
     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_struct<F>(&mut self, name: &str, len: usize, f: F)
                             -> Result<(), Self::Error>
         where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
     fn emit_tuple_struct_arg<F>(&mut self, f_idx: usize, f: F)
                                 -> Result<(), Self::Error>
         where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

     // 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>;
     fn emit_option_some<F>(&mut self, f: F) -> Result<(), Self::Error>
         where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

     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>;

     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>;
 }

 pub trait Decoder {
     type Error;

     // Primitive types:
     fn read_nil(&mut self) -> Result<(), Self::Error>;
     fn read_uint(&mut self) -> Result<usize, Self::Error>;
     fn read_u64(&mut self) -> Result<u64, Self::Error>;
     fn read_u32(&mut self) -> Result<u32, Self::Error>;
     fn read_u16(&mut self) -> Result<u16, Self::Error>;
     fn read_u8(&mut self) -> Result<u8, Self::Error>;
     fn read_int(&mut self) -> Result<isize, Self::Error>;
     fn read_i64(&mut self) -> Result<i64, Self::Error>;
     fn read_i32(&mut self) -> Result<i32, Self::Error>;
     fn read_i16(&mut self) -> Result<i16, Self::Error>;
     fn read_i8(&mut self) -> Result<i8, Self::Error>;
     fn read_bool(&mut self) -> Result<bool, Self::Error>;
     fn read_f64(&mut self) -> Result<f64, Self::Error>;
     fn read_f32(&mut self) -> Result<f32, Self::Error>;
     fn read_char(&mut self) -> Result<char, Self::Error>;
     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_variant<T, F>(&mut self, names: &[&str], 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)
                                    -> Result<T, Self::Error>
         where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

     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>;
     fn read_enum_struct_variant_field<T, F>(&mut self,
                                             &f_name: &str,
                                             f_idx: usize,
                                             f: F)
                                             -> Result<T, Self::Error>
         where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

     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>;
     fn read_struct_field<T, F>(&mut self,
                                f_name: &str,
                                f_idx: usize,
                                f: F)
                                -> Result<T, Self::Error>
         where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

     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)
                             -> Result<T, Self::Error>
         where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

     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>;
     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>;

     // 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_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>;

     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)
                               -> 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)
                               -> Result<T, Self::Error>
         where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

     // Failure
     fn error(&mut self, err: &str) -> Self::Error;
 }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 impl< T: Decodable> Decodable for Box<[T]> {
     fn decode<D: Decoder>(d: &mut D) -> Result<Box<[T]>, D::Error> {
         let v: Vec<T> = Decodable::decode(d)?;
         Ok(v.into_boxed_slice())
     }
 }

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

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

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

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

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

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

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

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

 /// Evaluates to the number of identifiers passed to it, for example: `count_idents!(a, b, c) == 3
 macro_rules! count_idents {
     () => { 0 };
     ($_i:ident, $($rest:ident,)*) => { 1 + count_idents!($($rest,)*) }
 }

 macro_rules! tuple {
     () => ();
     ( $($name:ident,)+ ) => (
         impl<$($name:Decodable),*> Decodable for ($($name,)*) {
             #[allow(non_snake_case)]
             fn decode<D: Decoder>(d: &mut D) -> Result<($($name,)*), D::Error> {
                 let len: usize = count_idents!($($name,)*);
                 d.read_tuple(len, |d| {
                     let mut i = 0;
                     let ret = ($(try!(d.read_tuple_arg({ i+=1; i-1 },
                                                        |d| -> Result<$name,D::Error> {
                         Decodable::decode(d)
                     })),)*);
                     Ok(ret)
                 })
             }
         }
         impl<$($name:Encodable),*> Encodable for ($($name,)*) {
             #[allow(non_snake_case)]
             fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
                 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_tuple_arg({ 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 Encodable for path::PathBuf {
     fn encode<S: Encoder>(&self, e: &mut S) -> Result<(), S::Error> {
         self.to_str().unwrap().encode(e)
     }
 }

 impl Decodable for path::PathBuf {
     fn decode<D: Decoder>(d: &mut D) -> Result<path::PathBuf, D::Error> {
         let bytes: String = Decodable::decode(d)?;
         Ok(path::PathBuf::from(bytes))
     }
 }

 impl<T: Encodable + Copy> Encodable for Cell<T> {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         self.get().encode(s)
     }
 }

 impl<T: Decodable + Copy> Decodable for Cell<T> {
     fn decode<D: Decoder>(d: &mut D) -> Result<Cell<T>, D::Error> {
         Ok(Cell::new(Decodable::decode(d)?))
     }
 }

 // FIXME: #15036
 // Should use `try_borrow`, returning a
 // `encoder.error("attempting to Encode borrowed RefCell")`
 // from `encode` when `try_borrow` returns `None`.

 impl<T: Encodable> Encodable for RefCell<T> {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         self.borrow().encode(s)
     }
 }

 impl<T: Decodable> Decodable for RefCell<T> {
     fn decode<D: Decoder>(d: &mut D) -> Result<RefCell<T>, D::Error> {
         Ok(RefCell::new(Decodable::decode(d)?))
     }
 }

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

 impl<T:Decodable+Send+Sync> Decodable for Arc<T> {
     fn decode<D: Decoder>(d: &mut D) -> Result<Arc<T>, D::Error> {
         Ok(Arc::new(Decodable::decode(d)?))
     }
 }

 // ___________________________________________________________________________
 // Helper routines

 pub trait EncoderHelpers: Encoder {
     fn emit_from_vec<T, F>(&mut self, v: &[T], f: F)
                            -> Result<(), Self::Error>
         where F: FnMut(&mut Self, &T) -> Result<(), Self::Error>;
 }

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

 pub trait DecoderHelpers: Decoder {
     fn read_to_vec<T, F>(&mut self, f: F)
                          -> Result<Vec<T>, Self::Error> where
         F: FnMut(&mut Self) -> Result<T, Self::Error>;
 }

 impl<D: Decoder> DecoderHelpers for D {
     fn read_to_vec<T, F>(&mut self, mut f: F) -> Result<Vec<T>, D::Error> where F:
         FnMut(&mut D) -> Result<T, D::Error>,
     {
         self.read_seq(|this, len| {
             let mut v = Vec::with_capacity(len);
             for i in 0..len {
                 v.push(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::cell::{Cell, RefCell};
	use std::sync::Arc;

	pub trait Encoder {
	type Error;

	// Primitive types:
	fn emit_nil(&mut self) -> Result<(), Self::Error>;
	fn emit_uint(&mut self, v: usize) -> Result<(), Self::Error>;
	fn emit_u64(&mut self, v: u64) -> Result<(), Self::Error>;
	fn emit_u32(&mut self, v: u32) -> Result<(), Self::Error>;
	fn emit_u16(&mut self, v: u16) -> Result<(), Self::Error>;
	fn emit_u8(&mut self, v: u8) -> Result<(), Self::Error>;
	fn emit_int(&mut self, v: isize) -> Result<(), Self::Error>;
	fn emit_i64(&mut self, v: i64) -> Result<(), Self::Error>;
	fn emit_i32(&mut self, v: i32) -> Result<(), Self::Error>;
	fn emit_i16(&mut self, v: i16) -> Result<(), Self::Error>;
	fn emit_i8(&mut self, v: i8) -> Result<(), Self::Error>;
	fn emit_bool(&mut self, v: bool) -> Result<(), Self::Error>;
	fn emit_f64(&mut self, v: f64) -> Result<(), Self::Error>;
	fn emit_f32(&mut self, v: f32) -> Result<(), Self::Error>;
	fn emit_char(&mut self, v: char) -> Result<(), Self::Error>;
	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_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>;
	fn emit_enum_variant_arg<F>(&mut self, a_idx: usize, f: F)
	-> Result<(), Self::Error>
	where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

	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>;
	fn emit_enum_struct_variant_field<F>(&mut self,
	f_name: &str,
	f_idx: usize,
	f: F) -> Result<(), Self::Error>
	where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

	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)
	-> 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>;
	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_struct<F>(&mut self, name: &str, len: usize, f: F)
	-> Result<(), Self::Error>
	where F: FnOnce(&mut Self) -> Result<(), Self::Error>;
	fn emit_tuple_struct_arg<F>(&mut self, f_idx: usize, f: F)
	-> Result<(), Self::Error>
	where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

	// 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>;
	fn emit_option_some<F>(&mut self, f: F) -> Result<(), Self::Error>
	where F: FnOnce(&mut Self) -> Result<(), Self::Error>;

	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>;

	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>;
	}

	pub trait Decoder {
	type Error;

	// Primitive types:
	fn read_nil(&mut self) -> Result<(), Self::Error>;
	fn read_uint(&mut self) -> Result<usize, Self::Error>;
	fn read_u64(&mut self) -> Result<u64, Self::Error>;
	fn read_u32(&mut self) -> Result<u32, Self::Error>;
	fn read_u16(&mut self) -> Result<u16, Self::Error>;
	fn read_u8(&mut self) -> Result<u8, Self::Error>;
	fn read_int(&mut self) -> Result<isize, Self::Error>;
	fn read_i64(&mut self) -> Result<i64, Self::Error>;
	fn read_i32(&mut self) -> Result<i32, Self::Error>;
	fn read_i16(&mut self) -> Result<i16, Self::Error>;
	fn read_i8(&mut self) -> Result<i8, Self::Error>;
	fn read_bool(&mut self) -> Result<bool, Self::Error>;
	fn read_f64(&mut self) -> Result<f64, Self::Error>;
	fn read_f32(&mut self) -> Result<f32, Self::Error>;
	fn read_char(&mut self) -> Result<char, Self::Error>;
	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_variant<T, F>(&mut self, names: &[&str], 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)
	-> Result<T, Self::Error>
	where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

	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>;
	fn read_enum_struct_variant_field<T, F>(&mut self,
	&f_name: &str,
	f_idx: usize,
	f: F)
	-> Result<T, Self::Error>
	where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

	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>;
	fn read_struct_field<T, F>(&mut self,
	f_name: &str,
	f_idx: usize,
	f: F)
	-> Result<T, Self::Error>
	where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

	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)
	-> Result<T, Self::Error>
	where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

	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>;
	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>;

	// 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_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>;

	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)
	-> 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)
	-> Result<T, Self::Error>
	where F: FnOnce(&mut Self) -> Result<T, Self::Error>;

	// Failure
	fn error(&mut self, err: &str) -> Self::Error;
	}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	impl< T: Decodable> Decodable for Box<[T]> {
	fn decode<D: Decoder>(d: &mut D) -> Result<Box<[T]>, D::Error> {
	let v: Vec<T> = Decodable::decode(d)?;
	Ok(v.into_boxed_slice())
	}
	}

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

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

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

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

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

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

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

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

	/// Evaluates to the number of identifiers passed to it, for example: `count_idents!(a, b, c) == 3
	macro_rules! count_idents {
	() => { 0 };
	($_i:ident, $($rest:ident,)) => { 1 + count_idents!($($rest,)) }
	}

	macro_rules! tuple {
	() => ();
	( $($name:ident,)+ ) => (
	impl<$($name:Decodable),> Decodable for ($($name,)) {
	#[allow(non_snake_case)]
	fn decode<D: Decoder>(d: &mut D) -> Result<($($name,)*), D::Error> {
	let len: usize = count_idents!($($name,)*);
	d.read_tuple(len, \|d\| {
	let mut i = 0;
	let ret = ($(try!(d.read_tuple_arg({ i+=1; i-1 },
	\|d\| -> Result<$name,D::Error> {
	Decodable::decode(d)
	})),)*);
	Ok(ret)
	})
	}
	}
	impl<$($name:Encodable),> Encodable for ($($name,)) {
	#[allow(non_snake_case)]
	fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
	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_tuple_arg({ 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 Encodable for path::PathBuf {
	fn encode<S: Encoder>(&self, e: &mut S) -> Result<(), S::Error> {
	self.to_str().unwrap().encode(e)
	}
	}

	impl Decodable for path::PathBuf {
	fn decode<D: Decoder>(d: &mut D) -> Result<path::PathBuf, D::Error> {
	let bytes: String = Decodable::decode(d)?;
	Ok(path::PathBuf::from(bytes))
	}
	}

	impl<T: Encodable + Copy> Encodable for Cell<T> {
	fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
	self.get().encode(s)
	}
	}

	impl<T: Decodable + Copy> Decodable for Cell<T> {
	fn decode<D: Decoder>(d: &mut D) -> Result<Cell<T>, D::Error> {
	Ok(Cell::new(Decodable::decode(d)?))
	}
	}

	// FIXME: #15036
	// Should use `try_borrow`, returning a
	// `encoder.error("attempting to Encode borrowed RefCell")`
	// from `encode` when `try_borrow` returns `None`.

	impl<T: Encodable> Encodable for RefCell<T> {
	fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
	self.borrow().encode(s)
	}
	}

	impl<T: Decodable> Decodable for RefCell<T> {
	fn decode<D: Decoder>(d: &mut D) -> Result<RefCell<T>, D::Error> {
	Ok(RefCell::new(Decodable::decode(d)?))
	}
	}

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

	impl<T:Decodable+Send+Sync> Decodable for Arc<T> {
	fn decode<D: Decoder>(d: &mut D) -> Result<Arc<T>, D::Error> {
	Ok(Arc::new(Decodable::decode(d)?))
	}
	}

	// ___________________________________________________________________________
	// Helper routines

	pub trait EncoderHelpers: Encoder {
	fn emit_from_vec<T, F>(&mut self, v: &[T], f: F)
	-> Result<(), Self::Error>
	where F: FnMut(&mut Self, &T) -> Result<(), Self::Error>;
	}

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

	pub trait DecoderHelpers: Decoder {
	fn read_to_vec<T, F>(&mut self, f: F)
	-> Result<Vec<T>, Self::Error> where
	F: FnMut(&mut Self) -> Result<T, Self::Error>;
	}

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