pull extra::{serialize, ebml} into a separate libserialize crate

- `extra::json` didn't make the cut, because of `extra::json` required
   dep on `extra::TreeMap`. If/when `extra::TreeMap` moves out of `extra`,
   then `extra::json` could move into `serialize`
- `libextra`, `libsyntax` and `librustc` depend on the newly created
  `libserialize`
- The extensions to various `extra` types like `DList`, `RingBuf`, `TreeMap`
  and `TreeSet` for `Encodable`/`Decodable` were moved into the respective
  modules in `extra`
- There is some trickery, evident in `src/libextra/lib.rs` where a stub
  of `extra::serialize` is set up (in `src/libextra/serialize.rs`) for
  use in the stage0 build, where the snapshot rustc is still making
  deriving for `Encodable` and `Decodable` point at extra. Big props to
  @huonw for help working out the re-export solution for this

extra: inline extra::serialize stub

fix stuff clobbered in rebase + don't reexport serialize::serialize

no more globs in libserialize

syntax: fix import of libserialize traits

librustc: fix bad imports in encoder/decoder

add serialize dep to librustdoc

fix failing run-pass tests w/ serialize dep

adjust uuid dep

more rebase de-clobbering for libserialize

fixing tests, pushing libextra dep into cfg(test)

fix doc code in extra::json

adjust index.md links to serialize and uuid library

1 files changed, 760 insertions, 0 deletions

diff --git a/src/libserialize/serialize.rs b/src/libserialize/serialize.rs
new file mode 100644
index 00000000000..c4f0a7a1830
--- /dev/null
+++ b/src/libserialize/serialize.rs
@@ -0,0 +1,760 @@
+// 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::hashmap::{HashMap, HashSet};
+use std::rc::Rc;
+use std::trie::{TrieMap, TrieSet};
+use std::vec;
+
+pub trait Encoder {
+    // Primitive types:
+    fn emit_nil(&mut self);
+    fn emit_uint(&mut self, v: uint);
+    fn emit_u64(&mut self, v: u64);
+    fn emit_u32(&mut self, v: u32);
+    fn emit_u16(&mut self, v: u16);
+    fn emit_u8(&mut self, v: u8);
+    fn emit_int(&mut self, v: int);
+    fn emit_i64(&mut self, v: i64);
+    fn emit_i32(&mut self, v: i32);
+    fn emit_i16(&mut self, v: i16);
+    fn emit_i8(&mut self, v: i8);
+    fn emit_bool(&mut self, v: bool);
+    fn emit_f64(&mut self, v: f64);
+    fn emit_f32(&mut self, v: f32);
+    fn emit_char(&mut self, v: char);
+    fn emit_str(&mut self, v: &str);
+
+    // Compound types:
+    fn emit_enum(&mut self, name: &str, f: |&mut Self|);
+
+    fn emit_enum_variant(&mut self,
+                         v_name: &str,
+                         v_id: uint,
+                         len: uint,
+                         f: |&mut Self|);
+    fn emit_enum_variant_arg(&mut self, a_idx: uint, f: |&mut Self|);
+
+    fn emit_enum_struct_variant(&mut self,
+                                v_name: &str,
+                                v_id: uint,
+                                len: uint,
+                                f: |&mut Self|);
+    fn emit_enum_struct_variant_field(&mut self,
+                                      f_name: &str,
+                                      f_idx: uint,
+                                      f: |&mut Self|);
+
+    fn emit_struct(&mut self, name: &str, len: uint, f: |&mut Self|);
+    fn emit_struct_field(&mut self,
+                         f_name: &str,
+                         f_idx: uint,
+                         f: |&mut Self|);
+
+    fn emit_tuple(&mut self, len: uint, f: |&mut Self|);
+    fn emit_tuple_arg(&mut self, idx: uint, f: |&mut Self|);
+
+    fn emit_tuple_struct(&mut self, name: &str, len: uint, f: |&mut Self|);
+    fn emit_tuple_struct_arg(&mut self, f_idx: uint, f: |&mut Self|);
+
+    // Specialized types:
+    fn emit_option(&mut self, f: |&mut Self|);
+    fn emit_option_none(&mut self);
+    fn emit_option_some(&mut self, f: |&mut Self|);
+
+    fn emit_seq(&mut self, len: uint, f: |this: &mut Self|);
+    fn emit_seq_elt(&mut self, idx: uint, f: |this: &mut Self|);
+
+    fn emit_map(&mut self, len: uint, f: |&mut Self|);
+    fn emit_map_elt_key(&mut self, idx: uint, f: |&mut Self|);
+    fn emit_map_elt_val(&mut self, idx: uint, f: |&mut Self|);
+}
+
+pub trait Decoder {
+    // Primitive types:
+    fn read_nil(&mut self) -> ();
+    fn read_uint(&mut self) -> uint;
+    fn read_u64(&mut self) -> u64;
+    fn read_u32(&mut self) -> u32;
+    fn read_u16(&mut self) -> u16;
+    fn read_u8(&mut self) -> u8;
+    fn read_int(&mut self) -> int;
+    fn read_i64(&mut self) -> i64;
+    fn read_i32(&mut self) -> i32;
+    fn read_i16(&mut self) -> i16;
+    fn read_i8(&mut self) -> i8;
+    fn read_bool(&mut self) -> bool;
+    fn read_f64(&mut self) -> f64;
+    fn read_f32(&mut self) -> f32;
+    fn read_char(&mut self) -> char;
+    fn read_str(&mut self) -> ~str;
+
+    // Compound types:
+    fn read_enum<T>(&mut self, name: &str, f: |&mut Self| -> T) -> T;
+
+    fn read_enum_variant<T>(&mut self,
+                            names: &[&str],
+                            f: |&mut Self, uint| -> T)
+                            -> T;
+    fn read_enum_variant_arg<T>(&mut self,
+                                a_idx: uint,
+                                f: |&mut Self| -> T)
+                                -> T;
+
+    fn read_enum_struct_variant<T>(&mut self,
+                                   names: &[&str],
+                                   f: |&mut Self, uint| -> T)
+                                   -> T;
+    fn read_enum_struct_variant_field<T>(&mut self,
+                                         &f_name: &str,
+                                         f_idx: uint,
+                                         f: |&mut Self| -> T)
+                                         -> T;
+
+    fn read_struct<T>(&mut self, s_name: &str, len: uint, f: |&mut Self| -> T)
+                      -> T;
+    fn read_struct_field<T>(&mut self,
+                            f_name: &str,
+                            f_idx: uint,
+                            f: |&mut Self| -> T)
+                            -> T;
+
+    fn read_tuple<T>(&mut self, f: |&mut Self, uint| -> T) -> T;
+    fn read_tuple_arg<T>(&mut self, a_idx: uint, f: |&mut Self| -> T) -> T;
+
+    fn read_tuple_struct<T>(&mut self,
+                            s_name: &str,
+                            f: |&mut Self, uint| -> T)
+                            -> T;
+    fn read_tuple_struct_arg<T>(&mut self,
+                                a_idx: uint,
+                                f: |&mut Self| -> T)
+                                -> T;
+
+    // Specialized types:
+    fn read_option<T>(&mut self, f: |&mut Self, bool| -> T) -> T;
+
+    fn read_seq<T>(&mut self, f: |&mut Self, uint| -> T) -> T;
+    fn read_seq_elt<T>(&mut self, idx: uint, f: |&mut Self| -> T) -> T;
+
+    fn read_map<T>(&mut self, f: |&mut Self, uint| -> T) -> T;
+    fn read_map_elt_key<T>(&mut self, idx: uint, f: |&mut Self| -> T) -> T;
+    fn read_map_elt_val<T>(&mut self, idx: uint, f: |&mut Self| -> T) -> T;
+}
+
+pub trait Encodable<S:Encoder> {
+    fn encode(&self, s: &mut S);
+}
+
+pub trait Decodable<D:Decoder> {
+    fn decode(d: &mut D) -> Self;
+}
+
+impl<S:Encoder> Encodable<S> for uint {
+    fn encode(&self, s: &mut S) {
+        s.emit_uint(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for uint {
+    fn decode(d: &mut D) -> uint {
+        d.read_uint()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for u8 {
+    fn encode(&self, s: &mut S) {
+        s.emit_u8(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for u8 {
+    fn decode(d: &mut D) -> u8 {
+        d.read_u8()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for u16 {
+    fn encode(&self, s: &mut S) {
+        s.emit_u16(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for u16 {
+    fn decode(d: &mut D) -> u16 {
+        d.read_u16()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for u32 {
+    fn encode(&self, s: &mut S) {
+        s.emit_u32(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for u32 {
+    fn decode(d: &mut D) -> u32 {
+        d.read_u32()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for u64 {
+    fn encode(&self, s: &mut S) {
+        s.emit_u64(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for u64 {
+    fn decode(d: &mut D) -> u64 {
+        d.read_u64()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for int {
+    fn encode(&self, s: &mut S) {
+        s.emit_int(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for int {
+    fn decode(d: &mut D) -> int {
+        d.read_int()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for i8 {
+    fn encode(&self, s: &mut S) {
+        s.emit_i8(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for i8 {
+    fn decode(d: &mut D) -> i8 {
+        d.read_i8()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for i16 {
+    fn encode(&self, s: &mut S) {
+        s.emit_i16(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for i16 {
+    fn decode(d: &mut D) -> i16 {
+        d.read_i16()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for i32 {
+    fn encode(&self, s: &mut S) {
+        s.emit_i32(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for i32 {
+    fn decode(d: &mut D) -> i32 {
+        d.read_i32()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for i64 {
+    fn encode(&self, s: &mut S) {
+        s.emit_i64(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for i64 {
+    fn decode(d: &mut D) -> i64 {
+        d.read_i64()
+    }
+}
+
+impl<'a, S:Encoder> Encodable<S> for &'a str {
+    fn encode(&self, s: &mut S) {
+        s.emit_str(*self)
+    }
+}
+
+impl<S:Encoder> Encodable<S> for ~str {
+    fn encode(&self, s: &mut S) {
+        s.emit_str(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for ~str {
+    fn decode(d: &mut D) -> ~str {
+        d.read_str()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for f32 {
+    fn encode(&self, s: &mut S) {
+        s.emit_f32(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for f32 {
+    fn decode(d: &mut D) -> f32 {
+        d.read_f32()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for f64 {
+    fn encode(&self, s: &mut S) {
+        s.emit_f64(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for f64 {
+    fn decode(d: &mut D) -> f64 {
+        d.read_f64()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for bool {
+    fn encode(&self, s: &mut S) {
+        s.emit_bool(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for bool {
+    fn decode(d: &mut D) -> bool {
+        d.read_bool()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for char {
+    fn encode(&self, s: &mut S) {
+        s.emit_char(*self)
+    }
+}
+
+impl<D:Decoder> Decodable<D> for char {
+    fn decode(d: &mut D) -> char {
+        d.read_char()
+    }
+}
+
+impl<S:Encoder> Encodable<S> for () {
+    fn encode(&self, s: &mut S) {
+        s.emit_nil()
+    }
+}
+
+impl<D:Decoder> Decodable<D> for () {
+    fn decode(d: &mut D) -> () {
+        d.read_nil()
+    }
+}
+
+impl<'a, S:Encoder,T:Encodable<S>> Encodable<S> for &'a T {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s)
+    }
+}
+
+impl<S:Encoder,T:Encodable<S>> Encodable<S> for ~T {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s)
+    }
+}
+
+impl<D:Decoder,T:Decodable<D>> Decodable<D> for ~T {
+    fn decode(d: &mut D) -> ~T {
+        ~Decodable::decode(d)
+    }
+}
+
+impl<S:Encoder,T:Encodable<S>> Encodable<S> for @T {
+    fn encode(&self, s: &mut S) {
+        (**self).encode(s)
+    }
+}
+
+impl<S:Encoder,T:Encodable<S>> Encodable<S> for Rc<T> {
+    #[inline]
+    fn encode(&self, s: &mut S) {
+        self.borrow().encode(s)
+    }
+}
+
+impl<D:Decoder,T:Decodable<D>> Decodable<D> for Rc<T> {
+    #[inline]
+    fn decode(d: &mut D) -> Rc<T> {
+        Rc::new(Decodable::decode(d))
+    }
+}
+
+impl<D:Decoder,T:Decodable<D> + 'static> Decodable<D> for @T {
+    fn decode(d: &mut D) -> @T {
+        @Decodable::decode(d)
+    }
+}
+
+impl<'a, S:Encoder,T:Encodable<S>> Encodable<S> for &'a [T] {
+    fn encode(&self, s: &mut S) {
+        s.emit_seq(self.len(), |s| {
+            for (i, e) in self.iter().enumerate() {
+                s.emit_seq_elt(i, |s| e.encode(s))
+            }
+        })
+    }
+}
+
+impl<S:Encoder,T:Encodable<S>> Encodable<S> for ~[T] {
+    fn encode(&self, s: &mut S) {
+        s.emit_seq(self.len(), |s| {
+            for (i, e) in self.iter().enumerate() {
+                s.emit_seq_elt(i, |s| e.encode(s))
+            }
+        })
+    }
+}
+
+impl<D:Decoder,T:Decodable<D>> Decodable<D> for ~[T] {
+    fn decode(d: &mut D) -> ~[T] {
+        d.read_seq(|d, len| {
+            vec::from_fn(len, |i| {
+                d.read_seq_elt(i, |d| Decodable::decode(d))
+            })
+        })
+    }
+}
+
+impl<S:Encoder,T:Encodable<S>> Encodable<S> for Option<T> {
+    fn encode(&self, s: &mut S) {
+        s.emit_option(|s| {
+            match *self {
+                None => s.emit_option_none(),
+                Some(ref v) => s.emit_option_some(|s| v.encode(s)),
+            }
+        })
+    }
+}
+
+impl<D:Decoder,T:Decodable<D>> Decodable<D> for Option<T> {
+    fn decode(d: &mut D) -> Option<T> {
+        d.read_option(|d, b| {
+            if b {
+                Some(Decodable::decode(d))
+            } else {
+                None
+            }
+        })
+    }
+}
+
+impl<S:Encoder,T0:Encodable<S>,T1:Encodable<S>> Encodable<S> for (T0, T1) {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            (ref t0, ref t1) => {
+                s.emit_seq(2, |s| {
+                    s.emit_seq_elt(0, |s| t0.encode(s));
+                    s.emit_seq_elt(1, |s| t1.encode(s));
+                })
+            }
+        }
+    }
+}
+
+impl<D:Decoder,T0:Decodable<D>,T1:Decodable<D>> Decodable<D> for (T0, T1) {
+    fn decode(d: &mut D) -> (T0, T1) {
+        d.read_seq(|d, len| {
+            assert_eq!(len, 2);
+            (
+                d.read_seq_elt(0, |d| Decodable::decode(d)),
+                d.read_seq_elt(1, |d| Decodable::decode(d))
+            )
+        })
+    }
+}
+
+impl<
+    S: Encoder,
+    T0: Encodable<S>,
+    T1: Encodable<S>,
+    T2: Encodable<S>
+> Encodable<S> for (T0, T1, T2) {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            (ref t0, ref t1, ref t2) => {
+                s.emit_seq(3, |s| {
+                    s.emit_seq_elt(0, |s| t0.encode(s));
+                    s.emit_seq_elt(1, |s| t1.encode(s));
+                    s.emit_seq_elt(2, |s| t2.encode(s));
+                })
+            }
+        }
+    }
+}
+
+impl<
+    D: Decoder,
+    T0: Decodable<D>,
+    T1: Decodable<D>,
+    T2: Decodable<D>
+> Decodable<D> for (T0, T1, T2) {
+    fn decode(d: &mut D) -> (T0, T1, T2) {
+        d.read_seq(|d, len| {
+            assert_eq!(len, 3);
+            (
+                d.read_seq_elt(0, |d| Decodable::decode(d)),
+                d.read_seq_elt(1, |d| Decodable::decode(d)),
+                d.read_seq_elt(2, |d| Decodable::decode(d))
+            )
+        })
+    }
+}
+
+impl<
+    S: Encoder,
+    T0: Encodable<S>,
+    T1: Encodable<S>,
+    T2: Encodable<S>,
+    T3: Encodable<S>
+> Encodable<S> for (T0, T1, T2, T3) {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            (ref t0, ref t1, ref t2, ref t3) => {
+                s.emit_seq(4, |s| {
+                    s.emit_seq_elt(0, |s| t0.encode(s));
+                    s.emit_seq_elt(1, |s| t1.encode(s));
+                    s.emit_seq_elt(2, |s| t2.encode(s));
+                    s.emit_seq_elt(3, |s| t3.encode(s));
+                })
+            }
+        }
+    }
+}
+
+impl<
+    D: Decoder,
+    T0: Decodable<D>,
+    T1: Decodable<D>,
+    T2: Decodable<D>,
+    T3: Decodable<D>
+> Decodable<D> for (T0, T1, T2, T3) {
+    fn decode(d: &mut D) -> (T0, T1, T2, T3) {
+        d.read_seq(|d, len| {
+            assert_eq!(len, 4);
+            (
+                d.read_seq_elt(0, |d| Decodable::decode(d)),
+                d.read_seq_elt(1, |d| Decodable::decode(d)),
+                d.read_seq_elt(2, |d| Decodable::decode(d)),
+                d.read_seq_elt(3, |d| Decodable::decode(d))
+            )
+        })
+    }
+}
+
+impl<
+    S: Encoder,
+    T0: Encodable<S>,
+    T1: Encodable<S>,
+    T2: Encodable<S>,
+    T3: Encodable<S>,
+    T4: Encodable<S>
+> Encodable<S> for (T0, T1, T2, T3, T4) {
+    fn encode(&self, s: &mut S) {
+        match *self {
+            (ref t0, ref t1, ref t2, ref t3, ref t4) => {
+                s.emit_seq(5, |s| {
+                    s.emit_seq_elt(0, |s| t0.encode(s));
+                    s.emit_seq_elt(1, |s| t1.encode(s));
+                    s.emit_seq_elt(2, |s| t2.encode(s));
+                    s.emit_seq_elt(3, |s| t3.encode(s));
+                    s.emit_seq_elt(4, |s| t4.encode(s));
+                })
+            }
+        }
+    }
+}
+
+impl<
+    D: Decoder,
+    T0: Decodable<D>,
+    T1: Decodable<D>,
+    T2: Decodable<D>,
+    T3: Decodable<D>,
+    T4: Decodable<D>
+> Decodable<D> for (T0, T1, T2, T3, T4) {
+    fn decode(d: &mut D) -> (T0, T1, T2, T3, T4) {
+        d.read_seq(|d, len| {
+            assert_eq!(len, 5);
+            (
+                d.read_seq_elt(0, |d| Decodable::decode(d)),
+                d.read_seq_elt(1, |d| Decodable::decode(d)),
+                d.read_seq_elt(2, |d| Decodable::decode(d)),
+                d.read_seq_elt(3, |d| Decodable::decode(d)),
+                d.read_seq_elt(4, |d| Decodable::decode(d))
+            )
+        })
+    }
+}
+
+impl<
+    E: Encoder,
+    K: Encodable<E> + Hash + IterBytes + Eq,
+    V: Encodable<E>
+> Encodable<E> for HashMap<K, V> {
+    fn encode(&self, e: &mut E) {
+        e.emit_map(self.len(), |e| {
+            let mut i = 0;
+            for (key, val) in self.iter() {
+                e.emit_map_elt_key(i, |e| key.encode(e));
+                e.emit_map_elt_val(i, |e| val.encode(e));
+                i += 1;
+            }
+        })
+    }
+}
+
+impl<
+    D: Decoder,
+    K: Decodable<D> + Hash + IterBytes + Eq,
+    V: Decodable<D>
+> Decodable<D> for HashMap<K, V> {
+    fn decode(d: &mut D) -> HashMap<K, V> {
+        d.read_map(|d, len| {
+            let mut map = HashMap::with_capacity(len);
+            for i in range(0u, len) {
+                let key = d.read_map_elt_key(i, |d| Decodable::decode(d));
+                let val = d.read_map_elt_val(i, |d| Decodable::decode(d));
+                map.insert(key, val);
+            }
+            map
+        })
+    }
+}
+
+impl<
+    S: Encoder,
+    T: Encodable<S> + Hash + IterBytes + Eq
+> Encodable<S> for HashSet<T> {
+    fn encode(&self, s: &mut S) {
+        s.emit_seq(self.len(), |s| {
+            let mut i = 0;
+            for e in self.iter() {
+                s.emit_seq_elt(i, |s| e.encode(s));
+                i += 1;
+            }
+        })
+    }
+}
+
+impl<
+    D: Decoder,
+    T: Decodable<D> + Hash + IterBytes + Eq
+> Decodable<D> for HashSet<T> {
+    fn decode(d: &mut D) -> HashSet<T> {
+        d.read_seq(|d, len| {
+            let mut set = HashSet::with_capacity(len);
+            for i in range(0u, len) {
+                set.insert(d.read_seq_elt(i, |d| Decodable::decode(d)));
+            }
+            set
+        })
+    }
+}
+
+impl<
+    E: Encoder,
+    V: Encodable<E>
+> Encodable<E> for TrieMap<V> {
+    fn encode(&self, e: &mut E) {
+        e.emit_map(self.len(), |e| {
+                for (i, (key, val)) in self.iter().enumerate() {
+                    e.emit_map_elt_key(i, |e| key.encode(e));
+                    e.emit_map_elt_val(i, |e| val.encode(e));
+                }
+            });
+    }
+}
+
+impl<
+    D: Decoder,
+    V: Decodable<D>
+> Decodable<D> for TrieMap<V> {
+    fn decode(d: &mut D) -> TrieMap<V> {
+        d.read_map(|d, len| {
+            let mut map = TrieMap::new();
+            for i in range(0u, len) {
+                let key = d.read_map_elt_key(i, |d| Decodable::decode(d));
+                let val = d.read_map_elt_val(i, |d| Decodable::decode(d));
+                map.insert(key, val);
+            }
+            map
+        })
+    }
+}
+
+impl<S: Encoder> Encodable<S> for TrieSet {
+    fn encode(&self, s: &mut S) {
+        s.emit_seq(self.len(), |s| {
+                for (i, e) in self.iter().enumerate() {
+                    s.emit_seq_elt(i, |s| e.encode(s));
+                }
+            })
+    }
+}
+
+impl<D: Decoder> Decodable<D> for TrieSet {
+    fn decode(d: &mut D) -> TrieSet {
+        d.read_seq(|d, len| {
+            let mut set = TrieSet::new();
+            for i in range(0u, len) {
+                set.insert(d.read_seq_elt(i, |d| Decodable::decode(d)));
+            }
+            set
+        })
+    }
+}
+
+// ___________________________________________________________________________
+// Helper routines
+//
+// In some cases, these should eventually be coded as traits.
+
+pub trait EncoderHelpers {
+    fn emit_from_vec<T>(&mut self, v: &[T], f: |&mut Self, v: &T|);
+}
+
+impl<S:Encoder> EncoderHelpers for S {
+    fn emit_from_vec<T>(&mut self, v: &[T], f: |&mut S, &T|) {
+        self.emit_seq(v.len(), |this| {
+            for (i, e) in v.iter().enumerate() {
+                this.emit_seq_elt(i, |this| {
+                    f(this, e)
+                })
+            }
+        })
+    }
+}
+
+pub trait DecoderHelpers {
+    fn read_to_vec<T>(&mut self, f: |&mut Self| -> T) -> ~[T];
+}
+
+impl<D:Decoder> DecoderHelpers for D {
+    fn read_to_vec<T>(&mut self, f: |&mut D| -> T) -> ~[T] {
+        self.read_seq(|this, len| {
+            vec::from_fn(len, |i| {
+                this.read_seq_elt(i, |this| f(this))
+            })
+        })
+    }
+}