diff --git a/serde2/src/json/builder.rs b/serde2/src/json/builder.rs
new file mode 100644
index 00000000..c66b63bc
--- /dev/null
+++ b/serde2/src/json/builder.rs
@@ -0,0 +1,131 @@
+// 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.
+
+use std::collections::TreeMap;
+use std::str::StrAllocating;
+
+use ser::{mod, Serialize};
+use json::value::{mod, Value};
+
+pub struct ArrayBuilder {
+    array: Vec<Value>,
+}
+
+impl ArrayBuilder {
+    pub fn new() -> ArrayBuilder {
+        ArrayBuilder { array: Vec::new() }
+    }
+
+    pub fn unwrap(self) -> Value {
+        Value::Array(self.array)
+    }
+
+    pub fn push<T: ser::Serialize>(mut self, v: T) -> ArrayBuilder {
+        self.array.push(value::to_value(&v));
+        self
+    }
+
+    pub fn push_array(mut self, f: |ArrayBuilder| -> ArrayBuilder) -> ArrayBuilder {
+        let builder = ArrayBuilder::new();
+        self.array.push(f(builder).unwrap());
+        self
+    }
+
+    pub fn push_object(mut self, f: |ObjectBuilder| -> ObjectBuilder) -> ArrayBuilder {
+        let builder = ObjectBuilder::new();
+        self.array.push(f(builder).unwrap());
+        self
+    }
+}
+
+pub struct ObjectBuilder {
+    object: TreeMap<String, Value>,
+}
+
+impl ObjectBuilder {
+    pub fn new() -> ObjectBuilder {
+        ObjectBuilder { object: TreeMap::new() }
+    }
+
+    pub fn unwrap(self) -> Value {
+        Value::Object(self.object)
+    }
+
+    pub fn insert<K: StrAllocating, V: ser::Serialize>(mut self, k: K, v: V) -> ObjectBuilder {
+        self.object.insert(k.into_string(), value::to_value(&v));
+        self
+    }
+
+    pub fn insert_array<S: StrAllocating>(mut self, key: S, f: |ArrayBuilder| -> ArrayBuilder) -> ObjectBuilder {
+        let builder = ArrayBuilder::new();
+        self.object.insert(key.into_string(), f(builder).unwrap());
+        self
+    }
+
+    pub fn insert_object<S: StrAllocating>(mut self, key: S, f: |ObjectBuilder| -> ObjectBuilder) -> ObjectBuilder {
+        let builder = ObjectBuilder::new();
+        self.object.insert(key.into_string(), f(builder).unwrap());
+        self
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::TreeMap;
+
+    use json::value::Value;
+    use super::{ArrayBuilder, ObjectBuilder};
+
+    #[test]
+    fn test_array_builder() {
+        let value = ArrayBuilder::new().unwrap();
+        assert_eq!(value, Value::Array(Vec::new()));
+
+        let value = ArrayBuilder::new()
+            .push(1i)
+            .push(2i)
+            .push(3i)
+            .unwrap();
+        assert_eq!(value, Value::Array(vec!(Value::I64(1), Value::I64(2), Value::I64(3))));
+
+        let value = ArrayBuilder::new()
+            .push_array(|bld| bld.push(1i).push(2i).push(3i))
+            .unwrap();
+        assert_eq!(value, Value::Array(vec!(Value::Array(vec!(Value::I64(1), Value::I64(2), Value::I64(3))))));
+
+        let value = ArrayBuilder::new()
+            .push_object(|bld|
+                bld
+                    .insert("a".to_string(), 1i)
+                    .insert("b".to_string(), 2i))
+            .unwrap();
+
+        let mut map = TreeMap::new();
+        map.insert("a".to_string(), Value::I64(1));
+        map.insert("b".to_string(), Value::I64(2));
+        assert_eq!(value, Value::Array(vec!(Value::Object(map))));
+    }
+
+    #[test]
+    fn test_object_builder() {
+        let value = ObjectBuilder::new().unwrap();
+        assert_eq!(value, Value::Object(TreeMap::new()));
+
+        let value = ObjectBuilder::new()
+            .insert("a".to_string(), 1i)
+            .insert("b".to_string(), 2i)
+            .unwrap();
+
+        let mut map = TreeMap::new();
+        map.insert("a".to_string(), Value::I64(1));
+        map.insert("b".to_string(), Value::I64(2));
+        assert_eq!(value, Value::Object(map));
+    }
+}
diff --git a/serde2/src/json/error.rs b/serde2/src/json/error.rs
new file mode 100644
index 00000000..911f94d2
--- /dev/null
+++ b/serde2/src/json/error.rs
@@ -0,0 +1,126 @@
+use std::error;
+use std::fmt;
+use std::io;
+
+/// The errors that can arise while parsing a JSON stream.
+#[deriving(Clone, PartialEq)]
+pub enum ErrorCode {
+    EOFWhileParsingList,
+    EOFWhileParsingObject,
+    EOFWhileParsingString,
+    EOFWhileParsingValue,
+    ExpectedColon,
+    ExpectedConversion,
+    ExpectedEnumEnd,
+    ExpectedEnumEndToken,
+    ExpectedEnumMapStart,
+    ExpectedEnumToken,
+    ExpectedEnumVariantString,
+    ExpectedListCommaOrEnd,
+    ExpectedName,
+    ExpectedObjectCommaOrEnd,
+    ExpectedSomeIdent,
+    ExpectedSomeValue,
+    InvalidEscape,
+    InvalidNumber,
+    InvalidUnicodeCodePoint,
+    KeyMustBeAString,
+    LoneLeadingSurrogateInHexEscape,
+    MissingField(&'static str),
+    NotFourDigit,
+    NotUtf8,
+    TrailingCharacters,
+    UnexpectedEndOfHexEscape,
+    UnknownVariant,
+    UnrecognizedHex,
+}
+
+impl fmt::Show for ErrorCode {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            //ErrorCode::ConversionError(ref token) => write!(f, "failed to convert {}", token),
+            ErrorCode::EOFWhileParsingList => "EOF While parsing list".fmt(f),
+            ErrorCode::EOFWhileParsingObject => "EOF While parsing object".fmt(f),
+            ErrorCode::EOFWhileParsingString => "EOF While parsing string".fmt(f),
+            ErrorCode::EOFWhileParsingValue => "EOF While parsing value".fmt(f),
+            ErrorCode::ExpectedColon => "expected `:`".fmt(f),
+            ErrorCode::ExpectedConversion => "expected conversion".fmt(f),
+            ErrorCode::ExpectedEnumEnd => "expected enum end".fmt(f),
+            ErrorCode::ExpectedEnumEndToken => "expected enum map end".fmt(f),
+            ErrorCode::ExpectedEnumMapStart => "expected enum map start".fmt(f),
+            ErrorCode::ExpectedEnumToken => "expected enum token".fmt(f),
+            ErrorCode::ExpectedEnumVariantString => "expected variant".fmt(f),
+            ErrorCode::ExpectedListCommaOrEnd => "expected `,` or `]`".fmt(f),
+            ErrorCode::ExpectedName => "expected name".fmt(f),
+            ErrorCode::ExpectedObjectCommaOrEnd => "expected `,` or `}`".fmt(f),
+            ErrorCode::ExpectedSomeIdent => "expected ident".fmt(f),
+            ErrorCode::ExpectedSomeValue => "expected value".fmt(f),
+            //ErrorCode::ExpectedTokens(ref token, tokens) => write!(f, "expected {}, found {}", tokens, token),
+            ErrorCode::InvalidEscape => "invalid escape".fmt(f),
+            ErrorCode::InvalidNumber => "invalid number".fmt(f),
+            ErrorCode::InvalidUnicodeCodePoint => "invalid unicode code point".fmt(f),
+            ErrorCode::KeyMustBeAString => "key must be a string".fmt(f),
+            ErrorCode::LoneLeadingSurrogateInHexEscape => "lone leading surrogate in hex escape".fmt(f),
+            ErrorCode::MissingField(ref field) => write!(f, "missing field \"{}\"", field),
+            ErrorCode::NotFourDigit => "invalid \\u escape (not four digits)".fmt(f),
+            ErrorCode::NotUtf8 => "contents not utf-8".fmt(f),
+            ErrorCode::TrailingCharacters => "trailing characters".fmt(f),
+            ErrorCode::UnexpectedEndOfHexEscape => "unexpected end of hex escape".fmt(f),
+            //ErrorCode::UnexpectedName(ref name) => write!(f, "unexpected name {}", name),
+            ErrorCode::UnknownVariant => "unknown variant".fmt(f),
+            ErrorCode::UnrecognizedHex => "invalid \\u escape (unrecognized hex)".fmt(f),
+        }
+    }
+}
+
+#[deriving(Clone, PartialEq, Show)]
+pub enum Error {
+    /// msg, line, col
+    SyntaxError(ErrorCode, uint, uint),
+    IoError(io::IoError),
+    /*
+    ExpectedError(String, String),
+    MissingFieldError(String),
+    UnknownVariantError(String),
+    */
+}
+
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        match *self {
+            Error::SyntaxError(..) => "syntax error",
+            Error::IoError(ref error) => error.description(),
+            /*
+            Error::ExpectedError(ref expected, _) => expected.as_slice(),
+            Error::MissingFieldError(_) => "missing field",
+            Error::UnknownVariantError(_) => "unknown variant",
+            */
+        }
+    }
+
+    fn detail(&self) -> Option<String> {
+        match *self {
+            Error::SyntaxError(ref code, line, col) => {
+                Some(format!("{} at line {} column {}", code, line, col))
+            }
+            Error::IoError(ref error) => error.detail(),
+            /*
+            Error::ExpectedError(ref expected, ref found) => {
+                Some(format!("expected {}, found {}", expected, found))
+            }
+            Error::MissingFieldError(ref field) => {
+                Some(format!("missing field {}", field))
+            }
+            Error::UnknownVariantError(ref variant) => {
+                Some(format!("unknown variant {}", variant))
+            }
+            */
+        }
+    }
+}
+
+impl error::FromError<io::IoError> for Error {
+    fn from_error(error: io::IoError) -> Error {
+        Error::IoError(error)
+    }
+}
diff --git a/serde2/src/json/mod.rs b/serde2/src/json/mod.rs
index bfbad813..55b6bab3 100644
--- a/serde2/src/json/mod.rs
+++ b/serde2/src/json/mod.rs
@@ -4,6 +4,8 @@ pub use self::ser::escape_str;
 
 pub use self::de::from_str;
 
-pub mod ser;
+pub mod builder;
 pub mod de;
 pub mod error;
+pub mod ser;
+pub mod value;
diff --git a/serde2/src/json/ser.rs b/serde2/src/json/ser.rs
index c122fd0d..e7817eb6 100644
--- a/serde2/src/json/ser.rs
+++ b/serde2/src/json/ser.rs
@@ -1,6 +1,5 @@
 use std::f64;
-use std::io::IoError;
-use std::io;
+use std::io::{mod, ByRefWriter, IoError};
 use std::num::{Float, FPNaN, FPInfinite};
 
 use ser;
@@ -230,14 +229,23 @@ fn fmt_f64_or_null<W: io::Writer>(wr: &mut W, value: f64) -> Result<(), IoError>
     }
 }
 
+#[inline]
+pub fn to_writer<
+    W: io::Writer,
+    T: ser::Serialize,
+>(wr: &mut W, value: &T) -> Result<(), IoError> {
+    let mut wr = Writer::new(wr.by_ref());
+    try!(wr.visit(value));
+    Ok(())
+}
+
 #[inline]
 pub fn to_vec<
     T: ser::Serialize,
 >(value: &T) -> Result<Vec<u8>, IoError> {
-    let writer = Vec::with_capacity(128);
-    let mut writer = Writer::new(writer);
-    try!(writer.visit(value));
-    Ok(writer.into_inner())
+    let mut wr = Vec::with_capacity(128);
+    to_writer(&mut wr, value).unwrap();
+    Ok(wr)
 }
 
 #[inline]
diff --git a/serde2/src/json/value.rs b/serde2/src/json/value.rs
index 83c214f5..821dcca8 100644
--- a/serde2/src/json/value.rs
+++ b/serde2/src/json/value.rs
@@ -1,122 +1,250 @@
+use std::collections::TreeMap;
+use std::fmt;
+use std::io;
+
+use ser::{mod, Serializer};
+
 #[deriving(PartialEq)]
-pub enum Json {
-    Integer(int),
+pub enum Value {
+    Null,
+    Bool(bool),
+    I64(i64),
+    F64(f64),
     String(String),
-    Array(Vec<Json>),
-    Object(TreeMap<String, Json>),
+    Array(Vec<Value>),
+    Object(TreeMap<String, Value>),
 }
 
-pub struct JsonSerializer {
-    key: Option<String>
-}
-
-impl JsonSerializer {
-    pub fn new() -> JsonSerializer {
-        JsonSerializer {
-            key: None
+impl ser::Serialize for Value {
+    #[inline]
+    fn visit<
+        S,
+        R,
+        E,
+        V: ser::Visitor<S, R, E>,
+    >(&self, s: &mut S, visitor: V) -> Result<R, E> {
+        match *self {
+            Value::Null => {
+                visitor.visit_null(s)
+            }
+            Value::Bool(v) => {
+                visitor.visit_bool(s, v)
+            }
+            Value::I64(v) => {
+                visitor.visit_i64(s, v)
+            }
+            Value::F64(v) => {
+                visitor.visit_f64(s, v)
+            }
+            Value::String(ref v) => {
+                visitor.visit_str(s, v.as_slice())
+            }
+            Value::Array(ref v) => {
+                v.visit(s, visitor)
+            }
+            Value::Object(ref v) => {
+                v.visit(s, visitor)
+            }
         }
     }
 }
 
-impl VisitorState<Json> for JsonSerializer {
-    fn visit_int(&mut self, value: int) -> Json {
-        Integer(value)
+struct WriterFormatter<'a, 'b: 'a>(&'a mut fmt::Formatter<'b>);
+
+impl<'a, 'b> io::Writer for WriterFormatter<'a, 'b> {
+    fn write(&mut self, buf: &[u8]) -> io::IoResult<()> {
+        let WriterFormatter(ref mut f) = *self;
+        f.write(buf).map_err(|_| io::IoError::last_error())
+    }
+}
+
+impl fmt::Show for Value {
+    /// Serializes a json value into a string
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut wr = WriterFormatter(f);
+        super::ser::to_writer(&mut wr, self).map_err(|_| fmt::Error)
+    }
+}
+
+pub fn to_value<
+    T: ser::Serialize,
+>(value: &T) -> Value {
+    let mut writer = Writer::new();
+    writer.visit(value).unwrap();
+    writer.unwrap()
+}
+
+enum State {
+    Value(Value),
+    Array(Vec<Value>),
+    Object(TreeMap<String, Value>),
+}
+
+pub struct Writer {
+    state: Vec<State>,
+}
+
+impl Writer {
+    pub fn new() -> Writer {
+        Writer {
+            state: Vec::with_capacity(4),
+        }
     }
 
-    fn visit_str(&mut self, value: &'static str) -> Json {
-        String(value.to_string())
+    pub fn unwrap(mut self) -> Value {
+        match self.state.pop().unwrap() {
+            State::Value(value) => value,
+            _ => panic!(),
+        }
+    }
+}
+
+impl ser::Serializer<Writer, (), ()> for Writer {
+    #[inline]
+    fn visit<
+        T: ser::Serialize,
+    >(&mut self, value: &T) -> Result<(), ()> {
+        value.visit(self, Visitor)
+    }
+}
+
+struct Visitor;
+
+impl ser::Visitor<Writer, (), ()> for Visitor {
+    #[inline]
+    fn visit_null(&self, state: &mut Writer) -> Result<(), ()> {
+        state.state.push(State::Value(Value::Null));
+        Ok(())
     }
 
+    #[inline]
+    fn visit_bool(&self, state: &mut Writer, value: bool) -> Result<(), ()> {
+        state.state.push(State::Value(Value::Bool(value)));
+        Ok(())
+    }
+
+    #[inline]
+    fn visit_i64(&self, state: &mut Writer, value: i64) -> Result<(), ()> {
+        state.state.push(State::Value(Value::I64(value)));
+        Ok(())
+    }
+
+    #[inline]
+    fn visit_u64(&self, state: &mut Writer, value: u64) -> Result<(), ()> {
+        state.state.push(State::Value(Value::I64(value as i64)));
+        Ok(())
+    }
+
+    #[inline]
+    fn visit_f64(&self, state: &mut Writer, value: f64) -> Result<(), ()> {
+        state.state.push(State::Value(Value::F64(value as f64)));
+        Ok(())
+    }
+
+    #[inline]
+    fn visit_char(&self, state: &mut Writer, value: char) -> Result<(), ()> {
+        state.state.push(State::Value(Value::String(value.to_string())));
+        Ok(())
+    }
+
+    #[inline]
+    fn visit_str(&self, state: &mut Writer, value: &str) -> Result<(), ()> {
+        state.state.push(State::Value(Value::String(value.to_string())));
+        Ok(())
+    }
+
+    #[inline]
     fn visit_seq<
-        T: Serialize<JsonSerializer, Json>,
-        Iter: Iterator<T>
-    >(&mut self, mut iter: Iter) -> Json {
-        let (len, _) = iter.size_hint();
-        let mut v = Vec::with_capacity(len);
+        V: ser::SeqVisitor<Writer, (), ()>
+    >(&self, state: &mut Writer, mut visitor: V) -> Result<(), ()> {
+        let len = match visitor.size_hint() {
+            (_, Some(len)) => len,
+            (len, None) => len,
+        };
 
-        let mut first = true;
-        for elt in iter {
-            v.push(self.visit_seq_elt(first, elt));
-            first = false;
+        let values = Vec::with_capacity(len);
+
+        state.state.push(State::Array(values));
+
+        loop {
+            match try!(visitor.visit(state, Visitor)) {
+                Some(()) => { }
+                None => { break; }
+            }
         }
 
-        Array(v)
+        match state.state.pop().unwrap() {
+            State::Array(values) => { state.state.push(State::Value(Value::Array(values))); }
+            _ => panic!(),
+        }
+
+        Ok(())
     }
 
+    #[inline]
     fn visit_seq_elt<
-        T: Serialize<JsonSerializer, Json>
-    >(&mut self, _first: bool, value: T) -> Json {
-        value.serialize(self)
-    }
+        T: ser::Serialize,
+    >(&self, state: &mut Writer, _first: bool, value: T) -> Result<(), ()> {
+        try!(value.visit(state, Visitor));
+        let value = match state.state.pop().unwrap() {
+            State::Value(value) => value,
+            _ => panic!(),
+        };
 
-    fn visit_tuple<
-        V: Visitor<JsonSerializer, Json>
-    >(&mut self, mut visitor: V) -> Json {
-        let (len, _) = visitor.size_hint();
-        let mut v = Vec::with_capacity(len);
-
-        loop {
-            match visitor.visit(self) {
-                Some(value) => { v.push(value); }
-                None => { break; }
-            }
+        match *state.state.last_mut().unwrap() {
+            State::Array(ref mut values) => { values.push(value); }
+            _ => panic!(),
         }
 
-        Array(v)
-    }
-
-    fn visit_tuple_struct<
-        V: Visitor<JsonSerializer, Json>
-    >(&mut self, _name: &'static str, visitor: V) -> Json {
-        self.visit_tuple(visitor)
-    }
-
-    fn visit_enum<
-        V: Visitor<JsonSerializer, Json>
-    >(&mut self, _name: &'static str, _variant: &'static str, visitor: V) -> Json {
-        self.visit_tuple(visitor)
+        Ok(())
     }
 
+    #[inline]
     fn visit_map<
-        K: Serialize<JsonSerializer, Json>,
-        V: Serialize<JsonSerializer, Json>,
-        Iter: Iterator<(K, V)>
-    >(&mut self, mut iter: Iter) -> Json {
-        let mut v = TreeMap::new();
-        let mut first = true;
+        V: ser::MapVisitor<Writer, (), ()>
+    >(&self, state: &mut Writer, mut visitor: V) -> Result<(), ()> {
+        let values = TreeMap::new();
 
-        for (key, value) in iter {
-            let value = self.visit_map_elt(first, key, value);
-            v.insert(self.key.take().unwrap(), value);
-            first = false;
-        }
-
-        Object(v)
-    }
-
-    fn visit_map_elt<
-        K: Serialize<JsonSerializer, Json>,
-        V: Serialize<JsonSerializer, Json>
-    >(&mut self, _first: bool, key: K, value: V) -> Json {
-        match key.serialize(self) {
-            String(key) => { self.key = Some(key); }
-            _ => { fail!() }
-        }
-        value.serialize(self)
-    }
-
-    fn visit_struct<
-        V: Visitor<JsonSerializer, Json>
-    >(&mut self, _name: &'static str, mut visitor: V) -> Json {
-        let mut v = TreeMap::new();
+        state.state.push(State::Object(values));
 
         loop {
-            match visitor.visit(self) {
-                Some(value) => { v.insert(self.key.take().unwrap(), value); }
+            match try!(visitor.visit(state, Visitor)) {
+                Some(()) => { }
                 None => { break; }
             }
         }
 
-        Object(v)
+        match state.state.pop().unwrap() {
+            State::Object(values) => { state.state.push(State::Value(Value::Object(values))); }
+            _ => panic!(),
+        }
+
+        Ok(())
+    }
+
+    #[inline]
+    fn visit_map_elt<
+        K: ser::Serialize,
+        V: ser::Serialize,
+    >(&self, state: &mut Writer, _first: bool, key: K, value: V) -> Result<(), ()> {
+        try!(key.visit(state, Visitor));
+        try!(value.visit(state, Visitor));
+
+        let key = match state.state.pop().unwrap() {
+            State::Value(Value::String(value)) => value,
+            _ => panic!(),
+        };
+
+        let value = match state.state.pop().unwrap() {
+            State::Value(value) => value,
+            _ => panic!(),
+        };
+
+        match *state.state.last_mut().unwrap() {
+            State::Object(ref mut values) => { values.insert(key, value); }
+            _ => panic!(),
+        }
+
+        Ok(())
     }
 }