Direct serialization

implementations/rust/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "preserves"
-version = "0.5.1"
+version = "0.6.0"
 authors = ["Tony Garnock-Jones <tonyg@leastfixedpoint.com>"]
 edition = "2018"
 description = "Implementation of the Preserves serialization format via serde."

implementations/rust/src/lib.rs

@@ -1,9 +1,11 @@
-pub mod value;
+pub mod de;
+pub mod ser;
 pub mod symbol;
+pub mod value;
 
 #[cfg(test)]
 mod dom {
-    use super::value::{Value, PlainValue, NestedValue, Domain, Encoder, Codec};
+    use super::value::{Value, PlainValue, NestedValue, Domain, Encoder, Codec, writer::Writer};
 
     #[derive(Debug, Hash, Clone, Ord, PartialEq, Eq, PartialOrd)]
     pub enum Dom {
@@ -12,12 +14,16 @@ mod dom {
     }
 
     impl Domain for Dom {
-        fn encode<'a, 'b, W: std::io::Write, N: NestedValue<Self>>(
+        fn encode<'a, 'b, W: Writer, N: NestedValue<Self>>(
             &self, enc: &mut Encoder<'a, 'b, W, N, Self>) ->
             super::value::encoder::Result
         {
             match self {
-                Dom::One => enc.write_all(&[255, 255, 255, 255]),
+                Dom::One => {
+                    enc.write.stream_bytes()?;
+                    enc.write.write_bytes(&[255, 255, 255, 255])?;
+                    enc.write.close_stream()
+                }
                 Dom::Two => enc.write(&self.as_preserves()?)
             }
         }
@@ -33,7 +39,7 @@ mod dom {
                                                 Value::from(2).wrap()])
             .wrap();
         assert_eq!(Codec::without_placeholders().encode_bytes(&v).unwrap(),
-                   [147, 49, 255, 255, 255, 255, 50]);
+                   [147, 49, 38, 100, 255, 255, 255, 255, 4, 50]);
     }
 
     #[test] fn test_two() {
@@ -44,16 +50,6 @@ mod dom {
         assert_eq!(Codec::without_placeholders().encode_bytes(&v).unwrap(),
                    [147, 49, 120, 68, 111, 109, 58, 58, 84, 119, 111, 50]);
     }
-
-    #[test] fn test_unit() {
-        let v: PlainValue<_> = Value::from(vec![Value::from(1).wrap(),
-                                                Value::Domain(()).wrap(),
-                                                Value::from(2).wrap()])
-            .wrap();
-        let e = Codec::without_placeholders().encode_bytes(&v).err().unwrap();
-        assert_eq!(e.kind(), std::io::ErrorKind::InvalidData);
-        assert_eq!(e.to_string(), "Cannot Preserves-encode domain-specific value ()");
-    }
 }
 
 #[cfg(test)]
@@ -372,8 +368,11 @@ mod samples_tests {
     }
 
     #[test] fn simple_to_value() {
+        use serde::Serialize;
         #[derive(Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
         struct SimpleValue<'a>(String,
+                               #[serde(with = "crate::symbol")] String,
+                               Symbol,
                                #[serde(with = "crate::symbol")] String,
                                Symbol,
                                &'a str,
@@ -384,16 +383,28 @@ mod samples_tests {
         let v = SimpleValue("hello".to_string(),
                             "sym1".to_string(),
                             Symbol("sym2".to_string()),
+                            "sym3".to_string(),
+                            Symbol("sym4".to_string()),
                             "world",
                             &b"slice"[..],
                             b"vec".to_vec(),
                             12345,
                             Value::from("hi").wrap());
-        println!("{:#?}", v);
+        println!("== v: {:#?}", v);
         let w: PlainValue<Dom> = to_value(&v).unwrap();
-        println!("{:#?}", w);
+        println!("== w: {:#?}", w);
         let x = from_value(&w).unwrap();
-        println!("{:#?}", &x);
+        println!("== x: {:#?}", &x);
         assert_eq!(v, x);
+        let mut placeholders = Map::new();
+        placeholders.insert(5, Value::symbol("sym1"));
+        placeholders.insert(500, Value::symbol("sym2"));
+        placeholders.insert(0, Value::symbol("SimpleValue"));
+        let v_bytes_1 = Codec::new(placeholders.clone()).encode_bytes(&w).unwrap();
+        let mut v_bytes_2 = Vec::new();
+        v.serialize(&mut crate::ser::Serializer::new(&mut v_bytes_2, placeholders)).unwrap();
+        println!("== w bytes = {:?}", v_bytes_1);
+        println!("== v bytes = {:?}", v_bytes_2);
+        assert_eq!(v_bytes_1, v_bytes_2);
     }
 }

implementations/rust/src/ser.rs

@@ -0,0 +1,400 @@
+use serde::Serialize;
+use super::value::writer::{self, Writer};
+use super::value::{
+    Value, NestedValue, PlainValue,
+    Domain, NullDomain,
+    DecodePlaceholderMap, EncodePlaceholderMap, invert_map,
+    Decoder, Encoder, to_value,
+};
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug)]
+pub struct Error {
+    inner: writer::Error,
+}
+
+impl std::convert::From<writer::Error> for Error {
+    fn from(inner: writer::Error) -> Self {
+        Error { inner }
+    }
+}
+
+impl<D: super::value::Domain> std::convert::From<crate::value::error::Error<D>> for Error {
+    fn from(_inner: crate::value::error::Error<D>) -> Self {
+        magic_error()
+    }
+}
+
+impl serde::ser::Error for Error {
+    fn custom<T: std::fmt::Display>(msg: T) -> Self {
+        Error { inner: writer::Error::new(std::io::ErrorKind::Other, msg.to_string()) }
+    }
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::result::Result<(), std::fmt::Error> {
+        self.inner.fmt(f)
+    }
+}
+
+impl std::error::Error for Error {}
+
+#[derive(Debug)]
+pub struct Serializer<W: Writer, N: NestedValue<D>, D: Domain> {
+    pub write: W,
+    placeholders: Option<EncodePlaceholderMap<N, D>>,
+}
+
+impl<W: Writer, N: NestedValue<D>, D: Domain> Serializer<W, N, D> {
+    pub fn new(write: W, placeholders: DecodePlaceholderMap<N, D>) -> Self {
+        Serializer { write, placeholders: Some(invert_map(&placeholders)) }
+    }
+
+    fn write_symbol(&mut self, s: &str) -> Result<()> {
+        match self.placeholders.as_ref().and_then(|m| m.get(&Value::symbol(s))) {
+            Some(&n) => Ok(self.write.write_placeholder_ref(n)?),
+            None => Ok(self.write.write_symbol(s)?),
+        }
+    }
+}
+
+impl<W: Writer> Serializer<W, PlainValue<NullDomain>, NullDomain> {
+    pub fn without_placeholders(write: W) -> Self {
+        Serializer { write, placeholders: None }
+    }
+}
+
+#[derive(Debug)]
+pub struct SerializeCompound<'a, W: Writer, N: NestedValue<D>, D: Domain> {
+    ser: &'a mut Serializer<W, N, D>,
+    count: Option<usize>,
+}
+
+fn magic_error() -> Error {
+    Error { inner: writer::Error::new(std::io::ErrorKind::InvalidData,
+                                      "Internal error handling magic Value encoding") }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::Serializer for &'a mut Serializer<W, N, D> {
+    type Ok = ();
+    type Error = Error;
+    type SerializeSeq = SerializeCompound<'a, W, N, D>;
+    type SerializeTuple = SerializeCompound<'a, W, N, D>;
+    type SerializeTupleStruct = SerializeCompound<'a, W, N, D>;
+    type SerializeTupleVariant = SerializeCompound<'a, W, N, D>;
+    type SerializeMap = SerializeCompound<'a, W, N, D>;
+    type SerializeStruct = SerializeCompound<'a, W, N, D>;
+    type SerializeStructVariant = SerializeCompound<'a, W, N, D>;
+
+    fn serialize_bool(self, v: bool) -> Result<()> {
+        Ok(self.write.write_bool(v)?)
+    }
+
+    fn serialize_i8(self, v: i8) -> Result<()> {
+        Ok(self.write.write_i8(v)?)
+    }
+
+    fn serialize_i16(self, v: i16) -> Result<()> {
+        Ok(self.write.write_i16(v)?)
+    }
+
+    fn serialize_i32(self, v: i32) -> Result<()> {
+        Ok(self.write.write_i32(v)?)
+    }
+
+    fn serialize_i64(self, v: i64) -> Result<()> {
+        Ok(self.write.write_i64(v)?)
+    }
+
+    fn serialize_u8(self, v: u8) -> Result<()> {
+        Ok(self.write.write_u8(v)?)
+    }
+
+    fn serialize_u16(self, v: u16) -> Result<()> {
+        Ok(self.write.write_u16(v)?)
+    }
+
+    fn serialize_u32(self, v: u32) -> Result<()> {
+        Ok(self.write.write_u32(v)?)
+    }
+
+    fn serialize_u64(self, v: u64) -> Result<()> {
+        Ok(self.write.write_u64(v)?)
+    }
+
+    fn serialize_f32(self, v: f32) -> Result<()> {
+        Ok(self.write.write_f32(v)?)
+    }
+
+    fn serialize_f64(self, v: f64) -> Result<()> {
+        Ok(self.write.write_f64(v)?)
+    }
+
+    fn serialize_char(self, v: char) -> Result<()> {
+        self.write.open_record(1)?;
+        self.write_symbol("UnicodeScalar")?;
+        self.write.write_u32(v as u32)?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_str(self, v: &str) -> Result<()> {
+        Ok(self.write.write_string(v)?)
+    }
+
+    fn serialize_bytes(self, v: &[u8]) -> Result<()> {
+        Ok(self.write.write_bytes(v)?)
+    }
+
+    fn serialize_none(self) -> Result<()> {
+        self.write.open_record(0)?;
+        self.write_symbol("None")?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_some<T: ?Sized>(self, v: &T) -> Result<()> where T: Serialize {
+        self.write.open_record(1)?;
+        self.write_symbol("Some")?;
+        v.serialize(&mut *self)?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_unit(self) -> Result<()> {
+        self.write.open_record(0)?;
+        self.write_symbol("tuple")?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_unit_struct(self, name: &'static str) -> Result<()> {
+        self.write.open_record(0)?;
+        self.write_symbol(name)?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_unit_variant(self,
+                              _name: &'static str,
+                              _variant: u32,
+                              variant_name: &'static str) ->
+        Result<()>
+    {
+        self.write.open_record(0)?;
+        self.write_symbol(variant_name)?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_newtype_struct<T: ?Sized>(self, name: &'static str, value: &T) ->
+        Result<()> where T: Serialize
+    {
+        if name == crate::value::value::MAGIC {
+            let v0: N = to_value(value)?;
+            let mut buf: &[u8] = v0.value().as_bytestring().ok_or_else(magic_error)?;
+            let v1: N = Decoder::new(&mut buf, None).next().or_else(|_| Err(magic_error()))?;
+            Encoder::new(&mut self.write, self.placeholders.as_ref()).write(&v1)?;
+            Ok(())
+        } else {
+            // TODO: This is apparently discouraged, and we should apparently just serialize `value`?
+            self.write.open_record(1)?;
+            self.write_symbol(name)?;
+            value.serialize(&mut *self)?;
+            Ok(self.write.close_record()?)
+        }
+    }
+
+    fn serialize_newtype_variant<T: ?Sized>(self,
+                                            _name: &'static str,
+                                            _variant: u32,
+                                            variant_name: &'static str,
+                                            value: &T) ->
+        Result<()> where T: Serialize
+    {
+        self.write.open_record(1)?;
+        self.write_symbol(variant_name)?;
+        value.serialize(&mut *self)?;
+        Ok(self.write.close_record()?)
+    }
+
+    fn serialize_seq(self, count: Option<usize>) -> Result<Self::SerializeSeq> {
+        match count {
+            Some(n) => self.write.open_sequence(n)?,
+            None => self.write.stream_sequence()?,
+        }
+        Ok(SerializeCompound { ser: self, count })
+    }
+
+    fn serialize_tuple(self, count: usize) -> Result<Self::SerializeTuple> {
+        self.write.open_record(count)?;
+        self.write_symbol("tuple")?;
+        Ok(SerializeCompound { ser: self, count: Some(count) })
+    }
+
+    fn serialize_tuple_struct(self, name: &'static str, count: usize) ->
+        Result<Self::SerializeTupleStruct>
+    {
+        self.write.open_record(count)?;
+        self.write_symbol(name)?;
+        Ok(SerializeCompound { ser: self, count: Some(count) })
+    }
+
+    fn serialize_tuple_variant(self,
+                               _name: &'static str,
+                               _variant: u32,
+                               variant_name: &'static str,
+                               count: usize) ->
+        Result<Self::SerializeTupleVariant>
+    {
+        self.write.open_record(count)?;
+        self.write_symbol(variant_name)?;
+        Ok(SerializeCompound { ser: self, count: Some(count) })
+    }
+
+    fn serialize_map(self, count: Option<usize>) -> Result<Self::SerializeMap> {
+        match count {
+            Some(n) => self.write.open_dictionary(n)?,
+            None => self.write.stream_dictionary()?,
+        }
+        Ok(SerializeCompound { ser: self, count })
+    }
+
+    fn serialize_struct(self, name: &'static str, count: usize) -> Result<Self::SerializeStruct> {
+        self.write.open_record(count)?;
+        self.write_symbol(name)?;
+        Ok(SerializeCompound { ser: self, count: Some(count) })
+    }
+
+    fn serialize_struct_variant(self,
+                                _name: &'static str,
+                                _variant: u32,
+                                variant_name: &'static str,
+                                count: usize) ->
+        Result<Self::SerializeStructVariant>
+    {
+        self.write.open_record(count)?;
+        self.write_symbol(variant_name)?;
+        Ok(SerializeCompound { ser: self, count: Some(count) })
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeMap for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_key<T: ?Sized>(&mut self, key: &T) -> Result<()> where T: Serialize {
+        Ok(key.serialize(&mut *self.ser)?)
+    }
+
+    fn serialize_value<T: ?Sized>(&mut self, value: &T) -> Result<()> where T: Serialize {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_dictionary()?),
+        }
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeStruct for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T: ?Sized>(&mut self, _name: &'static str, value: &T) -> Result<()>
+    where T: Serialize
+    {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_record()?),
+        }
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeStructVariant for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T: ?Sized>(&mut self, _name: &'static str, value: &T) -> Result<()>
+    where T: Serialize
+    {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_record()?),
+        }
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeTuple for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T: ?Sized>(&mut self, value: &T) -> Result<()> where T: Serialize {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_record()?),
+        }
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeTupleStruct for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T: ?Sized>(&mut self, value: &T) -> Result<()> where T: Serialize {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_record()?),
+        }
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeTupleVariant for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T: ?Sized>(&mut self, value: &T) -> Result<()> where T: Serialize {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_record()?),
+        }
+    }
+}
+
+impl<'a, W: Writer, N: NestedValue<D>, D: Domain> serde::ser::SerializeSeq for SerializeCompound<'a, W, N, D> {
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T: ?Sized>(&mut self, value: &T) -> Result<()> where T: Serialize {
+        Ok(value.serialize(&mut *self.ser)?)
+    }
+
+    fn end(self) -> Result<()> {
+        match self.count {
+            None => Ok(self.ser.write.close_stream()?),
+            Some(_) => Ok(self.ser.write.close_sequence()?),
+        }
+    }
+}
+
+pub fn to_writer<W: Writer, T: Serialize>(write: W, value: &T) -> Result<()> {
+    let mut ser = Serializer::without_placeholders(write);
+    value.serialize(&mut ser)
+}

implementations/rust/src/symbol.rs

@@ -1,17 +1,17 @@
-use crate::value::{Value, PlainValue, NestedValue};
+use crate::value::{Value, PlainValue, NestedValue, NullDomain};
 
-#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
 pub struct Symbol(pub String);
 
 impl serde::Serialize for Symbol {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error> where S: serde::Serializer {
-        Value::<PlainValue<()>, ()>::symbol(&self.0).wrap().serialize(serializer)
+        Value::<PlainValue<NullDomain>, NullDomain>::symbol(&self.0).wrap().serialize(serializer)
     }
 }
 
 impl<'de> serde::Deserialize<'de> for Symbol {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where D: serde::Deserializer<'de> {
-        let v = PlainValue::<()>::deserialize(deserializer)?;
+        let v = PlainValue::<NullDomain>::deserialize(deserializer)?;
         let s = v.value().as_symbol().ok_or_else(|| serde::de::Error::custom("Expected symbol"))?;
         Ok(Symbol(s.clone()))
     }

implementations/rust/src/value/encoder.rs

@@ -1,82 +1,23 @@
-use std::io::Write;
-use crate::value::value::{Value, NestedValue, Float, Double, Map, Domain};
-use num::bigint::BigInt;
-use num::cast::ToPrimitive;
-use crate::value::constants::{Op, AtomMinor, CompoundMinor};
+use super::value::{Value, NestedValue, Float, Double, Map, Domain};
+use super::writer::Writer;
 
-pub type Error = std::io::Error;
-pub type Result = std::result::Result<(), Error>;
+pub use super::writer::{Error, Result};
 
 pub type EncodePlaceholderMap<N, D> = Map<Value<N, D>, usize>;
 
-pub struct Encoder<'a, 'b, W: Write, N: NestedValue<D>, D: Domain> {
+pub struct Encoder<'a, 'b, W: Writer, N: NestedValue<D>, D: Domain> {
     pub write: &'a mut W,
     pub placeholders: Option<&'b EncodePlaceholderMap<N, D>>,
 }
 
-impl<'a, 'b, W: Write, N: NestedValue<D>, D: Domain> Encoder<'a, 'b, W, N, D> {
+impl<'a, 'b, W: Writer, N: NestedValue<D>, D: Domain> Encoder<'a, 'b, W, N, D> {
     pub fn new(write: &'a mut W, placeholders: Option<&'b EncodePlaceholderMap<N, D>>) -> Self {
         Encoder{ write, placeholders }
     }
 
-    pub fn _write(&mut self, v: u8) -> Result {
-        self.write_all(&[v])
-    }
-
-    pub fn write_all(&mut self, vs: &[u8]) -> Result {
-        self.write.write_all(vs)
-    }
-
-    pub fn varint(&mut self, v: usize) -> Result {
-        if v < 128 {
-            self._write(v as u8)
-        } else {
-            self._write(((v & 0x7f) + 128) as u8)?;
-            self.varint(v >> 7)
-        }
-    }
-
-    pub fn write_op(&mut self, op: Op, arg: u8) -> Result {
-        self._write((u8::from(op) << 4) | (arg & 15))
-    }
-
-    pub fn write_header(&mut self, op: Op, wirelength: usize) -> Result {
-        if wirelength < 15 {
-            self.write_op(op, wirelength as u8)
-        } else {
-            self.write_op(op, 15)?;
-            self.varint(wirelength)
-        }
-    }
-
-    pub fn write_int(&mut self, v: &BigInt) -> Result {
-        match v.to_i8() {
-            Some(n) if n >= 0 && n <= 12 => self.write_op(Op::Misc(3), n as u8),
-            Some(n) if n >= -3 && n < 0 => self.write_op(Op::Misc(3), (n + 16) as u8),
-            _ => self.write_atom(AtomMinor::SignedInteger, &v.to_signed_bytes_be()),
-        }
-    }
-
-    pub fn write_stream_header(&mut self, op: Op) -> Result {
-        self.write_op(Op::Misc(2), u8::from(op))
-    }
-
-    pub fn write_stream_footer(&mut self) -> Result {
-        self.write_op(Op::Misc(0), 4)
-    }
-
-    pub fn write_atom(&mut self, minor: AtomMinor, bs: &[u8]) -> Result {
-        self.write_header(Op::Atom(minor), bs.len())?;
-        self.write_all(bs)
-    }
-
-    pub fn write_noop(&mut self) -> Result {
-        self.write_op(Op::Reserved(3), 15)
-    }
-
     pub fn write(&mut self, v: &N) -> Result {
         for ann in v.annotations() {
-            self.write_header(Op::Misc(0), 5)?;
+            self.write.write_annotation_prefix()?;
             self.write(ann)?;
         }
         self.write_value(v.value())
@@ -84,42 +25,35 @@ impl<'a, 'b, W: Write, N: NestedValue<D>, D: Domain> Encoder<'a, 'b, W, N, D> {
 
     pub fn write_value(&mut self, v: &Value<N, D>) -> Result {
         match self.placeholders.and_then(|m| m.get(v)) {
-            Some(&n) => self.write_header(Op::Misc(1), n),
+            Some(&n) => self.write.write_placeholder_ref(n),
             None => match v {
-                Value::Boolean(false) => self.write_op(Op::Misc(0), 0),
-                Value::Boolean(true) => self.write_op(Op::Misc(0), 1),
-                Value::Float(Float(f)) => {
-                    self.write_op(Op::Misc(0), 2)?;
-                    self.write_all(&u32::to_be_bytes(f32::to_bits(*f)))
-                }
-                Value::Double(Double(d)) => {
-                    self.write_op(Op::Misc(0), 3)?;
-                    self.write_all(&u64::to_be_bytes(f64::to_bits(*d)))
-                }
-                Value::SignedInteger(ref b) => self.write_int(b),
-                Value::String(ref s) => self.write_atom(AtomMinor::String, s.as_bytes()),
-                Value::ByteString(ref bs) => self.write_atom(AtomMinor::ByteString, bs),
-                Value::Symbol(ref s) => self.write_atom(AtomMinor::Symbol, s.as_bytes()),
+                Value::Boolean(b) => self.write.write_bool(*b),
+                Value::Float(Float(f)) => self.write.write_f32(*f),
+                Value::Double(Double(d)) => self.write.write_f64(*d),
+                Value::SignedInteger(ref b) => self.write.write_int(b),
+                Value::String(ref s) => self.write.write_string(s),
+                Value::ByteString(ref bs) => self.write.write_bytes(bs),
+                Value::Symbol(ref s) => self.write.write_symbol(s),
                 Value::Record((ref l, ref fs)) => {
-                    self.write_header(Op::Compound(CompoundMinor::Record), fs.len() + 1)?;
+                    self.write.open_record(fs.len())?;
                     self.write(N::boxunwrap(l))?;
                     for f in fs { self.write(f)?; }
-                    Ok(())
+                    self.write.close_record()
                 }
                 Value::Sequence(ref vs) => {
-                    self.write_header(Op::Compound(CompoundMinor::Sequence), vs.len())?;
+                    self.write.open_sequence(vs.len())?;
                     for v in vs { self.write(v)?; }
-                    Ok(())
+                    self.write.close_sequence()
                 }
                 Value::Set(ref vs) => {
-                    self.write_header(Op::Compound(CompoundMinor::Set), vs.len())?;
+                    self.write.open_set(vs.len())?;
                     for v in vs { self.write(v)?; }
-                    Ok(())
+                    self.write.close_set()
                 }
                 Value::Dictionary(ref vs) => {
-                    self.write_header(Op::Compound(CompoundMinor::Dictionary), vs.len() << 1)?;
+                    self.write.open_dictionary(vs.len())?;
                     for (k, v) in vs { self.write(k)?; self.write(v)?; }
-                    Ok(())
+                    self.write.close_dictionary()
                 }
                 Value::Domain(ref d) => d.encode(self),
             }

implementations/rust/src/value/mod.rs

@@ -6,6 +6,7 @@ pub mod encoder;
 pub mod error;
 pub mod ser;
 pub mod value;
+pub mod writer;
 
 pub use codec::Codec;
 pub use de::Deserializer;
@@ -32,3 +33,7 @@ pub fn invert_map<A, B>(m: &Map<A, B>) -> Map<B, A>
     use std::iter::FromIterator;
     Map::from_iter(m.iter().map(|(a, b)| (b.clone(), a.clone())))
 }
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub enum NullDomain {}
+impl Domain for NullDomain {}

implementations/rust/src/value/value.rs

@@ -12,7 +12,7 @@ pub use std::collections::BTreeSet as Set;
 pub use std::collections::BTreeMap as Map;
 
 pub trait Domain: Sized + Debug + Clone + Eq + Hash + Ord {
-    fn encode<'a, 'b, W: std::io::Write, N: NestedValue<Self>>(
+    fn encode<'a, 'b, W: super::writer::Writer, N: NestedValue<Self>>(
         &self, enc: &mut super::encoder::Encoder<'a, 'b, W, N, Self>) ->
         super::encoder::Result
     {
@@ -823,7 +823,3 @@ impl<'de, Dom: Domain> serde::Deserialize<'de> for ArcValue<Dom> {
         deserialize_nested_value(deserializer)
     }
 }
-
-//---------------------------------------------------------------------------
-
-impl Domain for () {}

implementations/rust/src/value/writer.rs

@@ -0,0 +1,274 @@
+use num::bigint::BigInt;
+use num::cast::ToPrimitive;
+use std::convert::TryInto;
+use super::constants::{Op, AtomMinor, CompoundMinor};
+
+pub type Error = std::io::Error;
+pub type Result = std::result::Result<(), Error>;
+
+pub trait Writer {
+    fn write_annotation_prefix(&mut self) -> Result;
+    fn write_placeholder_ref(&mut self, v: usize) -> Result;
+    fn write_noop(&mut self) -> Result;
+
+    fn write_bool(&mut self, v: bool) -> Result;
+
+    fn write_f32(&mut self, v: f32) -> Result;
+    fn write_f64(&mut self, v: f64) -> Result;
+
+    fn write_i8(&mut self, v: i8) -> Result;
+    fn write_u8(&mut self, v: u8) -> Result;
+    fn write_i16(&mut self, v: i16) -> Result;
+    fn write_u16(&mut self, v: u16) -> Result;
+    fn write_i32(&mut self, v: i32) -> Result;
+    fn write_u32(&mut self, v: u32) -> Result;
+    fn write_i64(&mut self, v: i64) -> Result;
+    fn write_u64(&mut self, v: u64) -> Result;
+    fn write_int(&mut self, v: &BigInt) -> Result;
+
+    fn write_string(&mut self, v: &str) -> Result;
+    fn write_bytes(&mut self, v: &[u8]) -> Result;
+    fn write_symbol(&mut self, v: &str) -> Result;
+
+    fn open_record(&mut self, field_count: usize) -> Result;
+    fn open_sequence(&mut self, item_count: usize) -> Result;
+    fn open_set(&mut self, item_count: usize) -> Result;
+    fn open_dictionary(&mut self, entry_count: usize) -> Result;
+
+    fn close_record(&mut self) -> Result;
+    fn close_sequence(&mut self) -> Result;
+    fn close_set(&mut self) -> Result;
+    fn close_dictionary(&mut self) -> Result;
+
+    fn stream_string(&mut self) -> Result;
+    fn stream_bytes(&mut self) -> Result;
+    fn stream_symbol(&mut self) -> Result;
+
+    fn stream_record(&mut self) -> Result;
+    fn stream_sequence(&mut self) -> Result;
+    fn stream_set(&mut self) -> Result;
+    fn stream_dictionary(&mut self) -> Result;
+
+    fn close_stream(&mut self) -> Result;
+}
+
+pub fn varint<W: std::io::Write>(w: &mut W, mut v: usize) -> Result {
+    loop {
+        if v < 128 {
+            return w.write_all(&[v as u8])
+        } else {
+            w.write_all(&[((v & 0x7f) + 128) as u8])?;
+            v = v >> 7;
+        }
+    }
+}
+
+pub fn write_op<W: std::io::Write>(w: &mut W, op: Op, arg: u8) -> Result {
+    w.write_all(&[(u8::from(op) << 4) | (arg & 15)])
+}
+
+pub fn write_header<W: std::io::Write>(w: &mut W, op: Op, wirelength: usize) -> Result {
+    if wirelength < 15 {
+        write_op(w, op, wirelength as u8)
+    } else {
+        write_op(w, op, 15)?;
+        varint(w, wirelength)
+    }
+}
+
+pub fn write_atom<W: std::io::Write>(w: &mut W, minor: AtomMinor, bs: &[u8]) -> Result {
+    write_header(w, Op::Atom(minor), bs.len())?;
+    w.write_all(bs)
+}
+
+impl<W: std::io::Write> Writer for W {
+    fn write_annotation_prefix(&mut self) -> Result {
+        write_header(self, Op::Misc(0), 5)
+    }
+
+    fn write_placeholder_ref(&mut self, v: usize) -> Result {
+        write_header(self, Op::Misc(1), v)
+    }
+
+    fn write_noop(&mut self) -> Result {
+        write_op(self, Op::Reserved(3), 15)
+    }
+
+    fn write_bool(&mut self, v: bool) -> Result {
+        write_op(self, Op::Misc(0), if v { 1 } else { 0 })
+    }
+
+    fn write_f32(&mut self, v: f32) -> Result {
+        write_op(self, Op::Misc(0), 2)?;
+        self.write_all(&u32::to_be_bytes(f32::to_bits(v)))
+    }
+
+    fn write_f64(&mut self, v: f64) -> Result {
+        write_op(self, Op::Misc(0), 3)?;
+        self.write_all(&u64::to_be_bytes(f64::to_bits(v)))
+    }
+
+    fn write_i8(&mut self, v: i8) -> Result {
+        if v >= 0 && v <= 12 { return write_op(self, Op::Misc(3), v as u8) }
+        if v >= -3 && v < 0 { return write_op(self, Op::Misc(3), (v + 16) as u8) }
+        write_atom(self, AtomMinor::SignedInteger, &[v as u8])
+    }
+
+    fn write_u8(&mut self, v: u8) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i8(w) }
+        write_atom(self, AtomMinor::SignedInteger, &[0, v])
+    }
+
+    fn write_i16(&mut self, v: i16) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i8(w) }
+        write_atom(self, AtomMinor::SignedInteger, &[(v >> 8) as u8, (v & 255) as u8])
+    }
+
+    fn write_u16(&mut self, v: u16) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i16(w) }
+        write_atom(self, AtomMinor::SignedInteger, &[0, (v >> 8) as u8, (v & 255) as u8])
+    }
+
+    fn write_i32(&mut self, v: i32) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i16(w) }
+        if v >= -(2 << 23) && v < (2 << 23) {
+            return write_atom(self, AtomMinor::SignedInteger, &[(v >> 16) as u8,
+                                                                (v >> 8) as u8,
+                                                                (v & 255) as u8]);
+        }
+        return write_atom(self, AtomMinor::SignedInteger, &[(v >> 24) as u8,
+                                                            (v >> 16) as u8,
+                                                            (v >> 8) as u8,
+                                                            (v & 255) as u8]);
+    }
+
+    fn write_u32(&mut self, v: u32) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i32(w) }
+        return write_atom(self, AtomMinor::SignedInteger, &[0,
+                                                            (v >> 24) as u8,
+                                                            (v >> 16) as u8,
+                                                            (v >> 8) as u8,
+                                                            (v & 255) as u8]);
+    }
+
+    fn write_i64(&mut self, v: i64) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i32(w) }
+        if v >= -(2 << 39) && v < (2 << 39) {
+            return write_atom(self, AtomMinor::SignedInteger, &[(v >> 32) as u8,
+                                                                (v >> 24) as u8,
+                                                                (v >> 16) as u8,
+                                                                (v >> 8) as u8,
+                                                                (v & 255) as u8]);
+        }
+        if v >= -(2 << 47) && v < (2 << 47) {
+            return write_atom(self, AtomMinor::SignedInteger, &[(v >> 40) as u8,
+                                                                (v >> 32) as u8,
+                                                                (v >> 24) as u8,
+                                                                (v >> 16) as u8,
+                                                                (v >> 8) as u8,
+                                                                (v & 255) as u8]);
+        }
+        if v >= -(2 << 55) && v < (2 << 55) {
+            return write_atom(self, AtomMinor::SignedInteger, &[(v >> 48) as u8,
+                                                                (v >> 40) as u8,
+                                                                (v >> 32) as u8,
+                                                                (v >> 24) as u8,
+                                                                (v >> 16) as u8,
+                                                                (v >> 8) as u8,
+                                                                (v & 255) as u8]);
+        }
+        return write_atom(self, AtomMinor::SignedInteger, &[(v >> 56) as u8,
+                                                            (v >> 48) as u8,
+                                                            (v >> 40) as u8,
+                                                            (v >> 32) as u8,
+                                                            (v >> 24) as u8,
+                                                            (v >> 16) as u8,
+                                                            (v >> 8) as u8,
+                                                            (v & 255) as u8]);
+    }
+
+    fn write_u64(&mut self, v: u64) -> Result {
+        if let Ok(w) = v.try_into() { return self.write_i64(w) }
+        return write_atom(self, AtomMinor::SignedInteger, &[0,
+                                                            (v >> 56) as u8,
+                                                            (v >> 48) as u8,
+                                                            (v >> 40) as u8,
+                                                            (v >> 32) as u8,
+                                                            (v >> 24) as u8,
+                                                            (v >> 16) as u8,
+                                                            (v >> 8) as u8,
+                                                            (v & 255) as u8]);
+    }
+
+    fn write_int(&mut self, v: &BigInt) -> Result {
+        match v.to_i8() {
+            Some(n) => self.write_i8(n),
+            None => write_atom(self, AtomMinor::SignedInteger, &v.to_signed_bytes_be()),
+        }
+    }
+
+    fn write_string(&mut self, v: &str) -> Result {
+        write_atom(self, AtomMinor::String, v.as_bytes())
+    }
+
+    fn write_bytes(&mut self, v: &[u8]) -> Result {
+        write_atom(self, AtomMinor::ByteString, v)
+    }
+
+    fn write_symbol(&mut self, v: &str) -> Result {
+        write_atom(self, AtomMinor::Symbol, v.as_bytes())
+    }
+
+    fn open_record(&mut self, field_count: usize) -> Result {
+        write_header(self, Op::Compound(CompoundMinor::Record), field_count + 1)
+    }
+
+    fn open_sequence(&mut self, item_count: usize) -> Result {
+        write_header(self, Op::Compound(CompoundMinor::Sequence), item_count)
+    }
+
+    fn open_set(&mut self, item_count: usize) -> Result {
+        write_header(self, Op::Compound(CompoundMinor::Set), item_count)
+    }
+
+    fn open_dictionary(&mut self, entry_count: usize) -> Result {
+        write_header(self, Op::Compound(CompoundMinor::Dictionary), entry_count << 1)
+    }
+
+    fn close_record(&mut self) -> Result { Ok(()) }
+    fn close_sequence(&mut self) -> Result { Ok(()) }
+    fn close_set(&mut self) -> Result { Ok(()) }
+    fn close_dictionary(&mut self) -> Result { Ok(()) }
+
+    fn stream_string(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Atom(AtomMinor::String).into())
+    }
+
+    fn stream_bytes(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Atom(AtomMinor::ByteString).into())
+    }
+
+    fn stream_symbol(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Atom(AtomMinor::Symbol).into())
+    }
+
+    fn stream_record(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Compound(CompoundMinor::Record).into())
+    }
+
+    fn stream_sequence(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Compound(CompoundMinor::Sequence).into())
+    }
+
+    fn stream_set(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Compound(CompoundMinor::Set).into())
+    }
+
+    fn stream_dictionary(&mut self) -> Result {
+        write_op(self, Op::Misc(2), Op::Compound(CompoundMinor::Dictionary).into())
+    }
+
+    fn close_stream(&mut self) -> Result {
+        write_op(self, Op::Misc(0), 4)
+    }
+}