Encode/decode to/from references to readers

src/lib.rs

@@ -1,10 +1,16 @@
+#![crate_name = "binary_encode"]
+#![crate_type = "rlib"]
+#![crate_type = "dylib"]
+
 #![feature(struct_variant)]
 
 extern crate serialize;
 
+use std::io::Buffer;
 use std::io::MemWriter;
 use std::io::MemReader;
 use std::io::IoError;
+use std::io::IoResult;
 use serialize::Encodable;
 use serialize::Decodable;
 
@@ -14,43 +20,32 @@ pub use reader::DecoderReader;
 mod writer;
 mod reader;
 
-pub fn encode<T: Encodable<EncoderWriter<MemWriter>, IoError>>(t: &T) ->
-Result<Vec<u8>, IoError> {
-    match encode_into(t, MemWriter::new()) {
-        Ok(w) => Ok(w.unwrap()),
-        Err((_, e)) => Err(e)
+pub fn encode<'a, T: Encodable<EncoderWriter<'a, MemWriter>, IoError>>(t: &T) ->IoResult<Vec<u8>> {
+    let mut w = MemWriter::new();
+    match encode_into(t, &mut w) {
+        Ok(()) => Ok(w.unwrap()),
+        Err(e) => Err(e)
     }
 }
 
-pub fn decode<T: Decodable<DecoderReader<MemReader>, IoError>>(b: Vec<u8>) ->
-Result<T, (IoError, Vec<u8>)> {
-    match decode_from(MemReader::new(b)) {
-        Ok((t, _)) => Ok(t),
-        Err((e, r)) => Err((e, r.unwrap()))
-    }
+pub fn decode<'a, T: Decodable<DecoderReader<'a, MemReader>, IoError>>(b: Vec<u8>) -> IoResult<T> {
+    decode_from(&mut MemReader::new(b))
 }
 
-pub fn encode_into<W: Writer, T: Encodable<EncoderWriter<W>, IoError>>
-(t: &T, w: W)
--> Result<W, (W, IoError)> {
-    let mut writer = writer::EncoderWriter::new(w);
-    match t.encode(&mut writer) {
-        Ok(()) => Ok(writer.unwrap()),
-        Err(e) => Err((writer.unwrap(), e))
+// In order to be able to pass MemReaders/MemWriters by reference, I borrowed the method used in
+// the current json encoder in the stdlib
+
+// TODO: Make code safe https://github.com/rust-lang/rust/issues/14302
+pub fn encode_into<'a, W: 'a+Writer, T: Encodable<EncoderWriter<'a, W>, IoError>>(t: &T, w: &mut W) -> IoResult<()> {
+    unsafe {
+        t.encode(std::mem::transmute(&mut writer::EncoderWriter::new(w)))
     }
 }
 
-// TODO: When higher order lifetimes land, make this so that the
-// reader is passed in by &mut instead of by ownership.
-pub fn decode_from<R: Reader, T: Decodable<DecoderReader<R>, IoError>>(r: R) ->
-Result<(T, R), (IoError, R)> {
-    let mut reader = reader::DecoderReader::new(r);
-    let x: Result<T, IoError> = Decodable::decode(&mut reader);
-    let mem = reader.unwrap();
-
-    match x {
-        Ok(t) => Ok((t, mem)),
-        Err(e) => Err((e, mem))
+// TODO: Make code safe https://github.com/rust-lang/rust/issues/14302
+pub fn decode_from<'a, R: 'a+Reader+Buffer, T: Decodable<DecoderReader<'a, R>, IoError>>(r: &mut R) -> IoResult<T> {
+    unsafe {
+        Decodable::decode(std::mem::transmute(&mut reader::DecoderReader::new(r)))
     }
 }
 

src/reader.rs

@@ -1,79 +1,75 @@
+use std::io::Buffer;
 use std::io::Reader;
-use std::io::BufferedReader;
 use std::io::IoError;
+use std::io::IoResult;
 use std::io::OtherIoError;
 use serialize::Decoder;
 
-type EwResult = Result<(), IoError>;
-
-pub struct DecoderReader<R> {
-    reader: BufferedReader<R>
+pub struct DecoderReader<'a, R: 'a> {
+    reader: &'a mut R
 }
 
-impl <R: Reader> DecoderReader<R> {
-    pub fn new(r: R) -> DecoderReader<R> {
+impl<'a, R: Reader+Buffer> DecoderReader<'a, R> {
+    pub fn new(r: &'a mut R) -> DecoderReader<'a, R> {
         DecoderReader {
-            reader: BufferedReader::new(r)
+            reader: r
         }
     }
-    pub fn unwrap(self) -> R {
-        self.reader.unwrap()
-    }
 }
 
-impl <R: Reader> Decoder<IoError> for DecoderReader<R> {
-    fn read_nil(&mut self) -> Result<(), IoError> {
+impl<'a, R: Reader+Buffer> Decoder<IoError> for DecoderReader<'a, R> {
+    fn read_nil(&mut self) -> IoResult<()> {
         Ok(())
     }
-    fn read_uint(&mut self) -> Result<uint, IoError> {
+    fn read_uint(&mut self) -> IoResult<uint> {
         match self.reader.read_be_u64() {
             Ok(x) => Ok(x as uint),
             Err(e) => Err(e)
         }
     }
-    fn read_u64(&mut self) -> Result<u64, IoError> {
+    fn read_u64(&mut self) -> IoResult<u64> {
         self.reader.read_be_u64()
     }
-    fn read_u32(&mut self) -> Result<u32, IoError> {
+    fn read_u32(&mut self) -> IoResult<u32> {
         self.reader.read_be_u32()
     }
-    fn read_u16(&mut self) -> Result<u16, IoError> {
+    fn read_u16(&mut self) -> IoResult<u16> {
         self.reader.read_be_u16()
     }
-    fn read_u8(&mut self) -> Result<u8, IoError> {
+    fn read_u8(&mut self) -> IoResult<u8> {
         self.reader.read_u8()
     }
-    fn read_int(&mut self) -> Result<int, IoError> {
+    fn read_int(&mut self) -> IoResult<int> {
         self.reader.read_be_int()
     }
-    fn read_i64(&mut self) -> Result<i64, IoError> {
+    fn read_i64(&mut self) -> IoResult<i64> {
         self.reader.read_be_i64()
     }
-    fn read_i32(&mut self) -> Result<i32, IoError> {
+    fn read_i32(&mut self) -> IoResult<i32> {
         self.reader.read_be_i32()
     }
-    fn read_i16(&mut self) -> Result<i16, IoError> {
+    fn read_i16(&mut self) -> IoResult<i16> {
         self.reader.read_be_i16()
     }
-    fn read_i8(&mut self) -> Result<i8, IoError> {
+    fn read_i8(&mut self) -> IoResult<i8> {
         self.reader.read_i8()
     }
-    fn read_bool(&mut self) -> Result<bool, IoError> {
+    fn read_bool(&mut self) -> IoResult<bool> {
         match try!(self.reader.read_i8()) {
             1 => Ok(true),
             _ => Ok(false)
         }
     }
-    fn read_f64(&mut self) -> Result<f64, IoError> {
+    fn read_f64(&mut self) -> IoResult<f64> {
         self.reader.read_be_f64()
     }
-    fn read_f32(&mut self) -> Result<f32, IoError> {
+    fn read_f32(&mut self) -> IoResult<f32> {
         self.reader.read_be_f32()
     }
-    fn read_char(&mut self) -> Result<char, IoError> {
+    fn read_char(&mut self) -> IoResult<char> {
         self.reader.read_char()
     }
-    fn read_str(&mut self) -> Result<String, IoError> {
+    fn read_str(&mut self) -> IoResult<String> {
         let len = try!(self.read_uint());
         let mut vector = Vec::with_capacity(len as uint);
         for _ in range(0, len) {
@@ -82,83 +78,83 @@ impl <R: Reader> Decoder<IoError> for DecoderReader<R> {
         Ok(String::from_utf8(vector).unwrap())
     }
     fn read_enum<T>(&mut self, _: &str,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_enum_variant<T>(&mut self, _: &[&str],
-    f: |&mut DecoderReader<R>, uint| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, uint| -> IoResult<T>) -> IoResult<T> {
         let id = try!(self.read_uint());
         f(self, id)
     }
     fn read_enum_variant_arg<T>(&mut self, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_enum_struct_variant<T>(&mut self, names: &[&str],
-    f: |&mut DecoderReader<R>, uint| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, uint| -> IoResult<T>) -> IoResult<T> {
         self.read_enum_variant(names, f)
     }
     fn read_enum_struct_variant_field<T>(&mut self, _: &str, f_idx: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         self.read_enum_variant_arg(f_idx, f)
     }
     fn read_struct<T>(&mut self, _: &str, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_struct_field<T>(&mut self, _: &str, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_tuple<T>(&mut self,
-    f: |&mut DecoderReader<R>, uint| -> Result<T, IoError>) ->
-    Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, uint| -> IoResult<T>) ->
+    IoResult<T> {
         let len = try!(self.read_uint());
         f(self, len)
     }
     fn read_tuple_arg<T>(&mut self, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_tuple_struct<T>(&mut self, _: &str,
-    f: |&mut DecoderReader<R>, uint| -> Result<T, IoError>) ->
-    Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, uint| -> IoResult<T>) ->
+    IoResult<T> {
         self.read_tuple(f)
     }
     fn read_tuple_struct_arg<T>(&mut self, a_idx: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         self.read_tuple_arg(a_idx, f)
     }
     fn read_option<T>(&mut self,
-    f: |&mut DecoderReader<R>, bool| -> Result<T, IoError>) ->
-    Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, bool| -> IoResult<T>) ->
+    IoResult<T> {
         match try!(self.reader.read_u8()) {
             1 => f(self, true),
             _ => f(self, false)
         }
     }
     fn read_seq<T>(&mut self,
-    f: |&mut DecoderReader<R>, uint| -> Result<T, IoError>) ->
-    Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, uint| -> IoResult<T>) ->
+    IoResult<T> {
         let len = try!(self.read_uint());
         f(self, len)
     }
     fn read_seq_elt<T>(&mut self, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_map<T>(&mut self,
-    f: |&mut DecoderReader<R>, uint| -> Result<T, IoError>) ->
-    Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>, uint| -> IoResult<T>) ->
+    IoResult<T> {
         let len = try!(self.read_uint());
         f(self, len)
     }
     fn read_map_elt_key<T>(&mut self, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn read_map_elt_val<T>(&mut self, _: uint,
-    f: |&mut DecoderReader<R>| -> Result<T, IoError>) -> Result<T, IoError> {
+    f: |&mut DecoderReader<'a, R>| -> IoResult<T>) -> IoResult<T> {
         f(self)
     }
     fn error(&mut self, err: &str) -> IoError {

src/test.rs

@@ -16,9 +16,9 @@ use super::DecoderReader;
 use super::encode;
 use super::decode;
 
-fn the_same<
-            V: Encodable<EncoderWriter<MemWriter>, IoError>  +
-               Decodable<DecoderReader<MemReader>, IoError> +
+fn the_same<'a,
+            V: Encodable<EncoderWriter<'a, MemWriter>, IoError>  +
+               Decodable<DecoderReader<'a, MemReader>, IoError> +
                PartialEq + Show>(element: V) {
     assert!(element == decode(encode(&element).unwrap()).unwrap());
 }