Start on bytecode decoding stuff

Author: hawkw

seax_svm/src/bytecode/mod.rs

@@ -0,0 +1,71 @@
+use std::io::Read;
+
+use super::SVMCell::*;
+use super::Inst::*;
+use super::Inst;
+
+#[unstable(feature="decode")]
+pub struct Decoder<'a, R: 'a> {
+    source: &'a mut R,
+    read: usize
+}
+
+
+#[unstable(feature="decode")]
+impl<'a, R> Decoder<'a, R> where R: Read {
+
+    #[unstable(feature="decode")]
+    pub fn new(src: &'a mut R) -> Decoder<'a, R>{
+        Decoder {
+            source: src,
+            read: 0
+        }
+    }
+
+    #[unstable(feature="decode")]
+    fn decode_inst(byte: &u8) -> Result<Inst, String> {
+        match *byte {
+            0xA0u8 => Ok(NIL),
+            0xA1u8 => Ok(LDC),
+            0xA2u8 => Ok(LD),
+            0xA3u8 => Ok(LDF),
+            0xA4u8 => Ok(AP),
+            0xA5u8 => Ok(JOIN),
+            0xA6u8 => Ok(RAP),
+            0xA7u8 => Ok(RET),
+            0xA8u8 => Ok(DUM),
+            0xA9u8 => Ok(SEL),
+            0xAAu8 => Ok(ADD),
+            0xABu8 => Ok(SUB),
+            0xACu8 => Ok(MUL),
+            0xADu8 => Ok(DIV),
+            0xAFu8 => Ok(FDIV),
+            0xB0u8 => Ok(MOD),
+            0xB1u8 => Ok(EQ),
+            0xB2u8 => Ok(GT),
+            0xB3u8 => Ok(GTE),
+            0xB4u8 => Ok(LT),
+            0xB5u8 => Ok(LTE),
+            0xB6u8 => Ok(ATOM),
+            0xB7u8 => Ok(NULL),
+            0xB8u8 => Ok(READC),
+            0xB9u8 => Ok(WRITEC),
+            0xBAu8 => Ok(APCC),
+            0xC0u8 => Ok(CONS),
+            0xCDu8 => Ok(CDR),
+            0xCAu8 => Ok(CAR),
+            b if b < 0xA0u8 => Err(String::from("byte too low")),
+            b if b > 0xB9u8 && b < 0xC0u8 => Err(format!("reserved byte {:?}", b)),
+            b if b > 0xCAu8 => Err(String::from("byte too high")),
+            _               => panic!("Got a byte that was weird")
+        }
+    }
+
+    /// Returns the number of bytes read by the decoder
+    #[unstable(feature="decode")]
+    pub fn read(&self) -> usize {
+        self.read
+    }
+
+
+}

seax_svm/src/lib.rs

@@ -5,7 +5,6 @@
 #![feature(staged_api)]
 #![staged_api]
 
-
 #[cfg(test)]
 extern crate quickcheck;
 
@@ -29,6 +28,12 @@ pub mod slist;
 #[stable(feature="vm_core", since="0.1.2")]
 pub mod cell;
 
+/// Bytecode
+///
+/// Contains code for encoding and decoding Seax bytecode files.
+#[unstable(feature="bytecode")]
+pub mod bytecode;
+
 #[cfg(test)]
 mod tests;