Add data types for raw PSBT key-value pairs

- Add (en)decoding logic for said data types

src/util/psbt/error.rs

@@ -2,6 +2,7 @@ use std::error;
 use std::fmt;
 
 use blockdata::transaction::Transaction;
+use util::psbt::raw;
 
 /// Ways that a Partially Signed Transaction might fail.
 #[derive(Debug)]
@@ -12,9 +13,9 @@ pub enum Error {
     /// The separator for a PSBT must be `0xff`.
     InvalidSeparator,
     /// Known keys must be according to spec.
-    InvalidKey,
+    InvalidKey(raw::Key),
     /// Keys within key-value map should never be duplicated.
-    DuplicateKey,
+    DuplicateKey(raw::Key),
     /// The scriptSigs for the unsigned transaction must be empty.
     UnsignedTxHasScriptSigs,
     /// The scriptWitnesses for the unsigned transaction must be empty.
@@ -38,12 +39,12 @@ pub enum Error {
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
+            Error::InvalidKey(ref rkey) => write!(f, "{}: {}", error::Error::description(self), rkey),
+            Error::DuplicateKey(ref rkey) => write!(f, "{}: {}", error::Error::description(self), rkey),
             Error::UnexpectedUnsignedTx { expected: ref e, actual: ref a } => write!(f, "{}: expected {}, actual {}", error::Error::description(self), e.txid(), a.txid()),
             Error::NonStandardSigHashType(ref sht) => write!(f, "{}: {}", error::Error::description(self), sht),
             Error::InvalidMagic
             | Error::InvalidSeparator
-            | Error::InvalidKey
-            | Error::DuplicateKey
             | Error::UnsignedTxHasScriptSigs
             | Error::UnsignedTxHasScriptWitnesses
             | Error::MustHaveUnsignedTx
@@ -57,8 +58,8 @@ impl error::Error for Error {
         match *self {
             Error::InvalidMagic => "invalid magic",
             Error::InvalidSeparator => "invalid separator",
-            Error::InvalidKey => "invalid key",
-            Error::DuplicateKey => "duplicate key",
+            Error::InvalidKey(..) => "invalid key",
+            Error::DuplicateKey(..) => "duplicate key",
             Error::UnsignedTxHasScriptSigs => "the unsigned transaction has script sigs",
             Error::UnsignedTxHasScriptWitnesses => "the unsigned transaction has script witnesses",
             Error::MustHaveUnsignedTx => {

src/util/psbt/mod.rs

@@ -6,3 +6,26 @@
 
 mod error;
 pub use self::error::Error;
+
+pub mod raw;
+
+#[cfg(test)]
+mod tests {
+    use consensus::encode::{deserialize, serialize};
+    use util::psbt::raw;
+
+    #[test]
+    fn serialize_then_deserialize_psbtkvpair() {
+        let expected = raw::Pair {
+            key: raw::Key {
+                type_value: 0u8,
+                key: vec![42u8, 69u8],
+            },
+            value: vec![69u8, 42u8, 4u8],
+        };
+
+        let actual: raw::Pair = deserialize(&serialize(&expected)).unwrap();
+
+        assert_eq!(expected, actual);
+    }
+}

src/util/psbt/raw.rs

@@ -0,0 +1,94 @@
+//! # Raw PSBT Key-Value Pairs
+//!
+//! Raw PSBT key-value pairs as defined at
+//! https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki.
+
+use std::fmt;
+
+use consensus::encode::{Decodable, Encodable, VarInt, MAX_VEC_SIZE};
+use consensus::encode::{self, Decoder, Encoder};
+use util::psbt::Error;
+
+/// A PSBT key in its raw byte form.
+#[derive(Debug, PartialEq, Hash, Eq, Clone)]
+pub struct Key {
+    /// The type of this PSBT key.
+    pub type_value: u8,
+    /// The key itself in raw byte form.
+    pub key: Vec<u8>,
+}
+
+/// A PSBT key-value pair in its raw byte form.
+#[derive(Debug, PartialEq)]
+pub struct Pair {
+    /// The key of this key-value pair.
+    pub key: Key,
+    /// The value of this key-value pair in raw byte form.
+    pub value: Vec<u8>,
+}
+
+impl fmt::Display for Key {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use hex;
+
+        write!(f, "type: {:#x}, key: {}", self.type_value, hex::encode(&self.key))
+    }
+}
+
+impl<D: Decoder> Decodable<D> for Key {
+    fn consensus_decode(d: &mut D) -> Result<Self, encode::Error> {
+        let VarInt(byte_size): VarInt = Decodable::consensus_decode(d)?;
+
+        if byte_size == 0 {
+            return Err(Error::NoMorePairs.into());
+        }
+
+        let key_byte_size: u64 = byte_size - 1;
+
+        if key_byte_size > MAX_VEC_SIZE as u64 {
+            return Err(encode::Error::OversizedVectorAllocation { requested: key_byte_size as usize, max: MAX_VEC_SIZE } )
+        }
+
+        let type_value: u8 = Decodable::consensus_decode(d)?;
+
+        let mut key = Vec::with_capacity(key_byte_size as usize);
+        for _ in 0..key_byte_size {
+            key.push(Decodable::consensus_decode(d)?);
+        }
+
+        Ok(Key {
+            type_value: type_value,
+            key: key,
+        })
+    }
+}
+
+impl<S: Encoder> Encodable<S> for Key {
+    fn consensus_encode(&self, s: &mut S) -> Result<(), encode::Error> {
+        VarInt((self.key.len() + 1) as u64).consensus_encode(s)?;
+
+        self.type_value.consensus_encode(s)?;
+
+        for key in &self.key {
+            key.consensus_encode(s)?
+        }
+
+        Ok(())
+    }
+}
+
+impl<S: Encoder> Encodable<S> for Pair {
+    fn consensus_encode(&self, s: &mut S) -> Result<(), encode::Error> {
+        self.key.consensus_encode(s)?;
+        self.value.consensus_encode(s)
+    }
+}
+
+impl<D: Decoder> Decodable<D> for Pair {
+    fn consensus_decode(d: &mut D) -> Result<Self, encode::Error> {
+        Ok(Pair {
+            key: Decodable::consensus_decode(d)?,
+            value: Decodable::consensus_decode(d)?,
+        })
+    }
+}