From 7015b064dd62163490117dd1e24e6646b7454a71 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Wed, 22 May 2019 18:21:15 -0400
Subject: [PATCH] Add slice consensus encode/decode functions and use for short
 arrays

---
 src/consensus/encode.rs | 48 +++++++++++++++++++++++++++++++++--------
 src/util/uint.rs        |  5 ++++-
 2 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/src/consensus/encode.rs b/src/consensus/encode.rs
index de01451..7101be2 100644
--- a/src/consensus/encode.rs
+++ b/src/consensus/encode.rs
@@ -262,6 +262,9 @@ pub trait Encoder {
 
     /// Output a boolean
     fn emit_bool(&mut self, v: bool) -> Result<(), Error>;
+
+    /// Output a byte slice
+    fn emit_slice(&mut self, v: &[u8]) -> Result<(), Error>;
 }
 
 /// A simple Decoder trait
@@ -286,6 +289,9 @@ pub trait Decoder {
 
     /// Read a boolean
     fn read_bool(&mut self) -> Result<bool, Error>;
+
+    /// Read a byte slice
+    fn read_slice(&mut self, slice: &mut [u8]) -> Result<(), Error>;
 }
 
 macro_rules! encoder_fn {
@@ -326,6 +332,10 @@ impl<W: Write> Encoder for W {
     fn emit_bool(&mut self, v: bool) -> Result<(), Error> {
         self.write_i8(if v {1} else {0}).map_err(Error::Io)
     }
+    #[inline]
+    fn emit_slice(&mut self, v: &[u8]) -> Result<(), Error> {
+        self.write_all(v).map_err(Error::Io)
+    }
 }
 
 impl<R: Read> Decoder for R {
@@ -348,6 +358,10 @@ impl<R: Read> Decoder for R {
     fn read_bool(&mut self) -> Result<bool, Error> {
         Decoder::read_i8(self).map(|bit| bit != 0)
     }
+    #[inline]
+    fn read_slice(&mut self, slice: &mut [u8]) -> Result<(), Error> {
+        self.read_exact(slice).map_err(Error::Io)
+    }
 }
 
 /// Maximum size, in bytes, of a vector we are allowed to decode
@@ -491,21 +505,18 @@ impl<D: Decoder> Decodable<D> for String {
 // Arrays
 macro_rules! impl_array {
     ( $size:expr ) => (
-        impl<S: Encoder, T: Encodable<S>> Encodable<S> for [T; $size] {
+        impl<S: Encoder> Encodable<S> for [u8; $size] {
             #[inline]
             fn consensus_encode(&self, s: &mut S) -> Result<(), self::Error> {
-                for i in self.iter() { i.consensus_encode(s)?; }
-                Ok(())
+                s.emit_slice(&self[..])
             }
         }
 
-        impl<D: Decoder, T:Decodable<D> + Copy> Decodable<D> for [T; $size] {
+        impl<D: Decoder> Decodable<D> for [u8; $size] {
             #[inline]
-            fn consensus_decode(d: &mut D) -> Result<[T; $size], self::Error> {
-                // Set everything to the first decode
-                let mut ret = [Decodable::consensus_decode(d)?; $size];
-                // Set the rest
-                for item in ret.iter_mut().take($size).skip(1) { *item = Decodable::consensus_decode(d)?; }
+            fn consensus_decode(d: &mut D) -> Result<[u8; $size], self::Error> {
+                let mut ret = [0; $size];
+                d.read_slice(&mut ret)?;
                 Ok(ret)
             }
         }
@@ -520,6 +531,25 @@ impl_array!(16);
 impl_array!(32);
 impl_array!(33);
 
+impl<D: Decoder> Decodable<D> for [u16; 8] {
+    #[inline]
+    fn consensus_decode(d: &mut D) -> Result<[u16; 8], self::Error> {
+        let mut res = [0; 8];
+        for i in 0..8 {
+            res[i] = Decodable::consensus_decode(d)?;
+        }
+        Ok(res)
+    }
+}
+
+impl<S: Encoder> Encodable<S> for [u16; 8] {
+    #[inline]
+    fn consensus_encode(&self, s: &mut S) -> Result<(), self::Error> {
+        for c in self.iter() { c.consensus_encode(s)?; }
+        Ok(())
+    }
+}
+
 impl<S: Encoder, T: Encodable<S>> Encodable<S> for [T] {
     #[inline]
     fn consensus_encode(&self, s: &mut S) -> Result<(), self::Error> {
diff --git a/src/util/uint.rs b/src/util/uint.rs
index 6a0c9f6..05d4a95 100644
--- a/src/util/uint.rs
+++ b/src/util/uint.rs
@@ -348,7 +348,10 @@ macro_rules! construct_uint {
         impl<D: ::consensus::encode::Decoder> ::consensus::encode::Decodable<D> for $name {
             fn consensus_decode(d: &mut D) -> Result<$name, encode::Error> {
                 use consensus::encode::Decodable;
-                let ret: [u64; $n_words] = Decodable::consensus_decode(d)?;
+                let mut ret: [u64; $n_words] = [0; $n_words];
+                for i in 0..$n_words {
+                    ret[i] = Decodable::consensus_decode(d)?;
+                }
                 Ok($name(ret))
             }
         }