Make from_be_slice() enforce the length and return a Result

src/util/uint.rs

@@ -93,12 +93,20 @@ macro_rules! construct_uint {
             /// Creates big integer value from a byte array using
             /// big-endian encoding
             pub fn from_be_bytes(bytes: [u8; $n_words * 8]) -> $name {
-                Self::from_be_slice(&bytes)
+                Self::_from_be_slice(&bytes)
             }
 
             /// Creates big integer value from a byte slice using
             /// big-endian encoding
-            pub fn from_be_slice(bytes: &[u8]) -> $name {
+            pub fn from_be_slice(bytes: &[u8]) -> Result<$name, Error> {
+                if bytes.len() != $n_words * 8 {
+                    Err(Error::InvalidLength(bytes.len(), $n_words*8))
+                } else {
+                    Ok(Self::_from_be_slice(bytes))
+                }
+            }
+
+            fn _from_be_slice(bytes: &[u8]) -> $name {
                 use super::endian::slice_to_u64_be;
                 let mut slice = [0u64; $n_words];
                 slice.iter_mut()
@@ -454,11 +462,8 @@ macro_rules! construct_uint {
                     {
                         let bytes = Vec::from_hex(s)
                             .map_err(|_| de::Error::invalid_value(de::Unexpected::Str(s), &self))?;
-                        if bytes.len() != $n_words * 8 {
-                            Err(de::Error::invalid_length(bytes.len() * 2, &self))
-                        } else {
-                            Ok($name::from_be_slice(&bytes[..]))
-                        }
+                        $name::from_be_slice(&bytes[..])
+                            .map_err(|_| de::Error::invalid_length(bytes.len() * 2, &self))
                     }
                 }
                 deserializer.deserialize_str(Visitor)
@@ -470,6 +475,13 @@ macro_rules! construct_uint {
 construct_uint!(Uint256, 4);
 construct_uint!(Uint128, 2);
 
+/// Uint error
+#[derive(Debug)]
+pub enum Error {
+    /// Invalid slice length
+    InvalidLength(usize, usize), // (expected, actual)
+}
+
 impl Uint256 {
     /// Increment by 1
     #[inline]