Improve documentation around EcdsaSig

Improve the rustdocs for serialization methods of the `EcdsaSig` type.

Author: tcharding

src/util/ecdsa.rs

@@ -35,15 +35,15 @@ pub struct EcdsaSig {
 }
 
 impl EcdsaSig {
-    /// Constructs ECDSA bitcoin signature for [`EcdsaSighashType::All`]
+    /// Constructs an ECDSA bitcoin signature for [`EcdsaSighashType::All`].
     pub fn sighash_all(sig: secp256k1::ecdsa::Signature) -> EcdsaSig {
         EcdsaSig {
             sig,
             hash_ty: EcdsaSighashType::All
         }
     }
 
-    /// Deserialize from slice following the standardness rules for [`EcdsaSighashType`]
+    /// Deserializes from slice following the standardness rules for [`EcdsaSighashType`].
     pub fn from_slice(sl: &[u8]) -> Result<Self, EcdsaSigError> {
         let (hash_ty, sig) = sl.split_last()
             .ok_or(EcdsaSigError::EmptySignature)?;
@@ -54,7 +54,7 @@ impl EcdsaSig {
         Ok(EcdsaSig { sig, hash_ty })
     }
 
-    /// Serialize EcdsaSig
+    /// Serializes an ECDSA signature (inner secp256k1 signature in DER format).
     pub fn to_vec(&self) -> Vec<u8> {
         // TODO: add support to serialize to a writer to SerializedSig
         self.sig.serialize_der()