Merge #327: Implement MiniscriptKey for secp256k1 PublicKey

0888fe9 Implement MiniscriptKey for secp256k1 PublicKey (Dr Maxim Orlovsky)

Pull request description:

  Closes #326

ACKs for top commit:
  apoelstra:
    ACK 0888fe9
  sanket1729:
    ACK 0888fe9

Tree-SHA512: daeb500907426cef5a6add1ebc94ad77cd3216b5497abd0f2eca2726b02579678c2691e677cc8e2cbf6e5d208009a001dac04acc9ab08e82faa3e00efc64f317

Author: sanket1729

src/lib.rs

@@ -116,6 +116,7 @@ pub mod psbt;
 
 mod util;
 
+use std::io::Write;
 use std::str::FromStr;
 use std::{error, fmt, hash, str};
 
@@ -155,6 +156,23 @@ pub trait MiniscriptKey: Clone + Eq + Ord + fmt::Debug + fmt::Display + hash::Ha
     fn to_pubkeyhash(&self) -> Self::Hash;
 }
 
+impl MiniscriptKey for bitcoin::secp256k1::PublicKey {
+    /// `is_uncompressed` always returns `false`
+    fn is_uncompressed(&self) -> bool {
+        false
+    }
+
+    type Hash = hash160::Hash;
+
+    fn to_pubkeyhash(&self) -> Self::Hash {
+        let mut engine = hash160::Hash::engine();
+        engine
+            .write_all(&self.serialize())
+            .expect("engines don't error");
+        hash160::Hash::from_engine(engine)
+    }
+}
+
 impl MiniscriptKey for bitcoin::PublicKey {
     /// `is_uncompressed` returns true only for
     /// bitcoin::Publickey type if the underlying key is uncompressed.