Merge rust-bitcoin/rust-bitcoin#1250: Simplify `PublicKey` serialization code

b9a512330a Simplify `PublicKey` serialization code (Martin Habovstiak)

Pull request description:

  There were a bunch of `if self.serialized` expressions repeated in the code. This change simplifies it by putting the `if` in a function that calls a closure with a slice containing the serialized bytes.

ACKs for top commit:
  apoelstra:
    ACK b9a512330a
  sanket1729:
    utACK b9a512330a. I don't have strong preferences on naming. `serialize_and_call` sounds better because so far I have only seen `with_*` used with constructors.
  tcharding:
    ACK b9a512330a

Tree-SHA512: 5d90a73f87fa36bd45a5765542ec24994d601d32ad6529fff5d5140ded2b86eb40e00bfba4955e94d2c468983e3e7683ca5f8ece7a205d9b9944334a19b06015

src/util/key.rs

@@ -109,13 +109,17 @@ impl PublicKey {
         }
     }
 
+    fn with_serialized<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
+        if self.compressed {
+            f(&self.inner.serialize())
+        } else {
+            f(&self.inner.serialize_uncompressed())
+        }
+    }
+
     /// Returns bitcoin 160-bit hash of the public key
     pub fn pubkey_hash(&self) -> PubkeyHash {
-        if self.compressed {
+        self.with_serialized(PubkeyHash::hash)
-            PubkeyHash::hash(&self.inner.serialize())
-        } else {
-            PubkeyHash::hash(&self.inner.serialize_uncompressed())
-        }
     }
 
     /// Returns bitcoin 160-bit hash of the public key for witness program
@@ -133,11 +137,7 @@ impl PublicKey {
 
     /// Write the public key into a writer
     pub fn write_into<W: io::Write>(&self, mut writer: W) -> Result<(), io::Error> {
-        if self.compressed {
+        self.with_serialized(|bytes| writer.write_all(bytes))
-            writer.write_all(&self.inner.serialize())
-        } else {
-            writer.write_all(&self.inner.serialize_uncompressed())
-        }
     }
 
     /// Read the public key from a reader
@@ -272,16 +272,13 @@ pub struct SortKey(u8, [u8; 32], [u8; 32]);
 
 impl fmt::Display for PublicKey {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        if self.compressed {
+        // TODO: fast hex encoding
-            for ch in &self.inner.serialize()[..] {
+        self.with_serialized(|bytes| {
+            for ch in bytes {
                 write!(f, "{:02x}", ch)?;
             }
-        } else {
-            for ch in &self.inner.serialize_uncompressed()[..] {
-                write!(f, "{:02x}", ch)?;
-            }
-        }
             Ok(())
+        })
     }
 }
 
@@ -485,11 +482,7 @@ impl serde::Serialize for PublicKey {
         if s.is_human_readable() {
             s.collect_str(self)
         } else {
-            if self.compressed {
+            self.with_serialized(|bytes| s.serialize_bytes(bytes))
-                s.serialize_bytes(&self.inner.serialize()[..])
-            } else {
-                s.serialize_bytes(&self.inner.serialize_uncompressed()[..])
-            }
         }
     }
 }