Add is_standard_op_return

bitcoin/src/blockdata/script/borrowed.rs

@@ -349,7 +349,10 @@ impl Script {
             && self.0[1] == OP_PUSHBYTES_32.to_u8()
     }
 
-    /// Check if this is an OP_RETURN output.
+    /// Check if this is a consensus-valid OP_RETURN output.
+    ///
+    /// To validate if the OP_RETURN obeys Bitcoin Core's current standardness policy, use
+    /// [`is_standard_op_return()`](Self::is_standard_op_return) instead.
     #[inline]
     pub fn is_op_return(&self) -> bool {
         match self.0.first() {
@@ -358,6 +361,15 @@ impl Script {
         }
     }
 
+    /// Check if this is an OP_RETURN that obeys Bitcoin Core standardness policy.
+    ///
+    /// What this function considers to be standard may change without warning pending Bitcoin Core
+    /// changes.
+    #[inline]
+    pub fn is_standard_op_return(&self) -> bool {
+        self.is_op_return() && self.0.len() <= 80
+    }
+
     /// Checks whether a script is trivially known to have no satisfying input.
     ///
     /// This method has potentially confusing semantics and an unclear purpose, so it's going to be

bitcoin/src/blockdata/script/tests.rs

@@ -406,6 +406,20 @@ fn op_return_test() {
     assert!(!ScriptBuf::from_hex("").unwrap().is_op_return());
 }
 
+#[test]
+fn standard_op_return_test() {
+    assert!(ScriptBuf::from_hex("6aa9149eb21980dc9d413d8eac27314938b9da920ee53e87")
+        .unwrap()
+        .is_standard_op_return());
+    assert!(ScriptBuf::from_hex("6a48656c6c6f2c2074686973206973206d7920666972737420636f6e747269627574696f6e20746f207275737420626974636f696e2e20506c6561736520617070726f7665206d79205052206672656e")
+        .unwrap()
+        .is_standard_op_return());
+
+    assert!(!ScriptBuf::from_hex("6a48656c6c6f2c2074686973206973206d7920666972737420636f6e747269627574696f6e20746f207275737420626974636f696e2e20506c6561736520617070726f7665206d79205052206672656e21")
+        .unwrap()
+        .is_standard_op_return());
+}
+
 #[test]
 fn multisig() {
     // First multisig? 1-of-2