add Script#isPushOnly()

lib/script.js

@@ -1,16 +1,15 @@
 'use strict';
 
-var _ = require('lodash');
-var bu = require('./util/buffer');
-
 var Address = require('./address');
 var BufferReader = require('./encoding/bufferreader');
 var BufferWriter = require('./encoding/bufferwriter');
-var Errors = require('./errors');
 var Hash = require('./crypto/hash');
 var Opcode = require('./opcode');
 var PublicKey = require('./publickey');
 var PublicKey = require('./publickey');
+var Hash = require('./crypto/hash');
+var bu = require('./util/buffer');
+var _ = require('lodash');
 
 /**
  * A bitcoin transaction script. Each transaction's inputs and outputs
@@ -304,6 +303,17 @@ Script.prototype.isDataOut = function() {
         this.chunks[1].length === this.chunks.len)));
 };
 
+/**
+ * @returns true if the script is only composed of data pushing
+ * opcodes or small int opcodes (OP_0, OP_1, ..., OP_16)
+ */
+Script.prototype.isPushOnly = function() {
+  return _.every(this.chunks, function(chunk) {
+    var opcodenum = chunk.opcodenum;
+    return !_.isUndefined(opcodenum) || chunk <= Opcode.map.OP_16;
+  });
+};
+
 
 Script.types = {};
 Script.types.UNKNOWN = 'Unknown';
@@ -453,7 +463,7 @@ Script.prototype.removeCodeseparators = function() {
  * @returns a new Multisig output script for given public keys,
  * requiring m of those public keys to spend
  * @param {PublicKey[]} pubkeys - list of all public keys controlling the output
- * @param {number} m - amount of required signatures to spend the output 
+ * @param {number} m - amount of required signatures to spend the output
  */
 Script.buildMultisigOut = function(pubkeys, m) {
   var s = new Script();
@@ -513,7 +523,7 @@ Script.buildDataOut = function(data) {
 };
 
 /**
- * @param {Script} script - the redeemScript for the new p2sh output 
+ * @param {Script} script - the redeemScript for the new p2sh output
  * @returns Script new pay to script hash script for given script
  */
 Script.buildScriptHashOut = function(script) {

test/script.js

@@ -301,6 +301,17 @@ describe('Script', function() {
     });
   });
 
+  describe('#isPushOnly', function() {
+    it('should know these scripts are or aren\'t push only', function() {
+      Script('OP_NOP 1 0x01').isPushOnly().should.equal(false);
+      Script('OP_0').isPushOnly().should.equal(true);
+      Script('OP_0 OP_RETURN').isPushOnly().should.equal(false);
+      Script('OP_PUSHDATA1 5 0x1010101010').isPushOnly().should.equal(true);
+      // like bitcoind, we regard OP_RESERVED as being "push only"
+      Script('OP_RESERVED').isPushOnly().should.equal(true);
+    });
+  });
+
   describe('#classify', function() {
     it('should classify public key hash out', function() {
       Script('OP_DUP OP_HASH160 20 0000000000000000000000000000000000000000 OP_EQUALVERIFY OP_CHECKSIG').classify().should.equal(Script.types.PUBKEYHASH_OUT);