get-signature-count needed to measure txs with many inputs or outputs

lib/script/script.js

@@ -838,4 +838,43 @@ Script.prototype.checkMinimalPush = function(i) {
   return true;
 };
 
+/**
+ * Comes from bitcoind's script DecodOP_N function
+ * @param {number} opcode
+ * @returns {number} numeric value in range of -1 to 16
+ */
+Script.prototype._decodeOP_N = function(opcode) {
+  if (opcode === Opcode.OP_0)
+    return 0;
+  else if (opcode >= Opcode.OP_1 && opcode <= Opcode.OP_16)
+    return opcode - (Opcode.OP_1 - 1);
+  else
+    throw new Error('Invalid opcode: ' + JSON.stringify(opcode));
+};
+
+/**
+ * Comes from bitcoind's script GetSigOpCount(boolean) function
+ * @param {boolean} use current (true) or pre-version-0.6 (false) logic
+ * @returns {number} number of signature operations required by this script
+ */
+Script.prototype.getSignatureOperationsCount = function(fAccurate) {
+  var self = this;
+  var n = 0;
+  var lastOpcode = Opcode.OP_INVALIDOPCODE;
+  _.each(self.chunks, function getChunkOther(chunk) {
+    var opcode = chunk.opcodenum;
+    if (opcode == Opcode.OP_CHECKSIG || opcode == Opcode.OP_CHECKSIGVERIFY)
+      n++;
+    else if (opcode == Opcode.OP_CHECKMULTISIG ||
+      opcode == Opcode.OP_CHECKMULTISIGVERIFY) {
+      if (fAccurate && lastOpcode >= Opcode.OP_1 && lastOpcode <= Opcode.OP_16)
+        n += self._decodeOP_N(lastOpcode);
+      else
+        n += 20;
+    }
+    lastOpcode = opcode;
+  });
+  return n;
+};
+
 module.exports = Script;

test/script/script.js

@@ -775,5 +775,38 @@ describe('Script', function() {
     });
   });
 
-
+  describe('#getSignatureOperationsCount', function() {
+    // comes from bitcoind src/test/sigopcount_tests
+    // only test calls to function with boolean param, not signature ref param
+    it('should match bitcoind behavior', function() {
+      Script().getSignatureOperationsCount(false).should.equal(0);
+      Script().getSignatureOperationsCount(true).should.equal(0);
+      var s1 = 'OP_1 01 FF OP_2 OP_CHECKMULTISIG';
+      Script(s1).getSignatureOperationsCount(true).should.equal(2);
+      s1 += ' OP_IF OP_CHECKSIG OP_ENDIF';
+      Script(s1).getSignatureOperationsCount(true).should.equal(3);
+      Script(s1).getSignatureOperationsCount(false).should.equal(21);
+
+      // do not test BOOST_CHECK_EQUAL(p2sh.GetSigOpCount(scriptSig), 3U);
+
+      var pubkey_hexs = [
+        '022df8750480ad5b26950b25c7ba79d3e37d75f640f8e5d9bcd5b150a0f85014da',
+        '03e3818b65bcc73a7d64064106a859cc1a5a728c4345ff0b641209fba0d90de6e9',
+        '021f2f6e1e50cb6a953935c3601284925decd3fd21bc445712576873fb8c6ebc18',
+      ];
+      var sortkeys = pubkey_hexs.slice(0, 3).map(PublicKey);
+      var s2 = Script.buildMultisigOut(sortkeys, 1);
+      Script(s2).getSignatureOperationsCount(true).should.equal(3);
+      Script(s2).getSignatureOperationsCount(false).should.equal(20);
+
+      // create a bogus, well-formed signature
+      var signature = bitcore.crypto.Signature.fromString('30060201FF0201FF');
+      var signatures = [ signature.toBuffer() ];
+      var p2sh = Script.buildP2SHMultisigIn(pubkey_hexs, 1, signatures, {});
+      p2sh.getSignatureOperationsCount(true).should.equal(0);
+      p2sh.getSignatureOperationsCount(false).should.equal(0);
+
+      // do not test BOOST_CHECK_EQUAL(p2sh.GetSigOpCount(scriptSig2), 3U);
+    });
+  });
 });