add function to parse list of signatures buffers into proper list of TransactionSignature objects

lib/transaction/input/multisig.js

@@ -2,6 +2,7 @@
 
 var _ = require('lodash');
 var inherits = require('inherits');
+var Transaction = require('../transaction');
 var Input = require('./input');
 var Output = require('../output');
 var $ = require('../../util/preconditions');
@@ -152,6 +153,53 @@ MultiSigInput.prototype.isValidSignature = function(transaction, signature) {
   );
 };
 
+/**
+ *
+ * @param {Buffer[]} signatures
+ * @param {PublicKey[]} publicKeys
+ * @param {Transaction} transaction
+ * @param {Integer} inputIndex
+ * @param {Input} input
+ * @returns {TransactionSignature[]}
+ */
+MultiSigInput.normalizeSignatures = function(transaction, input, inputIndex, signatures, publicKeys) {
+  return publicKeys.map(function (pubKey) {
+    var signatureMatch = null;
+    signatures = signatures.filter(function (signatureBuffer) {
+      if (signatureMatch) {
+        return true;
+      }
+
+      var signature = new TransactionSignature({
+        signature: Signature.fromTxFormat(signatureBuffer),
+        publicKey: pubKey,
+        prevTxId: input.prevTxId,
+        outputIndex: input.outputIndex,
+        inputIndex: inputIndex,
+        sigtype: Signature.SIGHASH_ALL
+      });
+
+      signature.signature.nhashtype = signature.sigtype;
+      var isMatch = Sighash.verify(
+          transaction,
+          signature.signature,
+          signature.publicKey,
+          signature.inputIndex,
+          input.output.script
+      );
+
+      if (isMatch) {
+        signatureMatch = signature;
+        return false;
+      }
+
+      return true;
+    });
+
+    return signatureMatch ? signatureMatch : null;
+  });
+};
+
 MultiSigInput.OPCODES_SIZE = 7; // serialized size (<=3) + 0 .. N .. M OP_CHECKMULTISIG
 MultiSigInput.SIGNATURE_SIZE = 74; // size (1) + DER (<=72) + sighash (1)
 MultiSigInput.PUBKEY_SIZE = 34; // size (1) + DER (<=33)