Transaction: add isCoinbaseHash static method

src/transaction.js

@@ -85,6 +85,12 @@ Transaction.fromHex = function(hex) {
   return Transaction.fromBuffer(new Buffer(hex, 'hex'))
 }
 
+Transaction.isCoinbaseHash = function(buffer) {
+  return Array.prototype.every.call(buffer, function(x) {
+    return x === 0
+  })
+}
+
 /**
  * Create a new txIn.
  *

src/transaction_builder.js

@@ -7,12 +7,6 @@ var ECSignature = require('./ecsignature')
 var Script = require('./script')
 var Transaction = require('./transaction')
 
-function isCoinbase(txHash) {
-  return Array.prototype.every.call(txHash, function(x) {
-    return x === 0
-  })
-}
-
 function extractInput(txIn) {
   var redeemScript
   var scriptSig = txIn.script
@@ -116,7 +110,7 @@ TransactionBuilder.fromTransaction = function(transaction) {
   // Extract/add signatures
   txb.inputs = transaction.ins.map(function(txIn) {
     // TODO: remove me after testcase added
-    assert(!isCoinbase(txIn.hash), 'coinbase inputs not supported')
+    assert(!Transaction.isCoinbaseHash(txIn.hash), 'coinbase inputs not supported')
 
     // Ignore empty scripts
     if (txIn.script.buffer.length === 0) return