From 435932a760b95fd37bf07a3da46421a6cace0608 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Tue, 5 Jan 2016 20:40:36 +0000
Subject: [PATCH] Introduce isPrecompiled()

---
 README.md     |  7 +++++++
 index.js      | 12 +++++++++++-
 test/index.js | 14 ++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 8a5287c..4007586 100644
--- a/README.md
+++ b/README.md
@@ -126,6 +126,13 @@ Generates an address of a newly created contract. Don't forget to increment the
 
 **Return:** `Buffer`
 
+### `isPrecompiled(address)`
+**Parameters**
+- `address` - the address to check (`Buffer` or `String`)
+Return true if the supplied address belongs to a precompiled account
+
+**Return:** `Boolean`
+
 ### `sha3(a, bytes)`
 Returns a sha3 of `a` of the length of `bytes`  
 **Parameters**
diff --git a/index.js b/index.js
index b530794..e5273d5 100644
--- a/index.js
+++ b/index.js
@@ -292,6 +292,16 @@ exports.generateAddress = function (from, nonce) {
   return hash.slice(12)
 }
 
+/**
+ * Returns true if the supplied address belongs to a precompiled account
+ * @method isPrecompiled
+ * @param {Buffer|String}
+ */
+exports.isPrecompiled = function (address) {
+  var a = exports.unpad(address)
+  return a.length === 1 && a[0] > 0 && a[0] < 5
+}
+
 // Returns a Boolean on whether or not the a sting starts with 0x
 exports.isHexPrefixed = function (str) {
   return str.slice(0, 2) === '0x'
@@ -317,7 +327,7 @@ exports.addHexPrefix = function (str) {
 /**
  * defines properties on a `Object`
  * @method defineProperties
- * @para[M`Êm {Object} self the `Object` to define properties on
+ * @param {Object} self the `Object` to define properties on
  * @param {Array} fields an array fields to define
  */
 exports.defineProperties = function (self, fields, data) {
diff --git a/test/index.js b/test/index.js
index dc711d4..05b511f 100644
--- a/test/index.js
+++ b/test/index.js
@@ -204,3 +204,17 @@ describe('hex prefix', function () {
     assert.equal(ethUtils.addHexPrefix(string), '0x' + string)
   })
 })
+
+describe('isPrecompiled', function() {
+  it('should return true', function () {
+    assert.equal(ethUtils.isPrecompiled('0000000000000000000000000000000000000001'), true)
+    assert.equal(ethUtils.isPrecompiled('0000000000000000000000000000000000000002'), true)
+    assert.equal(ethUtils.isPrecompiled('0000000000000000000000000000000000000003'), true)
+    assert.equal(ethUtils.isPrecompiled('0000000000000000000000000000000000000004'), true)
+  })
+  it('should return false', function () {
+    assert.equal(ethUtils.isPrecompiled('0000000000000000000000000000000000000000'), false)
+    assert.equal(ethUtils.isPrecompiled('0000000000000000000000000000000000000005'), false)
+    assert.equal(ethUtils.isPrecompiled('1000000000000000000000000000000000000000'), false)
+  })
+})