From 45f1ef8adaf7d3b44e0f64121ed643dd3df6c74b Mon Sep 17 00:00:00 2001
From: Jared Wasinger <j-wasinger@hotmail.com>
Date: Mon, 30 Jul 2018 14:17:53 -0700
Subject: [PATCH] add EXTCODEHASH opcode implementation

add EXTCODEHASH rules for nonexistent accounts and precompiles

.

Replace removed state manager method

Fix lint
---
 lib/opFns.js   | 24 ++++++++++++++++++++++++
 lib/opcodes.js |  1 +
 2 files changed, 25 insertions(+)

diff --git a/lib/opFns.js b/lib/opFns.js
index cdef721e20..df6a88c21b 100644
--- a/lib/opFns.js
+++ b/lib/opFns.js
@@ -288,6 +288,30 @@ module.exports = {
       cb(null)
     })
   },
+  EXTCODEHASH: function (address, runState, cb) {
+    if (!runState._common.gteHardfork('constantinople')) {
+      trap(ERROR.INVALID_OPCODE)
+    }
+    var stateManager = runState.stateManager
+    address = addressToBuffer(address)
+
+    stateManager.getAccount(address, function (err, account) {
+      if (err) return cb(err)
+
+      if (account.isEmpty()) {
+        return cb(null, new BN(0))
+      }
+
+      stateManager.getContractCode(address, function (err, code) {
+        if (err) return cb(err)
+        if (code.length === 0) {
+          return cb(null, new BN(utils.KECCAK256_NULL))
+        }
+
+        return cb(null, new BN(utils.keccak256(code)))
+      })
+    })
+  },
   RETURNDATASIZE: function (runState) {
     return new BN(runState.lastReturned.length)
   },
diff --git a/lib/opcodes.js b/lib/opcodes.js
index bc23ce977e..6093e269f0 100644
--- a/lib/opcodes.js
+++ b/lib/opcodes.js
@@ -49,6 +49,7 @@ const codes = {
   0x3c: ['EXTCODECOPY', 700, 4, 0, true, true],
   0x3d: ['RETURNDATASIZE', 2, 0, 1, true],
   0x3e: ['RETURNDATACOPY', 3, 3, 0, true],
+  0x3f: ['EXTCODEHASH', 400, 1, 1, true, true],
 
   // '0x40' range - block operations
   0x40: ['BLOCKHASH', 20, 1, 1, true, true],