Merge pull request #850 from ethereumjs/memory-as-buffer

Make `memory.ts` use Buffers instead of Arrays

packages/vm/lib/evm/interpreter.ts

@@ -42,7 +42,7 @@ export interface InterpreterStep {
   pc: number
   depth: number
   address: Buffer
-  memory: number[]
+  memory: Buffer
   memoryWordCount: BN
   opcode: {
     name: string

packages/vm/lib/evm/memory.ts

@@ -5,10 +5,10 @@ import * as assert from 'assert'
  * for the ethereum virtual machine.
  */
 export default class Memory {
-  _store: number[]
+  _store: Buffer
 
   constructor() {
-    this._store = []
+    this._store = Buffer.alloc(0)
   }
 
   /**
@@ -23,7 +23,7 @@ export default class Memory {
     const newSize = ceil(offset + size, 32)
     const sizeDiff = newSize - this._store.length
     if (sizeDiff > 0) {
-      this._store = this._store.concat(new Array(sizeDiff).fill(0))
+      this._store = Buffer.concat([this._store, Buffer.alloc(sizeDiff)])
     }
   }
 

packages/vm/tests/api/evm/memory.js

@@ -10,7 +10,7 @@ tape('Memory', t => {
   })
 
   t.test('should return zeros from empty memory', st => {
-    st.deepEqual(m.read(0, 3), Buffer.from([0, 0, 0]))
+    st.ok(m.read(0, 3).equals(Buffer.from([0, 0, 0])))
     st.end()
   })
 
@@ -21,7 +21,7 @@ tape('Memory', t => {
   })
 
   t.test('should return zeros before writing', st => {
-    st.deepEqual(m.read(0, 2), Buffer.from([0, 0]))
+    st.ok(m.read(0, 2).equals(Buffer.from([0, 0])))
     st.end()
   })
 
@@ -32,7 +32,7 @@ tape('Memory', t => {
 
   t.test('should write value', st => {
     m.write(29, 3, Buffer.from([1, 2, 3]))
-    st.deepEqual(m.read(29, 5), Buffer.from([1, 2, 3, 0, 0]))
+    st.ok(m.read(29, 5).equals(Buffer.from([1, 2, 3, 0, 0])))
     st.end()
   })