Use charSet bytesNeeded

dingosky · dingosky · commit 1a5945c0e595 · 2017-08-18T13:31:43.000-07:00
diff --git a/lib/random.js b/lib/random.js
@@ -5,6 +5,8 @@ import WeakMap from 'weak-map'
 
 const propMap = new WeakMap()
 
+const BITS_PER_BYTE = 8
+
 export default class {
   constructor(arg) {
     let charSet
@@ -31,19 +33,21 @@ export default class {
   }
 
   string(entropyBits, charSet = propMap.get(this).charSet) {
-    return this.stringWithBytes(entropyBits, _cryptoBytes(entropyBits, charSet), charSet)
+    let bytesNeeded = charSet.bytesNeeded(entropyBits)
+    return this.stringWithBytes(entropyBits, _cryptoBytes(bytesNeeded), charSet)
   }
 
-  stringRandom (entropyBits, charSet = propMap.get(this).charSet) {
-    return this.stringWithBytes(entropyBits, _randomBytes(entropyBits, charSet), charSet)
+  stringRandom(entropyBits, charSet = propMap.get(this).charSet) {
+    let bytesNeeded = charSet.bytesNeeded(entropyBits)
+    return this.stringWithBytes(entropyBits, _randomBytes(bytesNeeded), charSet)
   }
 
   stringWithBytes(entropyBits,  bytes, charSet = propMap.get(this).charSet) {
     return _stringWithBytes(entropyBits, bytes, charSet)
   }
 
   bytesNeeded(entropyBits, charSet = propMap.get(this).charSet) {
-    return _bytesNeeded(entropyBits, charSet)
+    return charSet.bytesNeeded(entropyBits)
   }
 
   chars() {
@@ -63,16 +67,14 @@ export default class {
   }
 }
 
-const _bitsPerByte = 8
-
 const _stringWithBytes = (entropyBits,  bytes, charSet) => {
   if (entropyBits <= 0) { return '' }
 
   const bitsPerChar = charSet.getBitsPerChar()
   const count = Math.ceil(entropyBits / bitsPerChar)
   if (count <= 0) { return '' }
 
-  const needed = Math.ceil(count * (bitsPerChar / _bitsPerByte))
+  const needed = Math.ceil(count * (bitsPerChar / BITS_PER_BYTE))
   if (bytes.length < needed) {
     throw new Error('Insufficient bytes: need ' + needed + ' and got ' + bytes.length)
   }
@@ -98,32 +100,23 @@ const _stringWithBytes = (entropyBits,  bytes, charSet) => {
   return string
 }
 
-const _bytesNeeded = (entropyBits, charSet) => {
-  const bitsPerChar = charSet.getBitsPerChar()
-  const count = Math.ceil(entropyBits / bitsPerChar)
-  if (count <= 0) { return 0 }
-  
-  const bytesPerSlice = bitsPerChar / _bitsPerByte
-  return Math.ceil(count * bytesPerSlice)
-}
-
-const _cryptoBytes = (entropyBits, charSet) => {
+const _cryptoBytes = (bytesNeeded) => {
   const crypto = require('crypto')
-  return Buffer.from(crypto.randomBytes(_bytesNeeded(entropyBits, charSet)))
+  return Buffer.from(crypto.randomBytes(bytesNeeded))
 }
 
-const _randomBytes = (entropyBits, charSet) => {
-  const byteCount = _bytesNeeded(entropyBits, charSet)
-  const randCount = Math.ceil(byteCount / 6)
+const _randomBytes = (bytesNeeded) => {
+  let BYTES_USED_PER_RANDOM_CALL = 6
+  const randCount = Math.ceil(bytesNeeded / BYTES_USED_PER_RANDOM_CALL)
 
-  const buffer = new Buffer(byteCount)
-  var dataView = new DataView(new ArrayBuffer(_bitsPerByte))
+  const buffer = new Buffer(bytesNeeded)
+  var dataView = new DataView(new ArrayBuffer(BITS_PER_BYTE))
   for (let rNum = 0; rNum < randCount; rNum++) {
     dataView.setFloat64(0, Math.random())
-    for (let n = 0; n < 6; n++) {
+    for (let n = 0; n < BYTES_USED_PER_RANDOM_CALL; n++) {
       let fByteNum = _endianByteNum[n]
-      let bByteNum = 6*rNum + n
-      if (bByteNum < byteCount) {
+      let bByteNum = rNum*BYTES_USED_PER_RANDOM_CALL + n
+      if (bByteNum < bytesNeeded) {
         buffer[bByteNum] = dataView.getUint8(fByteNum)
       }
     }
