buffer: implement `iterable` interface

This makes possible to use `for..of` loop with
buffers. Also related `keys`, `values` and `entries`
methods are added for feature parity with `Uint8Array`.

PR-URL: https://github.com/iojs/io.js/pull/525
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 77 insertions, 0 deletions

diff --git a/lib/buffer.js b/lib/buffer.js
index dbc5d5f56..4c87726d5 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -930,3 +930,80 @@ Buffer.prototype.writeDoubleBE = function writeDoubleBE(val, offset, noAssert) {
   internal.writeDoubleBE(this, val, offset);
   return offset + 8;
 };
+
+// ES6 iterator
+
+var ITERATOR_KIND_KEYS = 1;
+var ITERATOR_KIND_ENTRIES = 3;
+
+function BufferIteratorResult(value, done) {
+  this.value = value;
+  this.done = done;
+}
+
+var resultCache = new Array(256);
+
+for (var i = 0; i < 256; i++)
+  resultCache[i] = Object.freeze(new BufferIteratorResult(i, false));
+
+var finalResult = Object.freeze(new BufferIteratorResult(undefined, true));
+
+function BufferIterator(buffer, kind) {
+  this._buffer = buffer;
+  this._kind = kind;
+  this._index = 0;
+}
+
+BufferIterator.prototype.next = function() {
+  var buffer = this._buffer;
+  var kind = this._kind;
+  var index = this._index;
+
+  if (index >= buffer.length)
+    return finalResult;
+
+  this._index++;
+
+  if (kind === ITERATOR_KIND_ENTRIES)
+    return new BufferIteratorResult([index, buffer[index]], false);
+
+  return new BufferIteratorResult(index, false);
+};
+
+function BufferValueIterator(buffer) {
+  BufferIterator.call(this, buffer, null);
+}
+
+BufferValueIterator.prototype.next = function() {
+  var buffer = this._buffer;
+  var index = this._index;
+
+  if (index >= buffer.length)
+    return finalResult;
+
+  this._index++;
+
+  return resultCache[buffer[index]];
+};
+
+
+BufferIterator.prototype[Symbol.iterator] = function() {
+  return this;
+};
+
+BufferValueIterator.prototype[Symbol.iterator] =
+    BufferIterator.prototype[Symbol.iterator];
+
+Buffer.prototype.keys = function() {
+  return new BufferIterator(this, ITERATOR_KIND_KEYS);
+};
+
+Buffer.prototype.entries = function() {
+  return new BufferIterator(this, ITERATOR_KIND_ENTRIES);
+};
+
+Buffer.prototype.values = function() {
+  return new BufferValueIterator(this);
+};
+
+Buffer.prototype[Symbol.iterator] = Buffer.prototype.values;