make IE10 use the Object implementation

IE10 has a broken `TypedArray.prototype.subarray` function which
returns arrays of incorrect length in some situations.

diff --git a/index.js b/index.js
index 73516cde6b45ccb17923a7107e304e2aaf07039d..0d0d6388bed633e238cdbe3bdedb6548b560523d 100644 (file)
--- a/index.js
+++ b/index.js
@@ -14,22 +14,35 @@ exports.INSPECT_MAX_BYTES = 50
 Buffer.poolSize = 8192
 
 /**
- * If `Buffer._useTypedArrays`:
+ * If `TYPED_ARRAY_SUPPORT`:
  *   === true    Use Uint8Array implementation (fastest)
- *   === false   Use Object implementation (compatible down to IE6)
+ *   === false   Use Object implementation (most compatible, even IE6)
+ *
+ * Browsers that support typed arrays are IE 10+, Firefox 4+, Chrome 7+, Safari 5.1+,
+ * Opera 11.6+, iOS 4.2+.
+ *
+ * Note:
+ *
+ * - Implementation must support adding new properties to `Uint8Array` instances.
+ *   Firefox 4-29 lacked support, fixed in Firefox 30+.
+ *   See: https://bugzilla.mozilla.org/show_bug.cgi?id=695438.
+ *
+ *  - Chrome 9-10 is missing the `TypedArray.prototype.subarray` function.
+ *
+ *  - IE10 has a broken `TypedArray.prototype.subarray` function which returns arrays of
+ *    incorrect length in some situations.
+ *
+ * We detect these buggy browsers and set `TYPED_ARRAY_SUPPORT` to `false` so they will
+ * get the Object implementation, which is slower but will work correctly.
  */
-Buffer._useTypedArrays = (function () {
-  // Detect if browser supports Typed Arrays. Supported browsers are IE 10+, Firefox 4+,
-  // Chrome 7+, Safari 5.1+, Opera 11.6+, iOS 4.2+. If the browser does not support adding
-  // properties to `Uint8Array` instances, then that's the same as no `Uint8Array` support
-  // because we need to be able to add all the node Buffer API methods. This is an issue
-  // in Firefox 4-29. Now fixed: https://bugzilla.mozilla.org/show_bug.cgi?id=695438
+var TYPED_ARRAY_SUPPORT = (function () {
   try {
     var buf = new ArrayBuffer(0)
     var arr = new Uint8Array(buf)
     arr.foo = function () { return 42 }
-    return 42 === arr.foo() &&
-        typeof arr.subarray === 'function' // Chrome 9-10 lack `subarray`
+    return 42 === arr.foo() && // typed array instances can be augmented
+        typeof arr.subarray === 'function' && // chrome 9-10 lack `subarray`
+        new Uint8Array(1).subarray(1, 1).byteLength === 0 // ie10 has broken `subarray`
   } catch (e) {
     return false
   }
@@ -69,7 +82,7 @@ function Buffer (subject, encoding, noZero) {
     throw new Error('First argument needs to be a number, array or string.')
 
   var buf
-  if (Buffer._useTypedArrays) {
+  if (TYPED_ARRAY_SUPPORT) {
     // Preferred: Return an augmented `Uint8Array` instance for best performance
     buf = Buffer._augment(new Uint8Array(length))
   } else {
@@ -80,7 +93,7 @@ function Buffer (subject, encoding, noZero) {
   }
 
   var i
-  if (Buffer._useTypedArrays && typeof subject.byteLength === 'number') {
+  if (TYPED_ARRAY_SUPPORT && typeof subject.byteLength === 'number') {
     // Speed optimization -- use set if we're copying from a typed array
     buf._set(subject)
   } else if (isArrayish(subject)) {
@@ -94,7 +107,7 @@ function Buffer (subject, encoding, noZero) {
     }
   } else if (type === 'string') {
     buf.write(subject, 0, encoding)
-  } else if (type === 'number' && !Buffer._useTypedArrays && !noZero) {
+  } else if (type === 'number' && !TYPED_ARRAY_SUPPORT && !noZero) {
     for (i = 0; i < length; i++) {
       buf[i] = 0
     }
@@ -401,7 +414,7 @@ Buffer.prototype.copy = function (target, target_start, start, end) {
 
   var len = end - start
 
-  if (len < 100 || !Buffer._useTypedArrays) {
+  if (len < 100 || !TYPED_ARRAY_SUPPORT) {
     for (var i = 0; i < len; i++) {
       target[i + target_start] = this[i + start]
     }
@@ -495,7 +508,7 @@ Buffer.prototype.slice = function (start, end) {
   if (end < start)
     end = start
 
-  if (Buffer._useTypedArrays) {
+  if (TYPED_ARRAY_SUPPORT) {
     return Buffer._augment(this.subarray(start, end))
   } else {
     var sliceLen = end - start
@@ -954,7 +967,7 @@ Buffer.prototype.inspect = function () {
  */
 Buffer.prototype.toArrayBuffer = function () {
   if (typeof Uint8Array !== 'undefined') {
-    if (Buffer._useTypedArrays) {
+    if (TYPED_ARRAY_SUPPORT) {
       return (new Buffer(this)).buffer
     } else {
       var buf = new Uint8Array(this.length)