Readme: explain that "parent tracking" works sometimes (close #9)

diff --git a/README.md b/README.md
index 7c65c929e36845a8f77c7ca4eac459d11f043446..542b45b62e0c6b9edf54dd1ba8113ae629348d67 100644 (file)
--- a/README.md
+++ b/README.md
@@ -35,6 +35,7 @@ By augmenting the instances, we can avoid modifying the Uint8Array prototype.
 ## Important Differences
 
 - **Use `Buffer.isBuffer` instead of `instanceof Buffer`.** `instanceof Buffer` doesn’t work because the Buffer constructor returns a `Uint8Array` (as discussed above) for performance reasons. In node `Buffer.isBuffer` just does `instanceof Buffer`, but in browserify we use a `Buffer.isBuffer` shim that detects our special `Uint8Array`-based Buffers.
+- **Don't rely on `slice()` to modify the memory of the parent buffer.** If the browser is using the Typed Array implementation then modifying a buffer created by `slice()` will modify the original memory, [just like in Node](http://nodejs.org/api/buffer.html#buffer_buf_slice_start_end). But for the Object implementation (used in unsupported browsers), this is not possible. Therefore, do not rely on this behavior until browser support gets better. (Note: currently even Firefox isn't using the Typed Array implementation because of [this bug](https://bugzilla.mozilla.org/show_bug.cgi?id=952403).)
 
 ## Performance