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Re: [Public WebGL] Differing TypedArray#set behavior




On 4/12/12 4:57 AM, Stéphan Kochen wrote:

While implementing TypedArrays, I came across a specific situation that seems to be missed by the conformance tests. Here's a test:

   https://github.com/stephank/node-arrays/blob/master/test/typed-array-copy.js

This does a copy using `TypedArray#set` between two TypedArrays of
different types, but with the same backing store and overlapping
regions.

The test passes on Firefox, but fails on Chrome, Safari, Opera and Node.js.

Is the Firefox behavior the correct one here?

The spec at http://www.khronos.org/registry/typedarray/specs/latest/ says:

  If the input array is a TypedArray, the two arrays may use the same
  underlying ArrayBuffer. In this situation, setting the values takes
  place as if all the data is first copied into a temporary buffer that
  does not overlap either of the arrays, and then the data from the
  temporary buffer is copied into the current array.

So in your test, that should lead to a[0] == a[1] == 5, and the Firefox
behavior is correct.  Would you mind filing bugs on JSC and V8 and Opera
here?

-Boris


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