IO.copy_stream fixes #6557
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IO.copy_stream fixes #6557
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* Don't copy the source bytes when we can access an underlying array. * Advance the incoming buffer the number of bytes that were written.
The CRuby logic here will use binwrite when the target has a real fd associated with it, which loops until everything is written, and does a single dynamic "write" call when the target is a pseudo-IO. This patch simulates this behavior by bailing out after as single write when the target channel is wrapping a pseudo-IO. Fixes jruby#6555
When the incoming bytes are on the heap, we can use them in-place for the string we pass to the Ruby write method. However, since the target IO-like may want to modify the incoming string, we must make sure it is marked as shared so our original src bytes will not be modified. This issue originally manifested in jruby#4903 and was fixed by always copying the incoming buffer, but marking the string shared has the same effecit if the target attempts to make any modifications.
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The "optimizations" here were overzealous: * The incoming ByteBuffer and its contents should not be referenced past the end of the call, as was done here by returning a String that directly wraps the buffer's underlying array. * The copy of bytes out of the native buffer is essentially the same as calling #duplicate, so this is just unnecessary double- copying. Fixes jruby#6767.
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Undo shared-buffer optimizations from #6557
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The last item fixes #6555.