Initialize the stream copier.
If neither the source nor the sink are buffered, buffering will
be automatically added to the sink.
| aSource | contains the data to be copied. |
| aSink | specifies the destination for the data. |
| aTarget | specifies the thread on which the copy will occur. a null value is permitted and will cause the copy to occur on an unspecified background thread. |
| aChunkSize | specifies how many bytes to read/write at a time. this controls the granularity of the copying. it should match the segment size of the "buffered" streams involved. |
| aCloseSource | true if aSource should be closed after copying (this is generally the desired behavior). |
| aCloseSink | true if aSink should be closed after copying (this is generally the desired behavior). |
asyncCopy triggers the start of the copy. The observer will be notified
when the copy completes.
| aObserver | receives notifications. |
| aObserverContext | passed to observer methods. |