ssumed__ to remain present, unmodified, at same address in memory!

  Note 3 : When input is structured as a double-buffer, each buffer can have any size, including < 64 KB.
           Make sure that buffers are separated, by at least one byte.
           This construction ensures that each block only depends on previous block.

  Note 4 : If input buffer is a ring-buffer, it can have any size, including < 64 KB.

  Note 5 : After an error, the stream status is invalid, it can only be reset or freed.
 
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