Using a ring buffer for buffered synchronous fileio is just unnecessary
complexity.
- when reading, we always consume the _entire_ buffer before getting
into syscalls. Thus we reset the buffer to its initial position before
when we actually read.
- when writing and buffer is full, we always flush the entire buffer
before starting to buffer again. So we can reset the buffer to its
initial state.
Also no static buffers are needed for writing and skipping. Needing an
extra copy for each write completely defeated the purpose of
a ring buffer (if there had been one)
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