specifies how much data has been placed into the empty portion of the
virtual ring buffer by the caller.
The caller will have called
to get the length of empty space in the buffer and a pointer to it,
and having placed some data into that space, starting from the
pointer obtained and placing no more that the length obtained.
specifies which virtual ring buffer.
specifies the length of data that has been placed into the
virtual ring buffer empty space by the caller.
On success, 0 is returned.
On error, -1 is returned.
If an error is returned, then
will have one of the following values:
An invalid virtual ring buffer pointer was specified.
The specified length is greater than the empty space in the
virtual ring buffer.