I propose addition of IO#writev.
It enables gather output from multiple buffers.
If writev(2) is not available, IO#writev uses Array#join to emulate atomic write.
#1 [ruby-core:60003] Updated by Eric Wong about 2 years ago
Unless we have use for it, I don't think rb_io_writev should be in
the C API, and even less reason for it to be public for extensions
Also, it'd probably be good to dedup the fptr->wbuf initialization
code in io_binwrite*.
Otherwise, I think this is fine.