Issue #5677 has been reported by Martin Bosslet.

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Feature #5677: IO C API
http://redmine.ruby-lang.org/issues/5677

Author: Martin Bosslet
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 2.0.0


This is related to the proposal in [ruby-core:41321][1].

I'd like to take advantage of streaming IO in an extension I am
working on. The problem I'm having is that I don't want to call
IO#read on the rb_funcall level because that would kill the
performance due to wrapping the bytes into Ruby objects back and
forth again.

I saw two solutions to my problem:

1. Duplicating the file descriptor to obtain a pure FILE*
like it is done in ext/openssl/ossl_bio.c[2] and continue
working on the raw FILE*.

2. Since I really only need to read and write on the stream,
I was looking for public Ruby C API that would support me
in the process, and I found

 - ssize_t rb_io_bufwrite(VALUE io, const void *buf, size_t size)
 - ssize_t rb_io_bufread(VALUE io, void *buf, size_t size)


I think both cases are valid use cases, 1. is likely necessary
if there is the need to pass a FILE* on to an external C library,
2. is for cases like mine where there is the need to operate
on raw C data types for performance reasons.

The problem, though, is that only rb_io_bufwrite is public API in io.h,
rb_io_bufread is declared private in internal.h and rb_cloexec_dup is 
semi-public in intern.h.

Could we make rb_io_bufread public API in io.h as well? What about
rb_cloexec_dup?

[1] http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/41321
[2] https://github.com/ruby/ruby/blob/trunk/ext/openssl/ossl_bio.c#L17


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