using the sendfile system call on Darwin

[Greg Lewis]

G'day Michael,

On Fri, Feb 19, 2010 at 01:07:35PM -0800, Michael Allman wrote:
> Ok, I have a patch.  How do I submit it?

Sending it to the list for review (either directly or by putting up a URL
people can see it at) is a good first step :).

> On Wed, 27 Jan 2010, Greg Lewis wrote:
> 
> > On Tue, Jan 26, 2010 at 01:33:06AM -0800, Michael Allman wrote:
> >> I would like to update jdk/src/solaris/native/sun/nio/ch/FileChannelImpl.c
> >> so that the Java_sun_nio_ch_FileChannelImpl_transferTo0 function calls the
> >> sendfile system call on Darwin.  I have a few questions:
> >>
> >> 1.  Is there a cpp #define for Darwin?  If not, how do I tell cpp whether
> >> the system is Darwin or not?
> >
> > The rest of the code uses
> >
> > #ifdef __APPLE__
> >
> >> 2.  Are there tests that exercise
> >> Java_sun_nio_ch_FileChannelImpl_transferTo0 or the java method
> >> FileChannel.transferTo?
> >
> > Some of the tests in jdk/test/java/nio/channels/FileChannel/ may be useful,
> > I haven't looked them over though.
> >
> >> 3.  Why doesn't the existing BSD code just return IOS_UNSUPPORTED?  For
> >> instance, look at lines 223 and 224.  If there's no sendfile function on
> >> Solaris, the function just returns IOS_UNSUPPORTED.  The caller handles
> >> that return value gracefully.  The existing BSD code looks needlessly
> >> complex to me.
> >
> > All of the BSDs have sendfile, its just limited to only sending the file to
> > a stream socket rather than any file descriptor, which Solaris and Linux
> > allow.  It's fairly easy to implement code that will do that though, so
> > that's what was done rather than throwing errors when a non-socket file
> > descriptor was used.
> >
> > Note that MacOS X seems to have the same limitations as all the other BSDs
> > in terms of what type of file descriptor can be used as the destination:
> >
> > http://developer.apple.com/Mac/library/documentation/Darwin/Reference/ManPages/man2/sendfile.2.html
> >
> > If NIO in general interests you, then a project we really need someone to
> > work on is porting NIO2 to BSD.  None of the BSDs have the epoll mechanism
> > used on Linux or whatever Solaris uses (which I can't recall off the top of
> > my head right now).  The suggestion is to use kqueue(2) on BSD.
> >
> > -- 
> > Greg Lewis                          Email   : glewis at eyesbeyond.com
> > Eyes Beyond                         Web     : http://www.eyesbeyond.com
> > Information Technology              FreeBSD : glewis at FreeBSD.org
> >

-- 
Greg Lewis                          Email   : glewis at eyesbeyond.com
Eyes Beyond                         Web     : http://www.eyesbeyond.com
Information Technology              FreeBSD : glewis at FreeBSD.org