using the sendfile system call on Darwin

Michael Allman msa at
Fri Feb 19 13:07:35 PST 2010

Ok, I have a patch.  How do I submit it?



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:
> 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
> Eyes Beyond                         Web     :
> Information Technology              FreeBSD : glewis at

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