On Mon, May 13, 2019 at 2:45 PM Dan Kortschak <d...@kortschak.io> wrote: > > Thanks, Jake. This was very helpful.
It does seem that the docs in this area should be improved. Alas. Ian > On Mon, 2019-05-13 at 09:19 -0700, jake6...@gmail.com wrote: > > On Thursday, May 9, 2019 at 2:54:17 AM UTC-4, kortschak wrote: > > > > > > > > > The Conn and UDPConn Read methods look like io.Reader Read methods, > > > but > > > there is no explicit claim that Conn is an io.Reader. Are the Read > > > methods of these two types identical in behaviour to io.Reader? > > > > > > > I can not say definitively, but on unix, UDPConn.Read() is actually > > net.conn.Read() <https://golang.org/src/net/net.go?s=6157:6199#L163>, > > whch > > calls net.netFD.Read(), which in turn calls poll.FD.Read() > > <https://golang.org/src/internal/poll/fd_unix.go#L144>. You can see > > there > > in the code: > > > > // Read implements io.Reader. > > > > The windows and plan9 versions also land in Read() functions that > > have the same comment. So it seems to me that UDPConn.Read() is an > > io.Reader. Of course, that only means that it conforms to the > > requirements of io.Reader <https://golang.org/pkg/io/#Reader>. > > > > Specifically, are the reads allowed to fill the buffer with > > arbitrary > > > > > > numbers of bytes in 0 <= len(p) <= n? > > > > > > > Yes, according to io.Reader <https://golang.org/pkg/io/#Reader> docs, > > an > > implementation may do that. Looking at the actual implementations of > > the > > poll.FD.Read functions, I would say that it seems like they will > > always > > return the full UDP packts, if it is <= len(p). A full search of the > > relevant platform docs would be required to say definitively. > > > > > > > > > > Also, can UPDConn.Read fill the buffer with more than one packet if > > > the > > > buffer would accommodate that? (I am guessing yes, and that if this > > > is > > > important then the ReadFrom method should be used). > > > > > > > > It looks to me like this will in fact read one packet at a time on > > amd64 > > unix. The function will return after a single successful > > syscall(SYS_READ) > > which, IIUC will just be one packet for UDP. Since there is no > > actual > > documentation guaranteeing this, you would have to look at the source > > code, > > and platform docs, for every platform you care about to be 100% > > sure. > > However, if it did not work this way, it would make UDP programming > > very > > hard, or even impossible. So I think it very likely. > > > > > > > > > > thanks > > > Dan > > > > > > > > > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/1557783886.17937.0.camel%40kortschak.io. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcXbyAt4zfYSqPGH-v%3DspTPykv%3D_4ByPA6Q8nhddob3cxg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
