Re: [Libguestfs] [PATCH nbdkit 7/9] server: Add hand-written replacement for poll for Windows.
On 8/18/20 5:50 AM, Richard W.M. Jones wrote:
---
configure.ac | 1 +
common/replacements/Makefile.am | 2 +
common/replacements/poll.h | 60 ++++++++++++++++++
server/public.c | 2 +-
server/sockets.c | 2 +-
common/replacements/poll.c | 106 ++++++++++++++++++++++++++++++++
6 files changed, 171 insertions(+), 2 deletions(-)
My native windows coding is weak, so take this review with a grain of salt.
+++ b/common/replacements/poll.c
+#ifndef HAVE_POLL
+
+#include "poll.h"
+
+#ifdef WIN32
+
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#include <windows.h>
+
+/* Windows doesn't have poll. It has something called WSAPoll in
+ * Winsock, but even MSFT admit it is broken. Gnulib contains an
Is MSFT considered plural, or should that be 'admits'
+ * elaborate emulation of poll written by Paolo, but it's
distributed
I know who you mean, but is it worth a surname?
+ * under an incompatible license. However Winsock has select so we
+ * can write a simple (but slow) emulation of poll using select.
+ */
+int
+poll (struct pollfd *fds, int n, int timeout)
+{
+ int i, nfds = 0, r;
+ fd_set readfds, writefds;
+ struct timeval tv, *tvp;
+
+ FD_ZERO (&readfds);
+ FD_ZERO (&writefds);
+
+ for (i = 0; i < n; ++i) {
+ if (fds[i].events & POLLIN)
+ FD_SET (fds[i].fd, &readfds);
+ if (fds[i].events & POLLOUT)
+ FD_SET (fds[i].fd, &writefds);
+ if (fds[i].fd > nfds)
+ nfds = fds[i].fd;
+ fds[i].revents = 0;
+ }
+ nfds++;
Do we need to make sure that nfds does not exceed the limits of select?
Calling FD_SET on a too-large fd causes memory corruption (twiddling
bits outside of the fixed-length bitset is never good). Offhand, I
didn't know the windows bitset length, but a quick google found:
https://docs.microsoft.com/en-us/windows/win32/winsock/maximum-number-of-...
where the default limit is 64 unless you set a compile-time macro prior
to winsock2.h.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org