Implement the subset of poll() semantics needed by git in terms of
select(), for use by the Interix port. Inspired by commit 6ed807f
(Windows: A rudimentary poll() emulation, 2007-12-01).
This will only poll on descriptors with value <= the maximum fd that
select() can portably handle, FD_SETSIZE - 1. On Windows (and not on
Unix), in principle git could permit higher fds as long as the number
of descriptors used in a single select() call was limited to
FD_SETSIZE; but such a facility would be rarely used, since the number
of sockets the ‘git daemon’ parent process keeps open tends to be very
small.
Helped-by: Erik Faye-Lund <kusmabite@xxxxxxxxxxxxxx>
Cc: Johannes Sixt <j6t@xxxxxxxx>
Cc: Jonathan Callen <abcd@xxxxxxxxxx>
Signed-off-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
---
Erik Faye-Lund wrote:
> But perhaps you should include a check along the lines of this:
>
> if (nfds > FD_SETSIZE)
> return errno = EINVAL, error("poll: nfds must be below %d", FD_SETSIZE);
>
> Just so we can know when the code fails :)
Good catch, thanks. I opted to check each fd instead so the NO_POLL
code can be safely used on Unix for debugging.
Other changes from v1:
. use COMPAT_CFLAGS instead of BASIC_CFLAGS
. timeout is a number of milliseconds, not seconds
. lightly tested on Linux
I would be interested to hear whether this works on msysgit and Interix.
Thanks again for the help.
Makefile | 8 +++++++
compat/poll.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
compat/poll.h | 13 ++++++++++++
git-compat-util.h | 6 ++++-
4 files changed, 82 insertions(+), 1 deletions(-)
create mode 100644 compat/poll.c
create mode 100644 compat/poll.h
diff --git a/Makefile b/Makefile
index 2f5d631..ed9f03b 100644
--- a/Makefile
+++ b/Makefile
@@ -111,6 +111,9 @@ all::
#
# Define NO_PTHREADS if you do not have or do not want to use Pthreads.
#
+# Define NO_POLL if you have a problem with the poll() system call (e.g.
+# Interix).
+#
# Define NO_PREAD if you have a problem with pread() system call (e.g.
# cygwin1.dll before v1.5.22).
#
@@ -470,6 +473,7 @@ LIB_H += commit.h
LIB_H += compat/bswap.h
LIB_H += compat/cygwin.h
LIB_H += compat/mingw.h
+LIB_H += compat/poll.h
LIB_H += compat/win32/pthread.h
LIB_H += csum-file.h
LIB_H += decorate.h
@@ -1284,6 +1288,10 @@ endif
ifdef OBJECT_CREATION_USES_RENAMES
COMPAT_CFLAGS += -DOBJECT_CREATION_MODE=1
endif
+ifdef NO_POLL
+ COMPAT_CFLAGS += -DNO_POLL
+ COMPAT_OBJS += compat/poll.o
+endif
ifdef NO_PREAD
COMPAT_CFLAGS += -DNO_PREAD
COMPAT_OBJS += compat/pread.o
diff --git a/compat/poll.c b/compat/poll.c
new file mode 100644
index 0000000..0b3c2ae
--- /dev/null
+++ b/compat/poll.c
@@ -0,0 +1,56 @@
+#include "../git-compat-util.h"
+
+static int msleep(int timeout)
+{
+ struct timeval tv;
+ tv.tv_sec = 0;
+ tv.tv_usec = 1000 * timeout;
+ return select(0, NULL, NULL, NULL, &tv);
+}
+
+static int validate_fd(const struct git_pollfd *ufd)
+{
+ const int fd = ufd->fd;
+ if (ufd->events != POLLIN) {
+ errno = EINVAL;
+ return error("poll: unsupported events");
+ }
+ if (fd >= FD_SETSIZE) {
+ errno = EINVAL;
+ return error("poll: fd must be below %d", FD_SETSIZE);
+ }
+ return fd;
+}
+
+int git_poll(struct git_pollfd *ufds, int nfds, int timeout)
+{
+ int i, maxfd, result;
+ fd_set fds;
+
+ if (timeout >= 0) {
+ if (nfds != 0) {
+ errno = EINVAL;
+ return error("poll timeout not supported");
+ }
+ return msleep(timeout);
+ }
+
+ FD_ZERO(&fds);
+ maxfd = -1;
+ for (i = 0; i < nfds; i++) {
+ const int fd = validate_fd(&ufds[i]);
+ if (fd < 0)
+ return fd;
+ maxfd = (fd > maxfd) ? fd : maxfd;
+ FD_SET(fd, &fds);
+ }
+
+ result = select(maxfd + 1, &fds, NULL, NULL, NULL);
+ if (result < 0)
+ return result;
+ for (i = 0; i < nfds; i++) {
+ if (FD_ISSET(ufds[i].fd, &fds))
+ ufds[i].revents |= POLLIN;
+ }
+ return result;
+}
diff --git a/compat/poll.h b/compat/poll.h
new file mode 100644
index 0000000..65775ab
--- /dev/null
+++ b/compat/poll.h
@@ -0,0 +1,13 @@
+#ifndef POLLIN
+#define POLLIN 1
+#define POLLHUP 2
+#endif
+
+#define pollfd git_pollfd
+#define poll git_poll
+struct git_pollfd {
+ int fd; /* file descriptor */
+ short events; /* requested events */
+ short revents; /* returned events */
+};
+extern int git_poll(struct git_pollfd *fds, int nfds, int timeout);
diff --git a/git-compat-util.h b/git-compat-util.h
index 824c175..2494378 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -94,13 +94,17 @@
#include <utime.h>
#ifndef __MINGW32__
#include <sys/wait.h>
-#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <termios.h>
#ifndef NO_SYS_SELECT_H
#include <sys/select.h>
#endif
+#ifdef NO_POLL
+#include "compat/poll.h"
+#else
+#include <sys/poll.h>
+#endif
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
--
1.7.1
--
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