[PATCH] compat: Add another rudimentary poll() emulation

[Jonathan Nieder <jrnieder@gmail.com>]

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).

Cc: Johannes Sixt <j6t@kdbg.org>
Cc: Jonathan Callen <abcd@gentoo.org>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
Jonathan Callen wrote:

> Some systems do not have sys/poll.h or poll(2).

Maybe this could help.  Thanks to DrNick on IRC for the suggestion.

Warning: untested.

 Makefile          |    8 ++++++++
 compat/poll.c     |   33 +++++++++++++++++++++++++++++++++
 compat/poll.h     |   13 +++++++++++++
 git-compat-util.h |    6 +++++-
 4 files changed, 59 insertions(+), 1 deletions(-)
 create mode 100644 compat/poll.c
 create mode 100644 compat/poll.h

diff --git a/Makefile b/Makefile
index 2f5d631..6715528 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
+	BASIC_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..33c6ae0
--- /dev/null
+++ b/compat/poll.c
@@ -0,0 +1,33 @@
+#include "../git-compat-util.h"
+
+int git_poll(struct git_pollfd *ufds, int nfds, int timeout)
+{
+	int i, maxfd, result;
+	fd_set fds;
+
+	if (timeout >= 0) {
+		if (nfds == 0) {
+			sleep(timeout);
+			return 0;
+		}
+		return errno = EINVAL, error("poll timeout not supported");
+	}
+
+	FD_ZERO(&fds);
+	maxfd = 0;
+	for (i = 0; i < nfds; i++) {
+		if (ufds[i].events != POLLIN)
+			return errno = EINVAL, error("poll: unsupported events");
+		maxfd = (ufds[i].fd > maxfd) ? ufds[i].fd : maxfd;
+		FD_SET(ufds[i].fd, &fds);
+	}
+
+	result = select(maxfd + 1, &fds, NULL, NULL, NULL);
+	if (result == -1)
+		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