From 94f98400bf950aa9835ff9b04c724f2aa3ebd0fc Mon Sep 17 00:00:00 2001
From: Edward Thomson <ethomson@edwardthomson.com>
Date: Fri, 12 May 2023 20:48:31 +0100
Subject: posix: introduce p_poll emulation with select

Not all systems have poll(2); emulate it with select(2).
---
 src/CMakeLists.txt           |  5 ++++
 src/libgit2/streams/socket.c |  9 ++++----
 src/util/git2_features.h.in  |  3 +++
 src/util/posix.c             | 54 ++++++++++++++++++++++++++++++++++++++++++++
 src/util/posix.h             | 19 ++++++++++++++++
 5 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 88d616cec..a00ab600a 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -87,6 +87,11 @@ check_prototype_definition_safe(qsort_s
 check_function_exists(getentropy GIT_RAND_GETENTROPY)
 check_function_exists(getloadavg GIT_RAND_GETLOADAVG)
 
+# poll
+
+check_symbol_exists(poll poll.h GIT_IO_POLL)
+check_symbol_exists(select sys/select.h GIT_IO_SELECT)
+
 # determine architecture of the machine
 
 if(CMAKE_SIZEOF_VOID_P EQUAL 8)
diff --git a/src/libgit2/streams/socket.c b/src/libgit2/streams/socket.c
index 0e0aa6934..ecbdf7b7d 100644
--- a/src/libgit2/streams/socket.c
+++ b/src/libgit2/streams/socket.c
@@ -20,7 +20,6 @@
 # include <netdb.h>
 # include <netinet/in.h>
 # include <arpa/inet.h>
-# include <poll.h>
 #else
 # include <winsock2.h>
 # include <ws2tcpip.h>
@@ -135,13 +134,13 @@ static int connect_with_timeout(
 	fd.events = POLLOUT;
 	fd.revents = 0;
 
-	error = poll(&fd, 1, timeout);
+	error = p_poll(&fd, 1, timeout);
 
 	if (error == 0) {
 		return GIT_TIMEOUT;
 	} else if (error != 1) {
 		return -1;
-	} else if ((fd.revents & (POLLHUP | POLLERR))) {
+	} else if ((fd.revents & (POLLPRI | POLLHUP | POLLERR))) {
 		return handle_sockerr(socket);
 	} else if ((fd.revents & POLLOUT) != POLLOUT) {
 		git_error_set(GIT_ERROR_NET,
@@ -236,7 +235,7 @@ static ssize_t socket_write(
 		fd.events = POLLOUT;
 		fd.revents = 0;
 
-		ret = poll(&fd, 1, st->parent.timeout);
+		ret = p_poll(&fd, 1, st->parent.timeout);
 
 		if (ret == 1) {
 			ret = p_send(st->s, data, len, 0);
@@ -272,7 +271,7 @@ static ssize_t socket_read(
 		fd.events = POLLIN;
 		fd.revents = 0;
 
-		ret = poll(&fd, 1, st->parent.timeout);
+		ret = p_poll(&fd, 1, st->parent.timeout);
 
 		if (ret == 1) {
 			ret = p_recv(st->s, data, len, 0);
diff --git a/src/util/git2_features.h.in b/src/util/git2_features.h.in
index 18644c3cc..cf955122c 100644
--- a/src/util/git2_features.h.in
+++ b/src/util/git2_features.h.in
@@ -61,4 +61,7 @@
 #cmakedefine GIT_RAND_GETENTROPY 1
 #cmakedefine GIT_RAND_GETLOADAVG 1
 
+#cmakedefine GIT_IO_POLL 1
+#cmakedefine GIT_IO_SELECT 1
+
 #endif
diff --git a/src/util/posix.c b/src/util/posix.c
index b1f85dc94..cfc0e0751 100644
--- a/src/util/posix.c
+++ b/src/util/posix.c
@@ -301,3 +301,57 @@ int p_munmap(git_map *map)
 }
 
 #endif
+
+#if defined(GIT_IO_POLL) || defined(GIT_IO_WSAPOLL)
+
+/* Handled by posix.h; this test simplifies the final else */
+
+#elif defined(GIT_IO_SELECT)
+
+int p_poll(struct pollfd *fds, unsigned int nfds, int timeout_ms)
+{
+	fd_set read_fds, write_fds, except_fds;
+	struct timeval timeout = { 0, 0 };
+	unsigned int i;
+	int max_fd = -1, ret;
+
+	FD_ZERO(&read_fds);
+	FD_ZERO(&write_fds);
+	FD_ZERO(&except_fds);
+
+	for (i = 0; i < nfds; i++) {
+		if ((fds[i].events & POLLIN))
+			FD_SET(fds[i].fd, &read_fds);
+
+		if ((fds[i].events & POLLOUT))
+			FD_SET(fds[i].fd, &write_fds);
+
+		if ((fds[i].events & POLLPRI))
+			FD_SET(fds[i].fd, &except_fds);
+
+		max_fd = MAX(max_fd, fds[i].fd);
+	}
+
+	if (timeout_ms > 0) {
+		timeout.tv_sec = timeout_ms / 1000;
+		timeout.tv_usec = (timeout_ms % 1000) * 1000;
+	}
+
+	if ((ret = select(max_fd + 1, &read_fds, &write_fds, &except_fds,
+	                  timeout_ms < 0 ? NULL : &timeout)) < 0)
+		goto done;
+
+	for (i = 0; i < nfds; i++) {
+		fds[i].revents = 0 |
+			FD_ISSET(fds[i].fd, &read_fds) ? POLLIN : 0 |
+			FD_ISSET(fds[i].fd, &write_fds) ? POLLOUT : 0 |
+			FD_ISSET(fds[i].fd, &except_fds) ? POLLPRI : 0;
+	}
+
+done:
+	return ret;
+}
+
+#else
+# error no poll compatible implementation
+#endif
diff --git a/src/util/posix.h b/src/util/posix.h
index 607aa9dce..f516bb3cc 100644
--- a/src/util/posix.h
+++ b/src/util/posix.h
@@ -195,4 +195,23 @@ extern const char *p_gai_strerror(int ret);
 #	define p_gai_strerror(c) gai_strerror(c)
 #endif /* NO_ADDRINFO */
 
+#ifdef GIT_IO_POLL
+# include <poll.h>
+# define p_poll poll
+#else
+# define POLLIN  0x01
+# define POLLPRI 0x02
+# define POLLOUT 0x04
+# define POLLERR 0x08
+# define POLLHUP 0x10
+
+struct pollfd {
+	int fd;
+	short events;
+	short revents;
+};
+
+extern int p_poll(struct pollfd *fds, unsigned int nfds, int timeout);
+#endif
+
 #endif
-- 
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