[Libguestfs] [PATCH nbdkit incomplete 3/5] server: sockets: Refactor accept_incoming_connections.

[Richard W.M. Jones]

This is a simple refactoring of the function, allowing us to
reimplement the inner loop for Windows in a future commit.  Note that
I made explicit that fds[nr_socks] is used for the quit_fd entry,
previously this was implicit which was somewhat confusing.
---
 server/sockets.c | 64 ++++++++++++++++++++++++++++++------------------
 1 file changed, 40 insertions(+), 24 deletions(-)

diff --git a/server/sockets.c b/server/sockets.c
index d92236f..cc15c5e 100644
--- a/server/sockets.c
+++ b/server/sockets.c
@@ -314,39 +314,55 @@ accept_connection (int listen_sock)
    */
 }
 
-void
-accept_incoming_connections (int *socks, size_t nr_socks)
+/* Check the list of sockets plus quit_fd until a POLLIN event occurs
+ * on any of them.
+ *
+ * If POLLIN occurs on quit_fd do nothing except returning early
+ * (don't call accept_connection in this case).
+ *
+ * If POLLIN occurs on one of the sockets, call
+ * accept_connection (socks[i]) on each of them.
+ */
+static void
+check_sockets_and_quit_fd (int *socks, size_t nr_socks)
 {
   struct pollfd fds[nr_socks + 1];
   size_t i;
   int r;
 
-  while (!quit) {
-    for (i = 0; i < nr_socks; ++i) {
-      fds[i].fd = socks[i];
-      fds[i].events = POLLIN;
-      fds[i].revents = 0;
-    }
-    fds[i].fd = quit_fd;
+  for (i = 0; i < nr_socks; ++i) {
+    fds[i].fd = socks[i];
     fds[i].events = POLLIN;
     fds[i].revents = 0;
+  }
+  fds[nr_socks].fd = quit_fd;
+  fds[nr_socks].events = POLLIN;
+  fds[nr_socks].revents = 0;
 
-    r = poll (fds, nr_socks + 1, -1);
-    if (r == -1) {
-      if (errno == EINTR || errno == EAGAIN)
-        continue;
-      perror ("poll");
-      exit (EXIT_FAILURE);
-    }
+  r = poll (fds, nr_socks + 1, -1);
+  if (r == -1) {
+    if (errno == EINTR || errno == EAGAIN)
+      return;
+    perror ("poll");
+    exit (EXIT_FAILURE);
+  }
 
-    /* We don't even have to read quit_fd - just knowing that it has data
-     * means the signal handler ran, so we are ready to quit the loop. */
+  /* We don't even have to read quit_fd - just knowing that it has
+   * data means the signal handler ran, so we are ready to quit the
+   * loop.
+   */
+  if (fds[nr_socks].revents & POLLIN)
+    return;
+
+  for (i = 0; i < nr_socks; ++i) {
     if (fds[i].revents & POLLIN)
-      continue;
-
-    for (i = 0; i < nr_socks; ++i) {
-      if (fds[i].revents & POLLIN)
-        accept_connection (fds[i].fd);
-    }
+      accept_connection (socks[i]);
   }
 }
+
+void
+accept_incoming_connections (int *socks, size_t nr_socks)
+{
+  while (!quit)
+    check_sockets_and_quit_fd (socks, nr_socks);
+}
-- 
2.20.1