feature/android 3e6eaa3cb2e: Update Android port

[Po Lu]

branch: feature/android
commit 3e6eaa3cb2eea00d83561458d8eb1e24b77d28cb
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Update Android port
    
    * src/android.c (android_run_select_thread): Correctly return
    the set of ready read and write descriptors on __ANDROID_API__ <
    16 systems.
    (android_select): Clear the set of ready file descriptors if
    events from the event queue are present despite pselect failing.
---
 src/android.c | 54 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 43 insertions(+), 11 deletions(-)

diff --git a/src/android.c b/src/android.c
index 4e9897f4648..065f90b3463 100644
--- a/src/android.c
+++ b/src/android.c
@@ -349,7 +349,7 @@ android_run_select_thread (void *data)
   int rc;
 #if __ANDROID_API__ < 16
   int nfds;
-  fd_set readfds, writefds;
+  fd_set readfds;
   char byte;
 #else
   sigset_t signals, waitset;
@@ -386,18 +386,30 @@ android_run_select_thread (void *data)
        nfds = select_pipe[0] + 1;
       FD_SET (select_pipe[0], &readfds);
 
-      rc = pselect (nfds, &readfds, &writefds,
+      rc = pselect (nfds, &readfds,
+                   android_pselect_writefds,
                    android_pselect_exceptfds,
                    android_pselect_timeout,
                    NULL);
 
-      /* Subtract 1 from rc if writefds contains the select pipe.  */
-      if (FD_ISSET (select_pipe[0], &writefds))
-       rc -= 1;
+      /* Subtract 1 from rc if readfds contains the select pipe, and
+        also remove it from that set.  */
+
+      if (rc != -1 && FD_ISSET (select_pipe[0], &readfds))
+       {
+         rc -= 1;
+         FD_CLR (fd, &readfds);
+
+         /* If no file descriptors aside from the select pipe are
+            ready, then pretend that an error has occurred.  */
+         if (!rc)
+           rc = -1;
+       }
+
+      /* Save the read file descriptor set back again.  */
 
-      /* Save the writefds back again.  */
-      if (android_pselect_writefds)
-       *android_pselect_writefds = writefds;
+      if (android_pselect_readfds)
+       *android_pselect_readfds = readfds;
 
       android_pselect_rc = rc;
       pthread_mutex_unlock (&event_queue.select_mutex);
@@ -795,13 +807,33 @@ android_select (int nfds, fd_set *readfds, fd_set 
*writefds,
     nfds_return = 1;
   pthread_mutex_unlock (&event_queue.mutex);
 
-  /* Add the return value of pselect.  */
+  /* Add the return value of pselect if it has also found ready file
+     descriptors.  */
+
   if (android_pselect_rc >= 0)
     nfds_return += android_pselect_rc;
-
-  if (!nfds_return && android_pselect_rc < 0)
+  else if (!nfds_return)
+    /* If pselect was interrupted and nfds_return is 0 (meaning that
+       no events have been read), indicate that an error has taken
+       place.  */
     nfds_return = android_pselect_rc;
 
+  if ((android_pselect_rc < 0) && nfds_return >= 0)
+    {
+      /* Clear the file descriptor sets if events will be delivered
+        but no file descriptors have become ready to prevent the
+        caller from misinterpreting a non-zero return value.  */
+
+      if (readfds)
+       FD_ZERO (readfds);
+
+      if (writefds)
+       FD_ZERO (writefds);
+
+      if (exceptfds)
+       FD_ZERO (exceptfds);
+    }
+
   /* This is to shut up process.c when pselect gets EINTR.  */
   if (nfds_return < 0)
     errno = EINTR;