bug#20978: [PATCH 5/7] : Refactor timeouts in wait_reading_process_output

[Ian Kelling]

* src/process.c (wait_reading_process_output): Simplify timeouts with
an enum. Remove a redundant condition.

diff --git a/src/process.c b/src/process.c
index 68a815f..538455c 100644
--- a/src/process.c
+++ b/src/process.c
@@ -4586,6 +4586,7 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
   int xerrno;
   Lisp_Object proc;
   struct timespec timeout, end_time;
+  enum { MINIMUM, TIMEOUT, INFINITY } wait;
   int got_some_output = -1;
   ptrdiff_t count = SPECPDL_INDEX ();

@@ -4601,21 +4602,19 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
                             waiting_for_user_input_p);
   waiting_for_user_input_p = read_kbd;

-  if (time_limit < 0)
-    {
-      time_limit = 0;
-      nsecs = -1;
-    }
-  else if (TYPE_MAXIMUM (time_t) < time_limit)
+  if (TYPE_MAXIMUM (time_t) < time_limit)
     time_limit = TYPE_MAXIMUM (time_t);

-  /* Since we may need to wait several times,
-     compute the absolute time to return at.  */
-  if (time_limit || nsecs > 0)
+  if (time_limit < 0 || nsecs < 0)
+    wait = MINIMUM;
+  else if (time_limit > 0 || nsecs > 0)
     {
-      timeout = make_timespec (time_limit, nsecs);
-      end_time = timespec_add (current_timespec (), timeout);
+      wait = TIMEOUT;
+      end_time = timespec_add (current_timespec (),
+                               make_timespec (time_limit, nsecs));
     }
+  else
+    wait = INFINITY;

   while (1)
     {
@@ -4635,19 +4634,15 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,

       /* After reading input, vacuum up any leftovers without waiting.  */
       if (0 <= got_some_output)
-       nsecs = -1;
+        wait = MINIMUM;

       /* Compute time from now till when time limit is up.  */
       /* Exit if already run out.  */
-      if (nsecs < 0)
+      if (wait == MINIMUM)
        {
-         /* A negative timeout means
-            gobble output available now
-            but don't wait at all.  */
-
-         timeout = make_timespec (0, 0);
+          timeout = make_timespec (0, 0);
        }
-      else if (time_limit || nsecs > 0)
+      else if (wait == TIMEOUT)
        {
          struct timespec now = current_timespec ();
          if (timespec_cmp (end_time, now) <= 0)
@@ -4698,24 +4693,20 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
              && requeued_events_pending_p ())
            break;

-         /* A negative timeout means do not wait at all.  */
-         if (nsecs >= 0)
-           {
-             if (timespec_valid_p (timer_delay))
-               {
-                 if (timespec_cmp (timer_delay, timeout) < 0)
-                   {
-                     timeout = timer_delay;
-                     timeout_reduced_for_timers = true;
-                   }
-               }
-             else
-               {
-                 /* This is so a breakpoint can be put here.  */
-                 wait_reading_process_output_1 ();
-               }
-           }
-       }
+          if (timespec_valid_p (timer_delay))
+            {
+              if (timespec_cmp (timer_delay, timeout) < 0)
+                {
+                  timeout = timer_delay;
+                  timeout_reduced_for_timers = true;
+                }
+            }
+          else
+            {
+              /* This is so a breakpoint can be put here.  */
+              wait_reading_process_output_1 ();
+            }
+        }

       /* Cause C-g and alarm signals to take immediate action,
         and cause input available signals to zero out timeout.
@@ -4964,7 +4955,7 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
       /*  If we woke up due to SIGWINCH, actually change size now.  */
       do_pending_window_change (0);

-      if ((time_limit || nsecs) && nfds == 0 && ! timeout_reduced_for_timers)
+      if (wait != INFINITY && nfds == 0 && ! timeout_reduced_for_timers)
        /* We waited the full specified time, so return now.  */
        break;
       if (nfds < 0)
@@ -6953,21 +6944,21 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
 {
   register int nfds;
   struct timespec end_time, timeout;
+  enum { MINIMUM, TIMEOUT, INFINITY } wait;

-  if (time_limit < 0)
-    {
-      time_limit = 0;
-      nsecs = -1;
-    }
-  else if (TYPE_MAXIMUM (time_t) < time_limit)
+  if (TYPE_MAXIMUM (time_t) < time_limit)
     time_limit = TYPE_MAXIMUM (time_t);

-  /* What does time_limit really mean?  */
-  if (time_limit || nsecs > 0)
+  if (time_limit < 0 || nsecs < 0)
+    wait = MINIMUM;
+  else if (time_limit > 0 || nsecs > 0)
     {
-      timeout = make_timespec (time_limit, nsecs);
-      end_time = timespec_add (current_timespec (), timeout);
+      wait = TIMEOUT;
+      end_time = timespec_add (current_timespec (),
+                               make_timespec (time_limit, nsecs));
     }
+  else
+    wait = INFINITY;

   /* Turn off periodic alarms (in case they are in use)
      and then turn off any other atimers,
@@ -6993,15 +6984,11 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,

       /* Compute time from now till when time limit is up.  */
       /* Exit if already run out.  */
-      if (nsecs < 0)
+      if (wait == MINIMUM)
        {
-         /* A negative timeout means
-            gobble output available now
-            but don't wait at all.  */
-
-         timeout = make_timespec (0, 0);
+          timeout = make_timespec (0, 0);
        }
-      else if (time_limit || nsecs > 0)
+      else if (wait == TIMEOUT)
        {
          struct timespec now = current_timespec ();
          if (timespec_cmp (end_time, now) <= 0)
@@ -7039,7 +7026,7 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
              && requeued_events_pending_p ())
            break;

-         if (timespec_valid_p (timer_delay) && nsecs >= 0)
+         if (timespec_valid_p (timer_delay))
            {
              if (timespec_cmp (timer_delay, timeout) < 0)
                {
@@ -7083,7 +7070,7 @@ wait_reading_process_output (intmax_t time_limit, int 
nsecs, int read_kbd,
       /*  If we woke up due to SIGWINCH, actually change size now.  */
       do_pending_window_change (0);

-      if ((time_limit || nsecs) && nfds == 0 && ! timeout_reduced_for_timers)
+      if (wait != INFINITY && nfds == 0 && ! timeout_reduced_for_timers)
        /* We waited the full specified time, so return now.  */
        break;

--
2.4.5