[glib] glib/gpoll W32: faster GPollFD lookup

[Руслан Ижбулатов <ruslanizhb src gnome org>]

commit 226ea946853cf4fa340988a8adb8774162acd231
Author: Руслан Ижбулатов <lrn1986 gmail com>
Date:   Sat Jul 29 08:09:05 2017 +0000

    glib/gpoll W32: faster GPollFD lookup
    
    Put all ptrs for GPollFDs that contribute handles into an array, the layout of which mirrors the handles 
array. This way finding GPollFD for a handle is a simple matter of knowing this handle's index in the handles 
array (which is something we always know). Removes the need to loop through all fds looking for the right 
one. And, with the message FD also passed along, it's now completely unnecessary to even pass fds to 
poll_rest() at all.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=785468

 glib/gpoll.c |   43 +++++++++++++++++++++----------------------
 1 files changed, 21 insertions(+), 22 deletions(-)
---
diff --git a/glib/gpoll.c b/glib/gpoll.c
index 7861913..9ebb104 100644
--- a/glib/gpoll.c
+++ b/glib/gpoll.c
@@ -129,12 +129,11 @@ g_poll (GPollFD *fds,
 #ifdef G_OS_WIN32
 
 static int
-poll_rest (GPollFD  *msg_fd,
-          HANDLE   *handles,
-          gint      nhandles,
-          GPollFD  *fds,
-          guint     nfds,
-          gint      timeout)
+poll_rest (GPollFD *msg_fd,
+           HANDLE  *handles,
+           GPollFD *handle_to_fd[],
+           gint     nhandles,
+           gint     timeout)
 {
   DWORD ready;
   GPollFD *f;
@@ -212,20 +211,15 @@ poll_rest (GPollFD  *msg_fd,
       /* If no timeout and handles to poll, recurse to poll them,
        * too.
        */
-      recursed_result = poll_rest (NULL, handles, nhandles, fds, nfds, 0);
+      recursed_result = poll_rest (NULL, handles, handle_to_fd, nhandles, 0);
       return (recursed_result == -1) ? -1 : 1 + recursed_result;
     }
   else if (ready >= WAIT_OBJECT_0 && ready < WAIT_OBJECT_0 + nhandles)
     {
-      for (f = fds; f < &fds[nfds]; ++f)
-       {
-         if ((HANDLE) f->fd == handles[ready - WAIT_OBJECT_0])
-           {
-             f->revents = f->events;
-             if (_g_main_poll_debug)
-               g_print ("  got event %p\n", (HANDLE) f->fd);
-           }
-       }
+      f = handle_to_fd[ready - WAIT_OBJECT_0];
+      f->revents = f->events;
+      if (_g_main_poll_debug)
+        g_print ("  got event %p\n", (HANDLE) f->fd);
 
       /* If no timeout and polling several handles, recurse to poll
        * the rest of them.
@@ -234,10 +228,13 @@ poll_rest (GPollFD  *msg_fd,
        {
          /* Remove the handle that fired */
          int i;
-         for (i = ready - WAIT_OBJECT_0 + 1; i < nhandles; i++)
-           handles[i-1] = handles[i];
+          for (i = ready - WAIT_OBJECT_0 + 1; i < nhandles; i++)
+            {
+              handles[i-1] = handles[i];
+              handle_to_fd[i-1] = handle_to_fd[i];
+            }
          nhandles--;
-         recursed_result = poll_rest (NULL, handles, nhandles, fds, nfds, 0);
+         recursed_result = poll_rest (NULL, handles, handle_to_fd, nhandles, 0);
          return (recursed_result == -1) ? -1 : 1 + recursed_result;
        }
       return 1;
@@ -252,6 +249,7 @@ g_poll (GPollFD *fds,
        gint     timeout)
 {
   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
+  GPollFD *handle_to_fd[MAXIMUM_WAIT_OBJECTS];
   GPollFD *msg_fd = NULL;
   GPollFD *f;
   gint nhandles = 0;
@@ -279,6 +277,7 @@ g_poll (GPollFD *fds,
             {
               if (_g_main_poll_debug)
                 g_print (" %p", (HANDLE) f->fd);
+              handle_to_fd[nhandles] = f;
               handles[nhandles++] = (HANDLE) f->fd;
             }
         }
@@ -297,21 +296,21 @@ g_poll (GPollFD *fds,
       /* First check if one or several of them are immediately
        * available
        */
-      retval = poll_rest (msg_fd, handles, nhandles, fds, nfds, 0);
+      retval = poll_rest (msg_fd, handles, handle_to_fd, nhandles, 0);
 
       /* If not, and we have a significant timeout, poll again with
        * timeout then. Note that this will return indication for only
        * one event, or only for messages.
        */
       if (retval == 0 && (timeout == INFINITE || timeout > 0))
-       retval = poll_rest (msg_fd, handles, nhandles, fds, nfds, timeout);
+       retval = poll_rest (msg_fd, handles, handle_to_fd, nhandles, timeout);
     }
   else
     {
       /* Just polling for one thing, so no need to check first if
        * available immediately
        */
-      retval = poll_rest (msg_fd, handles, nhandles, fds, nfds, timeout);
+      retval = poll_rest (msg_fd, handles, handle_to_fd, nhandles, timeout);
     }
 
   if (retval == -1)