From 305e766f0f3ad7f4008d8fdbbc6b6b70e2101e2a Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@wxwidgets.org>
Date: Sun, 23 Mar 2014 00:57:00 +0000
Subject: [PATCH] Small refactoring in wxFileSystemWatcher MSW implementation.

Make wxIOCPService::GetStatus() smarter about its return value, it makes sense
to encapsulate the convention used to indicate the thread exit condition
inside wxIOCPService class itself instead of sharing it between it
wxIOCPThread itself.

It will also make it easier to detect more detailed error conditions in this
code.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76185 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
---
 include/wx/msw/private/fswatcher.h | 37 ++++++++++++++++++++++--------
 src/msw/fswatcher.cpp              | 15 ++++++++----
 2 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/include/wx/msw/private/fswatcher.h b/include/wx/msw/private/fswatcher.h
index 1442432a35..6e1044ea1d 100644
--- a/include/wx/msw/private/fswatcher.h
+++ b/include/wx/msw/private/fswatcher.h
@@ -206,6 +206,7 @@ public:
     {
         wxCHECK_MSG( m_iocp != INVALID_HANDLE_VALUE, false, "IOCP not init" );
 
+        // The special values of 0 will make GetStatus() return Status_Exit.
         int ret = PostQueuedCompletionStatus(m_iocp, 0, 0, NULL);
         if (!ret)
         {
@@ -215,25 +216,41 @@ public:
         return ret != 0;
     }
 
+    // Possible return values of GetStatus()
+    enum Status
+    {
+        // Status successfully retrieved into the provided arguments.
+        Status_OK,
+
+        // Special status indicating that we should exit retrieved.
+        Status_Exit,
+
+        // Some error occurred.
+        Status_Error
+    };
+
     // Wait for completion status to arrive.
     // This function can block forever in it's wait for completion status.
     // Use PostEmptyStatus() to wake it up (and end the worker thread)
-    bool GetStatus(unsigned long* count, wxFSWatchEntryMSW** watch,
-                   OVERLAPPED** overlapped)
+    Status
+    GetStatus(unsigned long* count, wxFSWatchEntryMSW** watch,
+              OVERLAPPED** overlapped)
     {
-        wxCHECK_MSG( m_iocp != INVALID_HANDLE_VALUE, false, "IOCP not init" );
-        wxCHECK_MSG( count != NULL, false, "Null out parameter 'count'");
-        wxCHECK_MSG( watch != NULL, false, "Null out parameter 'watch'");
-        wxCHECK_MSG( overlapped != NULL, false,
-                     "Null out parameter 'overlapped'");
+        wxCHECK_MSG( m_iocp != INVALID_HANDLE_VALUE, Status_Error,
+                     "Invalid IOCP object" );
+        wxCHECK_MSG( count && watch && overlapped, Status_Error,
+                     "Output parameters can't be NULL" );
 
         int ret = GetQueuedCompletionStatus(m_iocp, count, (ULONG_PTR *)watch,
                                             overlapped, INFINITE);
-        if (!ret)
+        if ( ret != 0 )
         {
-            wxLogSysError(_("Unable to dequeue completion packet"));
+            return *count || *watch || *overlapped ? Status_OK : Status_Exit;
         }
-        return ret != 0;
+
+        wxLogSysError(_("Unable to dequeue completion packet"));
+
+        return Status_Error;
     }
 
 protected:
diff --git a/src/msw/fswatcher.cpp b/src/msw/fswatcher.cpp
index d179f67155..98b1c1609f 100644
--- a/src/msw/fswatcher.cpp
+++ b/src/msw/fswatcher.cpp
@@ -224,12 +224,17 @@ bool wxIOCPThread::ReadEvents()
     unsigned long count = 0;
     wxFSWatchEntryMSW* watch = NULL;
     OVERLAPPED* overlapped = NULL;
-    if (!m_iocp->GetStatus(&count, &watch, &overlapped))
-        return true; // error was logged already, we don't want to exit
+    switch ( m_iocp->GetStatus(&count, &watch, &overlapped) )
+    {
+        case wxIOCPService::Status_OK:
+            break; // nothing special to do, continue normally
 
-    // this is our exit condition, so we return false
-    if (!count && !watch && !overlapped)
-        return false;
+        case wxIOCPService::Status_Error:
+            return true; // error was logged already, we don't want to exit
+
+        case wxIOCPService::Status_Exit:
+            return false; // stop reading events
+    }
 
     // if the thread got woken up but we got an empty packet it means that
     // there was an overflow, too many events and not all could fit in