(Windows) Don't create a file mapping for each view that is mapped

Creating a file mapping for each view mapped to memory is sub-optimal
and slow. With this change, a single mapping is created and reused when
mapping subsequent views of the file.

The handle returned from CreateFileForMapping (used in WinCE 5) is now
discarded, since the kernel manages it automatically with the file
mapping. This simplifies use of the deprecated map API.

Reviewed-by: Maurice Kalinowski
Reviewed-by: Marius Storm-Olsen

3 files changed, 34 insertions, 62 deletions

diff --git a/src/corelib/io/qfsfileengine.cpp b/src/corelib/io/qfsfileengine.cpp
index fb096a7..2c5451d 100644
--- a/src/corelib/io/qfsfileengine.cpp
+++ b/src/corelib/io/qfsfileengine.cpp
@@ -122,11 +122,9 @@ void QFSFileEnginePrivate::init()
 #ifdef Q_OS_WIN
     fileAttrib = INVALID_FILE_ATTRIBUTES;
     fileHandle = INVALID_HANDLE_VALUE;
+    mapHandle = INVALID_HANDLE_VALUE;
     cachedFd = -1;
 #endif
-#ifdef Q_USE_DEPRECATED_MAP_API
-    fileMapHandle = INVALID_HANDLE_VALUE;
-#endif
 }
 
 /*!
diff --git a/src/corelib/io/qfsfileengine_p.h b/src/corelib/io/qfsfileengine_p.h
index ee127c1..87f0737 100644
--- a/src/corelib/io/qfsfileengine_p.h
+++ b/src/corelib/io/qfsfileengine_p.h
@@ -110,7 +110,8 @@ public:
     FILE *fh;
 #ifdef Q_WS_WIN
     HANDLE fileHandle;
-    QHash<uchar *, QPair<int /*offset*/, HANDLE /*handle*/> > maps;
+    HANDLE mapHandle;
+    QHash<uchar *, DWORD /* offset % AllocationGranularity */> maps;
     mutable int cachedFd;
     mutable DWORD fileAttrib;
 #else
@@ -119,11 +120,6 @@ public:
 #endif
     int fd;
 
-#ifdef Q_USE_DEPRECATED_MAP_API
-    void mapHandleClose();
-    HANDLE fileMapHandle;
-#endif
-
     enum LastIOCommand
     {
         IOFlushCommand,
diff --git a/src/corelib/io/qfsfileengine_win.cpp b/src/corelib/io/qfsfileengine_win.cpp
index 898447c..151eabd 100644
--- a/src/corelib/io/qfsfileengine_win.cpp
+++ b/src/corelib/io/qfsfileengine_win.cpp
@@ -455,17 +455,10 @@ bool QFSFileEnginePrivate::nativeClose()
 
     // Windows native mode.
     bool ok = true;
-    if ((fileHandle == INVALID_HANDLE_VALUE || !CloseHandle(fileHandle))
-#ifdef Q_USE_DEPRECATED_MAP_API
-            && (fileMapHandle == INVALID_HANDLE_VALUE || !CloseHandle(fileMapHandle))
-#endif
-        ) {
+    if ((fileHandle == INVALID_HANDLE_VALUE || !::CloseHandle(fileHandle))) {
         q->setError(QFile::UnspecifiedError, qt_error_string());
         ok = false;
     }
-#ifdef Q_USE_DEPRECATED_MAP_API
-    fileMapHandle = INVALID_HANDLE_VALUE;
-#endif
     fileHandle = INVALID_HANDLE_VALUE;
     cachedFd = -1;              // gets closed by CloseHandle above
 
@@ -1931,42 +1924,42 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size,
         return 0;
     }
 
+    if (mapHandle == INVALID_HANDLE_VALUE) {
+        // get handle to the file
+        HANDLE handle = fileHandle;
 
-    // get handle to the file
-    HANDLE handle = fileHandle;
 #ifndef Q_OS_WINCE
-    if (handle == INVALID_HANDLE_VALUE && fh)
-        handle = (HANDLE)_get_osfhandle(QT_FILENO(fh));
+        if (handle == INVALID_HANDLE_VALUE && fh)
+            handle = (HANDLE)::_get_osfhandle(QT_FILENO(fh));
 #endif
 
 #ifdef Q_USE_DEPRECATED_MAP_API
-    if (fileMapHandle == INVALID_HANDLE_VALUE) {
         nativeClose();
-        fileMapHandle = CreateFileForMapping((const wchar_t*)nativeFilePath.constData(),
+        // handle automatically closed by kernel with mapHandle (below).
+        handle = ::CreateFileForMapping((const wchar_t*)nativeFilePath.constData(),
                 GENERIC_READ | (openMode & QIODevice::WriteOnly ? GENERIC_WRITE : 0),
                 0,
                 NULL,
                 OPEN_EXISTING,
                 FILE_ATTRIBUTE_NORMAL,
                 NULL);
-    }
-    handle = fileMapHandle;
 #endif
 
-    if (handle == INVALID_HANDLE_VALUE) {
-        q->setError(QFile::PermissionsError, qt_error_string(ERROR_ACCESS_DENIED));
-        return 0;
-    }
+        if (handle == INVALID_HANDLE_VALUE) {
+            q->setError(QFile::PermissionsError, qt_error_string(ERROR_ACCESS_DENIED));
+            return 0;
+        }
 
-    // first create the file mapping handle
-    DWORD protection = (openMode & QIODevice::WriteOnly) ? PAGE_READWRITE : PAGE_READONLY;
-    HANDLE mapHandle = ::CreateFileMapping(handle, 0, protection, 0, 0, 0);
-    if (mapHandle == NULL) {
-        q->setError(QFile::PermissionsError, qt_error_string());
+        // first create the file mapping handle
+        DWORD protection = (openMode & QIODevice::WriteOnly) ? PAGE_READWRITE : PAGE_READONLY;
+        mapHandle = ::CreateFileMapping(handle, 0, protection, 0, 0, 0);
+        if (mapHandle == INVALID_HANDLE_VALUE) {
+            q->setError(QFile::PermissionsError, qt_error_string());
 #ifdef Q_USE_DEPRECATED_MAP_API
-        mapHandleClose();
+            ::CloseHandle(handle);
 #endif
-        return 0;
+            return 0;
+        }
     }
 
     // setup args to map
@@ -1978,17 +1971,17 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size,
     DWORD offsetLo = offset & Q_UINT64_C(0xffffffff);
     SYSTEM_INFO sysinfo;
     ::GetSystemInfo(&sysinfo);
-    int mask = sysinfo.dwAllocationGranularity - 1;
-    int extra = offset & mask;
+    DWORD mask = sysinfo.dwAllocationGranularity - 1;
+    DWORD extra = offset & mask;
     if (extra)
         offsetLo &= ~mask;
 
     // attempt to create the map
-    LPVOID mapAddress = MapViewOfFile(mapHandle, access,
+    LPVOID mapAddress = ::MapViewOfFile(mapHandle, access,
                                       offsetHi, offsetLo, size + extra);
     if (mapAddress) {
         uchar *address = extra + static_cast<uchar*>(mapAddress);
-        maps[address] = QPair<int, HANDLE>(extra, mapHandle);
+        maps[address] = extra;
         return address;
     }
 
@@ -2001,10 +1994,8 @@ uchar *QFSFileEnginePrivate::map(qint64 offset, qint64 size,
     default:
         q->setError(QFile::UnspecifiedError, qt_error_string());
     }
-    CloseHandle(mapHandle);
-#ifdef Q_USE_DEPRECATED_MAP_API
-    mapHandleClose();
-#endif
+
+    ::CloseHandle(mapHandle);
     return 0;
 }
 
@@ -2015,32 +2006,19 @@ bool QFSFileEnginePrivate::unmap(uchar *ptr)
         q->setError(QFile::PermissionsError, qt_error_string(ERROR_ACCESS_DENIED));
         return false;
     }
-    uchar *start = ptr - maps[ptr].first;
+    uchar *start = ptr - maps[ptr];
     if (!UnmapViewOfFile(start)) {
         q->setError(QFile::PermissionsError, qt_error_string());
         return false;
     }
 
-    if (!CloseHandle((HANDLE)maps[ptr].second)) {
-        q->setError(QFile::UnspecifiedError, qt_error_string());
-        return false;
-    }
     maps.remove(ptr);
-
-#ifdef Q_USE_DEPRECATED_MAP_API
-    mapHandleClose();
-#endif
-    return true;
-}
-
-#ifdef Q_USE_DEPRECATED_MAP_API
-void QFSFileEnginePrivate::mapHandleClose()
-{
     if (maps.isEmpty()) {
-        CloseHandle(fileMapHandle);
-        fileMapHandle = INVALID_HANDLE_VALUE;
+        ::CloseHandle(mapHandle);
+        mapHandle = INVALID_HANDLE_VALUE;
     }
+
+    return true;
 }
-#endif
 
 QT_END_NAMESPACE