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mapviewoffile (kernel32)
 
.
Summary

C# Signature:

[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr MapViewOfFile(
    IntPtr hFileMappingObject,
    FileMapAccess dwDesiredAccess,
    UInt32 dwFileOffsetHigh,
    UInt32 dwFileOffsetLow,
    UIntPtr dwNumberOfBytesToMap);

[Flags]
public enum FileMapAccess : uint
{
    FileMapCopy = 0x0001,
    FileMapWrite = 0x0002,
    FileMapRead = 0x0004,
    FileMapAllAccess = 0x001f,
    FileMapExecute = 0x0020,
}

VB .Net

Declare Function MapViewOfFile Lib "kernel32" (ByVal hFileMappingObject As IntPtr, ByVal dwDesiredAccess As UInt32, ByVal dwFileOffsetHigh As UInt32, ByVal dwFileOffsetLow As UInt32, ByVal dwNumberOfBytesToMap As UInt32) As UInt32

VB .Net Sample Code:

Declare Function MapViewOfFile Lib "kernel32" (ByVal hFileMappingObject As IntPtr, ByVal dwDesiredAccess As UInt32, ByVal dwFileOffsetHigh As UInt32, ByVal dwFileOffsetLow As UInt32, ByVal dwNumberOfBytesToMap As UInt32) As UInt32

Public Structure SECURITY_ATTRIBUTES
     Public lLength As Long
     Public lSecurityDescriptor As Long
     Public lInhertitHandle As Long
End Structure

Dim SecAttrib As SECURITY_ATTRIBUTES
Dim nAckEvent As Integer
Dim nReadyEvent As Integer
Dim nSharedFile As Long
Dim nSharedMem As Long
Dim nSecurityDesc As Integer

Public Const GPTR As Long = &H40
Public Const SECURITY_DESCRIPTOR_REVISION As Long = (1)
Public Const SECURITY_DESCRIPTOR_MIN_LENGTH As Long = (20)
Public Const PAGE_READWRITE As Int32 = &H4
Public Const FILE_MAP_READ As Int32 = &H40&, 512)

nSecurityDesc = GlobalAlloc(GPTR, SECURITY_DESCRIPTOR_MIN_LENGTH)

SecAttrib.lLength = SecAttrib.nLength
SecAttrib.lInheritHandle = Convert.ToInt32(True)
SecAttrib.lSecurityDescriptor = pSecurityDesc

nAckEvent = CreateEvent(SecAttrib, 0, 0, "DBWIN_BUFFER_READY")
nReadyEvent = CreateEvent(SecAttrib, 0, 0, "DBWIN_DATA_READY")
nSharedFile = CreateFileMapping(-1, SecAttrib, PAGE_READWRITE, 0&, 4096, "DBWIN_BUFFER")
nSharedMem = MapViewOfFile(nSharedFile, FILE_MAP_READ, 0&,  0&, 0&, 512)

User-Defined Types:

None.

Notes:

#define SECTION_QUERY        0x0001
#define SECTION_MAP_WRITE        0x0002
#define SECTION_MAP_READ         0x0004
#define SECTION_MAP_EXECUTE      0x0008
#define SECTION_EXTEND_SIZE      0x0010
#define SECTION_MAP_EXECUTE_EXPLICIT 0x0020 // not included in SECTION_ALL_ACCESS

#define SECTION_ALL_ACCESS (STANDARD_RIGHTS_REQUIRED|SECTION_QUERY|\
                 SECTION_MAP_WRITE |      \
                 SECTION_MAP_READ |       \
                 SECTION_MAP_EXECUTE |    \
                 SECTION_EXTEND_SIZE)

#define FILE_MAP_COPY       SECTION_QUERY
#define FILE_MAP_WRITE      SECTION_MAP_WRITE
#define FILE_MAP_READ       SECTION_MAP_READ
#define FILE_MAP_ALL_ACCESS SECTION_ALL_ACCESS
#define FILE_MAP_EXECUTE    SECTION_MAP_EXECUTE_EXPLICIT    // not included in FILE_MAP_ALL_ACCESS

Tips & Tricks:

Please add some!

C# Sample Code:

        const UInt32 STANDARD_RIGHTS_REQUIRED = 0x000F0000;
        const UInt32 SECTION_QUERY = 0x0001;
        const UInt32 SECTION_MAP_WRITE = 0x0002;
        const UInt32 SECTION_MAP_READ = 0x0004;
        const UInt32 SECTION_MAP_EXECUTE = 0x0008;
        const UInt32 SECTION_EXTEND_SIZE = 0x0010;
        const UInt32 SECTION_ALL_ACCESS = (STANDARD_RIGHTS_REQUIRED|SECTION_QUERY|
            SECTION_MAP_WRITE |      
            SECTION_MAP_READ |      
            SECTION_MAP_EXECUTE |    
            SECTION_EXTEND_SIZE);
        const UInt32 FILE_MAP_ALL_ACCESS = SECTION_ALL_ACCESS;
        private IntPtr hHandle;
        private IntPtr pBuffer;
        unsafe public void Attach(string SharedMemoryName, UInt32 NumBytes)
        {
            if (IntPtr.Zero != hHandle) return;
            hHandle = OpenFileMapping(FILE_MAP_ALL_ACCESS, false, SharedMemoryName);
            if (IntPtr.Zero == hHandle) return;
            pBuffer = MapViewOfFile(hHandle, FILE_MAP_ALL_ACCESS, 0, 0, NumBytes);
        }
        public void Detach()
        {
            if (IntPtr.Zero != hHandle)
            {
                CloseHandle(hHandle); //fair to leak if can't close
                hHandle = IntPtr.Zero;
            }
            pBuffer = IntPtr.Zero;
            lBufferSize = 0;
        }

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