Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / IO / MemoryMappedFiles / MemoryMappedView.cs / 1305376 / MemoryMappedView.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== /*============================================================ ** ** Class: MemoryMappedView ** ** Purpose: Internal class representing MemoryMappedFile view ** ** Date: February 7, 2007 ** ===========================================================*/ using System; using System.Diagnostics; using System.Runtime.InteropServices; using System.Runtime.CompilerServices; using Microsoft.Win32; using Microsoft.Win32.SafeHandles; namespace System.IO.MemoryMappedFiles { internal class MemoryMappedView : IDisposable { private SafeMemoryMappedViewHandle m_viewHandle; private Int64 m_pointerOffset; private Int64 m_size; private MemoryMappedFileAccess m_access; //// [System.Security.SecurityCritical] private unsafe MemoryMappedView(SafeMemoryMappedViewHandle viewHandle, Int64 pointerOffset, Int64 size, MemoryMappedFileAccess access) { m_viewHandle = viewHandle; m_pointerOffset = pointerOffset; m_size = size; m_access = access; } internal SafeMemoryMappedViewHandle ViewHandle { //// // [System.Security.SecurityCritical] get { return m_viewHandle; } } internal Int64 PointerOffset { get { return m_pointerOffset; } } internal Int64 Size { get { return m_size; } } internal MemoryMappedFileAccess Access { get { return m_access; } } // Callers must demand unmanaged code first //// // [System.Security.SecurityCritical] internal unsafe static MemoryMappedView CreateView(SafeMemoryMappedFileHandle memMappedFileHandle, MemoryMappedFileAccess access, Int64 offset, Int64 size) { // MapViewOfFile can only create views that start at a multiple of the system memory allocation // granularity. We decided to hide this restriction form the user by creating larger views than the // user requested and hiding the parts that the user did not request. extraMemNeeded is the amount of // extra memory we allocate before the start of the requested view. MapViewOfFile will also round the // capacity of the view to the nearest multiple of the system page size. Once again, we hide this // from the user by preventing them from writing to any memory that they did not request. ulong extraMemNeeded = (ulong)offset % (ulong)MemoryMappedFile.GetSystemPageAllocationGranularity(); // newOffset takes into account the fact that we have some extra memory allocated before the requested view ulong newOffset = (ulong)offset - extraMemNeeded; Debug.Assert(newOffset >= 0, "newOffset = (offset - extraMemNeeded) < 0"); // determine size to pass to MapViewOfFile ulong nativeSize; if (size != MemoryMappedFile.DefaultSize) { nativeSize = (ulong)size + (ulong)extraMemNeeded; } else { nativeSize = 0; } if (IntPtr.Size == 4 && nativeSize > UInt32.MaxValue) { throw new ArgumentOutOfRangeException("size", SR.GetString(SR.ArgumentOutOfRange_CapacityLargerThanLogicalAddressSpaceNotAllowed)); } // if request is >= than total virtual, then MapViewOfFile will fail with meaningless error message // "the parameter is incorrect"; this provides better error message in advance UnsafeNativeMethods.MEMORYSTATUSEX memStatus = new UnsafeNativeMethods.MEMORYSTATUSEX(); bool result = UnsafeNativeMethods.GlobalMemoryStatusEx(memStatus); ulong totalVirtual = memStatus.ullTotalVirtual; if (nativeSize >= totalVirtual) { throw new IOException(SR.GetString(SR.IO_NotEnoughMemory)); } // split the Int64 into two ints uint offsetLow = (uint)(newOffset & 0x00000000FFFFFFFFL); uint offsetHigh = (uint)(newOffset >> 32); // create the view SafeMemoryMappedViewHandle viewHandle = UnsafeNativeMethods.MapViewOfFile(memMappedFileHandle, MemoryMappedFile.GetFileMapAccess(access), offsetHigh, offsetLow, new UIntPtr(nativeSize)); if (viewHandle.IsInvalid) { __Error.WinIOError(Marshal.GetLastWin32Error(), String.Empty); } // Query the view for its size and allocation type UnsafeNativeMethods.MEMORY_BASIC_INFORMATION viewInfo = new UnsafeNativeMethods.MEMORY_BASIC_INFORMATION(); UnsafeNativeMethods.VirtualQuery(viewHandle, ref viewInfo, (IntPtr)Marshal.SizeOf(viewInfo)); ulong viewSize = (ulong)viewInfo.RegionSize; // allocate the pages if we were using the MemoryMappedFileOptions.DelayAllocatePages option if ((viewInfo.State & UnsafeNativeMethods.MEM_RESERVE) != 0) { IntPtr tempHandle = UnsafeNativeMethods.VirtualAlloc(viewHandle, (UIntPtr)viewSize, UnsafeNativeMethods.MEM_COMMIT, MemoryMappedFile.GetPageAccess(access)); int lastError = Marshal.GetLastWin32Error(); if (viewHandle.IsInvalid) { __Error.WinIOError(lastError, String.Empty); } } // if the user specified DefaultSize as the size, we need to get the actual size if (size == MemoryMappedFile.DefaultSize) { size = (Int64)(viewSize - extraMemNeeded); } else { Debug.Assert(viewSize >= (ulong)size, "viewSize < size"); } viewHandle.Initialize((ulong)size + extraMemNeeded); MemoryMappedView mmv = new MemoryMappedView(viewHandle, (long)extraMemNeeded, size, access); return mmv; } // Flushes the changes such that they are in [....] with the FileStream bits (ones obtained // with the win32 ReadFile and WriteFile functions). Need to call FileStream's Flush to // flush to the disk. // NOTE: This will flush all bytes before and after the view up until an offset that is a multiple // of SystemPageSize. //// // // // // // // // // // // // // [System.Security.SecurityCritical] public void Flush(IntPtr capacity) { if (m_viewHandle != null) { unsafe { byte* firstPagePtr = null; RuntimeHelpers.PrepareConstrainedRegions(); try { m_viewHandle.AcquirePointer(ref firstPagePtr); if (!UnsafeNativeMethods.FlushViewOfFile(firstPagePtr, capacity)) { __Error.WinIOError(Marshal.GetLastWin32Error(), String.Empty); } } finally { if (firstPagePtr != null) { m_viewHandle.ReleasePointer(); } } } } } //// // // // // // // // // // // [System.Security.SecurityCritical] protected virtual void Dispose(bool disposing) { if (m_viewHandle != null && !m_viewHandle.IsClosed) { m_viewHandle.Dispose(); } } //// // // // [System.Security.SecurityCritical] public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } internal bool IsClosed { get { return (m_viewHandle == null || m_viewHandle.IsClosed); } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.//
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