internal static MemoryMappedView CreateView(SafeMemoryMappedFileHandle safeMemoryMappedFileHandle, MemoryMappedFileAccess access, long offset, long size)
{
// http://msdn.microsoft.com/en-us/library/windows/desktop/aa366548(v=vs.85).aspx
UnsafeNative.SYSTEM_INFO info = new UnsafeNative.SYSTEM_INFO();
UnsafeNative.GetSystemInfo(ref info);
// To calculate where to start the file mapping, round down the
// offset of the data into the memory-mapped file to the nearest multiple of the
// system allocation granularity.
long fileMapStart = (offset / info.dwAllocationGranularity) * info.dwAllocationGranularity;
// How large will the file mapping object be?
long mapViewSize = (offset % info.dwAllocationGranularity) + size;
// The data of interest is not necessarily at the beginning of the
// view, so determine how far into the view to set the pointer.
long viewDelta = offset - fileMapStart;
SafeMemoryMappedViewHandle safeHandle = UnsafeNative.MapViewOfFile(safeMemoryMappedFileHandle, access.ToMapViewFileAccess(), (ulong)fileMapStart, new UIntPtr((ulong)mapViewSize));
var lastWin32Error = Marshal.GetLastWin32Error();
if (safeHandle.IsInvalid)
{
if (lastWin32Error == UnsafeNative.ERROR_FILE_NOT_FOUND)
{
throw new FileNotFoundException();
}
throw new System.IO.IOException(UnsafeNative.GetMessage(lastWin32Error));
}
return(new MemoryMappedView(safeHandle, viewDelta, size));
}
internal static string GetMessage(int errorCode)
{
StringBuilder stringBuilder = new StringBuilder(512);
if (UnsafeNative.FormatMessage(12800, IntPtr.Zero, errorCode, 0, stringBuilder, stringBuilder.Capacity, IntPtr.Zero) != 0)
{
return(stringBuilder.ToString());
}
return(string.Concat("UnknownError_Num ", errorCode));
}
public static MemoryMappedFile OpenExisting(string mapName)
{
SafeMemoryMappedFileHandle safeMemoryMappedFileHandle = UnsafeNative.OpenFileMapping((uint)MemoryMappedFileRights.ReadWrite, false, mapName);
int lastWin32Error = Marshal.GetLastWin32Error();
if (safeMemoryMappedFileHandle.IsInvalid)
{
if (lastWin32Error == UnsafeNative.ERROR_FILE_NOT_FOUND)
throw new FileNotFoundException();
throw new System.IO.IOException(UnsafeNative.GetMessage(lastWin32Error));
}
return new MemoryMappedFile(safeMemoryMappedFileHandle);
}
private static SafeMemoryMappedFileHandle DoCreate(string path, string mapName, long capacity, out bool exists, bool readCapacity = false)
{
exists = File.Exists(path);
FileStream file = File.Open(path, FileMode.OpenOrCreate);
if (exists && file.Length != capacity)
{
if (!readCapacity)
{
file.Close();
File.Copy(path, path + "_old", true);
File.Delete(path);
file = File.Open(path, FileMode.OpenOrCreate);
}
else
{
byte[] byt = new byte[8];
file.Read(byt, 0, 8);
capacity = BitConverter.ToInt32(byt, 0);
}
}
SafeFileHandle fileHandle = file.SafeFileHandle;
SafeMemoryMappedFileHandle safeHandle = UnsafeNative.CreateFileMapping(fileHandle,
(UnsafeNative.FileMapProtection)MemoryMappedFileAccess.ReadWrite,
capacity, mapName);
var lastWin32Error = Marshal.GetLastWin32Error();
if (!safeHandle.IsInvalid && (lastWin32Error == UnsafeNative.ERROR_ALREADY_EXISTS))
{
throw new System.IO.IOException(UnsafeNative.GetMessage(lastWin32Error));
}
else if (safeHandle.IsInvalid && lastWin32Error > 0)
{
throw new System.IO.IOException(UnsafeNative.GetMessage(lastWin32Error));
}
if (safeHandle == null || safeHandle.IsInvalid)
{
throw new InvalidOperationException("Cannot create file mapping");
}
return(safeHandle);
}
