/// <summary>
/// Factory method to create a file mapping for read only access.
/// </summary>
/// <param name="fileName">The name of the file to open memory mapped.</param>
/// <returns></returns>
public static RawMemoryMapping <T> OpenRead(string fileName)
{
if (fileName == null)
{
throw new ArgumentNullException("fileName");
}
var mapping = new RawMemoryMapping <T>();
mapping.teaFile = TeaFile <T> .OpenRead(fileName);
try
{
FileStream fs = mapping.teaFile.Stream as FileStream;
if (fs == null)
{
throw new InvalidOperationException("TeaFile used for MemoryMapping is not a file stream but memory mapping requires a file.");
}
mapping.mappingHandle = UnsafeNativeMethods.CreateFileMapping(
fs.SafeFileHandle,
IntPtr.Zero,
MapProtection.PageReadOnly,
0,
0,
null);
if (mapping.mappingHandle.IsInvalid)
{
throw new Win32Exception();
}
try
{
mapping.mappingStart = UnsafeNativeMethods.MapViewOfFile(
mapping.mappingHandle,
MapAccess.FileMapRead,
0,
0,
IntPtr.Zero);
if (mapping.mappingStart == (byte *)0)
{
throw new Win32Exception();
}
mapping.itemAreaStart = mapping.mappingStart + mapping.teaFile.ItemAreaStart;
mapping.itemAreaEnd = mapping.itemAreaStart + mapping.teaFile.ItemAreaSize;
}
catch
{
if (UnsafeNativeMethods.CloseHandle(mapping.mappingHandle) == 0)
{
// our view mapping failed above, but we still had a good mapping handle, so if
// closing failed, we should check why
throw new Win32Exception();
}
mapping.mappingHandle = null;
throw;
}
return(mapping);
}
catch
{
mapping.Dispose();
throw;
}
}
/// <summary>Opens a memory mapping of the file using unsafe memory mapping. </summary>
/// <param name="path">path of the file. </param>
/// <returns>An instance of <see cref="RawMemoryMapping{T}"/> providing access to the items in the file. </returns>
/// <remarks>
/// Compared to <see cref="OpenRawMemoryMapping"/>, this raw access performs much better.
/// </remarks>
public static RawMemoryMapping <T> OpenRawMemoryMapping(string path)
{
return(RawMemoryMapping <T> .OpenRead(path));
}
