/// <summary>
/// Sets the <see cref="ShuttingDown"/> flag, and disposes of the <see cref="MemoryMappedFile"/> and <see cref="MemoryMappedViewAccessor"/>.
/// Attempting to read/write to the buffer after closing will result in a <see cref="NullReferenceException"/>.
/// </summary>
public virtual void Close()
{
if (IsOwnerOfSharedMemory && View != null)
{
// Indicates to any open instances that the owner is no longer open
#pragma warning disable 0420 // ignore ref to volatile warning - Interlocked API
Interlocked.Exchange(ref Header->Shutdown, 1);
#pragma warning restore 0420
}
// Allow additional close logic
DoClose();
// Close the MemoryMappedFile and MemoryMappedViewAccessor
if (View != null)
{
View.SafeMemoryMappedViewHandle.ReleasePointer();
View.Dispose();
}
if (Mmf != null)
{
Mmf.Dispose();
}
Header = null;
ViewPtr = null;
BufferStartPtr = null;
View = null;
Mmf = null;
}
/// <summary>
/// Creates a new or opens an existing shared memory buffer with the name of <see cref="Name"/> depending on the value of <see cref="IsOwnerOfSharedMemory"/>.
/// </summary>
/// <exception cref="System.IO.IOException">Trying to create a new shared memory buffer with a duplicate name as buffer owner.</exception>
/// <exception cref="System.IO.FileNotFoundException">Trying to open a new shared memory buffer that does not exist as a consumer of existing buffer.</exception>
/// <exception cref="System.ArgumentOutOfRangeException">Trying to create a new shared memory buffer with a size larger than the logical addressable space.</exception>
/// <returns>`true` if the memory was successfully mapped. Otherwise, `false`.</returns>
/// <remarks>
/// If <see cref="IsOwnerOfSharedMemory"/> is `true`, the shared memory buffer will be created. Opening will fail in this case if the shared memory already
/// exists. Otherwise, if <see cref="IsOwnerOfSharedMemory"/> is `false`, the shared memory buffer will be opened, which will fail if it doesn't already exist.
/// </remarks>
protected bool Open()
{
Close();
try
{
// Attempts to create or open the shared memory with a name of this.Name
if (IsOwnerOfSharedMemory)
{
// Create a new shared memory mapping
Mmf = MemoryMappedFile.CreateNew(Name, SharedMemorySize);
// Create a view to the entire region of the shared memory
View = Mmf.CreateViewAccessor(0, SharedMemorySize, MemoryMappedFileAccess.ReadWrite);
View.SafeMemoryMappedViewHandle.AcquirePointer(ref ViewPtr);
Header = (SharedBufferHeader *)(ViewPtr + HeaderOffset);
BufferStartPtr = ViewPtr + BufferOffset;
// Initialise the header
InitializeHeader();
}
else
{
// Open an existing shared memory mapping
Mmf = MemoryMappedFile.OpenExisting(Name);
// Retrieve the header from the shared memory in order to initialise the correct size
using (var headerView = Mmf.CreateViewAccessor(0, HeaderOffset + Polyfill.GetMarshalSizeOf <SharedBufferHeader>(), MemoryMappedFileAccess.Read))
{
byte *headerPtr = null;
headerView.SafeMemoryMappedViewHandle.AcquirePointer(ref headerPtr);
var header = (SharedBufferHeader *)(headerPtr + HeaderOffset);
BufferSize = header->SharedMemorySize - Polyfill.GetMarshalSizeOf <SharedBufferHeader>();
headerView.SafeMemoryMappedViewHandle.ReleasePointer();
}
// Create a view to the entire region of the shared memory
View = Mmf.CreateViewAccessor(0, SharedMemorySize, MemoryMappedFileAccess.ReadWrite);
View.SafeMemoryMappedViewHandle.AcquirePointer(ref ViewPtr);
Header = (SharedBufferHeader *)(ViewPtr + HeaderOffset);
BufferStartPtr = ViewPtr + HeaderOffset + Polyfill.GetMarshalSizeOf <SharedBufferHeader>();
}
}
catch
{
Close();
throw;
}
// Complete any additional open logic
try
{
if (!DoOpen())
{
Close();
return(false);
}
else
{
return(true);
}
}
catch
{
Close();
throw;
}
}