/// <summary>
/// The completion callback for when the operation completes. This is
/// an internal callback that frees the native memory and subsequently
/// invokes the original caller's completion callback so it can
/// retrieve the result.
/// </summary>
private unsafe void CompletionCallback(
UInt32 errorCode,
UInt32 numBytes,
NativeOverlapped *nativeOverlapped
)
{
// First, free the NativeOverlapped structure and let this
// IAsyncResult be collectable by the garbage collector
Overlapped.Free(nativeOverlapped);
try
{
if (errorCode != 0)
{
// Check if an error occurred and record the error if so
base.SetAsCompleted(new Win32Exception((Int32)errorCode), false);
}
else
{
// No error occurred, so the output buffer must contain the
// result!
TResult result = (TResult)mOutDeviceBuffer.Target;
// The result is going to be an array of bytes, so we need
// to resize the array to the exact size so that the Length
// property is accurate
if ((result != null) && result.GetType().IsArray)
{
// Only resize if the number of elements initialized in
// the array is less than the size of the array itself
Type elementType = result.GetType().GetElementType();
Int64 numElements = numBytes / Marshal.SizeOf(elementType);
Array originalArray = (Array)(object)result;
if (numElements < originalArray.Length)
{
// Create a new array whose size is the number of
// initialized elements
Array newArray = Array.CreateInstance(elementType,
numElements
);
// Copy the initialized elements from the original
// array to the new one
Array.Copy(originalArray, newArray, numElements);
result = (TResult)(object)newArray;
}
}
// Record the result and call the AsyncCallback method
base.SetAsCompleted(result, false);
}
}
finally
{
// Make sure that the input and output buffers are unpinned
mOutDeviceBuffer.Dispose();
mOutDeviceBuffer = null; // Allow early GC
}
}
// This method is called by a thread pool thread when native overlapped I/O completes
private unsafe void CompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped *nativeOverlapped)
{
// Release the native OVERLAPPED structure and
// let the IAsyncResult object (this) be collectable.
Overlapped.Free(nativeOverlapped);
try {
if (errorCode != 0)
{
// An error occurred, record the Win32 error code
base.SetAsCompleted(new Win32Exception((Int32)errorCode), false);
}
else
{
// No error occurred, the output buffer contains the result
TResult result = (TResult)m_outBuffer.Target;
// If the result is an array of values, resize the array
// to the exact size so that the Length property is accurate
if ((result != null) && result.GetType().IsArray)
{
// Only resize if the number of elements initialized in the
// array is less than the size of the array itself
Type elementType = result.GetType().GetElementType();
Int64 numElements = numBytes / Marshal.SizeOf(elementType);
Array origArray = (Array)(Object)result;
if (numElements < origArray.Length)
{
// Create a new array whose size equals the number of initialized elements
Array newArray = Array.CreateInstance(elementType, numElements);
// Copy the initialized elements from the original array to the new array
Array.Copy(origArray, newArray, numElements);
result = (TResult)(Object)newArray;
}
}
// Record result and call AsyncCallback method passed to BeginXxx method
base.SetAsCompleted(result, false);
}
}
finally {
// Make sure that the input and output buffers are unpinned
m_inBuffer.Dispose();
m_outBuffer.Dispose();
m_inBuffer = m_outBuffer = null; // Allow early GC
}
}