Microsoft Internet Security and Acceleration Server 2000

IFWXIOBuffer

The buffer object points to a reference-counted memory buffer and provides means of managing the buffer.

The following rules apply to these buffers:

The allocator of a buffer owns the buffer. Only the allocator may alter the contents of the buffer. This means that the receiver must not modify a buffer received in the IFWXIOCompletion::CompleteAsyncIO method after a call to the IFWXSocket::Recv method with the IOBuffer parameter set to NULL.
A buffer that is sent (by way of the IFWXSocket::Send or IFWXSocket::SendTo method) must remain valid and unmodified until the reference count reaches zero. Even the owner of the buffer is not allowed to modify a buffer after it is sent.

The Send, SendTo, and Recv methods increment the reference count on the buffer. This reference is kept until CompleteAsyncIO returns. You must call Release for each AddRef that you called, and once more if you also created the buffer. Call AddRef if you keep a pointer to the buffer.

Methods in Vtable Order

IUnknown Methods	Description
QueryInterface	Returns pointers to supported interfaces.
AddRef	Increments the reference count.
Release	Decrements the reference count.

IFWXIOBuffer Methods	Description
GetBufferAndSize	Gets the actual buffer and its size.
SetDataSize	Sets the actual size of the buffer that was used.
Append	Appends a specified number of bytes of data to the buffer object.
ReadAt	Reads a specified number of bytes starting at a specified offset from the beginning of the buffer.
SendToBuffer	Appends data from this buffer to another buffer.
GetBufferSizes	Gets the allocated and actual buffer sizes.

Remarks

This interface is generally implemented by the Firewall service. You may want to implement IFWXIOBuffer in your filter if:

You already have an allocated buffer that you want to send, and want to avoid creating a buffer copy. For example, the buffer was received from an RPC call or an API that cannot work with the Firewall service buffers.
You have to read into a preallocated buffer.
You want to use your own allocator for the buffer.

Requirements

  Windows NT/2000: Requires Windows 2000.
  Version: Requires ISA Server 2000.
  Header: Wspfwext.idl.