IFWXIOBuffer interface
Applies to: desktop apps only
The IFWXIOBuffer interface points to a reference counted memory buffer and provides the means of managing the buffer. The interface is a wrapper around a memory buffer. This allows the buffer to be used by many filters in a chain, avoiding the inefficient copying of buffers. For more information about memory buffers, see Buffer Objects.
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 IFWXSocket::Send, IFWXSocket::SendTo, and IFWXSocket::Recv methods increment the reference count on the buffer. This reference count is maintained until the IFWXIOCompletion::CompleteAsyncIO method returns. You must call the Release method for each AddRef method that you called, and once more if you also created the buffer. Call AddRef if you keep a pointer to the buffer.
For more information about how the IFWXSocket interface is used in application filters, see Filter Object Model.
Members
The IFWXIOBuffer interface inherits from the IUnknown interface. IFWXIOBuffer also has these types of members:
- Methods
Methods
The IFWXIOBuffer interface has these methods.
| Method | Description |
|---|---|
| Append | Appends a specified number of bytes of data to the buffer object. |
| GetBufferAndSize | Gets the actual data from the memory buffer, and the actual size (not the allocated size) of the buffer. |
| GetBufferSizes | Gets the allocated and actual buffer sizes. |
| ReadAt | Reads a specified number of bytes starting at a specified offset from the beginning of the buffer. |
| SendToBuffer | Copies a specified number of bytes starting at a specified offset from the beginning of the buffer to the given destination buffer. |
| SetDataSize | Sets the actual size of the memory buffer that was used. |
Remarks
Consider the size of the buffer needed. Data length information provided on the Internet may be inaccurate and may result in a buffer overflow.
This interface is generally implemented by the Microsoft 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 a remote procedure call (RPC) 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.
You can rely on the Firewall service implementation of IFWXIOBuffer, and not code a filter implementation, if:
- You want to send a constant buffer.
- You want to send a section of another buffer.
- Your filter can handle or parse the data from IFWXIOBuffer
- Buffer copy is not of concern.
Requirements
Minimum supported client |
None supported |
Minimum supported server |
Windows Server 2008 R2, Windows Server 2008 with SP2 (64-bit only) |
Version |
Forefront Threat Management Gateway (TMG) 2010 |
Header |
Wspfwext.idl |
See also
Build date: 7/12/2010