CHANNEL_PDU_HEADER structure (pchannel.h)

Contains information about a data block being received by the server end of a virtual channel.

Syntax

typedef struct tagCHANNEL_PDU_HEADER {
  UINT32 length;
  UINT32 flags;
} CHANNEL_PDU_HEADER, *PCHANNEL_PDU_HEADER;

Members

length

Size, in bytes, of the data block, excluding this header.

flags

Information about the data block. The following bit flags will be set. Note that you should not make direct comparisons using the '==' operator when comparing the values in the following list; instead, use the comparison methods described in the list.

CHANNEL_FLAG_FIRST (1)

The chunk is the beginning of the data written by a single write operation.

Use bitwise comparisons when comparing this flag.

CHANNEL_FLAG_LAST (2)

The chunk is the end of the data written by a single write operation.

Use bitwise comparisons when comparing this flag.

CHANNEL_FLAG_MIDDLE (0)

This is the default. The chunk is in the middle of a block of data written by a single write operation.

Do not use bitwise comparisons to compare this flag value directly. Instead, use bitwise comparisons to determine that the flag value is not CHANNEL_FLAG_FIRST or CHANNEL_FLAG_LAST. This is done by using the following comparison:

Result = !(flags & CHANNEL_FLAG_FIRST) && !(flags & CHANNEL_FLAG_LAST)

CHANNEL_FLAG_ONLY (3)

Combines the CHANNEL_FLAG_FIRST and CHANNEL_FLAG_LAST values. The chunk contains all the data from a single write operation.

Use bitwise comparisons when comparing this flag.

Remarks

In certain cases, Remote Desktop Services places a CHANNEL_PDU_HEADER structure at the beginning of each chunk of data read by a call to the WTSVirtualChannelRead function. This will occur if the client DLL sets the CHANNEL_OPTION_SHOW_PROTOCOL option when it calls the VirtualChannelInit function to initialize the virtual channel. This will also occur if the channel is a dynamic virtual channel written to by using the IWTSVirtualChannel::Write method.

Requirements

See also

IWTSVirtualChannel::Write

VirtualChannelInit

VirtualChannelWrite

WTSVirtualChannelRead