Re: How does BFruit.exe poll for input from GUI without getting stuckwaiting for GUI? - PeekNamedPipe


2005-09-20 02:54:00 PM
cppbuilder32
w h mowery jr wrote:
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PeekNamedPipe function does the trick.
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The PeekNamedPipe function copies data from a named or anonymous pipe
into a buffer without removing it from the pipe. It also returns
information about data in the pipe.
BOOL PeekNamedPipe(
HANDLE hNamedPipe, // handle to pipe to copy from
LPVOID lpBuffer, // pointer to data buffer
DWORD nBufferSize, // size, in bytes, of data buffer
LPDWORD lpBytesRead, // pointer to number of bytes read
LPDWORD lpTotalBytesAvail, // pointer to total number of bytes
available
LPDWORD lpBytesLeftThisMessage // pointer to unread bytes in this
message
);
Parameters
hNamedPipe
Identifies the pipe. This parameter can be a handle to a named pipe
instance, as returned by the CreateNamedPipe or CreateFile function, or
it can be a handle to the read end of an anonymous pipe, as returned by
the CreatePipe function. The handle must have GENERIC_READ access to the
pipe.
lpBuffer
Points to a buffer that receives data read from the pipe. This parameter
can be NULL if no data is to be read.
nBufferSize
Specifies the size, in bytes, of the buffer specified by the lpBuffer
parameter. This parameter is ignored if lpBuffer is NULL.
lpBytesRead
Points to a 32-bit variable that receives the number of bytes read from
the pipe. This parameter can be NULL if no data is to be read.
lpTotalBytesAvail
Points to a 32-bit variable that receives the total number of bytes
available to be read from the pipe. This parameter can be NULL if no
data is to be read.
lpBytesLeftThisMessage
Points to a 32-bit variable that receives the number of bytes remaining
in this message. This parameter will be zero for byte-type named pipes
or for anonymous pipes. This parameter can be NULL if no data is to be
read.
Return Values
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error
information, call GetLastError.
Remarks
PeekNamedPipe is similar to the ReadFile function with the following
exceptions:
?The data read from the pipe is not removed from the pipe's buffer.
?The function always returns immediately, even if there is no data in
the pipe. The wait mode of a named pipe handle (blocking or nonblocking)
has no effect on the function.
?The function can return additional information about the contents of
the pipe.
If the specified handle is a named pipe handle in byte-read mode, the
function reads all available bytes up to the size specified in
nBufferSize. For a named pipe handle in message-read mode, the function
reads the next message in the pipe. If the message is larger than
nBufferSize, the function returns TRUE after reading the specified
number of bytes. In this situation, lpBytesLeftThisMessage will receive
the number of bytes remaining in the message.
See Also
CreateFile, CreateNamedPipe, CreatePipe, ReadFile, WriteFile