CreatePipe

The CreatePipe function creates an anonymous pipe, and returns handles to the read and write ends of the pipe.

BOOL CreatePipe(
  PHANDLE hReadPipe,                       // read handle
  PHANDLE hWritePipe,                      // write handle
  LPSECURITY_ATTRIBUTES lpPipeAttributes,  // security attributes
  DWORD nSize                              // pipe size
);

Parameters

hReadPipe

[out] Pointer to a variable that receives the read handle for the pipe.

hWritePipe

[out] Pointer to a variable that receives the write handle for the pipe.

lpPipeAttributes

[in] Pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpPipeAttributes is NULL, the handle cannot be inherited.

Windows NT/2000: The lpSecurityDescriptor member of the structure specifies a security descriptor for the new pipe. If lpPipeAttributes is NULL, the pipe gets a default security descriptor.

nSize

[in] Specifies the buffer size for the pipe, in bytes. The size is only a suggestion; the system uses the value to calculate an appropriate buffering mechanism. If this parameter is zero, the system uses the default buffer size.

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

CreatePipe creates the pipe, assigning the specified pipe size to the storage buffer. CreatePipe also creates handles that the process uses to read from and write to the buffer in subsequent calls to the ReadFile and WriteFile functions.

To read from the pipe, a process uses the read handle in a call to the ReadFile function. ReadFile returns when one of the following is true: a write operation completes on the write end of the pipe, the number of bytes requested has been read, or an error occurs.

When a process uses WriteFile to write to an anonymous pipe, the write operation is not completed until all bytes are written. If the pipe buffer is full before all bytes are written, WriteFile does not return until another process or thread uses ReadFile to make more buffer space available.

Windows NT/2000: Anonymous pipes are implemented using a named pipe with a unique name. Therefore, you can often pass a handle to an anonymous pipe to a function that requires a handle to a named pipe.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winbase.h; include Windows.h.
  Library: Use Kernel32.lib.

See Also

Pipes Overview, Pipe Functions, ReadFile, SECURITY_ATTRIBUTES, WriteFile