READFILEDATA(3A)                                 READFILEDATA(3A)



  NAME
       ReadFileData - asynchronously read a block of data from a
       file


  SYNOPSIS
       int ReadFileData (ready, error, arg, size, name)
       int (*ready)();
       char *(*error)();
       int arg;
       int size;
       char *name;

  DESCRIPTION
       ReadFileData reads a file for binary data.  The name of the
       file to read is in name.  The number of bytes to read is in
       size.  If size is zero, the entire file is read.  The
       function ready is called when the data has been read, and
       the function error is called upon an error.  Either function
       may be NULL, in which case it will not be called.  When
       there is an error, the file is closed, so exactly one of the
       two functions ready and error is called.  The argument arg
       is passed to both routines.

       The calling sequence for ready is as follows:

            ready (arg, buf, length)
            int arg;
            char *buf;
            int length;

       The first argument arg is the argument supplied to
       ReadFileData, buf is the data in allocated memory, and
       length is the number of bytes read.  The application is
       responsible for freeing the buffer when done with it using
       the library routine free (3).

       The calling sequence for error is as follows:

            error (arg, errno)


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  READFILEDATA(3A)                                 READFILEDATA(3A)



            int arg;
            int errno;

       The user-supplied data to ReadFileData is passed in arg and
       an error code interpreted the same as the system global
       variable errno is passed in errno.

       ReadFileData returns -1 if there was an error setting up the
       I/O procedure, or zero on success.

  NOTES
       There are lower-level asynchronous I/O routines AddIoProc
       and RemoveIoProc that provide greater flexibility at the
       expense of greater coding effort.  ReadFileData uses these
       routines to set up an asynchronous read procedure.

  SEE ALSO
       XtAppAddInput(3Xt), XtRemoveInput(3Xt), AddIoProc(3A),
       RemoveIoProc(3A), ReadFileLines(3A), ReadFileStrings(3A),
       ReadPipeData(3A), ReadPipeLines(3A), ReadPipeStrings(3A),
       WriteFileData(3A), WriteFileLines(3A), WritePipeData(3A),
       WritePipeLines(3A)




















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