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/* fifo_write.c -- Routines for writing to internally typed fifos.  */
#include <sys/typed.h>

/* Write a typed space into a FIFO.  */
typed_space *
fifo_write(ffp, space)
	FIFO *ffp;
	typed_space *space;
{
	return	(fifo_write_untyped(
			ffp,
			space->ts_data,
			(long) (space->ts_size - sizeof(typed_space)),
			space->ts_type)
		);
} /* fifo_write() */

/* Write a chunk of data into an open fifo as a typed space.
 * Takes a FIFO to be written to, ffp; a pointer to the data, datum; a
 * size for the datum, size; and a type for the new space, type.
 *
 * Returns a pointer to the newly written space.  Returns NULL if the
 * new space could not be written.
 *
 * Note that while sizes throughout this package refer to TOTAL sizes
 * including headers, the size argument here is ONLY for the datum.
 *
 * Only FIFOs of type T_FIFO_SIC are implimented.
 */
typed_space *
fifo_write_untyped(ffp, datum, size, type)
	FIFO *ffp;
	char *datum;
	long size;
	space_type type;
{
	long needed_space;	/* Total space we need to add.  */
	typed_space *retval;	/* Return the space we just wrote.  */

	/* Write MUST be set.  */
	if (F_WRITE != F_WRITE & ffp->f_flags ) {
		return(T_NULL);  /* This ffp is not open for writing.  */
	}

	/* From here to end of fifo_write_untyped() is really fifo_write_sic().  */

	/* Check to see that there is enough space for the new datum.
	 * We need space for another typed_space header, size bytes of
	 * data, and space for a terminating typed_space header.
	 */
	needed_space = sizeof(typed_space) + size + sizeof(typed_space);

	if (ffp->f_space->ts_size <
	    ((char *)ffp->f_offset - (char *)ffp->f_space) + needed_space) {
		return(T_NULL);		/* Insufficient space.  */
	}

	/* ASSERTION:  There is enough space remaining in ffp->f_space for
	 * two more headers and the datum.
	 */

	retval = ffp->f_offset;

	/* Create the new header.  */
	ffp->f_offset->ts_size = sizeof(typed_space) + size;
	ffp->f_offset->ts_type = type;

	/* Copy the datum in place.  */
	memcpy(ffp->f_offset->ts_data, datum, size);

	/* Advance the write pointer.  */
	ffp->f_offset += 1;		/* Skip the header.	*/
	(char *) ffp->f_offset += size;	/* Skip the data.	*/

	/* Terminate the fifo.  */
	ffp->f_offset->ts_size = (long) 0;
	ffp->f_offset->ts_type = T_UNKNOWN;

	return(retval);
} /* fifo_write_untyped() */

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