/* LINTLIBRARY */
/*
 * pupwrite.c
 *
 * Pupwrite takes a buffer and sends it in a pup packet over
 * a Pup channel.
 *
 * Jeffrey Mogul & Dan Kolkowitz	12-January-1981
 *					26-January-1981
 *
 */

#include <puppacket.h>
#include <pupconstants.h>
#include <pupstatus.h>

pupwrite(Pchan, Ptype, ID, buf,buflen)
struct	PupChan	*Pchan;			/* channel to use */
uchar	Ptype;				/* Pup type */
ulong	ID;				/* Pup ID */
char	*buf;				/* data buffer */
int	buflen;				/* data buffer length */
{
	struct	EnPacket enpack;	/* ether encapsulation */
	int	roundlen;		/* length rounded up to even number */

	roundlen = roundup(buflen);	/* rounds UP to even number of bytes */

	/*
	 * here we would switch on the Chan->transport to
	 * determine which lower-level encapsulation to use
	 * if there were any choice.
	 */
	
	enpack.Pup.PupLength = PUPACKOVER + buflen;
					/* contains TRUE length of data */
	enpack.Pup.PupType = Ptype;
	enpack.Pup.PupTransport = 0;	/* this has NOTHING to do with
					 * the tranport medium! */
	enpack.Pup.PupID = makelong(ID);

	PortPack(&Pchan->DstPort,&enpack.Pup.PupDst);
	PortPack(&Pchan->SrcPort,&enpack.Pup.PupSrc);

	if (buflen)	/* dont move on zero length buffers */
	    bmove(buf,enpack.Pup.PupData, roundlen);	/* put data in packet */

#ifdef	PUP__NNSO	/* non-standard byte order */

	if (Pchan->mode&PCM_WFIXLAST)	/* byte swap last word in buffer */
		if (buflen&1) {	/* if buffer length is odd */
			enpack.Pup.PupData[buflen] = buf[buflen-1];
			}
#else			/* standard byte order - no trouble */
#endif

	/* set checksum into first WORD following data */
	if (Pchan->mode&PCM_WCHECKSUM)  /* compute checksum */
		*((ushort *) &enpack.Pup.PupData[roundlen]) =
			checksum(&enpack.Pup,roundlen+PUPACKOVER-2);
	else	/* send null checksum */
		*((short *) &enpack.Pup.PupData[roundlen]) = NOCKSUM;

	return(enwrite(Pchan->ImmHost,PUP,Pchan->ofid,
			&enpack,roundlen+PUPACKOVER));
	}