pk3.c

unix v7是最后一个广泛发布的研究型UNIX版本

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/conf.h"
#include "../h/buf.h"

#define	XPRI	30
#define	NBLOCKS	10

int	bwaiting, wcount;
struct	buf *bufps[NBLOCKS];
char	*nbase[NBLOCKS];	/* normal allocations */
short	nmap[NBLOCKS];		/* 1 bit == 32 bytes */

char log[] ={0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4};
#define	FULL	-1
#define	LOCK	s = spl6()
#define	UNLOCK	splx(s)

/*
 * getepack: get empty packet
 * with size specified by bitmask.
 */
char *
getepack(bits)
{
register i;
int	s, savbits;
char	**base;
short	*map;

	base = nbase; map = nmap;
	savbits = bits;

	/*
	 * search for space
	 */
	LOCK;
	for(;;) {

		if (bits == FULL)
			goto force;

		for(i=0; i<NBLOCKS; i++) {
			register m;
			register unsigned n;
			register offset;

			m = map[i];
			if (m==FULL || base[i]==NULL)
				continue;
			if (bits == 1) {
				n = m;
				m |= m+1;
				n = m-n;
				for (offset=0; n > 16; n >>= 4) 
					offset += 4;
				offset += log[n];
			} else {
				bits = savbits;
				for(n=17; --n; bits <<= 1)
					if ((m&bits)==0)
						goto found;
				continue;
			found:
				offset = 16-n;
				m |= bits;
			}
			map[i] = m;
			UNLOCK;
			return(base[i] + 32*offset);
		}
		/*
		 * grab another block from the system
		 */
	force:
		for(i=0;i<NBLOCKS;i++) {
			register struct buf *bp;

			if (bufps[i]!=NULL)
				continue;
			bufps[i] = bp = geteblk();
			bp->b_flags |= B_PACK;
			bp->b_flags |= B_PBUSY;
			map[i] = bits;
			base[i] = bp->b_un.b_addr;
			UNLOCK;
			return(bp->b_un.b_addr);
		}
		/*
		 * sleep until something is released
		 */
		bwaiting++;
		wcount++;
		sleep((caddr_t)&bwaiting, XPRI);
		bwaiting--;
	}
}

/*
 * freepack: release space beginning
 * at address p with length specified
 * by bits.
 */
freepack(p, bits)
char *p;
{
register i, d, s;
char	**base;
short	*map;

	if (p==NULL)
		return;
	LOCK;
	base = nbase; map = nmap;

	for(i=0;i<NBLOCKS;i++) {
		d = p-base[i];
		if (d>=0 && d<=512) 
			goto found;
	}
	goto out;
found:
	d >>= 5;
	d = (bits<<d);
	map[i] &= ~d;
	if (map[i]==0) {
		register struct buf *bp;

		bp = bufps[i];
		bp->b_flags &= ~B_PBUSY;
		base[i] = NULL;
		bufps[i] = NULL;
		brelse(bp);
	}
	if (bwaiting)
		wakeup((caddr_t)&bwaiting);
out:
	splx(s);
}



/*
 * integer to bitmap conversion
 */
dtom(d)
register d;
{
register m;

	m = 1;
	while (d>32) {
		d -= 32;
		m |= m+1;
	}
	return(m);
}

#define NRECS	160
int reclist[NRECS];
int recbits[NRECS];