#include "sam.h" int	incache(Buffer*, Posn, Posn); Buffer *Bopen(Discdesc *dd){	Buffer *b; 	b = emalloc(sizeof(Buffer));	b->disc = Dopen(dd);	Strinit(&b->cache);	return b;} voidBclose(Buffer *b){	Dclose(b->disc);	Strclose(&b->cache);	free(b);} intBread(Buffer *b, Rune *addr, int n, Posn p0){	int m; 	if(b->c2>b->disc->nrunes || b->c1>b->disc->nrunes)		panic("bread cache");	if(p0 < 0)		panic("Bread p0<0");	if(p0+n > b->nrunes){		n = b->nrunes-p0;		if(n < 0)			panic("Bread<0");	}	if(!incache(b, p0, p0+n)){		Bflush(b);		if(n>=BLOCKSIZE/2)			return Dread(b->disc, addr, n, p0);		else{			Posn minp;			if(b->nrunes-p0>BLOCKSIZE/2)				m = BLOCKSIZE/2;			else				m = b->nrunes-p0;			if(m<n)				m = n;			minp = p0-BLOCKSIZE/2;			if(minp<0)				minp = 0;			m += p0-minp;			Strinsure(&b->cache, m);			if(Dread(b->disc, b->cache.s, m, minp)!=m)				panic("Bread");			b->cache.n = m;			b->c1 = minp;			b->c2 = minp+m;			b->dirty = FALSE;		}	}	memmove(addr, &b->cache.s[p0-b->c1], n*RUNESIZE);	return n;} voidBinsert(Buffer *b, String *s, Posn p0){	if(b->c2>b->disc->nrunes || b->c1>b->disc->nrunes)		panic("binsert cache");	if(p0<0)		panic("Binsert p0<0");	if(s->n == 0)		return;	if(incache(b, p0, p0) && b->cache.n+s->n<=STRSIZE){		Strinsert(&b->cache, s, p0-b->c1);		b->dirty = TRUE;		if(b->cache.n > BLOCKSIZE*2){			b->nrunes += s->n;			Bflush(b);			/* try to leave some cache around p0 */			if(p0 >= b->c1+BLOCKSIZE){				/* first BLOCKSIZE can go */				Strdelete(&b->cache, 0, BLOCKSIZE);				b->c1 += BLOCKSIZE;			}else if(p0 <= b->c2-BLOCKSIZE){				/* last BLOCKSIZE can go */				b->cache.n -= BLOCKSIZE;				b->c2 -= BLOCKSIZE;			}else{				/* too hard; negate the cache and pick up next time */				Strzero(&b->cache);				b->c1 = b->c2 = 0;			}			return;		}	}else{		Bflush(b);		if(s->n >= BLOCKSIZE/2){			b->cache.n = 0;			b->c1 = b->c2 = 0;			Dinsert(b->disc, s->s, s->n, p0);		}else{			int m;			Posn minp;			if(b->nrunes-p0 > BLOCKSIZE/2)				m = BLOCKSIZE/2;			else				m = b->nrunes-p0;			minp = p0-BLOCKSIZE/2;			if(minp < 0)				minp = 0;			m += p0-minp;			Strinsure(&b->cache, m);			if(Dread(b->disc, b->cache.s, m, minp)!=m)				panic("Bread");			b->cache.n = m;			b->c1 = minp;			b->c2 = minp+m;			Strinsert(&b->cache, s, p0-b->c1);			b->dirty = TRUE;		}	}	b->nrunes += s->n;} voidBdelete(Buffer *b, Posn p1, Posn p2){	if(p1<0 || p2<0)		panic("Bdelete p<0");	if(b->c2>b->disc->nrunes || b->c1>b->disc->nrunes)		panic("bdelete cache");	if(p1 == p2)		return;	if(incache(b, p1, p2)){		Strdelete(&b->cache, p1-b->c1, p2-b->c1);		b->dirty = TRUE;	}else{		Bflush(b);		Ddelete(b->disc, p1, p2);		b->cache.n = 0;		b->c1 = b->c2 = 0;	}	b->nrunes -= p2-p1;} voidBflush(Buffer *b){	if(b->dirty){		Dreplace(b->disc, b->c1, b->c2, b->cache.s, b->cache.n);		b->c2 = b->c1+b->cache.n;		b->dirty = FALSE;		if(b->nrunes != b->disc->nrunes)			panic("Bflush");	}} voidBclean(Buffer *b){	if(b->dirty){		Bflush(b);		b->c1 = b->c2 = 0;		Strzero(&b->cache);	}} /*int hits, misses; /**/ intincache(Buffer *b, Posn p1, Posn p2){	/*if(b->c1<=p1 && p2<=b->c1+b->cache.n)hits++; else misses++;/**/	return b->c1<=p1 && p2<=b->c1+b->cache.n;}