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/* Copyright (c) 1992 AT&T - All rights reserved. */
#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;
}
void
Bterm(Buffer *b)
{
Dclose(b->disc);
Strclose(&b->cache);
free(b);
}
int
Bread(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;
}
void
Binsert(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;
}
void
Bdelete(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;
}
void
Bflush(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");
}
}
void
Bclean(Buffer *b)
{
if(b->dirty){
Bflush(b);
b->c1 = b->c2 = 0;
Strzero(&b->cache);
}
}
/*int hits, misses; /**/
int
incache(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;
}
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