ref: 52cacba37c6f3a125ef931afa4b9c2cdb7438fef
dir: /sys/src/cmd/sam/buff.c/
#include "sam.h"
enum
{
Slop = 100, /* room to grow with reallocation */
};
static
void
sizecache(Buffer *b, uint n)
{
if(n <= b->cmax)
return;
b->cmax = n+Slop;
b->c = runerealloc(b->c, b->cmax);
}
static
void
addblock(Buffer *b, uint i, uint n)
{
if(i > b->nbl)
panic("internal error: addblock");
b->bl = realloc(b->bl, (b->nbl+1)*sizeof b->bl[0]);
if(i < b->nbl)
memmove(b->bl+i+1, b->bl+i, (b->nbl-i)*sizeof(Block*));
b->bl[i] = disknewblock(disk, n);
b->nbl++;
}
static
void
delblock(Buffer *b, uint i)
{
if(i >= b->nbl)
panic("internal error: delblock");
diskrelease(disk, b->bl[i]);
b->nbl--;
if(i < b->nbl)
memmove(b->bl+i, b->bl+i+1, (b->nbl-i)*sizeof(Block*));
b->bl = realloc(b->bl, b->nbl*sizeof b->bl[0]);
}
/*
* Move cache so b->cq <= q0 < b->cq+b->cnc.
* If at very end, q0 will fall on end of cache block.
*/
static
void
flush(Buffer *b)
{
if(b->cdirty || b->cnc==0){
if(b->cnc == 0)
delblock(b, b->cbi);
else
diskwrite(disk, &b->bl[b->cbi], b->c, b->cnc);
b->cdirty = FALSE;
}
}
static
void
setcache(Buffer *b, uint q0)
{
Block **blp, *bl;
uint i, q;
if(q0 > b->nc)
panic("internal error: setcache");
/*
* flush and reload if q0 is not in cache.
*/
if(b->nc == 0 || (b->cq<=q0 && q0<b->cq+b->cnc))
return;
/*
* if q0 is at end of file and end of cache, continue to grow this block
*/
if(q0==b->nc && q0==b->cq+b->cnc && b->cnc<=Maxblock)
return;
flush(b);
/* find block */
if(q0 < b->cq){
q = 0;
i = 0;
}else{
q = b->cq;
i = b->cbi;
}
blp = &b->bl[i];
while(q+(*blp)->n <= q0 && q+(*blp)->n < b->nc){
q += (*blp)->n;
i++;
blp++;
if(i >= b->nbl)
panic("block not found");
}
bl = *blp;
/* remember position */
b->cbi = i;
b->cq = q;
sizecache(b, bl->n);
b->cnc = bl->n;
/*read block*/
diskread(disk, bl, b->c, b->cnc);
}
void
bufinsert(Buffer *b, uint q0, Rune *s, uint n)
{
uint i, m, t, off;
if(q0 > b->nc)
panic("internal error: bufinsert");
while(n > 0){
setcache(b, q0);
off = q0-b->cq;
if(b->cnc+n <= Maxblock){
/* Everything fits in one block. */
t = b->cnc+n;
m = n;
if(b->bl == nil){ /* allocate */
if(b->cnc != 0)
panic("internal error: bufinsert1 cnc!=0");
addblock(b, 0, t);
b->cbi = 0;
}
sizecache(b, t);
runemove(b->c+off+m, b->c+off, b->cnc-off);
runemove(b->c+off, s, m);
b->cnc = t;
goto Tail;
}
/*
* We must make a new block. If q0 is at
* the very beginning or end of this block,
* just make a new block and fill it.
*/
if(q0==b->cq || q0==b->cq+b->cnc){
if(b->cdirty)
flush(b);
m = min(n, Maxblock);
if(b->bl == nil){ /* allocate */
if(b->cnc != 0)
panic("internal error: bufinsert2 cnc!=0");
i = 0;
}else{
i = b->cbi;
if(q0 > b->cq)
i++;
}
addblock(b, i, m);
sizecache(b, m);
runemove(b->c, s, m);
b->cq = q0;
b->cbi = i;
b->cnc = m;
goto Tail;
}
/*
* Split the block; cut off the right side and
* let go of it.
*/
m = b->cnc-off;
if(m > 0){
i = b->cbi+1;
addblock(b, i, m);
diskwrite(disk, &b->bl[i], b->c+off, m);
b->cnc -= m;
}
/*
* Now at end of block. Take as much input
* as possible and tack it on end of block.
*/
m = min(n, Maxblock-b->cnc);
sizecache(b, b->cnc+m);
runemove(b->c+b->cnc, s, m);
b->cnc += m;
Tail:
b->nc += m;
q0 += m;
s += m;
n -= m;
b->cdirty = TRUE;
}
}
void
bufdelete(Buffer *b, uint q0, uint q1)
{
uint m, n, off;
if(!(q0<=q1 && q0<=b->nc && q1<=b->nc))
panic("internal error: bufdelete");
while(q1 > q0){
setcache(b, q0);
off = q0-b->cq;
if(q1 > b->cq+b->cnc)
n = b->cnc - off;
else
n = q1-q0;
m = b->cnc - (off+n);
if(m > 0)
runemove(b->c+off, b->c+off+n, m);
b->cnc -= n;
b->cdirty = TRUE;
q1 -= n;
b->nc -= n;
}
}
uint
bufload(Buffer *b, uint q0, int fd, int *nulls)
{
char *p;
Rune *r;
int l, m, n, nb, nr;
uint q1;
if(q0 > b->nc)
panic("internal error: bufload");
p = malloc((Maxblock+UTFmax+1)*sizeof p[0]);
if(p == nil)
panic("bufload: malloc failed");
r = runemalloc(Maxblock);
m = 0;
n = 1;
q1 = q0;
/*
* At top of loop, may have m bytes left over from
* last pass, possibly representing a partial rune.
*/
while(n > 0){
n = read(fd, p+m, Maxblock);
if(n < 0){
error(Ebufload);
break;
}
m += n;
p[m] = 0;
l = m;
if(n > 0)
l -= UTFmax;
cvttorunes(p, l, r, &nb, &nr, nulls);
memmove(p, p+nb, m-nb);
m -= nb;
bufinsert(b, q1, r, nr);
q1 += nr;
}
free(p);
free(r);
return q1-q0;
}
void
bufread(Buffer *b, uint q0, Rune *s, uint n)
{
uint m;
if(!(q0<=b->nc && q0+n<=b->nc))
panic("bufread: internal error");
while(n > 0){
setcache(b, q0);
m = min(n, b->cnc-(q0-b->cq));
runemove(s, b->c+(q0-b->cq), m);
q0 += m;
s += m;
n -= m;
}
}
void
bufreset(Buffer *b)
{
int i;
b->nc = 0;
b->cnc = 0;
b->cq = 0;
b->cdirty = 0;
b->cbi = 0;
/* delete backwards to avoid n² behavior */
for(i=b->nbl-1; --i>=0; )
delblock(b, i);
}
void
bufclose(Buffer *b)
{
bufreset(b);
free(b->c);
b->c = nil;
b->cnc = 0;
free(b->bl);
b->bl = nil;
b->nbl = 0;
}