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#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>
struct Ndbcache
{
Ndbcache *next;
char *attr;
char *val;
Ndbs s;
Ndbtuple *t;
};
enum
{
Maxcached= 128
};
static void
ndbcachefree(Ndbcache *c)
{
free(c->val);
free(c->attr);
if(c->t)
ndbfree(c->t);
free(c);
}
static Ndbtuple*
ndbcopy(Ndb *db, Ndbtuple *from_t, Ndbs *from_s, Ndbs *to_s)
{
Ndbtuple *first, *to_t, *last, *line;
int newline;
*to_s = *from_s;
to_s->t = nil;
to_s->db = db;
newline = 1;
last = nil;
first = nil;
line = nil;
for(; from_t != nil; from_t = from_t->entry){
to_t = ndbnew(from_t->attr, from_t->val);
/* have s point to matching tuple */
if(from_s->t == from_t)
to_s->t = to_t;
if(newline)
line = to_t;
else
last->line = to_t;
if(last != nil)
last->entry = to_t;
else {
first = to_t;
line = to_t;
}
to_t->entry = nil;
to_t->line = line;
last = to_t;
newline = from_t->line != from_t->entry;
}
return first;
}
/*
* if found, move to front
*/
int
_ndbcachesearch(Ndb *db, Ndbs *s, char *attr, char *val, Ndbtuple **t)
{
Ndbcache *c, **l;
*t = nil;
c = nil;
for(l = &db->cache; *l != nil; l = &(*l)->next){
c = *l;
if(strcmp(c->attr, attr) == 0 && strcmp(c->val, val) == 0)
break;
}
if(*l == nil)
return -1;
/* move to front */
*l = c->next;
c->next = db->cache;
db->cache = c;
*t = ndbcopy(db, c->t, &c->s, s);
return 0;
}
Ndbtuple*
_ndbcacheadd(Ndb *db, Ndbs *s, char *attr, char *val, Ndbtuple *t)
{
Ndbcache *c, **l;
c = mallocz(sizeof *c, 1);
if(c == nil)
return nil;
c->attr = strdup(attr);
if(c->attr == nil)
goto err;
c->val = strdup(val);
if(c->val == nil)
goto err;
c->t = ndbcopy(db, t, s, &c->s);
if(c->t == nil && t != nil)
goto err;
/* add to front */
c->next = db->cache;
db->cache = c;
/* trim list */
if(db->ncache < Maxcached){
db->ncache++;
return t;
}
for(l = &db->cache; (*l)->next; l = &(*l)->next)
;
c = *l;
*l = nil;
err:
ndbcachefree(c);
return t;
}
void
_ndbcacheflush(Ndb *db)
{
Ndbcache *c;
while(db->cache != nil){
c = db->cache;
db->cache = c->next;
ndbcachefree(c);
}
db->ncache = 0;
}
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