new

src/libndb/ndbcache.c

@@ -0,0 +1,144 @@
+#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;
+}