1 #include <u.h>
2 #include <libc.h>
3 #include <bio.h>
4 #include <ndb.h>
5 
6 struct Ndbcache
7 {
8 	Ndbcache	*next;
9 	char		*attr;
10 	char		*val;
11 	Ndbs		s;
12 	Ndbtuple	*t;
13 };
14 
15 enum
16 {
17 	Maxcached=	128
18 };
19 
20 static void
21 ndbcachefree(Ndbcache *c)
22 {
23 	free(c->val);
24 	free(c->attr);
25 	if(c->t)
26 		ndbfree(c->t);
27 	free(c);
28 }
29 
30 static Ndbtuple*
31 ndbcopy(Ndb *db, Ndbtuple *from_t, Ndbs *from_s, Ndbs *to_s)
32 {
33 	Ndbtuple *first, *to_t, *last, *line;
34 	int newline;
35 
36 	*to_s = *from_s;
37 	to_s->t = nil;
38 	to_s->db = db;
39 
40 	newline = 1;
41 	last = nil;
42 	first = nil;
43 	line = nil;
44 	for(; from_t != nil; from_t = from_t->entry){
45 		to_t = ndbnew(from_t->attr, from_t->val);
46 
47 		/* have s point to matching tuple */
48 		if(from_s->t == from_t)
49 			to_s->t = to_t;
50 
51 		if(newline)
52 			line = to_t;
53 		else
54 			last->line = to_t;
55 
56 		if(last != nil)
57 			last->entry = to_t;
58 		else {
59 			first = to_t;
60 			line = to_t;
61 		}
62 		to_t->entry = nil;
63 		to_t->line = line;
64 		last = to_t;
65 		newline = from_t->line != from_t->entry;
66 	}
67 	return first;
68 }
69 
70 /*
71  *  if found, move to front
72  */
73 int
74 _ndbcachesearch(Ndb *db, Ndbs *s, char *attr, char *val, Ndbtuple **t)
75 {
76 	Ndbcache *c, **l;
77 
78 	*t = nil;
79 	c = nil;
80 	for(l = &db->cache; *l != nil; l = &(*l)->next){
81 		c = *l;
82 		if(strcmp(c->attr, attr) == 0 && strcmp(c->val, val) == 0)
83 			break;
84 	}
85 	if(*l == nil)
86 		return -1;
87 
88 	/* move to front */
89 	*l = c->next;
90 	c->next = db->cache;
91 	db->cache = c;
92 
93 	*t = ndbcopy(db, c->t, &c->s, s);
94 	return 0;
95 }
96 
97 Ndbtuple*
98 _ndbcacheadd(Ndb *db, Ndbs *s, char *attr, char *val, Ndbtuple *t)
99 {
100 	Ndbcache *c, **l;
101 
102 	c = mallocz(sizeof *c, 1);
103 	if(c == nil)
104 		return nil;
105 	c->attr = strdup(attr);
106 	if(c->attr == nil)
107 		goto err;
108 	c->val = strdup(val);
109 	if(c->val == nil)
110 		goto err;
111 	c->t = ndbcopy(db, t, s, &c->s);
112 	if(c->t == nil && t != nil)
113 		goto err;
114 
115 	/* add to front */
116 	c->next = db->cache;
117 	db->cache = c;
118 
119 	/* trim list */
120 	if(db->ncache < Maxcached){
121 		db->ncache++;
122 		return t;
123 	}
124 	for(l = &db->cache; (*l)->next; l = &(*l)->next)
125 		;
126 	c = *l;
127 	*l = nil;
128 err:
129 	ndbcachefree(c);
130 	return t;
131 }
132 
133 void
134 _ndbcacheflush(Ndb *db)
135 {
136 	Ndbcache *c;
137 
138 	while(db->cache != nil){
139 		c = db->cache;
140 		db->cache = c->next;
141 		ndbcachefree(c);
142 	}
143 	db->ncache = 0;
144 }