use trie for map lookup

trie.c

@@ -0,0 +1,130 @@
+#include "dat.h"
+#include "fn.h"
+
+static int
+newnode(Trie *t)
+{
+	int i;
+
+	if(t->n >= t->cap){
+		t->cap *= 2;
+		t->nodes = erealloc(t->nodes, t->cap * sizeof(Tnode));
+	}
+	i = t->n++;
+	memset(&t->nodes[i], 0, sizeof(Tnode));
+	t->nodes[i].child = -1;
+	t->nodes[i].sibling = -1;
+	return i;
+}
+
+static int
+find(Trie *t, int ni, char c)
+{
+	int pi;
+
+	for(pi = t->nodes[ni].child; pi >= 0; pi = t->nodes[pi].sibling)
+		if(t->nodes[pi].c == c)
+			return pi;
+	return -1;
+}
+
+static int
+add(Trie *t, int ni, char c)
+{
+	int pi;
+
+	pi = newnode(t);
+	t->nodes[pi].c = c;
+	t->nodes[pi].sibling = t->nodes[ni].child;
+	t->nodes[ni].child = pi;
+	return pi;
+}
+
+static void
+insert(Trie *t, char *key, int klen, char *val, int vlen)
+{
+	int ni, ci;
+	int i;
+
+	ni = t->root;
+	for(i = 0; i < klen; i++){
+		ci = find(t, ni, key[i]);
+		if(ci < 0)
+			ci = add(t, ni, key[i]);
+		ni = ci;
+	}
+	t->nodes[ni].val = val;
+	t->nodes[ni].vlen = vlen;
+}
+
+Trie*
+trieopen(char *path)
+{
+	Trie *t;
+	Biobuf *b;
+	char *line, *tab, *key, *val;
+	int klen, vlen;
+
+	b = Bopen(path, OREAD);
+	if(b == nil)
+		die("can't open: %s", path);
+	t = emalloc(sizeof(*t));
+	t->cap = 1024;
+	t->nodes = emalloc(t->cap * sizeof(Tnode));
+	t->n = 0;
+	t->root = newnode(t);
+	while((line = Brdstr(b, '\n', 1)) != nil){
+		if(line[0] == '\0'){
+			free(line);
+			continue;
+		}
+		tab = strchr(line, '\t');
+		if(tab == nil || tab[1] == '\0')
+			die("malformed map: %s", path);
+		*tab = '\0';
+		key = line;
+		klen = tab - line;
+		val = tab + 1;
+		vlen = strlen(val);
+		insert(t, key, klen, val, vlen);
+	}
+	Bterm(b);
+	return t;
+}
+
+char*
+trieget(Trie *t, char *key, int klen, int *vlen)
+{
+	int ni;
+	int i;
+
+	ni = t->root;
+	for(i = 0; i < klen; i++){
+		ni = find(t, ni, key[i]);
+		if(ni < 0)
+			return nil;
+	}
+	if(t->nodes[ni].val == nil)
+		return nil;
+	*vlen = t->nodes[ni].vlen;
+	return t->nodes[ni].val;
+}
+
+int
+trielookup(Trie *t, char *key, int klen, char **val, int *vlen)
+{
+	int ni;
+	int i;
+
+	ni = t->root;
+	for(i = 0; i < klen; i++){
+		ni = find(t, ni, key[i]);
+		if(ni < 0)
+			return 0;
+	}
+	if(val != nil && t->nodes[ni].val != nil){
+		*val = t->nodes[ni].val;
+		*vlen = t->nodes[ni].vlen;
+	}
+	return 1;
+}