dict: use more characters in the hash function

dict.c

@@ -3,7 +3,6 @@
 #include <string.h>
 #include "post.h"
 
-#define DHASH(d, s)	((unsigned char) (s)[0])
 #define CNTMIN		(1 << 10)
 
 struct dict {
@@ -13,6 +12,7 @@ struct dict {
 	int size;
 	int n;
 	int notfound;		/* the value returned for missing keys */
+	int hashlen;		/* the number of characters used for hashing */
 	int dupkeys;		/* duplicate keys if set */
 };
 
@@ -23,11 +23,19 @@ static void dict_extend(struct dict *d, int size)
 	d->size = size;
 }
 
-struct dict *dict_make(int notfound, int dupkeys)
+/*
+ * initialise a dictionary
+ *
+ * notfound: the value returned for missing keys.
+ * dupkeys: if nonzero, store a copy of keys inserted via dict_put().
+ * hashlen: the number of characters used for hashing
+ */
+struct dict *dict_make(int notfound, int dupkeys, int hashlen)
 {
 	struct dict *d = malloc(sizeof(*d));
 	memset(d, 0, sizeof(*d));
 	d->n = 1;
+	d->hashlen = hashlen ? hashlen : 32;
 	d->dupkeys = dupkeys;
 	d->notfound = notfound;
 	d->map = iset_make();
@@ -47,6 +55,15 @@ void dict_free(struct dict *d)
 	free(d);
 }
 
+static int dict_hash(struct dict *d, char *key)
+{
+	unsigned long hash = (unsigned char) *key++;
+	int i = d->hashlen;
+	while (--i > 0 && *key)
+		hash = (hash << 5) + hash + (unsigned char) *key++;
+	return hash & 0x3ff;
+}
+
 void dict_put(struct dict *d, char *key, int val)
 {
 	int idx;
@@ -61,13 +78,13 @@ void dict_put(struct dict *d, char *key, int val)
 	idx = d->n++;
 	d->key[idx] = key;
 	d->val[idx] = val;
-	iset_put(d->map, DHASH(d, key), idx);
+	iset_put(d->map, dict_hash(d, key), idx);
 }
 
 /* return the index of key in d */
 int dict_idx(struct dict *d, char *key)
 {
-	int h = DHASH(d, key);
+	int h = dict_hash(d, key);
 	int *b = iset_get(d->map, h);
 	int *r = b + iset_len(d->map, h);
 	while (b && --r >= b)
@@ -95,7 +112,7 @@ int dict_get(struct dict *d, char *key)
 /* match a prefix of key; in the first call, *idx should be -1 */
 int dict_prefix(struct dict *d, char *key, int *pos)
 {
-	int *r = iset_get(d->map, DHASH(d, key));
+	int *r = iset_get(d->map, dict_hash(d, key));
 	while (r && r[++*pos] >= 0) {
 		int idx = r[*pos];
 		int plen = strlen(d->key[idx]);

font.c

@@ -117,9 +117,9 @@ struct font *font_open(char *path)
 	}
 	memset(fn, 0, sizeof(*fn));
 	snprintf(fn->desc, sizeof(fn->desc), "%s", path);
-	fn->gl_dict = dict_make(-1, 1);
-	fn->ch_dict = dict_make(-1, 1);
-	fn->ch_map = dict_make(-1, 1);
+	fn->gl_dict = dict_make(-1, 1, 0);
+	fn->ch_dict = dict_make(-1, 1, 0);
+	fn->ch_map = dict_make(-1, 1, 0);
 	while (fscanf(fin, "%s", tok) == 1) {
 		if (!strcmp("char", tok)) {
 			font_readchar(fn, fin, &ch_n, &ch_g);

post.h

@@ -96,7 +96,7 @@ void iset_put(struct iset *iset, int key, int ent);
 int iset_len(struct iset *iset, int key);
 
 /* mapping strings to longs */
-struct dict *dict_make(int notfound, int dupkeys);
+struct dict *dict_make(int notfound, int dupkeys, int hashlen);
 void dict_free(struct dict *d);
 void dict_put(struct dict *d, char *key, int val);
 int dict_get(struct dict *d, char *key);