1 files changed, 117 insertions, 0 deletions
diff --git a/6.6/hash.c b/6.6/hash.c
new file mode 100644
index 0000000..5d5d6f8
--- /dev/null
+++ b/6.6/hash.c
@@ -0,0 +1,117 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include "hash.h"
+
+void nlfree(struct nlist *p);
+uint32_t hash(char *s, uint32_t hashsize);
+void pnl(struct nlist *np);
+
+uint32_t hash(char *s, uint32_t hashsize)
+{
+	uint32_t hashval;
+
+	for (hashval = 0; *s != '\0'; ++s)
+		hashval = *s + 31*hashval;
+
+	return hashval % hashsize;
+}
+
+struct nlist *lookup(struct nlist *hashtab[], uint32_t hashsize, char *s)
+{
+	struct nlist *np;
+
+	for (np = hashtab[hash(s, hashsize)]; np != NULL; np = np->next)
+		if (!strcmp(s, np->name))
+			return np;
+
+	return NULL;
+}
+
+struct nlist *install(struct nlist *hashtab[], uint32_t hashsize,
+		      char *name, char *defn)
+{
+	struct nlist *np;
+	uint32_t hashval;
+
+	if ((np = lookup(hashtab, hashsize, name)) == NULL) {
+		np = (struct nlist *) malloc(sizeof(*np));
+		if (np == NULL || (np->name = strdup(name)) == NULL) {
+			nlfree(np);
+			return NULL;
+		}
+
+		hashval = hash(name, hashsize);
+		np->next = hashtab[hashval];
+		hashtab[hashval] = np;
+	} else {
+		free(np->defn);
+	}
+
+	if ((np->defn = strdup(defn)) == NULL) {
+		undef(hashtab, hashsize, name);
+		return NULL;
+	}
+
+	return np;
+}
+
+void undef(struct nlist *hashtab[], uint32_t hashsize, char *name)
+{
+	struct nlist *np, *prev;
+	uint32_t h;
+
+	prev = NULL;
+	h = hash(name, hashsize);
+	for (np = hashtab[h]; np != NULL; prev = np, np = np->next)
+		if (!strcmp(name, np->name))
+			break;
+
+	if (np != NULL) {
+		if (prev == NULL)
+			hashtab[h] = np->next;
+		else
+			prev->next = np->next;
+
+		np->next = NULL;
+		nlfree(np);
+		return;
+	}
+}
+
+void pnl(struct nlist *np)
+{
+	if (np != NULL) {
+		pnl(np->next);
+		printf("%10s %s\n", np->name, np->defn);
+	}
+}
+
+void phashtab(struct nlist *hashtab[], int lim)
+{
+	int i;
+
+	for (i = 0; i < lim; ++i)
+		pnl(hashtab[i]);
+}
+
+void nlfree(struct nlist *p)
+{
+	if (p != NULL ) {
+		nlfree(p->next);
+		if (p->defn != NULL)
+			free(p->defn);
+		if (p->name != NULL)
+			free(p->name);
+		free(p);
+	}
+}
+
+void hashfree(struct nlist *hashtab[], int lim)
+{
+	int i;
+
+	for (i = 0; i < lim; ++i)
+		nlfree(hashtab[i]);
+}