Implementation of the users table and a generic hashtable mechanism

core/hashtable.c

@@ -31,9 +31,22 @@
  * @endverbatim
  */
 
+/**
+ * Special null function used as default memory allfunctions in the hashtable
+ * implementation. This avoids havign to special case the code that manipulates
+ * the keys and values
+ *
+ * @param	data	The data pointer
+ * @return	Return the value we were called with
+ */
+static void *
+nullfn(void *data)
+{
+	return data;
+}
 
 /**
- * Allocate a new users table
+ * Allocate a new hash table
  *
  * @param size		The size of the hash table
  * @param hashfn	The user supplied hash function
@@ -50,6 +63,8 @@ HASHTABLE 	*rval;
 	rval->hashsize = size;
 	rval->hashfn = hashfn;
 	rval->cmpfn = cmpfn;
+	rval->copyfn = nullfn;
+	rval->freefn = nullfn;
 	if ((rval->entries = calloc(size, sizeof(HASHENTRIES))) == NULL)
 	{
 		free(rval);
@@ -60,3 +75,183 @@ HASHTABLE 	*rval;
 	return rval;
 }
 
+/**
+ * Delete an entire hash table
+ *
+ * @param	table	The hash table to delete
+ */
+void
+hashtable_free(HASHTABLE *table)
+{
+int		i;
+HASHENTRIES	*entry, *ptr;
+
+	for (i = 0; i < table->hashsize; i++)
+	{
+		entry = table->entries[i];
+		if (entry->key)
+		{
+			table->freefn(entry->key);
+			table->freefn(entry->value);
+		}
+		entry = entry->next;
+		while (entry)
+		{
+			ptr = entry->next;
+			table->freefn(entry->key);
+			table->freefn(entry->value);
+			free(entry);
+			entry = ptr;
+		}
+	}
+	free(table->entries);
+	free(table);
+}
+
+/**
+ * Provide memory management functions to the hash table. This allows
+ * function pointers to be registered that can make copies of the
+ * key and value.
+ *
+ * @param table		The hash table
+ * @param copyfn	The copy function
+ * @param freefn	The free function
+ */
+void
+hashtable_memory_fns(HASHTABLE *table, HASHMEMORYFN copyfn, HASHMEMORYFN freefn)
+{
+	table->copyfn = copyfn;
+	table->freefn = freefn;
+}
+
+/**
+ * Add an item to the hash table.
+ *
+ * @param table		The hash table to which to add the item
+ * @param key		The key of the item
+ * @param value		The value for the item
+ * @return	Return the number of items added
+ */
+int
+hashtable_add(HASHTABLE *table, void *key, void *value)
+{
+int		hashkey = table->hashfn(key);
+HASHENTRIES	*entry;
+
+	entry = table->entries[hashkey % table->hashsize];
+	while (entry->next && entry->key && table->cmpfn(key, entry->key) != 0)
+	{
+		entry = entry->next;
+	}
+	if (entry->key == NULL)
+	{
+		/* Entry is empty - special case for first insert */
+		entry->key = table->copyfn(key);
+		entry->value = table->copyfn(value);
+	}
+	else if (table->cmpfn(key, entry->key) == 0)
+	{
+		/* Duplicate key value */
+		return 0;
+	}
+	else
+	{
+		HASHENTRIES	*ptr = (HASHENTRIES *)malloc(sizeof(HASHENTRIES));
+		if (ptr == NULL)
+			return 0;
+		ptr->key = table->copyfn(key);
+		ptr->value = table->copyfn(value);
+		ptr->next = NULL;
+		entry->next = ptr;
+	}
+	return 1;
+}
+
+/**
+ * Delete an item from the hash table that has a given key
+ *
+ * @param table		The hash table to delete from
+ * @param key		The key value of the item to remove
+ * @return Return the number of items deleted
+ */
+int
+hashtable_delete(HASHTABLE *table, void *key)
+{
+int		hashkey = table->hashfn(key);
+HASHENTRIES	*entry, *ptr;
+
+	entry = table->entries[hashkey % table->hashsize];
+	while (entry && entry->key && table->cmpfn(key, entry->key) != 0)
+	{
+		entry = entry->next;
+	}
+	if (entry == NULL || entry->key == NULL)
+	{
+		/* Not found */
+		return 0;
+	}
+
+	if (entry == table->entries[hashkey % table->hashsize])
+	{
+		/* We are removing from the special first entry */
+		if (entry->next)
+		{
+			table->freefn(entry->key);
+			table->freefn(entry->value);
+			entry->key = entry->next->key;
+			entry->value = entry->next->value;
+			ptr = entry->next;
+			entry->next = ptr->next;
+			free(ptr);
+		}
+		else
+		{
+			table->freefn(entry->key);
+			table->freefn(entry->value);
+			entry->key = NULL;
+			entry->value = NULL;
+		}
+	}
+	else
+	{
+		ptr = table->entries[hashkey % table->hashsize];
+		while (ptr && ptr->next != entry)
+			ptr = ptr->next;
+		if (ptr == NULL)
+			return 0;	/* This should never happen */
+		ptr->next = entry->next;
+		table->freefn(entry->key);
+		table->freefn(entry->value);
+		free(entry);
+	}
+	return 1;
+}
+
+/**
+ * Fetch an item with a given key value from the hash table
+ *
+ * @param table		The hash table
+ * @param key		The key value
+ * @return The item or NULL if the item was not found
+ */
+void *
+hashtable_fetch(HASHTABLE *table, void *key)
+{
+int		hashkey = table->hashfn(key);
+HASHENTRIES	*entry;
+
+	entry = table->entries[hashkey % table->hashsize];
+	while (entry && entry->key && table->cmpfn(key, entry->key) != 0)
+	{
+		entry = entry->next;
+	}
+	if (entry == NULL || entry->key == NULL)
+	{
+		return NULL;
+	}
+	else
+	{
+		return entry->value;
+	}
+}
+