Index: src/Makefile
==================================================================
--- src/Makefile
+++ src/Makefile
@@ -6,9 +6,10 @@
        class.c	\
        object.c	\
        range.c	\
        string.c
 
-INCLUDES = ${SRCS:.c=.h} \
-	   corefw.h
+INCLUDES = ${SRCS:.c=.h}	\
+	   corefw.h		\
+	   hash.h
 
 include ../buildsys.mk

Index: src/array.c
==================================================================
--- src/array.c
+++ src/array.c
@@ -27,10 +27,11 @@
 #include <stdlib.h>
 #include <stdint.h>
 
 #include "object.h"
 #include "array.h"
+#include "hash.h"
 
 struct CFWArray {
 	CFWObject obj;
 	void **data;
 	size_t size;
@@ -85,10 +86,27 @@
 		if (cfw_equal(array1->data[i], array2->data[i]))
 			return false;
 
 	return true;
 }
+
+static uint32_t
+hash(void *ptr)
+{
+	CFWArray *array = ptr;
+	size_t i;
+	uint32_t hash;
+
+	CFW_HASH_INIT(hash);
+
+	for (i = 0; i < array->size; i++)
+		CFW_HASH_ADD_HASH(hash, cfw_hash(array->data[i]));
+
+	CFW_HASH_FINALIZE(hash);
+
+	return hash;
+}
 
 static void*
 copy(void *ptr)
 {
 	CFWArray *array = ptr;
@@ -256,8 +274,9 @@
 	.name = "CFWArray",
 	.size = sizeof(CFWArray),
 	.ctor = ctor,
 	.dtor = dtor,
 	.equal = equal,
+	.hash = hash,
 	.copy = copy
 };
 CFWClass *cfw_array = &class;

Index: src/class.h
==================================================================
--- src/class.h
+++ src/class.h
@@ -27,19 +27,21 @@
 #ifndef __COREFW_CLASS_H__
 #define __COREFW_CLASS_H__
 
 #include <stddef.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdarg.h>
 
 typedef struct CFWClass {
 	const char *name;
 	size_t size;
 	bool (*ctor)(void*, va_list args);
 	void (*dtor)(void*);
 	bool (*equal)(void*, void*);
+	uint32_t (*hash)(void*);
 	void* (*copy)(void*);
 } CFWClass;
 
 extern const char* cfw_class_name(CFWClass*);
 
 #endif

ADDED   src/hash.h
Index: src/hash.h
==================================================================
--- src/hash.h
+++ src/hash.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2012, Jonathan Schleifer <js@webkeks.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __COREFW_HASH_H__
+#define __COREFW_HASH_H__
+
+#define CFW_HASH_INIT(hash) hash = 0
+#define CFW_HASH_ADD(hash, byte)	\
+	{				\
+		hash += (uint8_t)byte;	\
+		hash += (hash << 10);	\
+		hash ^= (hash >> 6);	\
+	}
+#define CFW_HASH_FINALIZE(hash)		\
+	{				\
+		hash += (hash << 3);	\
+		hash ^= (hash >> 11);	\
+		hash += (hash << 15);	\
+	}
+#define CFW_HASH_ADD_HASH(hash, other_)				\
+	{							\
+		uint32_t other = other_;			\
+		CFW_HASH_ADD(hash, (other >> 24) & 0xFF);	\
+		CFW_HASH_ADD(hash, (other >> 16) & 0xFF);	\
+		CFW_HASH_ADD(hash, (other >>  8) & 0xFF);	\
+		CFW_HASH_ADD(hash, other & 0xFF);		\
+	}
+
+#endif

Index: src/object.c
==================================================================
--- src/object.c
+++ src/object.c
@@ -92,22 +92,33 @@
 	if (obj1->cls->equal != NULL) {
 		return obj1->cls->equal(obj1, obj2);
 	} else
 		return (obj1 == obj2);
 }
+
+uint32_t
+cfw_hash(void *ptr)
+{
+	CFWObject *obj = ptr;
+
+	if (obj->cls->hash != NULL)
+		return obj->cls->hash(obj);
+
+	return (uint32_t)(uintptr_t)ptr;
+}
 
 void*
 cfw_copy(void *ptr)
 {
 	CFWObject *obj = ptr;
 
 	if (obj->cls->copy != NULL)
 		return obj->cls->copy(obj);
-	else
-		return NULL;
+
+	return NULL;
 }
 
 static CFWClass class = {
 	.name = "CFWObject",
 	.size = sizeof(CFWObject),
 };
 CFWClass *cfw_object = &class;

Index: src/object.h
==================================================================
--- src/object.h
+++ src/object.h
@@ -38,8 +38,9 @@
 extern void* cfw_new(CFWClass*, ...);
 extern void* cfw_ref(void*);
 extern void cfw_unref(void*);
 extern void cfw_free(void*);
 extern bool cfw_equal(void*, void*);
+extern uint32_t cfw_hash(void*);
 extern void* cfw_copy(void*);
 
 #endif

Index: src/string.c
==================================================================
--- src/string.c
+++ src/string.c
@@ -28,10 +28,11 @@
 #include <stdint.h>
 #include <string.h>
 
 #include "object.h"
 #include "string.h"
+#include "hash.h"
 
 struct CFWString {
 	CFWObject obj;
 	char *data;
 	size_t len;
@@ -80,10 +81,27 @@
 	if (str1->len != str2->len)
 		return false;
 
 	return !memcmp(str1->data, str2->data, str1->len);
 }
+
+static uint32_t
+hash(void *ptr)
+{
+	CFWString *str = ptr;
+	size_t i;
+	uint32_t hash;
+
+	CFW_HASH_INIT(hash);
+
+	for (i = 0; i < str->len; i++)
+		CFW_HASH_ADD(hash, str->data[i]);
+
+	CFW_HASH_FINALIZE(hash);
+
+	return hash;
+}
 
 static void*
 copy(void *ptr)
 {
 	CFWString *str = ptr;
@@ -175,8 +193,9 @@
 	.name = "CFWString",
 	.size = sizeof(CFWString),
 	.ctor = ctor,
 	.dtor = dtor,
 	.equal = equal,
+	.hash = hash,
 	.copy = copy
 };
 CFWClass *cfw_string = &class;