@@ -14,11 +14,11 @@
 #define _GNU_SOURCE
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <ctype.h>
+#include <assert.h>
 
 #ifdef HAVE_MADVISE
 #include <sys/mman.h>
 #else
 #define madvise(addr, len, advise)
@@ -27,10 +27,13 @@
 #import "OFMutableString.h"
 #import "OFExceptions.h"
 #import "OFMacros.h"
 
 #import "asprintf.h"
+
+extern const of_unichar_t* const of_unicode_upper_table[0x1100];
+extern const of_unichar_t* const of_unicode_lower_table[0x1100];
 
 @implementation OFMutableString
 - setToCString: (const char*)str
 {
 	size_t len;
@@ -274,30 +277,196 @@
 	return self;
 }
 
 - upper
 {
-	char *p = string + length;
+	of_unichar_t c, uc;
+	of_unichar_t *ustr;
+	size_t ulen, nlen;
+	size_t i, j, d;
+	char *nstr;
+
+	if (!is_utf8) {
+		uint8_t *p = (uint8_t*)string + length;
+		uint8_t t;
+
+		while (--p >= (uint8_t*)string) {
+			t = of_unicode_upper_table[0][*p];
+			if (t != 0)
+				*p = t;
+		}
+
+		return self;
+	}
+
+	ulen = [self length];
+	ustr = [self allocMemoryForNItems: [self length]
+				 withSize: ulen];
+
+	j = 0;
+	nlen = 0;
+
+	for (i = 0; i < length; i++) {
+		c = of_string_utf8_to_unicode(string + i, length - i);
+
+		if (c == OF_INVALID_UNICHAR || c > 0x10FFFF) {
+			[self freeMemory: ustr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+
+		uc = of_unicode_upper_table[c >> 8][c & 0xFF];
+		if (uc == 0)
+			uc = c;
+		ustr[j++] = uc;
+
+		if (uc < 0x80)
+			nlen++;
+		else if (uc < 0x800)
+			nlen += 2;
+		else if (uc < 0x10000)
+			nlen += 3;
+		else if (uc < 0x110000)
+			nlen += 4;
+		else {
+			[self freeMemory: ustr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+
+		if (c < 0x80);
+		else if (c < 0x800)
+			i++;
+		else if (c < 0x10000)
+			i += 2;
+		else if (c < 0x110000)
+			i += 3;
+		else {
+			[self freeMemory: ustr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+	}
+
+	@try {
+		nstr = [self allocMemoryWithSize: nlen + 1];
+	} @catch (OFException *e) {
+		[self freeMemory: ustr];
+		@throw e;
+	}
+
+	j = 0;
+
+	for (i = 0; i < ulen; i++) {
+		if ((d = of_string_unicode_to_utf8(ustr[i], nstr + j)) == 0) {
+			[self freeMemory: ustr];
+			[self freeMemory: nstr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+		j += d;
+	}
 
-	if (is_utf8)
-		@throw [OFInvalidEncodingException newWithClass: isa];
+	assert(j == nlen);
+	nstr[j] = 0;
+	[self freeMemory: ustr];
 
-	while (--p >= string)
-		*p = toupper((int)*p);
+	[self freeMemory: string];
+	string = nstr;
+	length = nlen;
 
 	return self;
 }
 
 - lower
 {
-	char *p = string + length;
+	of_unichar_t c, lc;
+	of_unichar_t *ustr;
+	size_t ulen, nlen;
+	size_t i, j, d;
+	char *nstr;
+
+	if (!is_utf8) {
+		uint8_t *p = (uint8_t*)string + length;
+		uint8_t t;
+
+		while (--p >= (uint8_t*)string) {
+			t = of_unicode_lower_table[0][*p];
+			if (t != 0)
+				*p = t;
+		}
+
+		return self;
+	}
+
+	ulen = [self length];
+	ustr = [self allocMemoryForNItems: [self length]
+				 withSize: ulen];
+
+	j = 0;
+	nlen = 0;
+
+	for (i = 0; i < length; i++) {
+		c = of_string_utf8_to_unicode(string + i, length - i);
+
+		if (c == OF_INVALID_UNICHAR || c > 0x10FFFF) {
+			[self freeMemory: ustr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+
+		lc = of_unicode_lower_table[c >> 8][c & 0xFF];
+		if (lc == 0)
+			lc = c;
+		ustr[j++] = lc;
+
+		if (lc < 0x80)
+			nlen++;
+		else if (lc < 0x800)
+			nlen += 2;
+		else if (lc < 0x10000)
+			nlen += 3;
+		else if (lc < 0x110000)
+			nlen += 4;
+		else {
+			[self freeMemory: ustr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+
+		if (c < 0x80);
+		else if (c < 0x800)
+			i++;
+		else if (c < 0x10000)
+			i += 2;
+		else if (c < 0x110000)
+			i += 3;
+		else {
+			[self freeMemory: ustr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+	}
+
+	@try {
+		nstr = [self allocMemoryWithSize: nlen + 1];
+	} @catch (OFException *e) {
+		[self freeMemory: ustr];
+		@throw e;
+	}
+
+	j = 0;
+
+	for (i = 0; i < ulen; i++) {
+		if ((d = of_string_unicode_to_utf8(ustr[i], nstr + j)) == 0) {
+			[self freeMemory: ustr];
+			[self freeMemory: nstr];
+			@throw [OFInvalidEncodingException newWithClass: isa];
+		}
+		j += d;
+	}
 
-	if (is_utf8)
-		@throw [OFInvalidEncodingException newWithClass: isa];
+	assert(j == nlen);
+	nstr[j] = 0;
+	[self freeMemory: ustr];
 
-	while (--p >= string)
-		*p = tolower((int)*p);
+	[self freeMemory: string];
+	string = nstr;
+	length = nlen;
 
 	return self;
 }
 
 - removeCharactersFromIndex: (size_t)start