Index: src/OFURL.h
==================================================================
--- src/OFURL.h
+++ src/OFURL.h
@@ -45,23 +45,41 @@
 @property (copy) OFString *query;
 @property (copy) OFString *fragment;
 #endif
 
 /**
- * \param str A string describing an URL
+ * \param str A string describing a URL
  * \return A new, autoreleased OFURL
  */
 + URLWithString: (OFString*)str;
 
+/**
+ * \param str A string describing a URL
+ * \param url An URL to which the string is relative
+ * \return A new, autoreleased OFURL
+ */
++ URLWithString: (OFString*)str
+  relativeToURL: (OFURL*)url;
+
 /**
  * Initializes an already allocated OFURL.
  *
- * \param str A string describing an URL
+ * \param str A string describing a URL
  * \return An initialized OFURL
  */
 - initWithString: (OFString*)str;
 
+/**
+ * Initializes an already allocated OFURL.
+ *
+ * \param str A string describing a URL
+ * \param url A URL to which the string is relative
+ * \return An initialized OFURL
+ */
+- initWithString: (OFString*)str
+   relativeToURL: (OFURL*)url;
+
 /**
  * \return The scheme part of the URL
  */
 - (OFString*)scheme;
 

Index: src/OFURL.m
==================================================================
--- src/OFURL.m
+++ src/OFURL.m
@@ -20,10 +20,11 @@
 #include <string.h>
 #include <assert.h>
 
 #import "OFURL.h"
 #import "OFString.h"
+#import "OFArray.h"
 #import "OFAutoreleasePool.h"
 #import "OFExceptions.h"
 #import "macros.h"
 
 #define ADD_STR_HASH(str)			\
@@ -30,16 +31,68 @@
 	h = [str hash];				\
 	OF_HASH_ADD(hash, h >> 24);		\
 	OF_HASH_ADD(hash, (h >> 16) & 0xFF);	\
 	OF_HASH_ADD(hash, (h >> 8) & 0xFF);	\
 	OF_HASH_ADD(hash, h & 0xFF);
+
+static OF_INLINE OFString*
+resolve_relative_path(OFString *path)
+{
+	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
+	OFMutableArray *array;
+	OFString *ret;
+	BOOL done = NO;
+
+	array = [[[path componentsSeparatedByString: @"/"] mutableCopy]
+	    autorelease];
+
+	while (!done) {
+		id *array_c = [array cArray];
+		size_t i, array_len = [array count];
+
+		done = YES;
+
+		for (i = 0; i < array_len; i++) {
+			if ([array_c[i] isEqual: @"."]) {
+				[array removeObjectAtIndex: i];
+				done = NO;
+
+				break;
+			}
+
+			if ([array_c[i] isEqual: @".."]) {
+				[array removeObjectAtIndex: i];
+
+				if (i > 0)
+					[array removeObjectAtIndex: i - 1];
+
+				done = NO;
+
+				break;
+			}
+		}
+	}
+
+	ret = [[array componentsJoinedByString: @"/"] retain];
+
+	[pool release];
+
+	return [ret autorelease];
+}
 
 @implementation OFURL
 + URLWithString: (OFString*)str
 {
 	return [[[self alloc] initWithString: str] autorelease];
 }
+
++ URLWithString: (OFString*)str
+  relativeToURL: (OFURL*)url
+{
+	return [[[self alloc] initWithString: str
+			       relativeToURL: url] autorelease];
+}
 
 - initWithString: (OFString*)str
 {
 	char *str_c, *str_c2 = NULL;
 
@@ -141,10 +194,84 @@
 				parameters = [[OFString alloc]
 				    initWithCString: tmp + 1];
 			}
 
 			path = [[OFString alloc] initWithCString: str_c];
+		}
+	} @catch (id e) {
+		[self release];
+		@throw e;
+	} @finally {
+		if (str_c2 != NULL)
+			free(str_c2);
+	}
+
+	return self;
+}
+
+- initWithString: (OFString*)str
+   relativeToURL: (OFURL*)url
+{
+	char *str_c, *str_c2 = NULL;
+
+	if ([str containsString: @"://"])
+		return [self initWithString: str];
+
+	self = [super init];
+
+	@try {
+		char *tmp;
+
+		scheme = [url->scheme copy];
+		host = [url->host copy];
+		port = url->port;
+		user = [url->user copy];
+		password = [url->password copy];
+
+		if ((str_c2 = strdup([str cString])) == NULL)
+			@throw [OFOutOfMemoryException
+			     newWithClass: isa
+			    requestedSize: [str cStringLength]];
+
+		str_c = str_c2;
+
+		if ((tmp = strchr(str_c, '#')) != NULL) {
+			*tmp = '\0';
+			fragment = [[OFString alloc] initWithCString: tmp + 1];
+		}
+
+		if ((tmp = strchr(str_c, '?')) != NULL) {
+			*tmp = '\0';
+			query = [[OFString alloc] initWithCString: tmp + 1];
+		}
+
+		if ((tmp = strchr(str_c, ';')) != NULL) {
+			*tmp = '\0';
+			parameters = [[OFString alloc]
+			    initWithCString: tmp + 1];
+		}
+
+		if (*str_c == '/')
+			path = [[OFString alloc] initWithCString: str_c + 1];
+		else {
+			OFAutoreleasePool *pool;
+			OFString *s;
+
+			pool = [[OFAutoreleasePool alloc] init];
+
+			if ([url->path hasSuffix: @"/"])
+				s = [OFString stringWithFormat: @"%@%s",
+								url->path,
+								str_c];
+			else
+				s = [OFString stringWithFormat: @"%@/../%s",
+								url->path,
+								str_c];
+
+			path = [resolve_relative_path(s) copy];
+
+			[pool release];
 		}
 	} @catch (id e) {
 		[self release];
 		@throw e;
 	} @finally {

Index: tests/OFURLTests.m
==================================================================
--- tests/OFURLTests.m
+++ tests/OFURLTests.m
@@ -35,10 +35,23 @@
 	TEST(@"+[URLWithString:]",
 	    R(u1 = [OFURL URLWithString: url_str]) &&
 	    R(u2 = [OFURL URLWithString: @"http://foo:80"]) &&
 	    R(u3 = [OFURL URLWithString: @"http://bar/"]))
 
+	TEST(@"+[URLWithString:relativeToURL:]",
+	    [[[OFURL URLWithString: @"/foo"
+		     relativeToURL: u1] description] isEqual:
+	    @"http://u:p@h:1234/foo"] &&
+	    [[[OFURL URLWithString: @"foo/bar?q"
+		     relativeToURL: [OFURL URLWithString: @"http://h/qux/quux"]]
+	    description] isEqual: @"http://h/qux/foo/bar?q"] &&
+	    [[[OFURL URLWithString: @"foo/bar"
+		     relativeToURL: [OFURL URLWithString: @"http://h/qux/?x"]]
+	    description] isEqual: @"http://h/qux/foo/bar"] &&
+	    [[[OFURL URLWithString: @"http://foo/?q"
+		     relativeToURL: u1] description] isEqual: @"http://foo/?q"])
+
 	TEST(@"-[description]",
 	    [[u1 description] isEqual: url_str] &&
 	    [[u2 description] isEqual: @"http://foo"] &&
 	    [[u3 description] isEqual: @"http://bar/"])