KFLinkHeader.m

/*
    HTTP Link header parser (http://tools.ietf.org/html/rfc5988)
    License: BSD

    NSDictionary *links = KFParseRelativeLinks(@"<http://github.com?page=2>; rel=next");
    NSURL *nextURL = links[@"next"];
*/

NSDictionary *KFParseRelativeLinks(NSString *header) {
    NSMutableDictionary *links = [[NSMutableDictionary alloc] init];

    for (NSString *source in [header componentsSeparatedByString:@","]) {
        NSRange range = [source rangeOfString:@";"];

        if (range.location == NSNotFound) {
            continue;
        }

        NSString *urlString = [source substringToIndex:range.location];

        NSCharacterSet *urlCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@"<> "];
        urlString = [urlString stringByTrimmingCharactersInSet:urlCharacterSet];
        NSURL *URL = [[NSURL alloc] initWithString:urlString];

        if (URL == nil) {
            continue;
        }

        NSString *params = [source substringFromIndex:range.location + 1];
        NSMutableDictionary *parameters = [[NSMutableDictionary alloc] init];

        for (NSString *parameter in [params componentsSeparatedByString:@";"]) {
            NSRange range = [parameter rangeOfString:@"="];

            if (range.location == NSNotFound) {
                continue;
            }

            NSString *key = [[parameter substringToIndex:range.location] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
            NSString *value = [[parameter substringFromIndex:range.location + 1] stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"\"' "]];

            parameters[key] = value;
        }

        NSString *rel = parameters[@"rel"];
        if (rel) {
            links[rel] = URL;
        }
    }

    return [links copy];
}