- (NSString *)encodeToPercentEscapeString: (NSString *) input  
{  
    // Encode all the reserved characters, per RFC 3986  
    // ()  
    NSString *outputStr = (NSString *)   
    CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,  
                                            (CFStringRef)input,  
                                            NULL,  
                                            (CFStringRef)@"!*'();:@&=+$,/?%#[]",  
                                            kCFStringEncodingUTF8);  
    return outputStr;  
}  
  
- (NSString *)decodeFromPercentEscapeString: (NSString *) input  
{  
    NSMutableString *outputStr = [NSMutableString stringWithString:input];  
    [outputStr replaceOccurrencesOfString:@"+"  
                               withString:@" "  
                                  options:NSLiteralSearch  
                                    range:NSMakeRange(0, [outputStr length])];  
  
    return [outputStr stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];  
}