static void addHeadersFromHashMap(CFMutableURLRequestRef request, const HTTPHeaderMap& requestHeaders)
{
    if (!requestHeaders.size())
        return;

    HTTPHeaderMap::const_iterator end = requestHeaders.end();
    for (HTTPHeaderMap::const_iterator it = requestHeaders.begin(); it != end; ++it) {
        CFStringRef key = it->first.createCFString();
        CFStringRef value = it->second.createCFString();
        CFURLRequestSetHTTPHeaderFieldValue(request, key, value);
        CFRelease(key);
        CFRelease(value);
    }
}