static void dumpString(std::ostringstream& os, const char *s) {
    os.put('"');
    while (*s) {
        char c = *s++;
        switch (c) {
        case '\b':
            os << "\\b";
            break;
        case '\f':
            os << "\\f";
            break;
        case '\n':
            os << "\\n";
            break;
        case '\r':
            os << "\\r";
            break;
        case '\t':
            os << "\\t";
            break;
        case '\\':
            os << "\\\\";
            break;
        case '"':
            os << "\\\"";
            break;
        default:
            os.put(c);
        }
    }
    os << s << "\"";
}
static void dumpValue(std::ostringstream& os, const JsonValue& o, int shiftWidth, const std::string& linefeed = "", int indent = 0) {
    switch (o.getTag()) {
    case JSON_NUMBER:
        char buffer[32];
        sprintf(buffer, "%f", o.toNumber());
        os << buffer;
        break;
    case JSON_TRUE:
        os << "true";
        break;        
    case JSON_FALSE:
        os << "false";
        break;
    case JSON_STRING:
        dumpString(os, o.toString());
        break;
    case JSON_ARRAY:
        // It is not necessary to use o.toNode() to check if an array or object
        // is empty before iterating over its members, we do it here to allow
        // nicer pretty printing.
        if (!o.toNode()) {
            os << "[]";
            break;
        }
        os << "[" << linefeed;
        for (auto i : o) {
            if (shiftWidth > 0)
                os << std::setw(indent + shiftWidth) << " " << std::setw(0);
            dumpValue(os, i->value, shiftWidth, linefeed, indent + shiftWidth);
            if (i->next)
                os << ",";
            os << linefeed;
        }
        if (indent > 0)
            os << std::setw(indent) << " " << std::setw(0);
        os.put(']');
        break;
    case JSON_OBJECT:
        if (!o.toNode()) {
            os << "{}";
            break;
        }
        os << "{" << linefeed;
        for (auto i : o) {
            if (shiftWidth > 0)
                os << std::setw(indent + shiftWidth) << " " << std::setw(0);
            dumpString(os, i->key);
            os << ":";
            dumpValue(os, i->value, shiftWidth, linefeed, indent + shiftWidth);
            if (i->next)
                os << ",";
            os << linefeed;
        }
        if (indent > 0)
            os << std::setw(indent) << " " << std::setw(0);
        os.put('}');
        break;
    case JSON_NULL:
        os << "null";
        break;
    }
}