Beispiel #1
0
    // adds a value, returning false if the given token is not
    // "reasonable".  A reasonable token is one not currently in use,
    // and if any previously used tokens are available, it must be one
    // of the previously used ones.  If no previously used tokens are
    // available, it must be the smallest unused token.  You'll get
    // good performance if you never choose a bad token and use the
    // most recently dropped token.
    bool add(token_type known_token, T const& value) {
        if (free_.empty()) {
            if (known_token == values_.size()) {
                values_.push_back(value);
#ifndef NDEBUG
                is_free_.push_back(false);
#endif
                return true;
            } else {
                return false;
            }
        } else {
            // If a replicand used add(), then it picked the token
            // from the bock of its free list.  So the replicant, the
            // presumed caller of this function, searches in reverse
            // order.
            typename std::vector<token_t>::reverse_iterator p = std::find(free_.rbegin(), free_.rend(), known_token);
            if (p == free_.rend()) {
                return false;
            }

            if (values_.size() > known_token) {
                free_.erase(p.base() - 1);
                values_[known_token] = value;
                rassert(is_free_[known_token]);
#ifndef NDEBUG
                is_free_[known_token] = false;
#endif

                return true;
            } else {
                return false;
            }
        }
    }