// past the end of the string, e.g., a string that ends in a backslash.
// The second element is always the length.
std::pair<uint32_t, size_t> read_unigram(const std::string &s, size_t start);
// past the end of the string, e.g., a string that ends in a backslash.
// The second element is always the length.
std::pair<uint32_t, size_t> read_unigram(const std::string &s, size_t start);