text: #ifndef LM_BINARY_FORMAT__
  #define LM_BINARY_FORMAT__
  
  #include "lm/config.hh"
  #include "lm/read_arpa.hh"
  
  #include "util/file_piece.hh"
  #include "util/mmap.hh"
  #include "util/scoped.hh"
  
  #include <cstddef>
  #include <vector>
  
  #include <inttypes.h>
  
  namespace lm {
  namespace ngram {
  
  /* Not the best numbering system, but it grew this way for historical reasons
   * and I want to preserve existing binary files. */
  typedef enum {HASH_PROBING=0, HASH_SORTED=1, TRIE_SORTED=2, QUANT_TRIE_SORTED=3, ARRAY_TRIE_SORTED=4, QUANT_ARRAY_TRIE_SORTED=5} ModelType;
  
  const static ModelType kQuantAdd = static_cast<ModelType>(QUANT_TRIE_SORTED - TRIE_SORTED);
  const static ModelType kArrayAdd = static_cast<ModelType>(ARRAY_TRIE_SORTED - TRIE_SORTED);
  
  /*Inspect a file to determine if it is a binary lm.  If not, return false.  
   * If so, return true and set recognized to the type.  This is the only API in
   * this header designed for use by decoder authors.  
   */
  bool RecognizeBinary(const char *file, ModelType &recognized);
  
  struct FixedWidthParameters {
    unsigned char order;
    float probing_multiplier;
    // What type of model is this?  
    ModelType model_type;
    // Does the end of the file have the actual strings in the vocabulary?   
    bool has_vocabulary;
  };
  
  // Parameters stored in the header of a binary file.  
  struct Parameters {
    FixedWidthParameters fixed;
    std::vector<uint64_t> counts;
  };
  
  struct Backing {
    // File behind memory, if any.  
    util::scoped_fd file;
    // Vocabulary lookup table.  Not to be confused with the vocab words themselves.  
    util::scoped_memory vocab;
    // Raw block of memory backing the language model data structures
    util::scoped_memory search;
  };
  
  void SeekOrThrow(int fd, off_t off);
  // Seek forward
  void AdvanceOrThrow(int fd, off_t off);
  
  // Create just enough of a binary file to write vocabulary to it.  
  uint8_t *SetupJustVocab(const Config &config, uint8_t order, std::size_t memory_size, Backing &backing);
  // Grow the binary file for the search data structure and set backing.search, returning the memory address where the search data structure should begin.  
  uint8_t *GrowForSearch(const Config &config, std::size_t vocab_pad, std::size_t memory_size, Backing &backing);
  
  // Write header to binary file.  This is done last to prevent incomplete files
  // from loading.   
  void FinishFile(const Config &config, ModelType model_type, const std::vector<uint64_t> &counts, Backing &backing);
  
  namespace detail {
  
  bool IsBinaryFormat(int fd);
  
  void ReadHeader(int fd, Parameters &params);
  
  void MatchCheck(ModelType model_type, const Parameters &params);
  
  void SeekPastHeader(int fd, const Parameters &params);
  
  uint8_t *SetupBinary(const Config &config, const Parameters &params, std::size_t memory_size, Backing &backing);
  
  void ComplainAboutARPA(const Config &config, ModelType model_type);
  
  } // namespace detail
  
  template <class To> void LoadLM(const char *file, const Config &config, To &to) {
    Backing &backing = to.MutableBacking();
    backing.file.reset(util::OpenReadOrThrow(file));
  
    try {
      if (detail::IsBinaryFormat(backing.file.get())) {
        Parameters params;
        detail::ReadHeader(backing.file.get(), params);
        detail::MatchCheck(To::kModelType, params);
        // Replace the run-time configured probing_multiplier with the one in the file.  
        Config new_config(config);
        new_config.probing_multiplier = params.fixed.probing_multiplier;
        detail::SeekPastHeader(backing.file.get(), params);
        To::UpdateConfigFromBinary(backing.file.get(), params.counts, new_config);
        std::size_t memory_size = To::Size(params.counts, new_config);
        uint8_t *start = detail::SetupBinary(new_config, params, memory_size, backing);
        to.InitializeFromBinary(start, params, new_config, backing.file.get());
      } else {
        detail::ComplainAboutARPA(config, To::kModelType);
        to.InitializeFromARPA(file, config);
      }
    } catch (util::Exception &e) {
      e << " File: " << file;
      throw;
    }
  }
  
  } // namespace ngram
  } // namespace lm
  #endif // LM_BINARY_FORMAT__
  