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// A utility function that convert string array into exsistence filter
// data file.

#include "rewriter/gen_existence_data.h"

#include <algorithm>
#include <iostream>
#include <memory>
#include <vector>

#include "base/codegen_bytearray_stream.h"
#include "base/hash.h"
#include "base/logging.h"
#include "storage/existence_filter.h"

using mozc::storage::ExistenceFilter;

namespace mozc {
namespace {

void GenExistenceData(const std::vector<std::string> &entries,
                      double error_rate, char **existence_data,
                      size_t *existence_data_size) {
  const int n = entries.size();
  const int m =
      ExistenceFilter::MinFilterSizeInBytesForErrorRate(error_rate, n);
  LOG(INFO) << "entry: " << n << " err: " << error_rate << " bytes: " << m;

  std::unique_ptr<ExistenceFilter> filter(ExistenceFilter::CreateOptimal(m, n));
  DCHECK(filter.get());

  for (size_t i = 0; i < entries.size(); ++i) {
    const uint64 id = Hash::Fingerprint(entries[i]);
    filter->Insert(id);
  }
  filter->Write(existence_data, existence_data_size);
}

}  // namespace

void OutputExistenceHeader(const std::vector<std::string> &entries,
                           const std::string &data_namespace, std::ostream *ofs,
                           double error_rate) {
  char *existence_data = nullptr;
  size_t existence_data_size = 0;
  GenExistenceData(entries, error_rate, &existence_data, &existence_data_size);

  *ofs << "// This header file is generated by "
       << "gen_existence_data." << std::endl;

  *ofs << "namespace " << data_namespace << "{" << std::endl;

  CodeGenByteArrayOutputStream codegen_stream(ofs,
                                              codegenstream::NOT_OWN_STREAM);
  codegen_stream.OpenVarDef("ExistenceFilter");
  codegen_stream.write(existence_data, existence_data_size);
  codegen_stream.CloseVarDef();
  *ofs << "}  // namespace " << data_namespace << std::endl;
}

void OutputExistenceBinary(const std::vector<std::string> &entries,
                           std::ostream *ofs, double error_rate) {
  char *existence_data = nullptr;
  size_t existence_data_size = 0;
  GenExistenceData(entries, error_rate, &existence_data, &existence_data_size);
  ofs->write(existence_data, existence_data_size);
}
}  // namespace mozc
