compile-strings.cc

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// Copyright 2005-2020 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the 'License');
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an 'AS IS' BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.

#include <cmath>
#include <string>

#include <fst/flags.h>
#include <fst/extensions/far/compile-strings.h>
#include <fstream>

DEFINE_string(far_field_separator, "\t",
              "Set of characters used as a separator between printed fields");

namespace fst {
namespace internal {

// Computes the minimal length required to encode each line number as a decimal
// number, or zero if the number of lines could not be determined because the
// file was not seekable.
int KeySize(const std::string &source) {
  std::ifstream istrm(source);
  istrm.seekg(0);
  // TODO(jrosenstock): Change this to is_regular_file when <filesystem> is
  // no longer banned.
  // Stream not seekable. This is really a hack to approximate is_regular_file.
  // What we really want is that opening and reading the file twice gives the
  // same result, which is only true for regular files. There may be devices
  // that don't return an error on seek. At least we are able to catch the
  // common cases of /dev/stdin and fifos.
  if (istrm.rdstate() & std::ios_base::failbit) {
    return 0;
  }
  std::string s;
  int nline = 0;
  while (std::getline(istrm, s)) ++nline;
  return nline ? ceil(log10(nline + 1)) : 1;
}

}  // namespace internal
}  // namespace fst