Method parse

src/linux/perf.cpp:354–401

Convert a single line of perf output in CSV format (using PERF_DELIMITER as a separator) to a sample.

  // Convert a single line of perf output in CSV format (using
  // PERF_DELIMITER as a separator) to a sample.
  static Try<Sample> parse(const string& line)
  {
    // We use strings::split to separate the tokens
    // because the unit field can be empty.
    vector<string> tokens = strings::split(line, PERF_DELIMITER);

    // A number of CSV formats are possible.  Note that we do not
    // use the kernel version when parsing because OS vendors often
    // backport perf tool functionality into older kernel versions.

    switch (tokens.size()) {
      // value,event,cgroup (since Linux v2.6.39)
      case 3:
        return Sample({tokens[0], internal::normalize(tokens[1]), tokens[2]});

      // value,unit,event,cgroup (since Linux v3.14)
      case 4:

      // value,unit,event,cgroup,running,measurement-ratio (since Linux v4.1)
      case 6:

      // value,unit,event,cgroup,running,measurement-ratio,
      // aggregate-value,aggregate-unit (since Linux v4.6)
      case 8:
        return Sample({tokens[0], internal::normalize(tokens[2]), tokens[3]});

      // This is the same format as the one with 8 fields. Due to a
      // bug 'perf stat' may print 4 CSV separators instead of 2 empty
      // fields (https://lkml.org/lkml/2018/3/6/22).
      case 10:
        // Check that the last 4 fields are empty. Otherwise this is
        // an unknown format.
        for (int i = 6; i < 10; ++i) {
          if (!tokens[i].empty()) {
            return Error(
                "Unexpected number of fields (" + stringify(tokens.size()) +
                ")");
          }
        }

        return Sample({tokens[0], internal::normalize(tokens[2]), tokens[3]});

      // Bail out if the format is not recognized.
      default:
        return Error(
            "Unexpected number of fields (" + stringify(tokens.size()) + ")");
    }
  }
};