filelock.cc

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/*
 *
 *    Copyright (c) 2015,2017-2018,2022
 *      SMASH Team
 *
 *    GNU General Public License (GPLv3 or later)
 *
 */
 
#include "smash/filelock.h"
 
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
 
namespace smash {
 
FileLock::FileLock(const std::filesystem::path& path)
    : path_(path), acquired_(false) {}
 
bool FileLock::acquire() {
  if (acquired_) {
    throw std::runtime_error("FileLock \"" + path_.native() +
                             "\" was already acquired.");
  }
  // The following POSIX syscall fails if the file already exists and creates it
  // otherwise. This is atomic, so there cannot be a race.
  const int fd =
      open(path_.native().c_str(), O_EXCL | O_CREAT, S_IRUSR | S_IWUSR);
  if (fd < 0) {
    return false;
  }
  acquired_ = true;
  if (close(fd) != 0) {
    throw std::runtime_error("Could not close file lock.");
  }
  return true;
}
 
FileLock::~FileLock() {
  if (acquired_) {
    std::filesystem::remove(path_);
  }
}
 
}  // namespace smash