test/other/test_truncate_from_0.cpp

#include <cerrno>
#include <cstring>
#include <iostream>

#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

using std::endl;

//============================================================================
// :: Helpers

namespace
{
  // Returns the size of the regular file specified as 'path'.
  ::off_t getSize(const char* const path)
  {
    // Stat the file and make sure that it's the expected size.
    struct ::stat path_stat;
    if (::stat(path, &path_stat) != 0) {
      const int error = errno;
      std::cout
        << "Failed to lstat path: " << path << "; errno=" << error << "; "
        << std::strerror(error) << endl;
      return -1;
    }

    std::cout
      << "Size of file is: " << path_stat.st_size << endl;
    return path_stat.st_size;
  }

  // Causes the regular file specified in 'path' to have a size of 'length'
  // bytes.
  void resize(const char* const path,
              const ::off_t length)
  {
    std::cout
      << "Truncating file=" << path << " to length=" << length << endl;
    if (::truncate(path, length) == -1)
    {
      const int error = errno;
      std::cout
        << "Failed to truncate file=" << path << "; errno=" << error
        << "; " << std::strerror(error) << endl;
    }

    const ::off_t size = getSize(path);
    if (size != length) {
      std::cout
        << "Failed to truncate file=" << path << " to length=" << length
        << "; got size=" << size << endl;
    }
  }

  // Helper to create a file with the given content.
  void createFile(const std::string& path, const std::string& content)
  {
    std::cout
      << "Creating file: " << path << " with content=" << content << endl;

    const int fd = ::open(path.c_str(), O_CREAT | O_WRONLY, 0644);
    if (fd == -1) {
      const int error = errno;
      std::cout
        << "Failed to open file for writing: " << path << "; errno=" << error
        << "; " << std::strerror(error) << endl;
      return;
    }

    if (::write(fd, content.c_str(), content.size()) != content.size()) {
      const int error = errno;
      std::cout
        << "Failed to write content=" << content << " to file=" << path
        << "; errno=" << error << "; " << std::strerror(error) << endl;

      // Fall through to close FD.
    }

    ::close(fd);
  }
}

//============================================================================
// :: Entry Point
int main()
{
  const char* const file = "/tmp/file";
  createFile(file, "This is some content");
  getSize(file);
  resize(file, 32);
  resize(file, 17);
  resize(file, 0);

  // This throws a JS exception.
  resize(file, 32);
  return 0;
}