Function bytes_chunk_extract

src/split.c:1067–1114

/* -n K/N: Extract Kth of N chunks.  */

static void
bytes_chunk_extract (intmax_t k, intmax_t n, char *buf, idx_t bufsize,
                     ssize_t initial_read, off_t file_size)
{
  off_t start;
  off_t end;

  affirm (0 < k && k <= n);

  start = (k - 1) * (file_size / n) + MIN (k - 1, file_size % n);
  end = k == n ? file_size : k * (file_size / n) + MIN (k, file_size % n);

  if (start < initial_read)
    {
      memmove (buf, buf + start, initial_read - start);
      initial_read -= start;
    }
  else
    {
      if (initial_read < start
          && lseek (STDIN_FILENO, start - initial_read, SEEK_CUR) < 0)
        error (EXIT_FAILURE, errno, "%s", quotef (infile));
      initial_read = -1;
    }

  while (start < end)
    {
      ssize_t n_read;
      if (0 <= initial_read)
        {
          n_read = initial_read;
          initial_read = -1;
        }
      else
        {
          n_read = read (STDIN_FILENO, buf, bufsize);
          if (n_read < 0)
            error (EXIT_FAILURE, errno, "%s", quotef (infile));
        }
      if (n_read == 0)
        break; /* eof.  */
      n_read = MIN (n_read, end - start);
      if (full_write (STDOUT_FILENO, buf, n_read) != n_read
          && ! ignorable (errno))
        error (EXIT_FAILURE, errno, "%s", quotef ("-"));
      start += n_read;
    }
}

typedef struct of_info
{