Function wc_lines

src/wc.c:304–366

Read FD and return a summary. */

/* Read FD and return a summary.  */
static struct wc_lines
wc_lines (int fd)
{
#ifdef USE_AVX512_WC_LINECOUNT
  static signed char use_avx512;
  if (!use_avx512)
    use_avx512 = avx512_supported () ? 1 : -1;
  if (0 < use_avx512)
    return wc_lines_avx512 (fd);
#endif
#ifdef USE_AVX2_WC_LINECOUNT
  static signed char use_avx2;
  if (!use_avx2)
    use_avx2 = avx2_supported () ? 1 : -1;
  if (0 < use_avx2)
    return wc_lines_avx2 (fd);
#endif
#ifdef USE_NEON_WC_LINECOUNT
  static signed char use_neon;
  if (!use_neon)
    use_neon = neon_supported () ? 1 : -1;
  if (0 < use_neon)
    return wc_lines_neon (fd);
#endif

  intmax_t lines = 0, bytes = 0;
  bool long_lines = false;

  while (true)
    {
      char buf[IO_BUFSIZE + 1];
      ssize_t bytes_read = read (fd, buf, IO_BUFSIZE);
      if (bytes_read <= 0)
        return (struct wc_lines) { bytes_read == 0 ? 0 : errno, lines, bytes };

      bytes += bytes_read;
      char *end = buf + bytes_read;
      idx_t buflines = 0;

      if (! long_lines)
        {
          /* Avoid function call overhead for shorter lines.  */
          for (char *p = buf; p < end; p++)
            buflines += *p == '\n';
        }
      else
        {
          /* rawmemchr is more efficient with longer lines.  */
          *end = '\n';
          for (char *p = buf; (p = rawmemchr (p, '\n')) < end; p++)
            buflines++;
        }

      /* If the average line length in the block is >= 15, then use
          memchr for the next block, where system specific optimizations
          may outweigh function call overhead.
          FIXME: This line length was determined in 2015, on both
          x86_64 and ppc64, but it's worth re-evaluating in future with