Function cat

src/cat.c:229–515

   an explicit test for buffer end unnecessary.  */

static bool
cat (char *inbuf, idx_t insize, char *outbuf, idx_t outsize,
     bool show_nonprinting, bool show_tabs, bool number, bool number_nonblank,
     bool show_ends, bool squeeze_blank)
{
  /* Last character read from the input buffer.  */
  unsigned char ch;

  /* Determines how many consecutive newlines there have been in the
     input.  0 newlines makes NEWLINES -1, 1 newline makes NEWLINES 1,
     etc.  Initially 0 to indicate that we are at the beginning of a
     new line.  The "state" of the procedure is determined by
     NEWLINES.  */
  int newlines = newlines2;

#ifdef FIONREAD
  /* If nonzero, use the FIONREAD ioctl, as an optimization.
     (On Ultrix, it is not supported on NFS file systems.)  */
  bool use_fionread = true;
#endif

  /* The inbuf pointers are initialized so that BPIN > EOB, and thereby input
     is read immediately.  */

  /* Pointer to the first non-valid byte in the input buffer, i.e., the
     current end of the buffer.  */
  char *eob = inbuf;

  /* Pointer to the next character in the input buffer.  */
  char *bpin = eob + 1;

  /* Pointer to the position where the next character shall be written.  */
  char *bpout = outbuf;

  while (true)
    {
      do
        {
          /* Write if there are at least OUTSIZE bytes in OUTBUF.  */

          if (outbuf + outsize <= bpout)
            {
              char *wp = outbuf;
              idx_t remaining_bytes;
              do
                {
                  if (full_write (STDOUT_FILENO, wp, outsize) != outsize)
                    write_error ();
                  wp += outsize;
                  remaining_bytes = bpout - wp;
                }
              while (outsize <= remaining_bytes);

              /* Move the remaining bytes to the beginning of the
                 buffer.  */

              memmove (outbuf, wp, remaining_bytes);
              bpout = outbuf + remaining_bytes;