Re: next_char inlining (was: Re: M4 1.4.10b [beta] released)

| The speed-relevant code is only the case for INPUT_CHAIN. I added the one
| for INPUT_STRING because it may be useful it situations I don't know of.

And here is, for completeness, the handling of INPUT_FILE. It requires the
modules freadahead, freadptr, freadseek from gnulib. No speed improvement
measureable with autoconf.

*** input.c.patch11	2008-02-28 14:52:02.000000000 +0100
--- input.c	2008-02-29 01:53:41.000000000 +0100
***************
*** 60,65 ****
--- 60,69 ----
     swapping between input blocks updates the global variables
     accordingly.  */
  
+ #include "freadahead.h"
+ #include "freadptr.h"
+ #include "freadseek.h"
+ 
  #ifdef ENABLE_CHANGEWORD
  # include "regex.h"
  #endif /* ENABLE_CHANGEWORD */
***************
*** 1733,1738 ****
--- 1737,1799 ----
  		      continue;
  		    }
  		}
+ 	      else if (isp->type == INPUT_FILE)
+ 		{
+ 		  if (!isp->u.u_f.end)
+ 		    {
+ 		      size_t n = freadahead (isp->u.u_f.fp);
+ 		      if (n > 0)
+ 			{
+ 			  const char *readptr = freadptr (isp->u.u_f.fp);
+ 			  if (readptr != NULL)
+ 			    {
+ 			      unsigned char curr_quote_1 =
+ 				to_uchar (curr_quote.str1[0]);
+ 			      unsigned char curr_quote_2 =
+ 				to_uchar (curr_quote.str2[0]);
+ 			      const char *p = readptr;
+ 			      size_t count;
+ 
+ 			      do
+ 				{
+ 				  unsigned char ch;
+ 
+ 				  if (start_of_input_line)
+ 				    {
+ 				      start_of_input_line = false;
+ 				      current_line = ++isp->line;
+ 				    }
+ 				  ch = to_uchar (*p);
+ 				  if (ch == '\n')
+ 				    start_of_input_line = true;
+ 				  if (ch == curr_quote_2)
+ 				    {
+ 				      if (--quote_level == 0)
+ 					break;
+ 				    }
+ 				  else
+ 				    quote_level += (ch == curr_quote_1);
+ 				  p++;
+ 				  n--;
+ 				}
+ 			      while (n > 0);
+ 
+ 			      count = p - readptr;
+ 			      if (count > 0)
+ 				obstack_grow (obs_td, readptr, count);
+ 			      count += (quote_level == 0);
+ 			      assert (count > 0);
+ 			      if (freadseek (isp->u.u_f.fp, count) < 0)
+ 				/* freadseek should not fail, since
+ 				   count <= freadahead (isp->u.u_f.fp).  */
+ 				abort ();
+ 			      if (quote_level == 0)
+ 				break;
+ 			      continue;
+ 			    }
+ 			}
+ 		    }
+ 		}
  	    }
  
  	  /* The general case.  Proceed character by character.  */