🚀 go-pugleaf

I am reposting here a little patch to "insdel.c" that will dramatically
speed up the shifting of the gap. All of the other catastrophic
performance problems of using a buffer gap system, principally the fact
that it practically requires the entire buffer to be core resident or
else..., are not addressed, but at least gap shifts are no longer
performed one character at a time, and CPU time goes down a lot.

This patch comes in especially handy now as I have posted to comp.arch
and alt.sources a very portable, very efficient version of memcpy(3) or
bcopy(3) that beats them hands down on many architectures when copying
between unaligned addresses, e.g. most of the cases that the gap has to
be shifted.

You will want to provide suitable #define's for BSTRING_LTOR,
BSTRING_RTOL, bcopy in you s-*.h file, unless you are running a BSD-ish
system in which case the supplied defaults will be OK. You still havwe
to define BSTRING to enable everything.

RCS file: insdel.c,v
retrieving revision 18.55
diff -c -r18.55 insdel.c
*** /tmp/,RCSt1a10289	Mon Aug  6 22:52:45 1990
--- insdel.c	Mon Aug  6 11:43:57 1990
***************
*** 24,29 ****
--- 24,44 ----
  #include "buffer.h"
  #include "window.h"
  
+ #ifdef BSTRING
+ # ifdef BSTRING_LTOR
+ #   undef BSTRING_LTOR
+ #   define BSTRING_LTOR 1
+ # else
+ #   define BSTRING_LTOR 0
+ # endif
+ # ifdef BSTRING_RTOL
+ #   undef BSTRING_RTOL
+ #   define BSTRING_RTOL 1
+ # else
+ #   define BSTRING_RTOL 0
+ # endif
+ #endif
+ 
  /* Move gap to position `pos'.
     Note that this can quit!  */
  
***************
*** 33,38 ****
--- 48,58 ----
    if (bf_p2 != bf_gap + bf_p1)
      abort ();
  
+   /*
+     if pos == bs_s1 then the gap does not need moving at all. Remember
+     that bs_s1 points to 1 *below* the real start of the gap.
+   */
+ 
    if (pos <= bf_s1)
      gap_left (pos);
    else if (pos > bf_s1 + 1)
***************
*** 86,91 ****
--- 106,121 ----
        if (i > 32000)
  	i = 32000;
        new_s1 -= i;
+ #if defined(BSTRING)
+       /*
+         We are moving the gap to the left; this means moving
+ 	memory to the right (from <= to), and overlaps are safe
+ 	if we copy from right to left.
+       */
+       if (i >= 32 && (BSTRING_RTOL || /* no overlap */ from <= to-i))
+ 	from -= i, to -= i, (void) bcopy (from,to,i);
+       else
+ #endif
        while (--i >= 0)
  	*--to = *--from;
      }
***************
*** 146,151 ****
--- 176,192 ----
        if (i > 32000)
  	i = 32000;
        new_s1 += i;
+ 
+ #ifdef BSTRING
+       /*
+         We are moving the gap to the right; this means moving
+ 	memory to the left (to <= from), and overlaps are safe
+ 	if we copy from left to right.
+       */
+       if (i >= 32 && (BSTRING_LTOR || /* no overlap */ to+i <= from))
+ 	(void) bcopy (from,to,i), from += i, to += i;
+       else
+ #endif
        while (--i >= 0)
  	*to++ = *from++;
      }
***************
*** 204,210 ****
    if (bf_gap >= k)
      return;
  
!   k += 2000;			/* Get more than just enough */
  
    p1 = (unsigned char *) realloc (bf_p1 + 1, bf_s1 + bf_s2 + k);
    if (p1 == 0)
--- 245,251 ----
    if (bf_gap >= k)
      return;
  
!   k += 32000;			/* Get more than just enough */
  
    p1 = (unsigned char *) realloc (bf_p1 + 1, bf_s1 + bf_s2 + k);
    if (p1 == 0)

--
Piercarlo "Peter" Grandi           | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcsun!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk