In Perl_sv_pos_b2u, if we know the character offset of the end, we

can take advantage of this to count backwards if close.
Remove some now unnecessary casts.

p4raw-id: //depot/perl@27558

diff --git a/sv.c b/sv.c
index 992439c..2641da0 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -5681,7 +5681,7 @@ Perl_sv_pos_b2u(pTHX_ register SV* sv, I32* offsetp)
 
     s = (const U8*)SvPV_const(sv, len);
 
-    if ((I32)len < byte)
+    if (len < byte)
        Perl_croak(aTHX_ "panic: sv_pos_b2u: bad byte offset");
 
     send = s + byte;
@@ -5690,16 +5690,23 @@ Perl_sv_pos_b2u(pTHX_ register SV* sv, I32* offsetp)
        mg = mg_find(sv, PERL_MAGIC_utf8);
        if (mg && mg->mg_ptr) {
            STRLEN *cache = (STRLEN *) mg->mg_ptr;
-           if (cache[1] == (STRLEN)byte) {
+           if (cache[1] == byte) {
                /* An exact match. */
                *offsetp = cache[0];
 
                return;
            }
-           else if (cache[1] < (STRLEN)byte) {
+           else if (cache[1] < byte) {
                /* We already know part of the way. */
-               len = cache[0]
-                   + S_sv_pos_b2u_forwards(aTHX_ s + cache[1] , send);
+               if (mg->mg_len != -1) {
+                   /* Actually, we know the end too.  */
+                   len = cache[0]
+                       + S_sv_pos_b2u_midway(aTHX_ s + cache[1], send,
+                                             s + len, mg->mg_len - cache[0]);
+               } else {
+                   len = cache[0]
+                       + S_sv_pos_b2u_forwards(aTHX_ s + cache[1], send);
+               }
            }
            else { /* cache[1] > byte */
                len = S_sv_pos_b2u_midway(aTHX_ s, send, s + cache[1],