The simplest way to start on Perl_sv_pos_u2b seems to be to take out

all of the caching code.

p4raw-id: //depot/perl@27570

diff --git a/sv.c b/sv.c
index 6021c41..dfaf433 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -5501,6 +5501,22 @@ type coercion.
  *
  */
 
+static STRLEN
+S_sv_pos_u2b_forwards(pTHX_ const U8 *const start, const U8 *const send,
+                     STRLEN uoffset)
+{
+    const U8 *s = start;
+
+    while (s < send && uoffset--)
+       s += UTF8SKIP(s);
+    if (s > send) {
+       /* This is the existing behaviour. Possibly it should be a croak, as
+          it's actually a bounds error  */
+       s = send;
+    }
+    return s - start;
+}
+
 void
 Perl_sv_pos_u2b(pTHX_ register SV *sv, I32* offsetp, I32* lenp)
 {
@@ -5512,42 +5528,21 @@ Perl_sv_pos_u2b(pTHX_ register SV *sv, I32* offsetp, I32* lenp)
 
     start = (U8*)SvPV_const(sv, len);
     if (len) {
-       STRLEN boffset = 0;
-       STRLEN *cache = NULL;
-       const U8 *s = start;
-       I32 uoffset = *offsetp;
-       const U8 * const send = s + len;
-       MAGIC *mg = NULL;
-       bool found = utf8_mg_pos(sv, &mg, &cache, 0, offsetp, *offsetp, &s, start, send);
-
-        if (!found && uoffset > 0) {
-             while (s < send && uoffset--)
-                  s += UTF8SKIP(s);
-             if (s >= send)
-                  s = send;
-              if (utf8_mg_pos_init(sv, &mg, &cache, 0, *offsetp, s, start))
-                  boffset = cache[1];
-             *offsetp = s - start;
-        }
-        if (lenp) {
-             found = FALSE;
-             start = s;
-              if (utf8_mg_pos(sv, &mg, &cache, 2, lenp, *lenp, &s, start, send)) {
-                  *lenp -= boffset;
-                  found = TRUE;
-              }
-             if (!found && *lenp > 0) {
-                  I32 ulen = *lenp;
-                  if (ulen > 0)
-                       while (s < send && ulen--)
-                            s += UTF8SKIP(s);
-                  if (s >= send)
-                       s = send;
-                   utf8_mg_pos_init(sv, &mg, &cache, 2, *lenp, s, start);
-             }
-             *lenp = s - start;
-        }
-        ASSERT_UTF8_CACHE(cache);
+       STRLEN uoffset = (STRLEN) *offsetp;
+       const U8 * const send = start + len;
+       STRLEN boffset = S_sv_pos_u2b_forwards(aTHX_ start, send, uoffset);
+
+       *offsetp = (I32) boffset;
+
+       if (lenp) {
+           /* Recalculate things relative to the previously found pair,
+              as if the string started from here.  */
+           start += boffset;
+           uoffset = *lenp;
+
+           boffset = S_sv_pos_u2b_forwards(aTHX_ start, send, uoffset);
+           *lenp = boffset;
+       }
     }
     else {
         *offsetp = 0;