toke.c: Streamline a case

When we are parsing a constant, and the source and destination differ in
UTF-8ness, I realized, in single stepping through the code, that it's
simpler and more efficient to split these into two cases, rather than
try to do one case with some conditionals in the middle.

diff --git a/toke.c b/toke.c
index c2a8344..ab35ccf 100644 (file)
--- a/toke.c
+++ b/toke.c
@@ -4050,21 +4050,13 @@ S_scan_const(pTHX_ char *start)
             d += len;
             s += len;
         }
-        else { /* UTF8ness matters and doesn't match, need to convert */
-           STRLEN len = 1;
-           const UV nextuv   = (s_is_utf8)
-                                ? utf8n_to_uvchr((U8*)s, send - s, &len, 0)
-                                : (UV) ((U8) *s);
-           STRLEN need = UVCHR_SKIP(nextuv);
-
-           if (!d_is_utf8) {
+        else if (s_is_utf8) { /* UTF8ness matters: convert output to utf8 */
+            STRLEN need = send - s + 1; /* See Note on sizing above. */
+
                SvCUR_set(sv, d - SvPVX_const(sv));
                SvPOK_on(sv);
                *d = '\0';
 
-                /* See Note on sizing above. */
-                need += (STRLEN)(send - s) + 1;
-
                 if (utf8_variant_count == 0) {
                     SvUTF8_on(sv);
                     d = SvCUR(sv) + SvGROW(sv, SvCUR(sv) + need);
@@ -4076,17 +4068,18 @@ S_scan_const(pTHX_ char *start)
                     d = SvPVX(sv) + SvCUR(sv);
                 }
                d_is_utf8 = TRUE;
-           } else if (need > len) {
-               /* encoded value larger than old, may need extra space (NOTE:
-                * SvCUR() is not set correctly here).   See Note on sizing
-                * above.  */
-                const STRLEN extra = need + (send - s) + 1;
+            goto default_action; /* Redo, having upgraded so both are UTF-8 */
+        }
+        else {  /* UTF8ness matters: convert this non-UTF8 source char to
+                   UTF-8 for output.  It will occupy 2 bytes */
+            if (d + 2 >= SvEND(sv)) {
+                const STRLEN extra = 2 + (send - s - 1) + 1;
                const STRLEN off = d - SvPVX_const(sv);
                d = off + SvGROW(sv, off + extra);
            }
-           s += len;
-
-           d = (char*)uvchr_to_utf8((U8*)d, nextuv);
+            *d++ = UTF8_EIGHT_BIT_HI(*s);
+            *d++ = UTF8_EIGHT_BIT_LO(*s);
+            s++;
        }
     } /* while loop to process each character */