regmatch(): do nextchr=*locinput at top of loop

Currently each branch in the main regmatch() loop is responsible
re-initialising nextchar to UCHARAT(locinput) if locinput is modified.

By adding
    nextchr = UCHARAT(locinput);
to the head of the loop, we can remove most of the nextchar assignments
in the individual branches. We lose slightly for the zero-width assertions
like \b which will re-read the same nextchar, but this will make it
easier to handle non-null-terminated strings.

diff --git a/regexec.c b/regexec.c
index 81dc1be..da9b640 100644 (file)
--- a/regexec.c
+++ b/regexec.c
@@ -223,7 +223,7 @@
            sayNO;                                                            \
        }                                                                     \
        /* Matched a utf8-invariant, so don't have to worry about utf8 */     \
-       nextchr = UCHARAT(++locinput);                                        \
+       locinput++;                                        \
        break;                                                                \
     case NNAMEA:                                                              \
        if (locinput >= PL_regeol || FUNCA(nextchr)) {                        \
@@ -3313,6 +3313,7 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
 
       reenter_switch:
 
+        nextchr = UCHARAT(locinput);
         assert(nextchr >= 0);
 
        switch (state_num) {
@@ -3374,7 +3375,7 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
        case CANY:
            if (!nextchr && locinput >= PL_regeol)
                sayNO;
-           nextchr = UCHARAT(++locinput);
+           locinput++;
            break;
        case REG_ANY:
            if ((!nextchr && locinput >= PL_regeol) || nextchr == '\n')
@@ -3717,7 +3718,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
            });
 
            locinput = (char*)uc;
-           nextchr = UCHARAT(locinput);
            continue; /* execute rest of RE */
            assert(0); /* NOTREACHED */
         }
@@ -3785,7 +3785,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                    }
                }
                locinput = l;
-               nextchr = UCHARAT(locinput);
                break;
            }
            /* The target and the pattern have the same utf8ness. */
@@ -3797,7 +3796,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
            if (ln > 1 && memNE(s, locinput, ln))
                sayNO;
            locinput += ln;
-           nextchr = UCHARAT(locinput);
            break;
            }
        case EXACTFL: {
@@ -3847,7 +3845,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                    sayNO;
                }
                locinput = e;
-               nextchr = UCHARAT(locinput);
                break;
            }
 
@@ -3862,7 +3859,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
            if (ln > 1 && ! folder(s, locinput, ln))
                sayNO;
            locinput += ln;
-           nextchr = UCHARAT(locinput);
            break;
        }
 
@@ -3954,7 +3950,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                if (!reginclass(rex, scan, (U8*)locinput, &inclasslen, utf8_target))
                    sayNO;
                locinput += inclasslen;
-               nextchr = UCHARAT(locinput);
                break;
            }
            else {
@@ -3962,7 +3957,7 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                    sayNO;
                if (!REGINCLASS(rex, scan, (U8*)locinput))
                    sayNO;
-               nextchr = UCHARAT(++locinput);
+               locinput++;
                break;
            }
            break;
@@ -3989,7 +3984,7 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                 sayNO;
             }
             /* Matched a utf8-invariant, so don't have to worry about utf8 */
-            nextchr = UCHARAT(++locinput);
+            locinput++;
             break;
         case NPOSIXA:
             if (locinput >= PL_regeol || _generic_isCC_A(nextchr, FLAGS(scan))) {
@@ -4180,7 +4175,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
             exit_utf8:
                if (locinput > PL_regeol) sayNO;
            }
-           nextchr = UCHARAT(locinput);
            break;
             
        case NREFFL:
@@ -4299,7 +4293,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                    sayNO;
                }
                locinput = limit;
-               nextchr = UCHARAT(locinput);
                break;
            }
 
@@ -4316,7 +4309,6 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
                           : ! folder(s, locinput, ln)))
                sayNO;
            locinput += ln;
-           nextchr = UCHARAT(locinput);
            break;
        }
        case NOTHING:
@@ -5807,7 +5799,6 @@ NULL
            if (OP(ST.me) != SUSPEND) {
                 /* restore old position except for (?>...) */
                locinput = st->locinput;
-               nextchr = UCHARAT(locinput);
            }
            scan = ST.me + ARG(ST.me);
            if (scan == ST.me)
@@ -5916,7 +5907,6 @@ NULL
         case LNBREAK:
             if ((n=is_LNBREAK(locinput,utf8_target))) {
                 locinput += n;
-                nextchr = UCHARAT(locinput);
             } else
                 sayNO;
             break;
@@ -5927,7 +5917,6 @@ NULL
                sayNO;                                \
             if ((n=is_##nAmE(locinput,utf8_target))) {    \
                 locinput += n;                        \
-                nextchr = UCHARAT(locinput);          \
             } else                                    \
                 sayNO;                                \
             break;                                    \
@@ -5938,7 +5927,6 @@ NULL
                 sayNO;                                \
             } else {                                  \
                 locinput += UTF8SKIP(locinput);       \
-                nextchr = UCHARAT(locinput);          \
             }                                         \
             break
 
@@ -5958,10 +5946,9 @@ NULL
                 locinput += PL_utf8skip[nextchr];
                 if (locinput > PL_regeol)
                     sayNO;
-                nextchr = UCHARAT(locinput);
             }
             else
-                nextchr = UCHARAT(++locinput);
+                locinput++;
             break;
            
        } /* end switch */ 
@@ -6010,7 +5997,6 @@ NULL
            PL_regmatch_state = newst;
 
            locinput = pushinput;
-           nextchr = UCHARAT(locinput);
            st = newst;
            continue;
            assert(0); /* NOTREACHED */
@@ -6061,10 +6047,8 @@ yes:
        yes_state = st->u.yes.prev_yes_state;
        PL_regmatch_state = st;
         
-        if (no_final) {
+        if (no_final)
             locinput= st->locinput;
-            nextchr = UCHARAT(locinput);
-        }
        state_num = st->resume_state + no_final;
        goto reenter_switch;
     }
@@ -6109,7 +6093,6 @@ no_silent:
        }
        PL_regmatch_state = st;
        locinput= st->locinput;
-       nextchr = UCHARAT(locinput);
 
        DEBUG_STATE_pp("pop");
        depth--;