Minor fix/speedup to util.c:fbm_instr:

	Subject: 5.004_55: Minor regexp patch

p4raw-id: //depot/perl@355

diff --git a/util.c b/util.c
index cb7a4f1..0156375 100644 (file)
--- a/util.c
+++ b/util.c
@@ -822,18 +822,20 @@ fbm_compile(SV *sv)
     sv_upgrade(sv, SVt_PVBM);
     if (len > 255 || len == 0) /* TAIL might be on on a zero-length string. */
        return;                 /* can't have offsets that big */
-    Sv_Grow(sv,len+258);
-    table = (unsigned char*)(SvPVX(sv) + len + 1);
-    s = table - 2;
-    for (i = 0; i < 256; i++) {
-       table[i] = len;
-    }
-    i = 0;
-    while (s >= (unsigned char*)(SvPVX(sv)))
-    {
-       if (table[*s] == len)
-           table[*s] = i;
-       s--,i++;
+    if (len > 2) {
+       Sv_Grow(sv,len + 258);
+       table = (unsigned char*)(SvPVX(sv) + len + 1);
+       s = table - 2;
+       for (i = 0; i < 256; i++) {
+           table[i] = len;
+       }
+       i = 0;
+       while (s >= (unsigned char*)(SvPVX(sv)))
+           {
+               if (table[*s] == len)
+                   table[*s] = i;
+               s--,i++;
+           }
     }
     sv_magic(sv, Nullsv, 'B', Nullch, 0);      /* deep magic */
     SvVALID_on(sv);
@@ -865,7 +867,13 @@ fbm_instr(unsigned char *big, register unsigned char *bigend, SV *littlestr)
        STRLEN len;
        char *l = SvPV(littlestr,len);
        if (!len) {
-           if (SvTAIL(littlestr)) {
+           if (SvTAIL(littlestr)) {    /* Can be only 0-len constant
+                                          substr => we can ignore SvVALID */
+               if (multiline) {
+                   char *t = "\n";
+                   if ((s = ninstr((char*)big,(char*)bigend, t, t + len)))
+                       return s;
+               }
                if (bigend > big && bigend[-1] == '\n')
                    return (char *)(bigend - 1);
                else
@@ -882,13 +890,30 @@ fbm_instr(unsigned char *big, register unsigned char *bigend, SV *littlestr)
            return Nullch;
        little = (unsigned char*)SvPVX(littlestr);
        s = bigend - littlelen;
-       if (*s == *little && memEQ((char*)s,(char*)little,littlelen))
+       if (s > big
+           && bigend[-1] == '\n' 
+           && s[-1] == *little && memEQ((char*)s - 1,(char*)little,littlelen))
+           return (char*)s - 1;        /* how sweet it is */
+       else if (*s == *little && memEQ((char*)s,(char*)little,littlelen))
            return (char*)s;            /* how sweet it is */
-       else if (bigend[-1] == '\n' && little[littlelen-1] != '\n'
-                && s > big) {
-           s--;
-           if (*s == *little && memEQ((char*)s,(char*)little,littlelen))
-               return (char*)s;
+       return Nullch;
+    }
+    if (littlelen <= 2) {
+       unsigned char c1 = (unsigned char)SvPVX(littlestr)[0];
+       unsigned char c2 = (unsigned char)SvPVX(littlestr)[1];
+       /* This may do extra comparisons if littlelen == 2, but this
+          should be hidden in the noise since we do less indirection. */
+       
+       s = big;
+       bigend -= littlelen;
+       while (s <= bigend) {
+           if (s[0] == c1 
+               && (littlelen == 1 || s[1] == c2)
+               && (!SvTAIL(littlestr)
+                   || s == bigend
+                   || s[littlelen] == '\n')) /* Automatically multiline */
+               return s;               
+           s++;
        }
        return Nullch;
     }