In Perl_fbm_instr(), use a switch() statement for the special case code.

Previously the special-case code for lengths 0, 1 and 2 was in a nested set
of if() statements, which was slightly cryptic to read.

diff --git a/util.c b/util.c
index 7341117..74d7bb8 100644 (file)
--- a/util.c
+++ b/util.c
@@ -573,6 +573,8 @@ Perl_fbm_compile(pTHX_ SV *sv, U32 flags)
     SvNOK_off(sv);
     SvVALID_on(sv);
     if (len > 2) {
+       /* Shorter strings are special-cased in Perl_fbm_instr(), and don't use
+          the BM table.  */
        const unsigned char *sb;
        const U8 mlen = (len>255) ? 255 : (U8)len;
        register U8 *table;
@@ -647,9 +649,10 @@ Perl_fbm_instr(pTHX_ unsigned char *big, register unsigned char *bigend, SV *lit
        return NULL;
     }
 
-    if (littlelen <= 2) {              /* Special-cased */
-
-       if (littlelen == 1) {
+    switch (littlelen) { /* Special cases for 0, 1 and 2  */
+    case 0:
+       return (char*)big;              /* Cannot be SvTAIL! */
+    case 1:
            if (SvTAIL(littlestr) && !multiline) { /* Anchor only! */
                /* Know that bigend != big.  */
                if (bigend[-1] == '\n')
@@ -665,11 +668,7 @@ Perl_fbm_instr(pTHX_ unsigned char *big, register unsigned char *bigend, SV *lit
            if (SvTAIL(littlestr))
                return (char *) bigend;
            return NULL;
-       }
-       if (!littlelen)
-           return (char*)big;          /* Cannot be SvTAIL! */
-
-       /* littlelen is 2 */
+    case 2:
        if (SvTAIL(littlestr) && !multiline) {
            if (bigend[-1] == '\n' && bigend[-2] == *little)
                return (char*)bigend - 2;
@@ -729,7 +728,10 @@ Perl_fbm_instr(pTHX_ unsigned char *big, register unsigned char *bigend, SV *lit
        if (SvTAIL(littlestr) && (*bigend == *little))
            return (char *)bigend;      /* bigend is already decremented. */
        return NULL;
+    default:
+       break; /* Only lengths 0 1 and 2 have special-case code.  */
     }
+
     if (SvTAIL(littlestr) && !multiline) {     /* tail anchored? */
        s = bigend - littlelen;
        if (s >= big && bigend[-1] == '\n' && *s == *little