Clarification and cleanup of the XS SWASHGET code

Subject: Re: XS-assisted SWASHGET (esp. for t/uni/class.t speedup)
Message-Id: <20051204162508.D726.BQW10602@nifty.com>

p4raw-id: //depot/perl@26255

1 files changed, 19 insertions, 12 deletions

diff --git a/utf8.c b/utf8.c
index 813a64fcdd..8c9992f554 100644
--- a/utf8.c
+++ b/utf8.c
@@ -1243,7 +1243,7 @@ S_is_utf8_common(pTHX_ const U8 *const p, SV **swash,
     if (!is_utf8_char(p))
 	return FALSE;
     if (!*swash)
-	*swash = swash_init("utf8", swashname, &PL_sv_undef, 0, 0);
+	*swash = swash_init("utf8", swashname, &PL_sv_undef, 1, 0);
     return swash_fetch(*swash, p, TRUE) != 0;
 }
 
@@ -1545,8 +1545,12 @@ Perl_to_utf8_fold(pTHX_ const U8 *p, U8* ustrp, STRLEN *lenp)
                              &PL_utf8_tofold, "ToFold", "utf8::ToSpecFold");
 }
 
-/* a "swash" is a swatch hash */
-
+/* Note:
+ * A "swash" is a swatch hash.
+ * A "swatch" is a bit vector generated by utf8.c:S_swash_get().
+ * C<pkg> is a pointer to a package name for SWASHNEW, should be "utf8".
+ * For other parameters, see utf8::SWASHNEW in lib/utf8_heavy.pl.
+ */
 SV*
 Perl_swash_init(pTHX_ const char* pkg, const char* name, SV *listsv, I32 minbits, I32 none)
 {
@@ -1744,7 +1748,7 @@ STATIC SV*
 S_swash_get(pTHX_ SV* swash, UV start, UV span)
 {
     SV *swatch;
-    U8 *l, *lend, *x, *xend, *s, *nl;
+    U8 *l, *lend, *x, *xend, *s;
     STRLEN lcur, xcur, scur;
 
     HV* const hv = (HV*)SvRV(swash);
@@ -1801,7 +1805,7 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 	STRLEN numlen;
 	I32 flags = PERL_SCAN_SILENT_ILLDIGIT | PERL_SCAN_DISALLOW_PREFIX;
 
-	nl = (U8*)memchr(l, '\n', lend - l);
+	U8* nl = (U8*)memchr(l, '\n', lend - l);
 
 	numlen = lend - l;
 	min = grok_hex((char *)l, &numlen, &flags, NULL);
@@ -1846,6 +1850,8 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 		    }
 		}
 	    }
+	    else
+		val = 0; /* bits == 1, then val should be ignored */
 	}
 	else {
 	    max = min;
@@ -1855,6 +1861,8 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 		    Perl_croak(aTHX_ "%s: illegal mapping '%s'", typestr, l);
 		}
 	    }
+	    else
+		val = 0; /* bits == 1, then val should be ignored */
 	}
 
 	if (nl)
@@ -1895,7 +1903,7 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 		    ++val;
 	    }
 	}
-	else {
+	else { /* bits == 1, then val should be ignored */
 	    if (min < start)
 		min = start;
 	    for (key = min; key <= max; key++) {
@@ -1918,7 +1926,7 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 	HV* otherhv;
 	STRLEN otherbits;
 	SV **otherbitssvp, *other;
-	U8 *s, *o;
+	U8 *s, *o, *nl;
 	STRLEN slen, olen;
 
 	U8 opc = *x++;
@@ -1993,8 +2001,7 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 		break;
 	    }
 	}
-	else { /* bits >= 8 */
-	       /* XXX: but weirdly otherval is treated as boolean */
+	else {
 	    STRLEN otheroctets = otherbits >> 3;
 	    STRLEN offset = 0;
 	    U8* send = s + slen;
@@ -2015,8 +2022,8 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 		    }
 		}
 
-		if      (opc == '+' && otherval)
-		    otherval = 1;
+		if (opc == '+' && otherval)
+		    ; /* replace with otherval */
 		else if (opc == '!' && !otherval)
 		    otherval = 1;
 		else if (opc == '-' && otherval)
@@ -2024,7 +2031,7 @@ S_swash_get(pTHX_ SV* swash, UV start, UV span)
 		else if (opc == '&' && !otherval)
 		    otherval = 0;
 		else {
-		    s += octets; /* not modify orig swatch */
+		    s += octets; /* no replacement */
 		    continue;
 		}