Add macro OFFUNISKIP

This means use official Unicode code point numbering, not native.  Doing
this converts the existing UNISKIP calls in the code to refer to native
code points, which is what they meant anyway.  The terminology is
somewhat ambiguous, but I don't think it will cause real confusion.
NATIVE_SKIP is also introduced for situations where it is important to
be precise.

4 files changed, 18 insertions, 7 deletions

diff --git a/toke.c b/toke.c
index 73f35909b2..735e0db579 100644
--- a/toke.c
+++ b/toke.c
@@ -3772,7 +3772,7 @@ S_scan_const(pTHX_ char *start)
 	    const UV nextuv   = (this_utf8)
                                 ? utf8n_to_uvchr((U8*)s, send - s, &len, 0)
                                 : (UV) ((U8) *s);
-	    const STRLEN need = UNISKIP(NATIVE_TO_UNI(nextuv));
+	    const STRLEN need = UNISKIP(nextuv);
 	    if (!has_utf8) {
 		SvCUR_set(sv, d - SvPVX_const(sv));
 		SvPOK_on(sv);
diff --git a/utf8.c b/utf8.c
index 945e31c7bf..cc64ee6cd0 100644
--- a/utf8.c
+++ b/utf8.c
@@ -184,7 +184,7 @@ Perl_uvoffuni_to_utf8_flags(pTHX_ U8 *d, UV uv, UV flags)
     }
 #if defined(EBCDIC)
     else {
-	STRLEN len  = UNISKIP(uv);
+	STRLEN len  = OFFUNISKIP(uv);
 	U8 *p = d+len-1;
 	while (p > d) {
 	    *p-- = (U8) I8_TO_NATIVE_UTF8((uv & UTF_CONTINUATION_MASK) | UTF_CONTINUATION_MARK);
@@ -772,7 +772,7 @@ Perl_utf8n_to_uvoffuni(pTHX_ const U8 *s, STRLEN curlen, STRLEN *retlen, U32 fla
 #endif
 
     if (do_overlong_test
-	&& expectlen > (STRLEN)UNISKIP(uv)
+	&& expectlen > (STRLEN) OFFUNISKIP(uv)
 	&& ! (flags & UTF8_ALLOW_LONG))
     {
 	/* The overlong malformation has lower precedence than the others.
@@ -780,7 +780,7 @@ Perl_utf8n_to_uvoffuni(pTHX_ const U8 *s, STRLEN curlen, STRLEN *retlen, U32 fla
 	 * value, instead of the replacement character.  This is because this
 	 * value is actually well-defined. */
 	if (! (flags & UTF8_CHECK_ONLY)) {
-	    sv = sv_2mortal(Perl_newSVpvf(aTHX_ "%s (%d byte%s, need %d, after start byte 0x%02x)", malformed_text, (int)expectlen, expectlen == 1 ? "": "s", UNISKIP(uv), *s0));
+	    sv = sv_2mortal(Perl_newSVpvf(aTHX_ "%s (%d byte%s, need %d, after start byte 0x%02x)", malformed_text, (int)expectlen, expectlen == 1 ? "": "s", OFFUNISKIP(uv), *s0));
 	}
 	goto malformed;
     }
diff --git a/utf8.h b/utf8.h
index b3bf997efb..1ecb3b82d5 100644
--- a/utf8.h
+++ b/utf8.h
@@ -231,7 +231,8 @@ Perl's extended UTF-8 means we can have start bytes up to FF.
            - UTF_ACCUMULATION_SHIFT))
 
 #ifdef HAS_QUAD
-#define UNISKIP(uv) ( (uv) < 0x80           ? 1 : \
+/* Input is a true Unicode (not-native) code point */
+#define OFFUNISKIP(uv) ( (uv) < 0x80        ? 1 : \
 		      (uv) < 0x800          ? 2 : \
 		      (uv) < 0x10000        ? 3 : \
 		      (uv) < 0x200000       ? 4 : \
@@ -240,7 +241,7 @@ Perl's extended UTF-8 means we can have start bytes up to FF.
                       (uv) < UTF8_QUAD_MAX ? 7 : 13 )
 #else
 /* No, I'm not even going to *TRY* putting #ifdef inside a #define */
-#define UNISKIP(uv) ( (uv) < 0x80           ? 1 : \
+#define OFFUNISKIP(uv) ( (uv) < 0x80        ? 1 : \
 		      (uv) < 0x800          ? 2 : \
 		      (uv) < 0x10000        ? 3 : \
 		      (uv) < 0x200000       ? 4 : \
@@ -297,6 +298,15 @@ Perl's extended UTF-8 means we can have start bytes up to FF.
                                                && ( (e) - (s) > 1)             \
                                                && UTF8_IS_CONTINUATION(*((s)+1)))
 
+/* Number of bytes a code point occupies in UTF-8. */
+#define NATIVE_SKIP(uv) OFFUNISKIP(NATIVE_TO_UNI(uv))
+
+/* Most code which says UNISKIP is really thinking in terms of native code
+ * points (0-255) plus all those beyond.  This is an imprecise term, but having
+ * it means existing code continues to work.  For precision, use NATIVE_SKIP
+ * and OFFUNISKIP */
+#define UNISKIP(uv)   NATIVE_SKIP(uv)
+
 /* Convert a two (not one) byte utf8 character to a native code point value.
  * Needs just one iteration of accumulate.  Should not be used unless it is
  * known that the two bytes are legal: 1) two-byte start, and 2) continuation.
diff --git a/utfebcdic.h b/utfebcdic.h
index 09d59fa5de..856bcd7d07 100644
--- a/utfebcdic.h
+++ b/utfebcdic.h
@@ -701,7 +701,8 @@ END_EXTERN_C
 
  */
 
-#define UNISKIP(uv) ( (uv) < 0xA0           ? 1 : \
+/* Input is a true Unicode (not-native) code point */
+#define OFFUNISKIP(uv) ( (uv) < 0xA0        ? 1 : \
 		      (uv) < 0x400          ? 2 : \
 		      (uv) < 0x4000         ? 3 : \
 		      (uv) < 0x40000        ? 4 : \