utf8.c: Add utf8_to_uvchr_buf() and utf8_to_uvuni_buf()

The existing functions (utf8_to_uvchr and utf8_to_uvuni) have a
deficiency in that they could read beyond the end of the input string if
given malformed input.  This commit creates two new functions which
behave as the old ones did, but have an extra parameter each, which
gives the upper limit to the string, so no read beyond it is done.

1 files changed, 54 insertions, 1 deletions

diff --git a/utf8.c b/utf8.c
index 0aede4c3a6..1faa96d9fb 100644
--- a/utf8.c
+++ b/utf8.c
@@ -563,7 +563,7 @@ All other code points corresponding to Unicode characters, including private
 use and those yet to be assigned, are never considered malformed and never
 warn.
 
-Most code should use L</utf8_to_uvchr>() rather than call this directly.
+Most code should use L</utf8_to_uvchr_buf>() rather than call this directly.
 
 =cut
 */
@@ -795,6 +795,31 @@ malformed:
 }
 
 /*
+=for apidoc utf8_to_uvchr_buf
+
+Returns the native code point of the first character in the string C<s> which
+is assumed to be in UTF-8 encoding; C<send> points to 1 beyond the end of C<s>.
+C<retlen> will be set to the length, in bytes, of that character.
+
+If C<s> does not point to a well-formed UTF-8 character, zero is
+returned and C<retlen> is set, if possible, to -1.
+
+=cut
+*/
+
+
+UV
+Perl_utf8_to_uvchr_buf(pTHX_ const U8 *s, const U8 *send, STRLEN *retlen)
+{
+    PERL_ARGS_ASSERT_UTF8_TO_UVCHR_BUF;
+
+    assert(s < send);
+
+    return utf8n_to_uvchr(s, send - s, retlen,
+			  ckWARN_d(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+}
+
+/*
 =for apidoc utf8_to_uvchr
 
 Returns the native code point of the first character in the string C<s>
@@ -817,6 +842,34 @@ Perl_utf8_to_uvchr(pTHX_ const U8 *s, STRLEN *retlen)
 }
 
 /*
+=for apidoc utf8_to_uvuni_buf
+
+Returns the Unicode code point of the first character in the string C<s> which
+is assumed to be in UTF-8 encoding; C<send> points to 1 beyond the end of C<s>.
+C<retlen> will be set to the length, in bytes, of that character.
+
+This function should only be used when the returned UV is considered
+an index into the Unicode semantic tables (e.g. swashes).
+
+If C<s> does not point to a well-formed UTF-8 character, zero is
+returned and C<retlen> is set, if possible, to -1.
+
+=cut
+*/
+
+UV
+Perl_utf8_to_uvuni_buf(pTHX_ const U8 *s, const U8 *send, STRLEN *retlen)
+{
+    PERL_ARGS_ASSERT_UTF8_TO_UVUNI_BUF;
+
+    assert(send > s);
+
+    /* Call the low level routine asking for checks */
+    return Perl_utf8n_to_uvuni(aTHX_ s, send -s, retlen,
+			       ckWARN_d(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+}
+
+/*
 =for apidoc utf8_to_uvuni
 
 Returns the Unicode code point of the first character in the string C<s>