xfs_scrub: hoist non-rendering character predicate

Hoist this predicate code into its own function; we're going to use it
elsewhere later on.  While we're at it, document how we generated this
list in the first place.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/scrub/unicrash.c b/scrub/unicrash.c
index 456caec27d6066a23107c647ae0617e0a408901b..1a86b5f8c5d8a71c62823f8f0b057c442db83cba 100644 (file)
--- a/scrub/unicrash.c
+++ b/scrub/unicrash.c
@@ -170,6 +170,36 @@ remove_ignorable(
        return dest;
 }
 
+/*
+ * Certain unicode codepoints are formatting hints that are not themselves
+ * supposed to be rendered by a display system.  These codepoints can be
+ * encoded in file names to try to confuse users.
+ *
+ * Download https://www.unicode.org/Public/UCD/latest/ucd/UnicodeData.txt and
+ * $ grep -E '(zero width|invisible|joiner|application)' -i UnicodeData.txt
+ */
+static inline bool is_nonrendering(UChar32 uchr)
+{
+       switch (uchr) {
+       case 0x034F:    /* combining grapheme joiner */
+       case 0x200B:    /* zero width space */
+       case 0x200C:    /* zero width non-joiner */
+       case 0x200D:    /* zero width joiner */
+       case 0x2028:    /* line separator */
+       case 0x2029:    /* paragraph separator */
+       case 0x2060:    /* word joiner */
+       case 0x2061:    /* function application */
+       case 0x2062:    /* invisible times (multiply) */
+       case 0x2063:    /* invisible separator (comma) */
+       case 0x2064:    /* invisible plus (addition) */
+       case 0x2D7F:    /* tifinagh consonant joiner */
+       case 0xFEFF:    /* zero width non breaking space */
+               return true;
+       }
+
+       return false;
+}
+
 /*
  * Generate normalized form and skeleton of the name.  If this fails, just
  * forget everything and return false; this is an advisory checker.
@@ -349,24 +379,9 @@ name_entry_examine(
 
        uiter_setString(&uiter, entry->normstr, entry->normstrlen);
        while ((uchr = uiter_next32(&uiter)) != U_SENTINEL) {
-               /* zero width character sequences */
-               switch (uchr) {
-               case 0x034F:    /* combining grapheme joiner */
-               case 0x200B:    /* zero width space */
-               case 0x200C:    /* zero width non-joiner */
-               case 0x200D:    /* zero width joiner */
-               case 0x2028:    /* line separator */
-               case 0x2029:    /* paragraph separator */
-               case 0x2060:    /* word joiner */
-               case 0x2061:    /* function application */
-               case 0x2062:    /* invisible times (multiply) */
-               case 0x2063:    /* invisible separator (comma) */
-               case 0x2064:    /* invisible plus (addition) */
-               case 0x2D7F:    /* tifinagh consonant joiner */
-               case 0xFEFF:    /* zero width non breaking space */
+               /* characters are invisible */
+               if (is_nonrendering(uchr))
                        *badflags |= UNICRASH_ZERO_WIDTH;
-                       break;
-               }
 
                /* control characters */
                if (u_iscntrl(uchr))