[Libguestfs] [hivex PATCH] lib: write: improve key collation compatibility with Windows
There are multiple problems with using strcasecmp() for ordering registry
keys:
(1) strcasecmp() is influenced by LC_CTYPE.
(2) strcasecmp() cannot implement case conversion for multibyte UTF-8
sequences.
(3) Even with LC_CTYPE=POSIX and key names consisting solely of ASCII
characters, strcasecmp() converts characters to lowercase, for
comparison. But on Windows, the CompareStringOrdinal() function
converts characters to uppercase. This makes a difference when
comparing a letter to one of the characters that fall between 'Z'
(0x5A) and 'a' (0x61), namely {'[', '\\', ']',
'^', '_', '`'}. For
example,
'c' (0x63) > '_' (0x5F)
'C' (0x43) < '_' (0x5F)
Compare key names byte for byte, eliminating problems (1) and (3).
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1648520
Signed-off-by: Laszlo Ersek <lersek(a)redhat.com>
---
lib/write.c | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/lib/write.c b/lib/write.c
index 70105c9d9907..d9a13a3c18b6 100644
--- a/lib/write.c
+++ b/lib/write.c
@@ -462,7 +462,37 @@ compare_name_with_nk_name (hive_h *h, const char *name, hive_node_h
nk_offs)
return 0;
}
- int r = strcasecmp (name, nname);
+ /* Perform a limited case-insensitive comparison. ASCII letters will be
+ * *upper-cased*. Multibyte sequences will produce nonsensical orderings.
+ */
+ int r = 0;
+ const char *s1 = name;
+ const char *s2 = nname;
+
+ for (;;) {
+ unsigned char c1 = *(s1++);
+ unsigned char c2 = *(s2++);
+
+ if (c1 >= 'a' && c1 <= 'z')
+ c1 = 'A' + (c1 - 'a');
+ if (c2 >= 'a' && c2 <= 'z')
+ c2 = 'A' + (c2 - 'a');
+ if (c1 < c2) {
+ /* Also covers the case when "name" is a prefix of "nname". */
+ r = -1;
+ break;
+ }
+ if (c1 > c2) {
+ /* Also covers the case when "nname" is a prefix of "name". */
+ r = 1;
+ break;
+ }
+ if (c1 == '\0') {
+ /* Both strings end. */
+ break;
+ }
+ }
+
free (nname);
return r;
--
2.19.1.3.g30247aa5d201