performance: improve ossl_lh_strcasehash
This improvement seems to roughly halve the time it takes to run the
ossl_lh_strcasehash function.
It should have no impact on the strings we hash and search for often (algorithm
names, property strings).
@@ -344,18 +344,37 @@ unsigned long OPENSSL_LH_strhash(const char *c)
return (ret >> 16) ^ ret;
}
+/*
+ * Case insensitive string hashing.
+ *
+ * The lower/upper case bit is masked out (forcing all letters to be capitals).
+ * The major side effect on non-alpha characters is mapping the symbols and
+ * digits into the control character range (which should be harmless).
+ * The duplication (with respect to the hash value) of printable characters
+ * are that '`', '{', '|', '}' and '~' map to '@', '[', '\', ']' and '^'
+ * respectively (which seems tolerable).
+ *
+ * For EBCDIC, the alpha mapping is to lower case, most symbols go to control
+ * characters. The only duplication is '0' mapping to '^', which is better
+ * than for ASCII.
+ */
unsigned long ossl_lh_strcasehash(const char *c)
{
unsigned long ret = 0;
long n;
unsigned long v;
int r;
+#if defined(CHARSET_EBCDIC) && !defined(CHARSET_EBCDIC_TEST)
+ const long int case_adjust = ~0x40;
+#else
+ const long int case_adjust = ~0x20;
+#endif
if (c == NULL || *c == '\0')
return ret;
for (n = 0x100; *c != '\0'; n += 0x100) {
- v = n | ossl_tolower(*c);
+ v = n | (case_adjust & *c);
r = (int)((v >> 2) ^ v) & 0x0f;
/* cast to uint64_t to avoid 32 bit shift of 32 bit value */
ret = (ret << r) | (unsigned long)((uint64_t)ret >> (32 - r));
