From: Aki Tuomi <aki.tuomi@dovecot.fi>
Date: Fri, 28 Jul 2017 06:47:09 +0000 (+0300)
Subject: lib: Add strfastcase_hash
X-Git-Tag: 2.3.0.rc1~1173
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=00bd7d0e21ffa84965fd6aa0ccbc54aab7fad77c;p=thirdparty%2Fdovecot%2Fcore.git

lib: Add strfastcase_hash

Fast case-insensitive hashing which works by masking signed
bytes with 0x20.
---

diff --git a/src/lib/hash.c b/src/lib/hash.c
index 2a2db8dfb5..aa9716865e 100644
--- a/src/lib/hash.c
+++ b/src/lib/hash.c
@@ -565,3 +565,19 @@ unsigned int mem_hash(const void *p, unsigned int size)
 	return h;
 }
 
+unsigned int strfastcase_hash(const char *p)
+{
+	const unsigned char *s = (const unsigned char *)p;
+	unsigned int g, h = 0;
+
+	while (*s != '\0') {
+		h = (h << 4) + ((*s) & ~0x20);
+		if ((g = h & 0xf0000000UL) != 0) {
+			h = h ^ (g >> 24);
+			h = h ^ g;
+		}
+		s++;
+	}
+
+	return h;
+}
diff --git a/src/lib/hash.h b/src/lib/hash.h
index d51d5cd8a5..53b2ffa89b 100644
--- a/src/lib/hash.h
+++ b/src/lib/hash.h
@@ -170,6 +170,12 @@ void hash_table_copy(struct hash_table *dest, struct hash_table *src);
 /* hash function for strings */
 unsigned int str_hash(const char *p) ATTR_PURE;
 unsigned int strcase_hash(const char *p) ATTR_PURE;
+
+/* fast hash function which uppercases a-z. Does not work well
+   with input that consists from non number/letter input, as
+   it works by dropping 0x20. */
+unsigned int strfastcase_hash(const char *p) ATTR_PURE;
+
 /* a generic hash for a given memory block */
 unsigned int mem_hash(const void *p, unsigned int size) ATTR_PURE;