From dbf59a6b141213b0afc962c71347eb83f8bcab73 Mon Sep 17 00:00:00 2001
From: Dan McGee <dan@archlinux.org>
Date: Tue, 14 Dec 2010 11:56:32 -0600
Subject: Add hash_sdbm function

This is prepping for the addition of a hash field to each package to greatly
speed up the string comparisons we frequently do on package name in
_alpm_pkg_find.

Signed-off-by: Dan McGee <dan@archlinux.org>
---
 lib/libalpm/util.c | 21 +++++++++++++++++++++
 lib/libalpm/util.h |  1 +
 2 files changed, 22 insertions(+)

(limited to 'lib')

diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c
index e425fa48..8e83bdac 100644
--- a/lib/libalpm/util.c
+++ b/lib/libalpm/util.c
@@ -845,4 +845,25 @@ int _alpm_splitname(const char *target, pmpkg_t *pkg)
 	return(0);
 }
 
+/**
+ * Hash the given string to an unsigned long value.
+ * This is the standard sdbm hashing algorithm.
+ * @param str string to hash
+ * @return the hash value of the given string
+ */
+unsigned long _alpm_hash_sdbm(const char *str)
+{
+	unsigned long hash = 0;
+	int c;
+
+	if(!str) {
+		return(hash);
+	}
+	while((c = *str++)) {
+		hash = c + (hash << 6) + (hash << 16) - hash;
+	}
+
+	return(hash);
+}
+
 /* vim: set ts=2 sw=2 noet: */
diff --git a/lib/libalpm/util.h b/lib/libalpm/util.h
index 78877a27..0b804205 100644
--- a/lib/libalpm/util.h
+++ b/lib/libalpm/util.h
@@ -78,6 +78,7 @@ int _alpm_lstat(const char *path, struct stat *buf);
 int _alpm_test_md5sum(const char *filepath, const char *md5sum);
 char *_alpm_archive_fgets(char *line, size_t size, struct archive *a);
 int _alpm_splitname(const char *target, pmpkg_t *pkg);
+unsigned long _alpm_hash_sdbm(const char *str);
 
 #ifndef HAVE_STRSEP
 char *strsep(char **, const char *);
-- 
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