[PATCH] exclude: improve wide-character hashing

[PATCH] exclude: improve wide-character hashing

[Paul Eggert]

* lib/exclude.c (string_hasher_ci): Take the modulo at the end
rather than each time a wide character is retrieved; this should
be more efficient and should hash better.
---
 ChangeLog     | 7 +++++++
 lib/exclude.c | 4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index d57d006ff..304599f81 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2021-06-11  Paul Eggert  <eggert@cs.ucla.edu>
+
+	exclude: improve wide-character hashing
+	* lib/exclude.c (string_hasher_ci): Take the modulo at the end
+	rather than each time a wide character is retrieved; this should
+	be more efficient and should hash better.
+
 2021-06-11  Bruno Haible  <bruno@clisp.org>
 
 	Make message in last commit more precise.
diff --git a/lib/exclude.c b/lib/exclude.c
index 4ef4e08f1..6287fbc68 100644
--- a/lib/exclude.c
+++ b/lib/exclude.c
@@ -219,10 +219,10 @@ string_hasher_ci (void const *data, size_t n_buckets)
       else
         wc = *m.ptr;
 
-      value = (value * 31 + wc) % n_buckets;
+      value = value * 31 + wc;
     }
 
-  return value;
+  return value % n_buckets;
 }
 
 /* compare two strings for equality */
-- 
2.30.2