Changeset 194213 in webkit

Timestamp:

Dec 16, 2015 11:49:45 PM (8 years ago)

Author:

commit-queue@webkit.org

Message:

Make SessionID use intHash
​https://bugs.webkit.org/show_bug.cgi?id=152356

Patch by Alex Christensen <​achristensen@webkit.org> on 2015-12-16
Reviewed by Darin Adler.

• page/SessionID.h:

(WTF::SessionIDHash::hash):
(WTF::SessionIDHash::equal):
(WTF::HashTraits<WebCore::SessionID>::emptyValue):
(WTF::HashTraits<WebCore::SessionID>::constructDeletedValue):
(WTF::HashTraits<WebCore::SessionID>::isDeletedValue):
Use intHash instead of just casting a uint64_t to an unsigned.
This reduces hash collisions in HashTables that are usually quite small so it isn't much of a problem.
Also, needsDestruction hasn't been in HashTraits since r156507.

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• page/SessionID.h (modified) (1 diff)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2015-12-16  Alex Christensen  <achristensen@webkit.org>
+
+        Make SessionID use intHash
+        https://bugs.webkit.org/show_bug.cgi?id=152356
+
+        Reviewed by Darin Adler.
+
+        * page/SessionID.h:
+        (WTF::SessionIDHash::hash):
+        (WTF::SessionIDHash::equal):
+        (WTF::HashTraits<WebCore::SessionID>::emptyValue):
+        (WTF::HashTraits<WebCore::SessionID>::constructDeletedValue):
+        (WTF::HashTraits<WebCore::SessionID>::isDeletedValue):
+        Use intHash instead of just casting a uint64_t to an unsigned.
+        This reduces hash collisions in HashTables that are usually quite small so it isn't much of a problem.
+        Also, needsDestruction hasn't been in HashTraits since r156507.
+
 2015-12-16  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebCore/page/SessionID.h

@@ -57 +57 @@
 // The empty value is emptySessionID(), the deleted value is (-1)
 struct SessionIDHash {
-    static unsigned hash(const WebCore::SessionID& p) { return (unsigned)p.sessionID(); }
+    static unsigned hash(const WebCore::SessionID& p) { return intHash(p.sessionID()); }
     static bool equal(const WebCore::SessionID& a, const WebCore::SessionID& b) { return a == b; }
     static const bool safeToCompareToEmptyOrDeleted = true;
 };
 template<> struct HashTraits<WebCore::SessionID> : GenericHashTraits<WebCore::SessionID> {
-    static const uint64_t deletedValueIdentifier = 0xffffffffffffffff;
-    static const bool needsDestruction = false;
+    static const uint64_t deletedValueIdentifier = std::numeric_limits<uint64_t>::max();
     static WebCore::SessionID emptyValue() { return WebCore::SessionID::emptySessionID(); }