Changeset 44145 in webkit for trunk/JavaScriptCore/runtime/UString.h

Timestamp:

May 25, 2009, 9:21:32 PM (16 years ago)

Author:

[email protected]

Message:

JavaScriptCore:

2009-05-25 David Levin <​[email protected]>

Reviewed by Maciej Stachowiak and Oliver Hunt.

​https://bugs.webkit.org/show_bug.cgi?id=25126
Allow the buffer underlying UString to be shared.

In order to not grow the underlying size of any structure,
there is a union in the Rep string which holds

+ m_sharedBuffer -- a pointer to the shared ref counted buffer

if the class is BaseString and the buffer is being shared OR

+ m_baseString -- the BaseString if the class is only UString::Rep

but not a UString::BaseString

Ideally, m_sharedBuffer would be a RefPtr, but it cannot be because
it is in a union.

No change in sunspider perf.

• JavaScriptCore.vcproj/WTF/WTF.vcproj:
• JavaScriptCore.xcodeproj/project.pbxproj:
• runtime/UString.cpp: (JSC::UString::Rep::share): (JSC::UString::Rep::destroy): (JSC::UString::BaseString::sharedBuffer): (JSC::UString::BaseString::setSharedBuffer): (JSC::UString::BaseString::slowIsBufferReadOnly): (JSC::expandCapacity): (JSC::UString::Rep::reserveCapacity): (JSC::UString::expandPreCapacity): (JSC::concatenate): (JSC::UString::append):
• runtime/UString.h: (JSC::UString::Rep::Rep): (JSC::UString::Rep::): (JSC::UString::BaseString::isShared): (JSC::UString::BaseString::isBufferReadOnly): (JSC::UString::Rep::baseString):
• wtf/CrossThreadRefCounted.h: (WTF::CrossThreadRefCounted::isShared):
• wtf/OwnFastMallocPtr.h: Added. (WTF::OwnFastMallocPtr::OwnFastMallocPtr): (WTF::OwnFastMallocPtr::~OwnFastMallocPtr): (WTF::OwnFastMallocPtr::get): (WTF::OwnFastMallocPtr::release):

JavaScriptGlue:

2009-05-25 David Levin <​[email protected]>

Reviewed by Maciej Stachowiak and Oliver Hunt.

​https://bugs.webkit.org/show_bug.cgi?id=25126

Added forwarding headers.

• ForwardingHeaders/wtf/CrossThreadRefCounted.h: Added.
• ForwardingHeaders/wtf/OwnFastMallocPtr.h: Added.

WebCore:

2009-05-25 David Levin <​[email protected]>

Reviewed by Maciej Stachowiak and Oliver Hunt.

Added forwarding headers.

• ForwardingHeaders/wtf/CrossThreadRefCounted.h: Added.
• ForwardingHeaders/wtf/OwnFastMallocPtr.h: Added.

File:

• trunk/JavaScriptCore/runtime/UString.h (modified) (10 diffs)

trunk/JavaScriptCore/runtime/UString.h

@@ -2 +2 @@
  *  Copyright (C) 1999-2000 Harri Porten ([email protected])
  *  Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
- *  Copyright (c) 2009, Google Inc. All rights reserved.
+ *  Copyright (C) 2009 Google Inc. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
@@ -28 +28 @@
 #include <string.h>
 #include <wtf/Assertions.h>
+#include <wtf/CrossThreadRefCounted.h>
+#include <wtf/OwnFastMallocPtr.h>
 #include <wtf/PassRefPtr.h>
 #include <wtf/PtrAndFlags.h>
@@ -76 +78 @@
 
     public:
+        typedef CrossThreadRefCounted<OwnFastMallocPtr<UChar> > SharedUChar;
         struct BaseString;
         struct Rep : Noncopyable {
@@ -102 +105 @@
             static PassRefPtr<Rep> createFromUTF8(const char*);
 
+            // Uses SharedUChar to have joint ownership over the UChar*.
+            static PassRefPtr<Rep> share(UChar*, int, PassRefPtr<SharedUChar>);
+
             void destroy();
 
@@ -146 +152 @@
 
         protected:
-            // constructor for use by BaseString subclass; they are their own bases
+            // Constructor for use by BaseString subclass; they use the union with m_baseString for another purpose.
             Rep(int length)
                 : offset(0)
@@ -152 +158 @@
                 , rc(1)
                 , _hash(0)
-                , m_baseString(static_cast<BaseString*>(this))
+                , m_baseString(0)
             {
             }
@@ -166 +172 @@
             }
 
-
-            BaseString* m_baseString;
+            union {
+                // If !baseIsSelf()
+                BaseString* m_baseString;
+                // If baseIsSelf()
+                SharedUChar* m_sharedBuffer;
+            };
 
         private:
@@ -181 +191 @@
 
         struct BaseString : public Rep {
-            bool isShared() { return rc != 1; }
+            bool isShared() { return rc != 1 || isBufferReadOnly(); }
+            void setSharedBuffer(PassRefPtr<SharedUChar>);
+            SharedUChar* sharedBuffer();
+
+            bool isBufferReadOnly()
+            {
+                if (!m_sharedBuffer)
+                    return false;
+                return slowIsBufferReadOnly();
+            }
 
             // potentially shared data.
@@ -205 +224 @@
                 checkConsistency();
             }
+
+            bool slowIsBufferReadOnly();
 
             friend struct Rep;
@@ -454 +475 @@
     inline UString::BaseString* UString::Rep::baseString()
     {
-        return m_baseString;
+        return !baseIsSelf() ? m_baseString : reinterpret_cast<BaseString*>(this) ;
     }
 
     inline const UString::BaseString* UString::Rep::baseString() const
     {
-        return m_baseString;
+        return const_cast<Rep*>(this)->baseString();
     }