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<title>[185486] trunk/Source/JavaScriptCore</title>
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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/185486">185486</a></dd>
<dt>Author</dt> <dd>akling@apple.com</dd>
<dt>Date</dt> <dd>2015-06-11 21:09:11 -0700 (Thu, 11 Jun 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>jsSubstring() should support creating substrings from substrings.
<https://webkit.org/b/145427>
Reviewed by Geoffrey Garen
Tweak jsSubstring() to support base strings that are themselves substrings.
They will now share the same grandparent base. This avoids creating a new StringImpl.
* runtime/JSString.h:
(JSC::jsSubstring): Don't force rope resolution here. Instead do that in finishCreation()
if the base string is a non-substring rope. Note that resolveRope() is the very last thing
called, since it may allocate and the JSRopeString needs to be ready for marking.
(JSC::JSString::isSubstring): Added a helper to find out if a JSString is
a substring. This is just for internal use, so you don't have to cast to
JSRopeString for the real substringness flag.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSStringh">trunk/Source/JavaScriptCore/runtime/JSString.h</a></li>
</ul>
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<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (185485 => 185486)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2015-06-12 02:59:59 UTC (rev 185485)
+++ trunk/Source/JavaScriptCore/ChangeLog 2015-06-12 04:09:11 UTC (rev 185486)
</span><span class="lines">@@ -1,3 +1,22 @@
</span><ins>+2015-06-11 Andreas Kling <akling@apple.com>
+
+ jsSubstring() should support creating substrings from substrings.
+ <https://webkit.org/b/145427>
+
+ Reviewed by Geoffrey Garen
+
+ Tweak jsSubstring() to support base strings that are themselves substrings.
+ They will now share the same grandparent base. This avoids creating a new StringImpl.
+
+ * runtime/JSString.h:
+ (JSC::jsSubstring): Don't force rope resolution here. Instead do that in finishCreation()
+ if the base string is a non-substring rope. Note that resolveRope() is the very last thing
+ called, since it may allocate and the JSRopeString needs to be ready for marking.
+
+ (JSC::JSString::isSubstring): Added a helper to find out if a JSString is
+ a substring. This is just for internal use, so you don't have to cast to
+ JSRopeString for the real substringness flag.
+
</ins><span class="cx"> 2015-06-11 Commit Queue <commit-queue@webkit.org>
</span><span class="cx">
</span><span class="cx"> Unreviewed, rolling out r185465.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSStringh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSString.h (185485 => 185486)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSString.h 2015-06-12 02:59:59 UTC (rev 185485)
+++ trunk/Source/JavaScriptCore/runtime/JSString.h 2015-06-12 04:09:11 UTC (rev 185486)
</span><span class="lines">@@ -186,6 +186,7 @@
</span><span class="cx"> friend class JSValue;
</span><span class="cx">
</span><span class="cx"> bool isRope() const { return m_value.isNull(); }
</span><ins>+ bool isSubstring() const;
</ins><span class="cx"> bool is8Bit() const { return m_flags & Is8Bit; }
</span><span class="cx"> void setIs8Bit(bool flag) const
</span><span class="cx"> {
</span><span class="lines">@@ -291,17 +292,29 @@
</span><span class="cx"> fiber(2).set(vm, this, s3);
</span><span class="cx"> }
</span><span class="cx">
</span><del>- void finishCreation(VM& vm, JSString* base, unsigned offset, unsigned length)
</del><ins>+ void finishCreation(ExecState& exec, JSString& base, unsigned offset, unsigned length)
</ins><span class="cx"> {
</span><ins>+ VM& vm = exec.vm();
</ins><span class="cx"> Base::finishCreation(vm);
</span><del>- ASSERT(!base->isRope());
</del><span class="cx"> ASSERT(!sumOverflows<int32_t>(offset, length));
</span><del>- ASSERT(offset + length <= base->length());
</del><ins>+ ASSERT(offset + length <= base.length());
</ins><span class="cx"> m_length = length;
</span><del>- setIs8Bit(base->is8Bit());
</del><ins>+ setIs8Bit(base.is8Bit());
</ins><span class="cx"> setIsSubstring(true);
</span><del>- substringBase().set(vm, this, base);
- substringOffset() = offset;
</del><ins>+ if (base.isSubstring()) {
+ JSRopeString& baseRope = static_cast<JSRopeString&>(base);
+ substringBase().set(vm, this, baseRope.substringBase().get());
+ substringOffset() = baseRope.substringOffset() + offset;
+ } else {
+ substringBase().set(vm, this, &base);
+ substringOffset() = offset;
+
+ // For now, let's not allow substrings with a rope base.
+ // Resolve non-substring rope bases so we don't have to deal with it.
+ // FIXME: Evaluate if this would be worth adding more branches.
+ if (base.isRope())
+ static_cast<JSRopeString&>(base).resolveRope(&exec);
+ }
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void finishCreation(VM& vm)
</span><span class="lines">@@ -342,10 +355,10 @@
</span><span class="cx"> return newString;
</span><span class="cx"> }
</span><span class="cx">
</span><del>- static JSString* create(VM& vm, JSString* base, unsigned offset, unsigned length)
</del><ins>+ static JSString* create(ExecState& exec, JSString& base, unsigned offset, unsigned length)
</ins><span class="cx"> {
</span><del>- JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(vm.heap)) JSRopeString(vm);
- newString->finishCreation(vm, base, offset, length);
</del><ins>+ JSRopeString* newString = new (NotNull, allocateCell<JSRopeString>(exec.vm().heap)) JSRopeString(exec.vm());
+ newString->finishCreation(exec, base, offset, length);
</ins><span class="cx"> return newString;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="lines">@@ -515,8 +528,7 @@
</span><span class="cx"> VM& vm = exec->vm();
</span><span class="cx"> if (!length)
</span><span class="cx"> return vm.smallStrings.emptyString();
</span><del>- s->value(exec); // For effect. We need to ensure that any string that is used as a substring base is not a rope.
- return JSRopeString::create(vm, s, offset, length);
</del><ins>+ return JSRopeString::create(*exec, *s, offset, length);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> inline JSString* jsSubstring8(VM* vm, const String& s, unsigned offset, unsigned length)
</span><span class="lines">@@ -703,6 +715,11 @@
</span><span class="cx"> return StringView(m_value);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+inline bool JSString::isSubstring() const
+{
+ return isRope() && static_cast<const JSRopeString*>(this)->isSubstring();
+}
+
</ins><span class="cx"> } // namespace JSC
</span><span class="cx">
</span><span class="cx"> #endif // JSString_h
</span></span></pre>
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