Changeset 43339 in webkit for trunk/JavaScriptCore/runtime/UString.h

Timestamp:

May 7, 2009, 1:27:58 AM (16 years ago)

Author:

[email protected]

Message:

2009-05-07 Gavin Barraclough <​[email protected]>

Reviewed by NOBODY (OOPS!).

Enable op_strcat across += assignments. This patch allows the lhs of a read/modify node
to be included within the concatenation operation, and also modifies the implementation
of the concatenation to attempt to reuse and cat onto the leftmost string, rather than
always allocating a new empty output string to copy into (as was previously the behaviour).

~0.5% progression, due to a 3%-3.5% progression on the string tests (particularly validate).

• parser/Nodes.cpp: (JSC::BinaryOpNode::emitStrcat): (JSC::emitReadModifyAssignment): (JSC::ReadModifyResolveNode::emitBytecode): (JSC::ReadModifyDotNode::emitBytecode): (JSC::ReadModifyBracketNode::emitBytecode):
• parser/Nodes.h:
• runtime/Operations.h: (JSC::concatenateStrings):
• runtime/UString.cpp: (JSC::UString::reserveCapacity):
• runtime/UString.h:

File:

• trunk/JavaScriptCore/runtime/UString.h (modified) (2 diffs)

trunk/JavaScriptCore/runtime/UString.h

@@ -143 +143 @@
             static BaseString& empty() { return *emptyBaseString; }
 
+            bool reserveCapacity(int capacity);
+
         protected:
             // constructor for use by BaseString subclass; they are their own bases
@@ -327 +329 @@
         size_t cost() const;
 
+        // Attempt to grow this string such that it can grow to a total length of 'capacity'
+        // without reallocation.  This may fail a number of reasons - if the BasicString is
+        // shared and another string is using part of the capacity beyond our end point, if
+        // the realloc fails, or if this string is empty and has no storage.
+        //
+        // This method returns a boolean indicating success.
+        bool reserveCapacity(int capacity)
+        {
+            return m_rep->reserveCapacity(capacity);
+        }
+
     private:
         void expandCapacity(int requiredLength);