Changeset 194017 in webkit for trunk/Source/JavaScriptCore/parser/SourceProvider.h

Timestamp:

Dec 13, 2015, 12:03:24 PM (10 years ago)

Author:

[email protected]

Message:

CachedScript could have a copy-free path for all-ASCII scripts.
<​https://webkit.org/b/152203>

Source/JavaScriptCore:

Reviewed by Antti Koivisto.

Make SourceProvider vend a StringView instead of a String.
This relaxes the promises that providers have to make about string lifetimes.

This means that on the WebCore side, CachedScript is free to cache a String
internally, while only ever exposing it as a temporary StringView.

A few extra copies (CPU, not memory) are introduced, none of them on hot paths.

• API/JSScriptRef.cpp:
• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::sourceCodeForTools):
(JSC::CodeBlock::dumpSource):

• inspector/ScriptDebugServer.cpp:

(Inspector::ScriptDebugServer::dispatchDidParseSource):
(Inspector::ScriptDebugServer::dispatchFailedToParseSource):

• interpreter/Interpreter.cpp:

(JSC::Interpreter::execute):

• jsc.cpp:

(functionFindTypeForExpression):
(functionHasBasicBlockExecuted):
(functionBasicBlockExecutionCount):

• parser/Lexer.cpp:

(JSC::Lexer<T>::setCode):

• parser/Lexer.h:

(JSC::Lexer<LChar>::setCodeStart):
(JSC::Lexer<UChar>::setCodeStart):

• parser/Parser.h:

(JSC::Parser::getToken):

• parser/SourceCode.cpp:

(JSC::SourceCode::toUTF8):

• parser/SourceCode.h:

(JSC::SourceCode::hash):
(JSC::SourceCode::view):
(JSC::SourceCode::toString): Deleted.

• parser/SourceCodeKey.h:

(JSC::SourceCodeKey::SourceCodeKey):
(JSC::SourceCodeKey::string):

• parser/SourceProvider.h:

(JSC::SourceProvider::getRange):

• runtime/Completion.cpp:

(JSC::loadAndEvaluateModule):
(JSC::loadModule):

• runtime/ErrorInstance.cpp:

(JSC::appendSourceToError):

• runtime/FunctionPrototype.cpp:

(JSC::functionProtoFuncToString):

• tools/FunctionOverrides.cpp:

(JSC::initializeOverrideInfo):
(JSC::FunctionOverrides::initializeOverrideFor):

Source/WebCore:

Reviewed by ANtti Koivisto.

Many (if not most) of script resources on the web contain nothing but ASCII characters.
Such resources, when streamed through a text decoder, will yield the exact same byte
sequence, except in anonymous heap memory instead of delicious file-backed pages.

Care is taken to ensure that the wrapper StringImpl is updated to target newly cached
resource data if an asynchronous caching notification comes in.

• loader/cache/CachedResource.cpp:

(WebCore::CachedResource::tryReplaceEncodedData):

• loader/cache/CachedResource.h:

(WebCore::CachedResource::didReplaceSharedBufferContents):

• loader/cache/CachedScript.cpp:

(WebCore::encodingMayBeAllASCII):
(WebCore::CachedScript::script):
(WebCore::CachedScript::didReplaceSharedBufferContents):

• loader/cache/CachedScript.h:
• platform/SharedBuffer.h:
• platform/cf/SharedBufferCF.cpp:

(WebCore::SharedBuffer::tryReplaceContentsWithPlatformBuffer):

File:

• trunk/Source/JavaScriptCore/parser/SourceProvider.h (modified) (3 diffs)

trunk/Source/JavaScriptCore/parser/SourceProvider.h

@@ -44 +44 @@
         JS_EXPORT_PRIVATE virtual ~SourceProvider();
 
-        virtual const String& source() const = 0;
-        String getRange(int start, int end) const
+        virtual unsigned hash() const = 0;
+        virtual StringView source() const = 0;
+        StringView getRange(int start, int end) const
         {
-            return source().substringSharingImpl(start, end - start);
+            return source().substring(start, end - start);
         }
 
@@ -87 +88 @@
             return adoptRef(*new StringSourceProvider(source, url, startPosition));
         }
+        
+        unsigned hash() const override
+        {
+            return m_source.impl()->hash();
+        }
 
-        virtual const String& source() const override
+        virtual StringView source() const override
         {
             return m_source;
@@ -111 +117 @@
         }
 
-        virtual const String& source() const override
+        unsigned hash() const override
+        {
+            return m_source.impl()->hash();
+        }
+
+        virtual StringView source() const override
         {
             return m_source;