Extract WebCoreStringResouce out of V8StringResource

third_party/WebKit/Source/bindings/core/v8/StringResource.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef StringResource_h
+#define StringResource_h
+
+#include "core/CoreExport.h"
+#include "platform/wtf/Allocator.h"
+#include "platform/wtf/Threading.h"
+#include "platform/wtf/text/AtomicString.h"
+#include "v8/include/v8.h"
+
+namespace blink {
+
+// StringResource is a helper class for v8ExternalString. It is used

[jbroman, 2017/04/18 15:37:44]

nit: V8ExternalString (post rename)

[adithyas, 2017/04/18 15:52:23]

Fixed.

+// to manage the life-cycle of the underlying buffer of the external string.
+class StringResourceBase {
+  USING_FAST_MALLOC(StringResourceBase);
+  WTF_MAKE_NONCOPYABLE(StringResourceBase);
+
+ public:
+  explicit StringResourceBase(const String& string) : plain_string_(string) {
+#if DCHECK_IS_ON()
+    thread_id_ = WTF::CurrentThread();
+#endif
+    DCHECK(!string.IsNull());
+    v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(
+        string.CharactersSizeInBytes());
+  }
+
+  explicit StringResourceBase(const AtomicString& string)
+      : plain_string_(string.GetString()), atomic_string_(string) {
+#if DCHECK_IS_ON()
+    thread_id_ = WTF::CurrentThread();
+#endif
+    DCHECK(!string.IsNull());
+    v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(
+        string.CharactersSizeInBytes());
+  }
+
+  virtual ~StringResourceBase() {
+#if DCHECK_IS_ON()
+    DCHECK(thread_id_ == WTF::CurrentThread());
+#endif
+    int64_t reduced_external_memory = plain_string_.CharactersSizeInBytes();
+    if (plain_string_.Impl() != atomic_string_.Impl() &&
+        !atomic_string_.IsNull())
+      reduced_external_memory += atomic_string_.CharactersSizeInBytes();
+    v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(
+        -reduced_external_memory);
+  }
+
+  const String& WebcoreString() { return plain_string_; }
+
+  const AtomicString& GetAtomicString() {
+#if DCHECK_IS_ON()
+    DCHECK(thread_id_ == WTF::CurrentThread());
+#endif
+    if (atomic_string_.IsNull()) {
+      atomic_string_ = AtomicString(plain_string_);
+      DCHECK(!atomic_string_.IsNull());
+      if (plain_string_.Impl() != atomic_string_.Impl()) {
+        v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(
+            atomic_string_.CharactersSizeInBytes());
+      }
+    }
+    return atomic_string_;
+  }
+
+ protected:
+  // A shallow copy of the string. Keeps the string buffer alive until the V8
+  // engine garbage collects it.
+  String plain_string_;
+  // If this string is atomic or has been made atomic earlier the
+  // atomic string is held here. In the case where the string starts
+  // off non-atomic and becomes atomic later it is necessary to keep
+  // the original string alive because v8 may keep derived pointers
+  // into that string.
+  AtomicString atomic_string_;
+
+ private:
+#if DCHECK_IS_ON()
+  WTF::ThreadIdentifier thread_id_;
+#endif
+};
+
+class StringResource16 final : public StringResourceBase,
+                               public v8::String::ExternalStringResource {
+  WTF_MAKE_NONCOPYABLE(StringResource16);
+
+ public:
+  explicit StringResource16(const String& string) : StringResourceBase(string) {
+    DCHECK(!string.Is8Bit());
+  }
+
+  explicit StringResource16(const AtomicString& string)
+      : StringResourceBase(string) {
+    DCHECK(!string.Is8Bit());
+  }
+
+  size_t length() const override { return plain_string_.Impl()->length(); }
+  const uint16_t* data() const override {
+    return reinterpret_cast<const uint16_t*>(
+        plain_string_.Impl()->Characters16());
+  }
+};
+
+class StringResource8 final : public StringResourceBase,
+                              public v8::String::ExternalOneByteStringResource {
+  WTF_MAKE_NONCOPYABLE(StringResource8);
+
+ public:
+  explicit StringResource8(const String& string) : StringResourceBase(string) {
+    DCHECK(string.Is8Bit());
+  }
+
+  explicit StringResource8(const AtomicString& string)
+      : StringResourceBase(string) {
+    DCHECK(string.Is8Bit());
+  }
+
+  size_t length() const override { return plain_string_.Impl()->length(); }
+  const char* data() const override {
+    return reinterpret_cast<const char*>(plain_string_.Impl()->Characters8());
+  }
+};
+
+enum ExternalMode { kExternalize, kDoNotExternalize };
+
+template <typename StringType>
+CORE_EXPORT StringType V8StringToWebCoreString(v8::Local<v8::String>,

[jbroman, 2017/04/18 15:37:44]

Since you renamed the other references to WebCore (wow, that name takes me
back...), maybe these should be renamed to *ToWTFString or something like that?
This might be a reasonable thing to file as a bug and mark GoodFirstBug.

[adithyas, 2017/04/18 15:52:23]

Ok, I'll file a bug.

+                                               ExternalMode);
+CORE_EXPORT String Int32ToWebCoreString(int value);
+
+}  // namespace blink
+
+#endif  // StringResource_h