[snapshot] encode resource before serializing.

src/snapshot/natives.h

 // Copyright 2011 the V8 project 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 V8_SNAPSHOT_NATIVES_H_
 #define V8_SNAPSHOT_NATIVES_H_
 
+#include "include/v8.h"
 #include "src/objects.h"
 #include "src/vector.h"
 
 namespace v8 { class StartupData; }  // Forward declaration.
 
 namespace v8 {
 namespace internal {
 
 enum NativeType {
   CORE,
@@ skipping 21 matching lines @@
   static int GetDebuggerCount();
 
   // These are used to access built-in scripts.  The debugger implementation
   // scripts have an index in the interval [0, GetDebuggerCount()).  The
   // non-debugger scripts have an index in the interval [GetDebuggerCount(),
   // GetNativesCount()).
   static int GetIndex(const char* name);
   static Vector<const char> GetScriptSource(int index);
   static Vector<const char> GetScriptName(int index);
   static Vector<const char> GetScriptsSource();
-
-  // The following methods are implemented in natives-common.cc:
-
-  static FixedArray* GetSourceCache(Heap* heap);
 };
 
 typedef NativesCollection<CORE> Natives;
 typedef NativesCollection<EXTRAS> ExtraNatives;
 typedef NativesCollection<EXPERIMENTAL_EXTRAS> ExperimentalExtraNatives;
 
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
 // Used for reading the natives at runtime. Implementation in natives-empty.cc
 void SetNativesFromFile(StartupData* natives_blob);
 void ReadNatives();
 void DisposeNatives();
 #endif
 
+class NativesExternalStringResource final
+    : public v8::String::ExternalOneByteStringResource {
+ public:
+  NativesExternalStringResource(NativeType type, int index);
+
+  const char* data() const override { return data_; }
+  size_t length() const override { return length_; }
+
+  v8::String::ExternalOneByteStringResource* EncodeForSerialization() const {
+    DCHECK(type_ == CORE || type_ == EXTRAS);
+    intptr_t val = (index_ << 1) | ((type_ == CORE) ? 0 : 1);
+    val = val << kPointerSizeLog2;  // Pointer align.
+    return reinterpret_cast<v8::String::ExternalOneByteStringResource*>(val);
+  }
+
+  // Decode from serialization.
+  static NativesExternalStringResource* DecodeForDeserialization(
+      const v8::String::ExternalOneByteStringResource* encoded) {
+    intptr_t val = reinterpret_cast<intptr_t>(encoded) >> kPointerSizeLog2;
+    NativeType type = (val & 1) ? EXTRAS : CORE;
+    int index = static_cast<int>(val >> 1);
+    return new NativesExternalStringResource(type, index);
+  }
+
+ private:
+  const char* data_;
+  size_t length_;
+  NativeType type_;
+  int index_;
+};
+
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_SNAPSHOT_NATIVES_H_