snapshot.h 2.85 KB
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// Copyright 2006-2008 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
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#include "src/isolate.h"
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#include "src/serialize.h"
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#ifndef V8_SNAPSHOT_H_
#define V8_SNAPSHOT_H_

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namespace v8 {
namespace internal {
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class Snapshot : public AllStatic {
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 public:
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  class Metadata {
   public:
    explicit Metadata(uint32_t data = 0) : data_(data) {}
    bool embeds_script() { return EmbedsScriptBits::decode(data_); }
    void set_embeds_script(bool v) {
      data_ = EmbedsScriptBits::update(data_, v);
    }

    uint32_t& RawValue() { return data_; }

   private:
    class EmbedsScriptBits : public BitField<bool, 0, 1> {};
    uint32_t data_;
  };

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  // Initialize the Isolate from the internal snapshot. Returns false if no
  // snapshot could be found.
  static bool Initialize(Isolate* isolate);
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  // Create a new context using the internal partial snapshot.
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  static MaybeHandle<Context> NewContextFromSnapshot(
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      Isolate* isolate, Handle<JSGlobalProxy> global_proxy,
      Handle<FixedArray>* outdated_contexts_out);
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  static bool HaveASnapshotToStartFrom(Isolate* isolate) {
    // Do not use snapshots if the isolate is used to create snapshots.
    return isolate->snapshot_blob() != NULL;
  }
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  static bool EmbedsScript(Isolate* isolate);

  static uint32_t SizeOfFirstPage(Isolate* isolate, AllocationSpace space);
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  // To be implemented by the snapshot source.
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  static const v8::StartupData* DefaultSnapshotBlob();
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  static v8::StartupData CreateSnapshotBlob(
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      const StartupSerializer& startup_ser,
      const PartialSerializer& context_ser, Snapshot::Metadata metadata);
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#ifdef DEBUG
  static bool SnapshotIsValid(v8::StartupData* snapshot_blob);
#endif  // DEBUG
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 private:
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  static Vector<const byte> ExtractStartupData(const v8::StartupData* data);
  static Vector<const byte> ExtractContextData(const v8::StartupData* data);
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  static Metadata ExtractMetadata(const v8::StartupData* data);

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  // Snapshot blob layout:
  // [0] metadata
  // [1 - 6] pre-calculated first page sizes for paged spaces
  // [7] serialized start up data length
  // ... serialized start up data
  // ... serialized context data

  static const int kNumPagedSpaces = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1;

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  static const int kMetadataOffset = 0;
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  static const int kFirstPageSizesOffset = kMetadataOffset + kInt32Size;
  static const int kStartupLengthOffset =
      kFirstPageSizesOffset + kNumPagedSpaces * kInt32Size;
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  static const int kStartupDataOffset = kStartupLengthOffset + kInt32Size;

  static int ContextOffset(int startup_length) {
    return kStartupDataOffset + startup_length;
  }
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  DISALLOW_IMPLICIT_CONSTRUCTORS(Snapshot);
};

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#ifdef V8_USE_EXTERNAL_STARTUP_DATA
void SetSnapshotFromFile(StartupData* snapshot_blob);
#endif

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} }  // namespace v8::internal

#endif  // V8_SNAPSHOT_H_