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// Copyright 2006-2008 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_SNAPSHOT_H_
#define V8_SNAPSHOT_SNAPSHOT_H_
#include "src/snapshot/partial-serializer.h"
#include "src/snapshot/startup-serializer.h"
#include "src/utils/utils.h"
namespace v8 {
namespace internal {
// Forward declarations.
class Isolate;
class PartialSerializer;
class SnapshotCompression;
class StartupSerializer;
// Wrapper around reservation sizes and the serialization payload.
class V8_EXPORT_PRIVATE SnapshotData : public SerializedData {
public:
// Used when producing.
explicit SnapshotData(const Serializer* serializer);
// Used when consuming.
explicit SnapshotData(const Vector<const byte> snapshot)
: SerializedData(const_cast<byte*>(snapshot.begin()), snapshot.length()) {
}
std::vector<Reservation> Reservations() const;
virtual Vector<const byte> Payload() const;
Vector<const byte> RawData() const {
return Vector<const byte>(data_, size_);
}
protected:
// Empty constructor used by SnapshotCompression so it can manually allocate
// memory.
SnapshotData() : SerializedData() {}
friend class SnapshotCompression;
// Resize used by SnapshotCompression so it can shrink the compressed
// SnapshotData.
void Resize(uint32_t size) { size_ = size; }
// The data header consists of uint32_t-sized entries:
// [0] magic number and (internal) external reference count
// [1] number of reservation size entries
// [2] payload length
// ... reservations
// ... serialized payload
static const uint32_t kNumReservationsOffset =
kMagicNumberOffset + kUInt32Size;
static const uint32_t kPayloadLengthOffset =
kNumReservationsOffset + kUInt32Size;
static const uint32_t kHeaderSize = kPayloadLengthOffset + kUInt32Size;
};
class Snapshot : public AllStatic {
public:
// ---------------- Deserialization ----------------
// Initialize the Isolate from the internal snapshot. Returns false if no
// snapshot could be found.
static bool Initialize(Isolate* isolate);
// Create a new context using the internal partial snapshot.
static MaybeHandle<Context> NewContextFromSnapshot(
Isolate* isolate, Handle<JSGlobalProxy> global_proxy,
size_t context_index,
v8::DeserializeEmbedderFieldsCallback embedder_fields_deserializer);
// ---------------- Helper methods ----------------
static bool HasContextSnapshot(Isolate* isolate, size_t index);
static bool EmbedsScript(Isolate* isolate);
// To be implemented by the snapshot source.
static const v8::StartupData* DefaultSnapshotBlob();
V8_EXPORT_PRIVATE static bool VerifyChecksum(const v8::StartupData* data);
// ---------------- Serialization ----------------
static v8::StartupData CreateSnapshotBlob(
const SnapshotData* startup_snapshot_in,
const SnapshotData* read_only_snapshot_in,
const std::vector<SnapshotData*>& context_snapshots_in,
bool can_be_rehashed);
#ifdef DEBUG
static bool SnapshotIsValid(const v8::StartupData* snapshot_blob);
#endif // DEBUG
static bool ExtractRehashability(const v8::StartupData* data);
private:
static uint32_t ExtractNumContexts(const v8::StartupData* data);
static uint32_t ExtractContextOffset(const v8::StartupData* data,
uint32_t index);
static Vector<const byte> ExtractStartupData(const v8::StartupData* data);
static Vector<const byte> ExtractReadOnlyData(const v8::StartupData* data);
static Vector<const byte> ExtractContextData(const v8::StartupData* data,
uint32_t index);
static uint32_t GetHeaderValue(const v8::StartupData* data, uint32_t offset) {
return base::ReadLittleEndianValue<uint32_t>(
reinterpret_cast<Address>(data->data) + offset);
}
static void SetHeaderValue(char* data, uint32_t offset, uint32_t value) {
base::WriteLittleEndianValue(reinterpret_cast<Address>(data) + offset,
value);
}
static void CheckVersion(const v8::StartupData* data);
// Snapshot blob layout:
// [0] number of contexts N
// [1] rehashability
// [2] checksum
// [3] (128 bytes) version string
// [4] offset to readonly
// [5] offset to context 0
// [6] offset to context 1
// ...
// ... offset to context N - 1
// ... startup snapshot data
// ... read-only snapshot data
// ... context 0 snapshot data
// ... context 1 snapshot data
static const uint32_t kNumberOfContextsOffset = 0;
// TODO(yangguo): generalize rehashing, and remove this flag.
static const uint32_t kRehashabilityOffset =
kNumberOfContextsOffset + kUInt32Size;
static const uint32_t kChecksumOffset = kRehashabilityOffset + kUInt32Size;
static const uint32_t kVersionStringOffset = kChecksumOffset + kUInt32Size;
static const uint32_t kVersionStringLength = 64;
static const uint32_t kReadOnlyOffsetOffset =
kVersionStringOffset + kVersionStringLength;
static const uint32_t kFirstContextOffsetOffset =
kReadOnlyOffsetOffset + kUInt32Size;
static Vector<const byte> ChecksummedContent(const v8::StartupData* data) {
STATIC_ASSERT(kVersionStringOffset == kChecksumOffset + kUInt32Size);
const uint32_t kChecksumStart = kVersionStringOffset;
return Vector<const byte>(
reinterpret_cast<const byte*>(data->data + kChecksumStart),
data->raw_size - kChecksumStart);
}
static uint32_t StartupSnapshotOffset(int num_contexts) {
return POINTER_SIZE_ALIGN(kFirstContextOffsetOffset +
num_contexts * kInt32Size);
}
static uint32_t ContextSnapshotOffsetOffset(int index) {
return kFirstContextOffsetOffset + index * kInt32Size;
}
DISALLOW_IMPLICIT_CONSTRUCTORS(Snapshot);
};
// Convenience wrapper around snapshot data blob creation used e.g. by tests and
// mksnapshot.
V8_EXPORT_PRIVATE v8::StartupData CreateSnapshotDataBlobInternal(
v8::SnapshotCreator::FunctionCodeHandling function_code_handling,
const char* embedded_source, v8::Isolate* isolate = nullptr);
// Convenience wrapper around snapshot data blob warmup used e.g. by tests and
// mksnapshot.
V8_EXPORT_PRIVATE v8::StartupData WarmUpSnapshotDataBlobInternal(
v8::StartupData cold_snapshot_blob, const char* warmup_source);
#ifdef V8_USE_EXTERNAL_STARTUP_DATA
void SetSnapshotFromFile(StartupData* snapshot_blob);
#endif
} // namespace internal
} // namespace v8
#endif // V8_SNAPSHOT_SNAPSHOT_H_
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