Support external startup data in V8.

src/snapshot-source-sink.h

+// Copyright 2012 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_SOURCE_SINK_H_
+#define V8_SNAPSHOT_SOURCE_SINK_H_
+
+#include "src/checks.h"
+#include "src/utils.h"
+
+namespace v8 {
+namespace internal {
+
+
+/**
+ * Source to read snapshot and builtins files from.
+ *
+ * Note: Memory ownership remains with callee.
+ */
+class SnapshotByteSource V8_FINAL {
+ public:
+  SnapshotByteSource(const byte* array, int length);
+  ~SnapshotByteSource();
+
+  bool HasMore() { return position_ < length_; }
+
+  int Get() {
+    ASSERT(position_ < length_);
+    return data_[position_++];
+  }
+
+  int32_t GetUnalignedInt();
+
+  void Advance(int by) { position_ += by; }
+
+  void CopyRaw(byte* to, int number_of_bytes);
+
+  inline int GetInt() {
+    // This way of variable-length encoding integers does not suffer from branch
+    // mispredictions.
+    uint32_t answer = GetUnalignedInt();
+    int bytes = answer & 3;
+    Advance(bytes);
+    uint32_t mask = 0xffffffffu;
+    mask >>= 32 - (bytes << 3);
+    answer &= mask;
+    answer >>= 2;
+    return answer;
+  }
+
+  bool GetBlob(const byte** data, int* number_of_bytes);
+
+  bool AtEOF();
+
+  int position() { return position_; }
+
+ private:
+  const byte* data_;
+  int length_;
+  int position_;
+
+  DISALLOW_COPY_AND_ASSIGN(SnapshotByteSource);
+};
+
+
+/**
+ * Sink to write snapshot files to.
+ *
+ * Subclasses must implement actual storage or i/o.
+ */
+class SnapshotByteSink {
+ public:
+  virtual ~SnapshotByteSink() { }
+  virtual void Put(int byte, const char* description) = 0;
+  virtual void PutSection(int byte, const char* description) {
+    Put(byte, description);
+  }
+  void PutInt(uintptr_t integer, const char* description);
+  void PutRaw(byte* data, int number_of_bytes, const char* description);
+  void PutBlob(byte* data, int number_of_bytes, const char* description);
+  virtual int Position() = 0;
+};
+
+
+}  // namespace v8::internal
+}  // namespace v8
+
+#endif  // V8_SNAPSHOT_SOURCE_SINK_H_