[ignition] Refactor array iterator to separate out access

src/interpreter/bytecode-array-accessor.h

-// Copyright 2015 the V8 project authors. All rights reserved.
+// Copyright 2016 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_INTERPRETER_BYTECODE_ARRAY_ITERATOR_H_
-#define V8_INTERPRETER_BYTECODE_ARRAY_ITERATOR_H_
+#ifndef V8_INTERPRETER_BYTECODE_ARRAY_ACCESSOR_H_
+#define V8_INTERPRETER_BYTECODE_ARRAY_ACCESSOR_H_
 
 #include "src/globals.h"
 #include "src/handles.h"
 #include "src/interpreter/bytecode-register.h"
 #include "src/interpreter/bytecodes.h"
 #include "src/objects.h"
 #include "src/runtime/runtime.h"
 
 namespace v8 {
 namespace internal {
 namespace interpreter {
 
-class V8_EXPORT_PRIVATE BytecodeArrayIterator {
+class V8_EXPORT_PRIVATE BytecodeArrayAccessor {
  public:
-  explicit BytecodeArrayIterator(Handle<BytecodeArray> bytecode_array);
+  BytecodeArrayAccessor(Handle<BytecodeArray> bytecode_array,
+                        int initial_offset);
 
-  void Advance();
-  bool done() const;
+  void SetOffset(int offset);
+
   Bytecode current_bytecode() const;
   int current_bytecode_size() const;
   int current_offset() const { return bytecode_offset_; }
   OperandScale current_operand_scale() const { return operand_scale_; }
   int current_prefix_offset() const { return prefix_offset_; }
   const Handle<BytecodeArray>& bytecode_array() const {
     return bytecode_array_;
   }
 
   uint32_t GetFlagOperand(int operand_index) const;
   uint32_t GetUnsignedImmediateOperand(int operand_index) const;
   int32_t GetImmediateOperand(int operand_index) const;
   uint32_t GetIndexOperand(int operand_index) const;
   uint32_t GetRegisterCountOperand(int operand_index) const;
   Register GetRegisterOperand(int operand_index) const;
   int GetRegisterOperandRange(int operand_index) const;
   Runtime::FunctionId GetRuntimeIdOperand(int operand_index) const;
   Runtime::FunctionId GetIntrinsicIdOperand(int operand_index) const;
   Handle<Object> GetConstantForIndexOperand(int operand_index) const;
 
   // Returns the absolute offset of the branch target at the current
   // bytecode. It is an error to call this method if the bytecode is
   // not for a jump or conditional jump.
   int GetJumpTargetOffset() const;
 
  private:
+  bool OffsetInBounds() const;
+
   uint32_t GetUnsignedOperand(int operand_index,
                               OperandType operand_type) const;
   int32_t GetSignedOperand(int operand_index, OperandType operand_type) const;
 
   void UpdateOperandScale();
 
   Handle<BytecodeArray> bytecode_array_;
   int bytecode_offset_;
   OperandScale operand_scale_;
   int prefix_offset_;
 
-  DISALLOW_COPY_AND_ASSIGN(BytecodeArrayIterator);
+  DISALLOW_COPY_AND_ASSIGN(BytecodeArrayAccessor);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
-#endif  // V8_INTERPRETER_BYTECODE_GRAPH_ITERATOR_H_
+#endif  // V8_INTERPRETER_BYTECODE_GRAPH_ACCESSOR_H_