[ignition] Refactor array iterator to separate out access

src/interpreter/bytecode-array-accessor.h

Index: src/interpreter/bytecode-array-accessor.h
diff --git a/src/interpreter/bytecode-array-iterator.h b/src/interpreter/bytecode-array-accessor.h
similarity index 80%
copy from src/interpreter/bytecode-array-iterator.h
copy to src/interpreter/bytecode-array-accessor.h
index 03279cbd431dcad7ed403d8193472204fc9150f5..3ac3ee3b45d8c6eb43ebd6fe95c658e48c80e0f1 100644
--- a/src/interpreter/bytecode-array-iterator.h
+++ b/src/interpreter/bytecode-array-accessor.h
@@ -1,9 +1,9 @@
-// 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"
@@ -16,12 +16,14 @@ 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 SetOffset(int offset);
+  bool OffsetInBounds() const;

[rmcilroy, 2016/11/21 14:14:26]

nit - make this private, and just OffsetIsValid() ? 

Maybe just DCHECK this on SetOffset and have the rest of the code assume it is
valid (no ifs) ?

[Leszek Swirski, 2016/11/21 16:49:03]

yes to private, I want to keep OffsetInBounds though because we're not doing
other validity checks (e.g. is a valid bytecode)

We can't do a DCHECK, because this would break the functionality of
BytecodeArrayIterator.Advance, which can advance the offset past the end of the
array, and relies on this to determine if it's done.

 
-  void Advance();
-  bool done() const;
   Bytecode current_bytecode() const;
   int current_bytecode_size() const;
   int current_offset() const { return bytecode_offset_; }
@@ -59,11 +61,11 @@ class V8_EXPORT_PRIVATE BytecodeArrayIterator {
   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_