First step towards implementing stack map descriptions for the optimizing compiler.

vm/bitmap.h

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef VM_BITMAP_H_
+#define VM_BITMAP_H_
+
+#include "vm/allocation.h"
+
+namespace dart {
+
+// Forward declarations.
+class RawStackmap;
+class Stackmap;
+
+
+// BitmapBuilder is used to build a bitmap. The implementation is optimized for
+// a dense set of small bit maps without an upper bound (e.g: a pointer map
+// description of a stack).
+class BitmapBuilder : public ZoneAllocated {
+ public:
+  BitmapBuilder() : size_in_bytes_(kInitialSizeInBytes),
+                    bit_list_(bit_list_data_) {
+    memset(bit_list_data_, 0, kInitialSizeInBytes);
+  }
+
+  intptr_t SizeInBits() const { return (size_in_bytes_ * kBitsPerByte); }
+  intptr_t SizeInBytes() const { return size_in_bytes_; }
+
+  // Get/Set individual bits in the bitmap, set expands the underlying bitmap
+  // if needed.
+  bool Get(intptr_t bit_offset) const;
+  void Set(intptr_t bit_offset, bool value);
+
+  // Return the bit offset of the highest bit set.
+  intptr_t Maximum() const;
+
+  // Return the bit offset of the lowest bit set.
+  intptr_t Minimum() const;
+
+  // Sets min..max (inclusive) to value.
+  void SetRange(intptr_t min, intptr_t max, bool value);
+
+  // Replicates the bit map setting of the passed in Stackmap object.
+  void SetBits(const Stackmap& bitmap);
+
+ private:
+  static const intptr_t kInitialSizeInBytes = 16;
+  static const intptr_t kIncrementSizeInBytes = 16;
+
+  bool InRange(intptr_t offset) const {
+    return (offset >= 0) && (offset < SizeInBits());
+  }
+
+  bool GetBit(intptr_t bit_offset) const;
+  void SetBit(intptr_t bit_offset, bool value);
+
+  intptr_t size_in_bytes_;
+  uint8_t bit_list_data_[kInitialSizeInBytes];
+  uint8_t* bit_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(BitmapBuilder);
+};
+
+}  // namespace dart
+
+#endif  // VM_BITMAP_H_