TerminatedArrayBuilder.h

// Copyright 2014 The Chromium 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 TerminatedArrayBuilder_h
#define TerminatedArrayBuilder_h

#include "wtf/Allocator.h"

namespace WTF {

template <typename T, template <typename> class ArrayType = TerminatedArray>
class TerminatedArrayBuilder {
  STACK_ALLOCATED();
  WTF_MAKE_NONCOPYABLE(TerminatedArrayBuilder);

 public:
  explicit TerminatedArrayBuilder(
      typename ArrayType<T>::Allocator::PassPtr array)
      : m_array(array), m_count(0), m_capacity(0) {
    if (!m_array)
      return;
    m_capacity = m_count = m_array->size();
    DCHECK(m_array->at(m_count - 1).isLastInArray());
  }

  void grow(size_t count) {
    DCHECK(count);
    if (!m_array) {
      DCHECK(!m_count);
      DCHECK(!m_capacity);
      m_capacity = count;
      m_array = ArrayType<T>::Allocator::create(m_capacity);
    } else {
      DCHECK(m_array->at(m_count - 1).isLastInArray());
      m_capacity += count;
      m_array = ArrayType<T>::Allocator::resize(
          ArrayType<T>::Allocator::release(m_array), m_capacity);
      m_array->at(m_count - 1).setLastInArray(false);
    }
    m_array->at(m_capacity - 1).setLastInArray(true);
  }

  void append(const T& item) {
    RELEASE_ASSERT(m_count < m_capacity);
    DCHECK(!item.isLastInArray());
    m_array->at(m_count++) = item;
    if (m_count == m_capacity)
      m_array->at(m_capacity - 1).setLastInArray(true);
  }

  typename ArrayType<T>::Allocator::PassPtr release() {
    RELEASE_ASSERT(m_count == m_capacity);
    assertValid();
    return ArrayType<T>::Allocator::release(m_array);
  }

 private:
#if DCHECK_IS_ON()
  void assertValid() {
    for (size_t i = 0; i < m_count; ++i) {
      bool isLastInArray = (i + 1 == m_count);
      DCHECK_EQ(m_array->at(i).isLastInArray(), isLastInArray);
    }
  }
#else
  void assertValid() {}
#endif

  typename ArrayType<T>::Allocator::Ptr m_array;
  size_t m_count;
  size_t m_capacity;
};

}  // namespace WTF

using WTF::TerminatedArrayBuilder;

#endif  // TerminatedArrayBuilder_h