| /* |
| * Copyright 2015 The WebRTC 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 in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #ifndef WEBRTC_BASE_ARRAY_VIEW_H_ |
| #define WEBRTC_BASE_ARRAY_VIEW_H_ |
| |
| #include <vector> |
| |
| #include "webrtc/base/checks.h" |
| |
| namespace rtc { |
| |
| // Keeps track of an array (a pointer and a size) that it doesn't own. |
| // ArrayView objects are immutable except for assignment, and small enough to |
| // be cheaply passed by value. |
| // |
| // Note that ArrayView<T> and ArrayView<const T> are distinct types; this is |
| // how you would represent mutable and unmutable views of an array. |
| template <typename T> |
| class ArrayView final { |
| public: |
| // Construct an empty ArrayView. |
| ArrayView() : ArrayView(static_cast<T*>(nullptr), 0) {} |
| |
| // Construct an ArrayView for a (pointer,size) pair. |
| template <typename U> |
| ArrayView(U* data, size_t size) |
| : data_(size == 0 ? nullptr : data), size_(size) { |
| CheckInvariant(); |
| } |
| |
| // Construct an ArrayView for an array. |
| template <typename U, size_t N> |
| ArrayView(U (&array)[N]) : ArrayView(&array[0], N) {} |
| |
| // Construct an ArrayView for any type U that has a size() method whose |
| // return value converts implicitly to size_t, and a data() method whose |
| // return value converts implicitly to T*. In particular, this means we allow |
| // conversion from ArrayView<T> to ArrayView<const T>, but not the other way |
| // around. Other allowed conversions include std::vector<T> to ArrayView<T> |
| // or ArrayView<const T>, const std::vector<T> to ArrayView<const T>, and |
| // rtc::Buffer to ArrayView<uint8_t> (with the same const behavior as |
| // std::vector). |
| template <typename U> |
| ArrayView(U& u) : ArrayView(u.data(), u.size()) {} |
| // TODO(kwiberg): Remove the special case for std::vector (and the include of |
| // <vector>); it is handled by the general case in C++11, since std::vector |
| // has a data() method there. |
| template <typename U> |
| ArrayView(std::vector<U>& u) |
| : ArrayView(u.empty() ? nullptr : &u[0], u.size()) {} |
| |
| // Indexing, size, and iteration. These allow mutation even if the ArrayView |
| // is const, because the ArrayView doesn't own the array. (To prevent |
| // mutation, use ArrayView<const T>.) |
| size_t size() const { return size_; } |
| T* data() const { return data_; } |
| T& operator[](size_t idx) const { |
| RTC_DCHECK_LT(idx, size_); |
| RTC_DCHECK(data_); // Follows from size_ > idx and the class invariant. |
| return data_[idx]; |
| } |
| T* begin() const { return data_; } |
| T* end() const { return data_ + size_; } |
| const T* cbegin() const { return data_; } |
| const T* cend() const { return data_ + size_; } |
| |
| private: |
| // Invariant: !data_ iff size_ == 0. |
| void CheckInvariant() const { RTC_DCHECK_EQ(!data_, size_ == 0); } |
| T* data_; |
| size_t size_; |
| }; |
| |
| } // namespace rtc |
| |
| #endif // WEBRTC_BASE_ARRAY_VIEW_H_ |