288886b2ec
Instead of in separate pointer and size arguments. Review URL: https://codereview.webrtc.org/1418423010 Cr-Commit-Position: refs/heads/master@{#10535}
95 lines
3.4 KiB
C++
95 lines
3.4 KiB
C++
/*
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* Copyright 2015 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef WEBRTC_BASE_ARRAY_VIEW_H_
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#define WEBRTC_BASE_ARRAY_VIEW_H_
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#include <vector>
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#include "webrtc/base/checks.h"
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namespace rtc {
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// Keeps track of an array (a pointer and a size) that it doesn't own.
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// ArrayView objects are immutable except for assignment, and small enough to
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// be cheaply passed by value.
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//
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// Note that ArrayView<T> and ArrayView<const T> are distinct types; this is
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// how you would represent mutable and unmutable views of an array.
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template <typename T>
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class ArrayView final {
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public:
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// Construct an empty ArrayView.
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ArrayView() : ArrayView(static_cast<T*>(nullptr), 0) {}
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// Construct an ArrayView for a (pointer,size) pair.
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template <typename U>
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ArrayView(U* data, size_t size)
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: data_(size == 0 ? nullptr : data), size_(size) {
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CheckInvariant();
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}
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// Construct an ArrayView for an array.
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template <typename U, size_t N>
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ArrayView(U (&array)[N]) : ArrayView(&array[0], N) {}
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// Construct an ArrayView for any type U that has a size() method whose
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// return value converts implicitly to size_t, and a data() method whose
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// return value converts implicitly to T*. In particular, this means we allow
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// conversion from ArrayView<T> to ArrayView<const T>, but not the other way
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// around. Other allowed conversions include std::vector<T> to ArrayView<T>
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// or ArrayView<const T>, const std::vector<T> to ArrayView<const T>, and
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// rtc::Buffer to ArrayView<uint8_t> (with the same const behavior as
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// std::vector).
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template <typename U>
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ArrayView(U& u) : ArrayView(u.data(), u.size()) {}
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// TODO(kwiberg): Remove the special case for std::vector (and the include of
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// <vector>); it is handled by the general case in C++11, since std::vector
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// has a data() method there.
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template <typename U>
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ArrayView(std::vector<U>& u)
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: ArrayView(u.empty() ? nullptr : &u[0], u.size()) {}
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// Indexing, size, and iteration. These allow mutation even if the ArrayView
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// is const, because the ArrayView doesn't own the array. (To prevent
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// mutation, use ArrayView<const T>.)
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size_t size() const { return size_; }
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bool empty() const { return size_ == 0; }
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T* data() const { return data_; }
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T& operator[](size_t idx) const {
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RTC_DCHECK_LT(idx, size_);
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RTC_DCHECK(data_); // Follows from size_ > idx and the class invariant.
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return data_[idx];
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}
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T* begin() const { return data_; }
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T* end() const { return data_ + size_; }
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const T* cbegin() const { return data_; }
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const T* cend() const { return data_ + size_; }
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// Comparing two ArrayViews compares their (pointer,size) pairs; it does
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// *not* dereference the pointers.
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friend bool operator==(const ArrayView& a, const ArrayView& b) {
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return a.data_ == b.data_ && a.size_ == b.size_;
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}
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friend bool operator!=(const ArrayView& a, const ArrayView& b) {
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return !(a == b);
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}
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private:
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// Invariant: !data_ iff size_ == 0.
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void CheckInvariant() const { RTC_DCHECK_EQ(!data_, size_ == 0); }
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T* data_;
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size_t size_;
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};
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} // namespace rtc
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#endif // WEBRTC_BASE_ARRAY_VIEW_H_
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