Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 330 insertions, 0 deletions

diff --git a/third_party/libwebrtc/api/array_view.h b/third_party/libwebrtc/api/array_view.h
new file mode 100644
index 0000000000..2d68f1650f
--- /dev/null
+++ b/third_party/libwebrtc/api/array_view.h
@@ -0,0 +1,330 @@
+/*
+ *  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 API_ARRAY_VIEW_H_
+#define API_ARRAY_VIEW_H_
+
+#include <algorithm>
+#include <array>
+#include <iterator>
+#include <type_traits>
+
+#include "rtc_base/checks.h"
+#include "rtc_base/type_traits.h"
+
+namespace rtc {
+
+// tl;dr: rtc::ArrayView is the same thing as gsl::span from the Guideline
+//        Support Library.
+//
+// Many functions read from or write to arrays. The obvious way to do this is
+// to use two arguments, a pointer to the first element and an element count:
+//
+//   bool Contains17(const int* arr, size_t size) {
+//     for (size_t i = 0; i < size; ++i) {
+//       if (arr[i] == 17)
+//         return true;
+//     }
+//     return false;
+//   }
+//
+// This is flexible, since it doesn't matter how the array is stored (C array,
+// std::vector, rtc::Buffer, ...), but it's error-prone because the caller has
+// to correctly specify the array length:
+//
+//   Contains17(arr, arraysize(arr));     // C array
+//   Contains17(arr.data(), arr.size());  // std::vector
+//   Contains17(arr, size);               // pointer + size
+//   ...
+//
+// It's also kind of messy to have two separate arguments for what is
+// conceptually a single thing.
+//
+// Enter rtc::ArrayView<T>. It contains a T pointer (to an array it doesn't
+// own) and a count, and supports the basic things you'd expect, such as
+// indexing and iteration. It allows us to write our function like this:
+//
+//   bool Contains17(rtc::ArrayView<const int> arr) {
+//     for (auto e : arr) {
+//       if (e == 17)
+//         return true;
+//     }
+//     return false;
+//   }
+//
+// And even better, because a bunch of things will implicitly convert to
+// ArrayView, we can call it like this:
+//
+//   Contains17(arr);                             // C array
+//   Contains17(arr);                             // std::vector
+//   Contains17(rtc::ArrayView<int>(arr, size));  // pointer + size
+//   Contains17(nullptr);                         // nullptr -> empty ArrayView
+//   ...
+//
+// ArrayView<T> stores both a pointer and a size, but you may also use
+// ArrayView<T, N>, which has a size that's fixed at compile time (which means
+// it only has to store the pointer).
+//
+// One important point is that ArrayView<T> and ArrayView<const T> are
+// different types, which allow and don't allow mutation of the array elements,
+// respectively. The implicit conversions work just like you'd hope, so that
+// e.g. vector<int> will convert to either ArrayView<int> or ArrayView<const
+// int>, but const vector<int> will convert only to ArrayView<const int>.
+// (ArrayView itself can be the source type in such conversions, so
+// ArrayView<int> will convert to ArrayView<const int>.)
+//
+// Note: ArrayView is tiny (just a pointer and a count if variable-sized, just
+// a pointer if fix-sized) and trivially copyable, so it's probably cheaper to
+// pass it by value than by const reference.
+
+namespace array_view_internal {
+
+// Magic constant for indicating that the size of an ArrayView is variable
+// instead of fixed.
+enum : std::ptrdiff_t { kArrayViewVarSize = -4711 };
+
+// Base class for ArrayViews of fixed nonzero size.
+template <typename T, std::ptrdiff_t Size>
+class ArrayViewBase {
+  static_assert(Size > 0, "ArrayView size must be variable or non-negative");
+
+ public:
+  ArrayViewBase(T* data, size_t size) : data_(data) {}
+
+  static constexpr size_t size() { return Size; }
+  static constexpr bool empty() { return false; }
+  T* data() const { return data_; }
+
+ protected:
+  static constexpr bool fixed_size() { return true; }
+
+ private:
+  T* data_;
+};
+
+// Specialized base class for ArrayViews of fixed zero size.
+template <typename T>
+class ArrayViewBase<T, 0> {
+ public:
+  explicit ArrayViewBase(T* data, size_t size) {}
+
+  static constexpr size_t size() { return 0; }
+  static constexpr bool empty() { return true; }
+  T* data() const { return nullptr; }
+
+ protected:
+  static constexpr bool fixed_size() { return true; }
+};
+
+// Specialized base class for ArrayViews of variable size.
+template <typename T>
+class ArrayViewBase<T, array_view_internal::kArrayViewVarSize> {
+ public:
+  ArrayViewBase(T* data, size_t size)
+      : data_(size == 0 ? nullptr : data), size_(size) {}
+
+  size_t size() const { return size_; }
+  bool empty() const { return size_ == 0; }
+  T* data() const { return data_; }
+
+ protected:
+  static constexpr bool fixed_size() { return false; }
+
+ private:
+  T* data_;
+  size_t size_;
+};
+
+}  // namespace array_view_internal
+
+template <typename T,
+          std::ptrdiff_t Size = array_view_internal::kArrayViewVarSize>
+class ArrayView final : public array_view_internal::ArrayViewBase<T, Size> {
+ public:
+  using value_type = T;
+  using const_iterator = const T*;
+
+  // Construct an ArrayView from a pointer and a length.
+  template <typename U>
+  ArrayView(U* data, size_t size)
+      : array_view_internal::ArrayViewBase<T, Size>::ArrayViewBase(data, size) {
+    RTC_DCHECK_EQ(size == 0 ? nullptr : data, this->data());
+    RTC_DCHECK_EQ(size, this->size());
+    RTC_DCHECK_EQ(!this->data(),
+                  this->size() == 0);  // data is null iff size == 0.
+  }
+
+  // Construct an empty ArrayView. Note that fixed-size ArrayViews of size > 0
+  // cannot be empty.
+  ArrayView() : ArrayView(nullptr, 0) {}
+  ArrayView(std::nullptr_t)  // NOLINT
+      : ArrayView() {}
+  ArrayView(std::nullptr_t, size_t size)
+      : ArrayView(static_cast<T*>(nullptr), size) {
+    static_assert(Size == 0 || Size == array_view_internal::kArrayViewVarSize,
+                  "");
+    RTC_DCHECK_EQ(0, size);
+  }
+
+  // Construct an ArrayView from a C-style array.
+  template <typename U, size_t N>
+  ArrayView(U (&array)[N])  // NOLINT
+      : ArrayView(array, N) {
+    static_assert(Size == N || Size == array_view_internal::kArrayViewVarSize,
+                  "Array size must match ArrayView size");
+  }
+
+  // (Only if size is fixed.) Construct a fixed size ArrayView<T, N> from a
+  // non-const std::array instance. For an ArrayView with variable size, the
+  // used ctor is ArrayView(U& u) instead.
+  template <typename U,
+            size_t N,
+            typename std::enable_if<
+                Size == static_cast<std::ptrdiff_t>(N)>::type* = nullptr>
+  ArrayView(std::array<U, N>& u)  // NOLINT
+      : ArrayView(u.data(), u.size()) {}
+
+  // (Only if size is fixed.) Construct a fixed size ArrayView<T, N> where T is
+  // const from a const(expr) std::array instance. For an ArrayView with
+  // variable size, the used ctor is ArrayView(U& u) instead.
+  template <typename U,
+            size_t N,
+            typename std::enable_if<
+                Size == static_cast<std::ptrdiff_t>(N)>::type* = nullptr>
+  ArrayView(const std::array<U, N>& u)  // NOLINT
+      : ArrayView(u.data(), u.size()) {}
+
+  // (Only if size is fixed.) Construct an ArrayView from any type U that has a
+  // static constexpr size() method whose return value is equal to Size, and a
+  // data() method whose return value converts implicitly to T*. In particular,
+  // this means we allow conversion from ArrayView<T, N> to ArrayView<const T,
+  // N>, but not the other way around. We also don't allow conversion from
+  // ArrayView<T> to ArrayView<T, N>, or from ArrayView<T, M> to ArrayView<T,
+  // N> when M != N.
+  template <
+      typename U,
+      typename std::enable_if<Size != array_view_internal::kArrayViewVarSize &&
+                              HasDataAndSize<U, T>::value>::type* = nullptr>
+  ArrayView(U& u)  // NOLINT
+      : ArrayView(u.data(), u.size()) {
+    static_assert(U::size() == Size, "Sizes must match exactly");
+  }
+  template <
+      typename U,
+      typename std::enable_if<Size != array_view_internal::kArrayViewVarSize &&
+                              HasDataAndSize<U, T>::value>::type* = nullptr>
+  ArrayView(const U& u)  // NOLINT(runtime/explicit)
+      : ArrayView(u.data(), u.size()) {
+    static_assert(U::size() == Size, "Sizes must match exactly");
+  }
+
+  // (Only if size is variable.) Construct an ArrayView from 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
+  // ArrayView<T, N> to ArrayView<T> or ArrayView<const T>,
+  // std::vector<T> to ArrayView<T> or ArrayView<const T>,
+  // const std::vector<T> to ArrayView<const T>,
+  // rtc::Buffer to ArrayView<uint8_t> or ArrayView<const uint8_t>, and
+  // const rtc::Buffer to ArrayView<const uint8_t>.
+  template <
+      typename U,
+      typename std::enable_if<Size == array_view_internal::kArrayViewVarSize &&
+                              HasDataAndSize<U, T>::value>::type* = nullptr>
+  ArrayView(U& u)  // NOLINT
+      : ArrayView(u.data(), u.size()) {}
+  template <
+      typename U,
+      typename std::enable_if<Size == array_view_internal::kArrayViewVarSize &&
+                              HasDataAndSize<U, T>::value>::type* = nullptr>
+  ArrayView(const U& u)  // NOLINT(runtime/explicit)
+      : ArrayView(u.data(), u.size()) {}
+
+  // Indexing and iteration. These allow mutation even if the ArrayView is
+  // const, because the ArrayView doesn't own the array. (To prevent mutation,
+  // use a const element type.)
+  T& operator[](size_t idx) const {
+    RTC_DCHECK_LT(idx, this->size());
+    RTC_DCHECK(this->data());
+    return this->data()[idx];
+  }
+  T* begin() const { return this->data(); }
+  T* end() const { return this->data() + this->size(); }
+  const T* cbegin() const { return this->data(); }
+  const T* cend() const { return this->data() + this->size(); }
+  std::reverse_iterator<T*> rbegin() const {
+    return std::make_reverse_iterator(end());
+  }
+  std::reverse_iterator<T*> rend() const {
+    return std::make_reverse_iterator(begin());
+  }
+  std::reverse_iterator<const T*> crbegin() const {
+    return std::make_reverse_iterator(cend());
+  }
+  std::reverse_iterator<const T*> crend() const {
+    return std::make_reverse_iterator(cbegin());
+  }
+
+  ArrayView<T> subview(size_t offset, size_t size) const {
+    return offset < this->size()
+               ? ArrayView<T>(this->data() + offset,
+                              std::min(size, this->size() - offset))
+               : ArrayView<T>();
+  }
+  ArrayView<T> subview(size_t offset) const {
+    return subview(offset, this->size());
+  }
+};
+
+// Comparing two ArrayViews compares their (pointer,size) pairs; it does *not*
+// dereference the pointers.
+template <typename T, std::ptrdiff_t Size1, std::ptrdiff_t Size2>
+bool operator==(const ArrayView<T, Size1>& a, const ArrayView<T, Size2>& b) {
+  return a.data() == b.data() && a.size() == b.size();
+}
+template <typename T, std::ptrdiff_t Size1, std::ptrdiff_t Size2>
+bool operator!=(const ArrayView<T, Size1>& a, const ArrayView<T, Size2>& b) {
+  return !(a == b);
+}
+
+// Variable-size ArrayViews are the size of two pointers; fixed-size ArrayViews
+// are the size of one pointer. (And as a special case, fixed-size ArrayViews
+// of size 0 require no storage.)
+static_assert(sizeof(ArrayView<int>) == 2 * sizeof(int*), "");
+static_assert(sizeof(ArrayView<int, 17>) == sizeof(int*), "");
+static_assert(std::is_empty<ArrayView<int, 0>>::value, "");
+
+template <typename T>
+inline ArrayView<T> MakeArrayView(T* data, size_t size) {
+  return ArrayView<T>(data, size);
+}
+
+// Only for primitive types that have the same size and aligment.
+// Allow reinterpret cast of the array view to another primitive type of the
+// same size.
+// Template arguments order is (U, T, Size) to allow deduction of the template
+// arguments in client calls: reinterpret_array_view<target_type>(array_view).
+template <typename U, typename T, std::ptrdiff_t Size>
+inline ArrayView<U, Size> reinterpret_array_view(ArrayView<T, Size> view) {
+  static_assert(sizeof(U) == sizeof(T) && alignof(U) == alignof(T),
+                "ArrayView reinterpret_cast is only supported for casting "
+                "between views that represent the same chunk of memory.");
+  static_assert(
+      std::is_fundamental<T>::value && std::is_fundamental<U>::value,
+      "ArrayView reinterpret_cast is only supported for casting between "
+      "fundamental types.");
+  return ArrayView<U, Size>(reinterpret_cast<U*>(view.data()), view.size());
+}
+
+}  // namespace rtc
+
+#endif  // API_ARRAY_VIEW_H_