1/*
2 * Copyright 2018 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkSpan_DEFINED
9#define SkSpan_DEFINED
10
11#include <cstddef>
12#include "include/private/SkTo.h"
13
14template <typename T>
15class SkSpan {
16public:
17 constexpr SkSpan() : fPtr{nullptr}, fSize{0} {}
18 constexpr SkSpan(T* ptr, size_t size) : fPtr{ptr}, fSize{size} {}
19 template <typename U, typename = typename std::enable_if<std::is_same<const U, T>::value>::type>
20 constexpr SkSpan(const SkSpan<U>& that) : fPtr(that.data()), fSize{that.size()} {}
21 constexpr SkSpan(const SkSpan& o) = default;
22 constexpr SkSpan& operator=(const SkSpan& that) {
23 fPtr = that.fPtr;
24 fSize = that.fSize;
25 return *this;
26 }
27 constexpr T& operator [] (size_t i) const { return fPtr[i]; }
28 constexpr T& front() const { return fPtr[0]; }
29 constexpr T& back() const { return fPtr[fSize - 1]; }
30 constexpr T* begin() const { return fPtr; }
31 constexpr T* end() const { return fPtr + fSize; }
32 constexpr const T* cbegin() const { return fPtr; }
33 constexpr const T* cend() const { return fPtr + fSize; }
34 constexpr auto rbegin() const { return std::make_reverse_iterator(this->end()); }
35 constexpr auto rend() const { return std::make_reverse_iterator(this->begin()); }
36 constexpr auto crbegin() const { return std::make_reverse_iterator(this->cend()); }
37 constexpr auto crend() const { return std::make_reverse_iterator(this->cbegin()); }
38 constexpr T* data() const { return fPtr; }
39 constexpr int count() const { return SkTo<int>(fSize); }
40 constexpr size_t size() const { return fSize; }
41 constexpr bool empty() const { return fSize == 0; }
42 constexpr size_t size_bytes() const { return fSize * sizeof(T); }
43 constexpr SkSpan<T> first(size_t prefixLen) const {
44 SkASSERT(prefixLen <= this->size());
45 if (prefixLen == 0) { return SkSpan{}; }
46 return SkSpan{fPtr, prefixLen};
47 }
48 constexpr SkSpan<T> last(size_t postfixLen) const {
49 SkASSERT(postfixLen <= this->size());
50 if (postfixLen == 0) { return SkSpan{}; }
51 return SkSpan{fPtr + (this->size() - postfixLen), postfixLen};
52 }
53
54private:
55 T* fPtr;
56 size_t fSize;
57};
58
59template <typename T, typename S>
60inline constexpr SkSpan<T> SkMakeSpan(T* p, S s) { return SkSpan<T>{p, SkTo<size_t>(s)}; }
61
62template <size_t N, typename T>
63inline constexpr SkSpan<T> SkMakeSpan(T(&a)[N]) { return SkSpan<T>{a, N}; }
64
65template <typename Container>
66inline auto SkMakeSpan(Container& c)
67 -> SkSpan<typename std::remove_reference<decltype(*(c.data()))>::type> {
68 return {c.data(), c.size()};
69}
70#endif // SkSpan_DEFINED
71