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[gecko.git] / mfbt / Range.h
blob35cd4a0e07495b5795464a9838ec2717af36a85c
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
7 #ifndef mozilla_Range_h
8 #define mozilla_Range_h
10 #include "mozilla/RangedPtr.h"
11 #include "mozilla/Span.h"
13 #include <stddef.h>
14 #include <type_traits>
16 namespace mozilla {
18 // Range<T> is a tuple containing a pointer and a length.
19 template <typename T>
20 class Range {
21 template <typename U>
22 friend class Range;
24 // Reassignment of RangedPtrs is so (subtly) restrictive that we just make
25 // Range immutable.
26 const RangedPtr<T> mStart;
27 const RangedPtr<T> mEnd;
29 public:
30 Range() : mStart(nullptr, 0), mEnd(nullptr, 0) {}
31 Range(T* aPtr, size_t aLength)
32 : mStart(aPtr, aPtr, aPtr + aLength),
33 mEnd(aPtr + aLength, aPtr, aPtr + aLength) {
34 if (!aPtr) {
35 MOZ_ASSERT_DEBUG_OR_FUZZING(
36 !aLength, "Range does not support nullptr with non-zero length.");
37 // ...because merely having a pointer to `nullptr + 1` is undefined
38 // behavior. UBSAN catches this as of clang-10.
41 Range(const RangedPtr<T>& aStart, const RangedPtr<T>& aEnd)
42 : mStart(aStart.get(), aStart.get(), aEnd.get()),
43 mEnd(aEnd.get(), aStart.get(), aEnd.get()) {
44 // Only accept two RangedPtrs within the same range.
45 aStart.checkIdenticalRange(aEnd);
46 MOZ_ASSERT_DEBUG_OR_FUZZING(aStart <= aEnd);
49 template <typename U, class = std::enable_if_t<
50 std::is_convertible_v<U (*)[], T (*)[]>, int>>
51 MOZ_IMPLICIT Range(const Range<U>& aOther)
52 : mStart(aOther.mStart), mEnd(aOther.mEnd) {}
54 MOZ_IMPLICIT Range(Span<T> aSpan) : Range(aSpan.Elements(), aSpan.Length()) {}
56 template <typename U, class = std::enable_if_t<
57 std::is_convertible_v<U (*)[], T (*)[]>, int>>
58 MOZ_IMPLICIT Range(const Span<U>& aSpan)
59 : Range(aSpan.Elements(), aSpan.Length()) {}
61 RangedPtr<T> begin() const { return mStart; }
62 RangedPtr<T> end() const { return mEnd; }
63 size_t length() const { return mEnd - mStart; }
65 T& operator[](size_t aOffset) const { return mStart[aOffset]; }
67 explicit operator bool() const { return mStart != nullptr; }
69 operator Span<T>() { return Span<T>(mStart.get(), length()); }
71 operator Span<const T>() const { return Span<T>(mStart.get(), length()); }
74 template <typename T>
75 Span(Range<T>&) -> Span<T>;
77 template <typename T>
78 Span(const Range<T>&) -> Span<const T>;
80 } // namespace mozilla
82 #endif /* mozilla_Range_h */