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83 lines
2.6 KiB
C++
83 lines
2.6 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_Range_h
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#define mozilla_Range_h
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#include "mozilla/RangedPtr.h"
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#include "mozilla/Span.h"
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#include <stddef.h>
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#include <type_traits>
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namespace mozilla {
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// Range<T> is a tuple containing a pointer and a length.
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template <typename T>
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class Range {
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template <typename U>
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friend class Range;
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// Reassignment of RangedPtrs is so (subtly) restrictive that we just make
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// Range immutable.
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const RangedPtr<T> mStart;
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const RangedPtr<T> mEnd;
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public:
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Range() : mStart(nullptr, 0), mEnd(nullptr, 0) {}
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Range(T* aPtr, size_t aLength)
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: mStart(aPtr, aPtr, aPtr + aLength),
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mEnd(aPtr + aLength, aPtr, aPtr + aLength) {
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if (!aPtr) {
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MOZ_ASSERT(!aLength,
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"Range does not support nullptr with non-zero length.");
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// ...because merely having a pointer to `nullptr + 1` is undefined
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// behavior. UBSAN catches this as of clang-10.
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}
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}
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Range(const RangedPtr<T>& aStart, const RangedPtr<T>& aEnd)
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: mStart(aStart.get(), aStart.get(), aEnd.get()),
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mEnd(aEnd.get(), aStart.get(), aEnd.get()) {
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// Only accept two RangedPtrs within the same range.
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aStart.checkIdenticalRange(aEnd);
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MOZ_ASSERT(aStart <= aEnd);
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}
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template <typename U, class = std::enable_if_t<
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std::is_convertible_v<U (*)[], T (*)[]>, int>>
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MOZ_IMPLICIT Range(const Range<U>& aOther)
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: mStart(aOther.mStart), mEnd(aOther.mEnd) {}
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MOZ_IMPLICIT Range(Span<T> aSpan) : Range(aSpan.Elements(), aSpan.Length()) {}
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template <typename U, class = std::enable_if_t<
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std::is_convertible_v<U (*)[], T (*)[]>, int>>
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MOZ_IMPLICIT Range(const Span<U>& aSpan)
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: Range(aSpan.Elements(), aSpan.Length()) {}
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RangedPtr<T> begin() const { return mStart; }
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RangedPtr<T> end() const { return mEnd; }
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size_t length() const { return mEnd - mStart; }
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T& operator[](size_t aOffset) const { return mStart[aOffset]; }
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explicit operator bool() const { return mStart != nullptr; }
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operator Span<T>() { return Span<T>(mStart.get(), length()); }
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operator Span<const T>() const { return Span<T>(mStart.get(), length()); }
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};
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template <typename T>
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Span(Range<T>&) -> Span<T>;
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template <typename T>
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Span(const Range<T>&) -> Span<const T>;
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} // namespace mozilla
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#endif /* mozilla_Range_h */
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