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