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/* 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_Buffer_h
#define mozilla_Buffer_h
#include <cstddef>
#include <iterator>
#include "mozilla/Assertions.h"
#include "mozilla/Maybe.h"
#include "mozilla/Span.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/UniquePtrExtensions.h"
namespace mozilla {
/**
* A move-only type that wraps a mozilla::UniquePtr<T[]> and the length of
* the T[].
*
* Unlike mozilla::Array, the length is a run-time property.
* Unlike mozilla::Vector and nsTArray, does not have capacity and
* assocatiated growth functionality.
* Unlike mozilla::Span, mozilla::Buffer owns the allocation it points to.
*/
template <typename T>
class Buffer final {
private:
mozilla::UniquePtr<T[]> mData;
size_t mLength;
public:
Buffer(const Buffer<T>& aOther) = delete;
Buffer<T>& operator=(const Buffer<T>& aOther) = delete;
/**
* Construct zero-lenth Buffer (without actually pointing to a heap
* allocation).
*/
Buffer() : mData(nullptr), mLength(0){};
/**
* Construct from raw parts.
*
* aLength must not be greater than the actual length of the buffer pointed
* to by aData.
*/
Buffer(mozilla::UniquePtr<T[]>&& aData, size_t aLength)
: mData(std::move(aData)), mLength(aLength) {}
/**
* Move constructor. Sets the moved-from Buffer to zero-length
* state.
*/
Buffer(Buffer<T>&& aOther)
: mData(std::move(aOther.mData)), mLength(aOther.mLength) {
aOther.mLength = 0;
}
/**
* Move assignment. Sets the moved-from Buffer to zero-length
* state.
*/
Buffer<T>& operator=(Buffer<T>&& aOther) {
mData = std::move(aOther.mData);
mLength = aOther.mLength;
aOther.mLength = 0;
return *this;
}
/**
* Construct by copying the elements of a Span.
*
* Allocates the internal buffer infallibly. Use CopyFrom for fallible
* allocation.
*/
explicit Buffer(mozilla::Span<const T> aSpan)
: mData(mozilla::MakeUniqueForOverwrite<T[]>(aSpan.Length())),
mLength(aSpan.Length()) {
std::copy(aSpan.cbegin(), aSpan.cend(), mData.get());
}
/**
* Create a new Buffer by copying the elements of a Span.
*
* Allocates the internal buffer fallibly.
*/
static mozilla::Maybe<Buffer<T>> CopyFrom(mozilla::Span<const T> aSpan) {
if (aSpan.IsEmpty()) {
return Some(Buffer());
}
auto data = mozilla::MakeUniqueForOverwriteFallible<T[]>(aSpan.Length());
if (!data) {
return mozilla::Nothing();
}
std::copy(aSpan.cbegin(), aSpan.cend(), data.get());
return mozilla::Some(Buffer(std::move(data), aSpan.Length()));
}
/**
* Construct a buffer of requested length.
*
* The contents will be initialized or uninitialized according
* to the behavior of mozilla::MakeUnique<T[]>(aLength) for T.
*
* Allocates the internal buffer infallibly. Use Alloc for fallible
* allocation.
*/
explicit Buffer(size_t aLength)
: mData(mozilla::MakeUnique<T[]>(aLength)), mLength(aLength) {}
/**
* Create a new Buffer with an internal buffer of requested length.
*
* The contents will be initialized or uninitialized according to the
* behavior of mozilla::MakeUnique<T[]>(aLength) for T.
*
* Allocates the internal buffer fallibly.
*/
static mozilla::Maybe<Buffer<T>> Alloc(size_t aLength) {
auto data = mozilla::MakeUniqueFallible<T[]>(aLength);
if (!data) {
return mozilla::Nothing();
}
return mozilla::Some(Buffer(std::move(data), aLength));
}
/**
* Create a new Buffer with an internal buffer of requested length.
*
* This uses MakeUniqueFallibleForOverwrite so the contents will be
* default-initialized.
*
* Allocates the internal buffer fallibly.
*/
static Maybe<Buffer<T>> AllocForOverwrite(size_t aLength) {
auto data = MakeUniqueForOverwriteFallible<T[]>(aLength);
if (!data) {
return Nothing();
}
return Some(Buffer(std::move(data), aLength));
}
auto AsSpan() const { return mozilla::Span<const T>{mData.get(), mLength}; }
auto AsWritableSpan() { return mozilla::Span<T>{mData.get(), mLength}; }
operator mozilla::Span<const T>() const { return AsSpan(); }
operator mozilla::Span<T>() { return AsWritableSpan(); }
/**
* Guarantees a non-null and aligned pointer
* even for the zero-length case.
*/
T* Elements() { return AsWritableSpan().Elements(); }
size_t Length() const { return mLength; }
T& operator[](size_t aIndex) {
MOZ_ASSERT(aIndex < mLength);
return mData.get()[aIndex];
}
const T& operator[](size_t aIndex) const {
MOZ_ASSERT(aIndex < mLength);
return mData.get()[aIndex];
}
typedef T* iterator;
typedef const T* const_iterator;
typedef std::reverse_iterator<T*> reverse_iterator;
typedef std::reverse_iterator<const T*> const_reverse_iterator;
// Methods for range-based for loops.
iterator begin() { return mData.get(); }
const_iterator begin() const { return mData.get(); }
const_iterator cbegin() const { return begin(); }
iterator end() { return mData.get() + mLength; }
const_iterator end() const { return mData.get() + mLength; }
const_iterator cend() const { return end(); }
// Methods for reverse iterating.
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(end());
}
const_reverse_iterator crbegin() const { return rbegin(); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const {
return const_reverse_iterator(begin());
}
const_reverse_iterator crend() const { return rend(); }
};
} /* namespace mozilla */
#endif /* mozilla_Buffer_h */
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