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/*
* Copyright (C) 2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/Atomics.h>
#include <wtf/FastMalloc.h>
#include <wtf/HashFunctions.h>
#include <wtf/Lock.h>
#include <wtf/Noncopyable.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
namespace WTF {
DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(ConcurrentBuffer);
// ConcurrentBuffer is suitable for when you plan to store immutable data and sometimes append to it.
// It supports storing data that is not copy-constructable but bit-copyable.
template<typename T>
class ConcurrentBuffer final {
WTF_MAKE_NONCOPYABLE(ConcurrentBuffer);
WTF_DEPRECATED_MAKE_FAST_ALLOCATED(ConcurrentBuffer);
public:
ConcurrentBuffer() = default;
~ConcurrentBuffer()
{
if (auto* array = m_array) {
for (auto& item : array->span())
item.~T();
}
}
// Growing is not concurrent. This assumes you are holding some other lock before you do this.
void growExact(size_t newSize)
{
auto* array = m_array;
if (array && newSize <= array->size)
return;
auto newArray = createArray(newSize);
// This allows us to do ConcurrentBuffer<std::unique_ptr<>>.
// asMutableByteSpan() avoids triggering -Wclass-memaccess.
if (array)
memcpySpan(asMutableByteSpan(newArray->span()), asByteSpan(array->span()));
for (auto& item : newArray->span().subspan(array ? array->size : 0))
new (&item) T();
WTF::storeStoreFence();
m_array = newArray.get();
WTF::storeStoreFence();
m_allArrays.append(WTFMove(newArray));
}
void grow(size_t newSize)
{
size_t size = m_array ? m_array->size : 0;
if (newSize <= size)
return;
growExact(std::max(newSize, size * 2));
}
struct Array {
size_t size; // This is an immutable size.
T data[1];
std::span<T> span() { return unsafeMakeSpan(data, size); }
std::span<const T> span() const { return unsafeMakeSpan(data, size); }
};
using ArrayPtr = std::unique_ptr<Array, NonDestructingDeleter<Array, ConcurrentBufferMalloc>>;
Array* array() const { return m_array; }
T& operator[](size_t index) { return m_array->span()[index]; }
const T& operator[](size_t index) const { return m_array->span()[index]; }
private:
ArrayPtr createArray(size_t size)
{
Checked<size_t> objectSize = sizeof(T);
objectSize *= size;
objectSize += static_cast<size_t>(OBJECT_OFFSETOF(Array, data));
auto* ptr = static_cast<Array*>(ConcurrentBufferMalloc::malloc(objectSize));
auto result = ArrayPtr(ptr, { });
result->size = size;
return result;
}
Array* m_array { nullptr };
Vector<ArrayPtr> m_allArrays;
};
} // namespace WTF
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