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/*
* Copyright (C) 2016-2017 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 <algorithm>
#include <limits.h>
namespace WTF {
class PrintStream;
}
namespace JSC {
#if USE(LARGE_TYPED_ARRAYS)
static_assert(sizeof(size_t) == sizeof(uint64_t));
#define MAX_ARRAY_BUFFER_SIZE (1ull << 32)
#else
static_assert(sizeof(size_t) == sizeof(uint32_t));
// Because we are using a size_t to store the size in bytes of array buffers, we cannot support 4GB on 32-bit platforms.
// So we are sticking with 2GB. It should in theory be possible to support up to (4GB - 1B) if anyone cares.
#define MAX_ARRAY_BUFFER_SIZE 0x7fffffffu
#endif
class PageCount {
public:
PageCount()
: m_pageCount(UINT_MAX)
{
static_assert(maxPageCount < UINT_MAX, "We rely on this here.");
}
PageCount(uint32_t pageCount)
: m_pageCount(pageCount)
{ }
void dump(WTF::PrintStream&) const;
uint64_t bytes() const { return static_cast<uint64_t>(m_pageCount) * static_cast<uint64_t>(pageSize); }
uint32_t pageCount() const { return m_pageCount; }
static bool isValid(uint32_t pageCount)
{
return pageCount <= maxPageCount;
}
bool isValid() const
{
return isValid(m_pageCount);
}
static PageCount fromBytes(uint64_t bytes)
{
RELEASE_ASSERT(bytes % pageSize == 0);
uint32_t numPages = bytes / pageSize;
RELEASE_ASSERT(PageCount::isValid(numPages));
return PageCount(numPages);
}
static PageCount fromBytesWithRoundUp(uint64_t bytes)
{
return fromBytes(roundUpToMultipleOf<pageSize>(bytes));
}
static PageCount max()
{
return PageCount(maxPageCount);
}
explicit operator bool() const
{
return m_pageCount != UINT_MAX;
}
bool operator<(const PageCount& other) const { return m_pageCount < other.m_pageCount; }
bool operator>(const PageCount& other) const { return m_pageCount > other.m_pageCount; }
bool operator>=(const PageCount& other) const { return m_pageCount >= other.m_pageCount; }
friend bool operator==(const PageCount&, const PageCount&) = default;
PageCount operator+(const PageCount& other) const
{
if (sumOverflows<uint32_t>(m_pageCount, other.m_pageCount))
return PageCount();
uint32_t newCount = m_pageCount + other.m_pageCount;
if (!PageCount::isValid(newCount))
return PageCount();
return PageCount(newCount);
}
static constexpr uint32_t pageSize = 64 * KB;
private:
// The spec requires we are able to instantiate a memory with a *maximum* size of 64K pages.
// This does not mean the memory can necessarily grow that big, and where the
// MAX_ARRAY_BUFFER_SIZE is smaller (e.g.: on 32-bit platforms), trying to grow the memory
// that large will fail, which is acceptable according to the spec. Nevertheless, we should
// be able to parse such a memory and instantiate it with a smaller initial size.
static constexpr uint32_t maxPageCount = std::max<uint32_t>(64*1024, MAX_ARRAY_BUFFER_SIZE / static_cast<uint64_t>(pageSize));
uint32_t m_pageCount;
};
} // namespace JSC
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