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/*
* Copyright (C) 2023 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. AND ITS CONTRIBUTORS ``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 ITS 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 "IPCSemaphore.h"
#include "StreamConnectionBuffer.h"
#include "StreamConnectionEncoder.h"
namespace IPC {
class StreamServerConnectionBuffer : public StreamConnectionBuffer {
public:
static std::optional<StreamServerConnectionBuffer> map(Handle&&);
StreamServerConnectionBuffer(StreamServerConnectionBuffer&&) = default;
StreamServerConnectionBuffer& operator=(StreamServerConnectionBuffer&&) = default;
std::optional<std::span<uint8_t>> tryAcquire();
std::span<uint8_t> acquireAll();
enum class WakeUpClient : bool { No, Yes };
WakeUpClient release(size_t readSize);
WakeUpClient releaseAll();
private:
using StreamConnectionBuffer::StreamConnectionBuffer;
static constexpr size_t minimumMessageSize = StreamConnectionEncoder::minimumMessageSize;
static constexpr size_t messageAlignment = StreamConnectionEncoder::messageAlignment;
std::span<uint8_t> alignedMutableSpan(size_t offset, size_t limit);
size_t size(size_t offset, size_t limit) const;
size_t alignOffset(size_t offset) const { return StreamConnectionBuffer::alignOffset<messageAlignment>(offset, minimumMessageSize); }
using ServerLimit = ClientOffset;
Atomic<ServerLimit>& sharedServerLimit() { return clientOffset(); }
Atomic<ServerOffset>& sharedServerOffset() { return serverOffset(); }
size_t clampedLimit(ServerLimit) const;
size_t m_serverOffset { 0 };
};
inline std::optional<StreamServerConnectionBuffer> StreamServerConnectionBuffer::map(Handle&& handle)
{
auto sharedMemory = WebCore::SharedMemory::map(WTFMove(handle), WebCore::SharedMemory::Protection::ReadWrite);
if (UNLIKELY(!sharedMemory))
return std::nullopt;
return StreamServerConnectionBuffer { sharedMemory.releaseNonNull() };
}
inline std::optional<std::span<uint8_t>> StreamServerConnectionBuffer::tryAcquire()
{
ServerLimit serverLimit = sharedServerLimit().load(std::memory_order_acquire);
if (serverLimit == ServerLimit::serverIsSleepingTag)
return std::nullopt;
auto result = alignedMutableSpan(m_serverOffset, clampedLimit(serverLimit));
if (result.size() < minimumMessageSize) {
serverLimit = sharedServerLimit().compareExchangeStrong(serverLimit, ServerLimit::serverIsSleepingTag, std::memory_order_acq_rel, std::memory_order_acquire);
result = alignedMutableSpan(m_serverOffset, clampedLimit(serverLimit));
}
if (result.size() < minimumMessageSize)
return std::nullopt;
return result;
}
inline std::span<uint8_t> StreamServerConnectionBuffer::acquireAll()
{
return alignedMutableSpan(0, dataSize() - 1);
}
inline StreamServerConnectionBuffer::WakeUpClient StreamServerConnectionBuffer::release(size_t readSize)
{
ASSERT(readSize);
readSize = std::max(readSize, minimumMessageSize);
ServerOffset serverOffset = static_cast<ServerOffset>(wrapOffset(alignOffset(m_serverOffset) + readSize));
ServerOffset oldServerOffset = sharedServerOffset().exchange(serverOffset, std::memory_order_acq_rel);
WakeUpClient wakeUpClient = WakeUpClient::No;
// If the client wrote over serverOffset, it means the client is waiting.
if (oldServerOffset == ServerOffset::clientIsWaitingTag)
wakeUpClient = WakeUpClient::Yes;
else
ASSERT(!(oldServerOffset & ServerOffset::clientIsWaitingTag));
m_serverOffset = serverOffset;
return wakeUpClient;
}
inline StreamServerConnectionBuffer::WakeUpClient StreamServerConnectionBuffer::releaseAll()
{
sharedServerLimit().store(static_cast<ServerLimit>(0), std::memory_order_release);
ServerOffset oldServerOffset = sharedServerOffset().exchange(static_cast<ServerOffset>(0), std::memory_order_acq_rel);
WakeUpClient wakeUpClient = WakeUpClient::No;
// If the client wrote over serverOffset, it means the client is waiting.
if (oldServerOffset == ServerOffset::clientIsWaitingTag)
wakeUpClient = WakeUpClient::Yes;
else
ASSERT(!(oldServerOffset & ServerOffset::clientIsWaitingTag));
m_serverOffset = 0;
return wakeUpClient;
}
inline std::span<uint8_t> StreamServerConnectionBuffer::alignedMutableSpan(size_t offset, size_t limit)
{
ASSERT(offset < dataSize());
ASSERT(limit < dataSize());
size_t aligned = alignOffset(offset);
size_t resultSize = 0;
if (offset < limit) {
if (offset <= aligned && aligned < limit)
resultSize = size(aligned, limit);
} else if (offset > limit) {
if (aligned >= offset || aligned < limit)
resultSize = size(aligned, limit);
}
return mutableSpan().subspan(aligned, resultSize);
}
inline size_t StreamServerConnectionBuffer::size(size_t offset, size_t limit) const
{
if (offset <= limit)
return limit - offset;
return dataSize() - offset;
}
inline size_t StreamServerConnectionBuffer::clampedLimit(ServerLimit serverLimit) const
{
ASSERT(!(serverLimit & ServerLimit::serverIsSleepingTag));
size_t limit = static_cast<size_t>(serverLimit);
ASSERT(limit <= dataSize() - 1);
return std::min(limit, dataSize() - 1);
}
}
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