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/*
* Copyright (C) 2010-2020 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 "ArgumentCoders.h"
#include "MessageNames.h"
#include <wtf/StdLibExtras.h>
namespace IPC {
template<typename, typename> struct ArgumentCoder;
// IPC encoder which:
// - Encodes to a caller buffer with fixed size, does not resize, stops when size runs out
// - Does not initialize alignment gaps
//
class StreamConnectionEncoder final {
public:
// Stream allocation needs to be at least size of StreamSetDestinationID message at any offset % messageAlignment.
// StreamSetDestinationID has MessageName+uint64_t, where uint64_t is expected to to be aligned at 8.
static constexpr size_t minimumMessageSize = 16;
static constexpr size_t messageAlignment = alignof(MessageName);
static constexpr bool isIPCEncoder = true;
StreamConnectionEncoder(MessageName messageName, std::span<uint8_t> stream)
: m_originalSize(stream.size())
{
// Instead of using *this << messageName, manually encode the messageName since we
// know the stream buffer is bigger than needed as per API contract.
auto bytes = asBytes(singleElementSpan(messageName));
ASSERT(stream.size() > bytes.size()); // By API contract.
memcpySpan(stream, bytes);
m_buffer = stream.subspan(bytes.size());
}
~StreamConnectionEncoder() = default;
template<typename T, size_t Extent>
bool encodeSpan(std::span<T, Extent> span)
{
auto bytes = asBytes(span);
size_t alignAdvance = distanceToMultipleOf<alignof(T)>(reinterpret_cast<uintptr_t>(m_buffer.data()));
auto requiredSize = alignAdvance + bytes.size();
if (m_buffer.size() < requiredSize) {
m_buffer = { };
return false;
}
memcpySpan(m_buffer.subspan(alignAdvance), bytes);
m_buffer = m_buffer.subspan(requiredSize);
return true;
}
template<typename T>
bool encodeObject(const T& object)
{
static_assert(std::is_trivially_copyable_v<T>);
return encodeSpan(singleElementSpan(object));
}
template<typename T>
StreamConnectionEncoder& operator<<(T&& t)
{
ArgumentCoder<std::remove_cvref_t<T>, void>::encode(*this, std::forward<T>(t));
return *this;
}
size_t size() const { ASSERT(isValid()); return m_originalSize - m_buffer.size(); }
bool isValid() const { return !!m_buffer.data(); }
operator bool() const { return isValid(); }
private:
std::span<uint8_t> m_buffer;
const size_t m_originalSize;
};
} // namespace IPC
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