src/dawn_wire/ChunkedCommandHandler.h

// Copyright 2020 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef DAWNWIRE_CHUNKEDCOMMANDHANDLER_H_
#define DAWNWIRE_CHUNKEDCOMMANDHANDLER_H_

#include "common/Assert.h"
#include "dawn_wire/Wire.h"
#include "dawn_wire/WireCmd_autogen.h"

#include <cstdint>
#include <memory>

namespace dawn_wire {

    class ChunkedCommandHandler : public CommandHandler {
      public:
        const volatile char* HandleCommands(const volatile char* commands, size_t size) override;
        ~ChunkedCommandHandler() override;

      protected:
        enum class ChunkedCommandsResult {
            Passthrough,
            Consumed,
            Error,
        };

        // Returns |true| if the commands were entirely consumed into the chunked command vector
        // and should be handled later once we receive all the command data.
        // Returns |false| if commands should be handled now immediately.
        ChunkedCommandsResult HandleChunkedCommands(const volatile char* commands, size_t size) {
            uint64_t commandSize64 =
                reinterpret_cast<const volatile CmdHeader*>(commands)->commandSize;

            if (commandSize64 > std::numeric_limits<size_t>::max()) {
                return ChunkedCommandsResult::Error;
            }
            size_t commandSize = static_cast<size_t>(commandSize64);
            if (size < commandSize) {
                return BeginChunkedCommandData(commands, commandSize, size);
            }
            return ChunkedCommandsResult::Passthrough;
        }

      private:
        virtual const volatile char* HandleCommandsImpl(const volatile char* commands,
                                                        size_t size) = 0;

        ChunkedCommandsResult BeginChunkedCommandData(const volatile char* commands,
                                                      size_t commandSize,
                                                      size_t initialSize);

        size_t mChunkedCommandRemainingSize = 0;
        size_t mChunkedCommandPutOffset = 0;
        std::unique_ptr<char[]> mChunkedCommandData;
    };

}  // namespace dawn_wire

#endif  // DAWNWIRE_CHUNKEDCOMMANDHANDLER_H_