src/dawn/wire/ChunkedCommandHandler.cpp

// Copyright 2020 The Dawn & Tint Authors
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#include "src/dawn/wire/ChunkedCommandHandler.h"

#include <algorithm>
#include <cstring>
#include <span>
#include <utility>

#include "src/utils/compiler.h"
#include "src/utils/heap_array.h"
#include "src/utils/numeric.h"

namespace dawn::wire {

ChunkedCommandHandler::ChunkedCommandHandler() = default;

ChunkedCommandHandler::~ChunkedCommandHandler() = default;

WireResult ChunkedCommandHandler::HandleChunkedCommand(DeserializeBuffer* deserializeBuffer) {
    ChunkedCommandCmd cmd;
    WIRE_TRY(cmd.Deserialize(deserializeBuffer, &mAllocator));

    ChunkedCommand* chunkedCommand = nullptr;
    if (auto it = mChunkedCommands.find(cmd.id); it != mChunkedCommands.end()) {
        // We already started handling this chunked command. Continue writing into that allocation.
        chunkedCommand = &(it->second);
    } else {
        // This is the first block of this chunked command. Make a new allocation to write into.
        ChunkedCommand newChunkedCommand = {};
        newChunkedCommand.data =
            // SAFETY: This will be incrementally initialized as we handle each chunk of the
            // command.
            DAWN_UNSAFE_BUFFERS(HeapArray<char>::Uninit(cmd.size, std::nothrow));
        if (!newChunkedCommand.data) {
            return WireResult::FatalError;
        }

        const auto& [newIt, inserted] =
            mChunkedCommands.insert({cmd.id, std::move(newChunkedCommand)});
        DAWN_ASSERT(inserted);
        chunkedCommand = &(newIt->second);
    }
    DAWN_ASSERT(chunkedCommand);

    if (cmd.chunkSize > chunkedCommand->GetRemainingSize()) {
        // If the chunk size is greater than the remaining size, something is wrong and we can no
        // longer handle it, so just return a FatalError.
        return WireResult::FatalError;
    }
    // TODO(https://crbug.com/524406299): Use Span::CopyFrom.
    std::ranges::copy(DAWN_UNSAFE_TODO(Span<const char>{cmd.chunkData, cmd.chunkSize}),
                      chunkedCommand->data.begin() + sign_cast(chunkedCommand->putOffset));
    chunkedCommand->putOffset += cmd.chunkSize;

    if (chunkedCommand->GetRemainingSize() == 0) {
        ChunkedCommand fullCommand = std::move(*chunkedCommand);
        mChunkedCommands.erase(cmd.id);
        if (HandleCommands(fullCommand.data.data(), fullCommand.putOffset) == nullptr) {
            return WireResult::FatalError;
        }
    }

    return WireResult::Success;
}

}  // namespace dawn::wire