src/dawn/wire/client/ObjectStore.cpp

// Copyright 2022 The Dawn & Tint Authors
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#include "dawn/wire/client/ObjectStore.h"

#include <limits>
#include <utility>

namespace dawn::wire::client {

ObjectHandle ObjectStore::ReserveHandle() {
    return mState.Use([](auto state) -> ObjectHandle {
        if (state->freeHandles.empty()) {
            return {state->currentId++, 0};
        }
        ObjectHandle handle = state->freeHandles.back();
        state->freeHandles.pop_back();
        return handle;
    });
}

void ObjectStore::Insert(ObjectBase* obj, const ClientBase* forClient) {
    ObjectHandle handle = obj->GetWireHandle(forClient);

    mState.Use([&](auto state) {
        if (handle.id >= state->objects.size()) {
            DAWN_ASSERT(handle.id == state->objects.size());
            state->objects.emplace_back(obj);
        } else {
            // The generation should never overflow. We don't recycle ObjectIds that would
            // overflow their next generation.
            DAWN_ASSERT(handle.generation != 0);
            DAWN_ASSERT(state->objects[handle.id] == nullptr);
            state->objects[handle.id] = obj;
        }
    });
}

void ObjectStore::Remove(ObjectBase* obj, const ClientBase* forClient) {
    // The wire reuses ID for objects to keep them in a packed array starting from 0.
    // To avoid issues with asynchronous server->client communication referring to an ID that's
    // already reused, each handle also has a generation that's increment by one on each reuse.
    // Avoid overflows by only reusing the ID if the increment of the generation won't overflow.
    const ObjectHandle& currentHandle = obj->GetWireHandle(forClient);
    mState.Use([&](auto state) {
        if (currentHandle.generation != std::numeric_limits<ObjectGeneration>::max()) [[likely]] {
            state->freeHandles.push_back({currentHandle.id, currentHandle.generation + 1});
        }
        state->objects[currentHandle.id] = nullptr;
    });
}

std::vector<raw_ptr<ObjectBase>> ObjectStore::GetAllObjects() const {
    return mState.Use(
        [](auto state) -> std::vector<raw_ptr<ObjectBase>> { return state->objects; });
}

ObjectBase* ObjectStore::Get(ObjectId id) const {
    return mState.ConstUse([&](auto state) -> ObjectBase* {
        if (id >= state->objects.size()) {
            return nullptr;
        }
        return state->objects[id];
    });
}

}  // namespace dawn::wire::client