src/dawn_native/Buffer.cpp - dawn - Git at Google

 // Copyright 2017 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.

 #include "dawn_native/Buffer.h"

 #include "common/Alloc.h"
 #include "common/Assert.h"
 #include "dawn_native/Commands.h"
 #include "dawn_native/Device.h"
 #include "dawn_native/DynamicUploader.h"
 #include "dawn_native/ErrorData.h"
 #include "dawn_native/Queue.h"
 #include "dawn_native/ValidationUtils_autogen.h"

 #include <cstdio>
 #include <cstring>
 #include <utility>

 namespace dawn_native {

     namespace {
         struct MapRequestTask : QueueBase::TaskInFlight {
             MapRequestTask(Ref<BufferBase> buffer, MapRequestID id)
                 : buffer(std::move(buffer)), id(id) {
             }
             void Finish() override {
                 buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_Success);
             }
             void HandleDeviceLoss() override {
                 buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_DeviceLost);
             }
             ~MapRequestTask() override = default;

           private:
             Ref<BufferBase> buffer;
             MapRequestID id;
         };

         class ErrorBuffer final : public BufferBase {
           public:
             ErrorBuffer(DeviceBase* device, const BufferDescriptor* descriptor)
                 : BufferBase(device, descriptor, ObjectBase::kError) {
                 if (descriptor->mappedAtCreation) {
                     // Check that the size can be used to allocate an mFakeMappedData. A malloc(0)
                     // is invalid, and on 32bit systems we should avoid a narrowing conversion that
                     // would make size = 1 << 32 + 1 allocate one byte.
                     bool isValidSize =
                         descriptor->size != 0 &&
                         descriptor->size < uint64_t(std::numeric_limits<size_t>::max());

                     if (isValidSize) {
                         mFakeMappedData =
                             std::unique_ptr<uint8_t[]>(AllocNoThrow<uint8_t>(descriptor->size));
                     }
                 }
             }

             void ClearMappedData() {
                 mFakeMappedData.reset();
             }

           private:
             bool IsCPUWritableAtCreation() const override {
                 UNREACHABLE();
             }

             MaybeError MapAtCreationImpl() override {
                 UNREACHABLE();
             }

             MaybeError MapAsyncImpl(wgpu::MapMode mode, size_t offset, size_t size) override {
                 UNREACHABLE();
             }
             void* GetMappedPointerImpl() override {
                 return mFakeMappedData.get();
             }
             void UnmapImpl() override {
                 UNREACHABLE();
             }
             void DestroyImpl() override {
                 UNREACHABLE();
             }

             std::unique_ptr<uint8_t[]> mFakeMappedData;
         };

     }  // anonymous namespace

     MaybeError ValidateBufferDescriptor(DeviceBase*, const BufferDescriptor* descriptor) {
         if (descriptor->nextInChain != nullptr) {
             return DAWN_VALIDATION_ERROR("nextInChain must be nullptr");
         }

         DAWN_TRY(ValidateBufferUsage(descriptor->usage));

         wgpu::BufferUsage usage = descriptor->usage;

         const wgpu::BufferUsage kMapWriteAllowedUsages =
             wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::CopySrc;
         if (usage & wgpu::BufferUsage::MapWrite && (usage & kMapWriteAllowedUsages) != usage) {
             return DAWN_VALIDATION_ERROR("Only CopySrc is allowed with MapWrite");
         }

         const wgpu::BufferUsage kMapReadAllowedUsages =
             wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;
         if (usage & wgpu::BufferUsage::MapRead && (usage & kMapReadAllowedUsages) != usage) {
             return DAWN_VALIDATION_ERROR("Only CopyDst is allowed with MapRead");
         }

         if (descriptor->mappedAtCreation && descriptor->size % 4 != 0) {
             return DAWN_VALIDATION_ERROR("size must be aligned to 4 when mappedAtCreation is true");
         }

         return {};
     }

     // Buffer

     BufferBase::BufferBase(DeviceBase* device, const BufferDescriptor* descriptor)
         : ObjectBase(device),
           mSize(descriptor->size),
           mUsage(descriptor->usage),
           mState(BufferState::Unmapped) {
         // Add readonly storage usage if the buffer has a storage usage. The validation rules in
         // ValidateSyncScopeResourceUsage will make sure we don't use both at the same time.
         if (mUsage & wgpu::BufferUsage::Storage) {
             mUsage |= kReadOnlyStorageBuffer;
         }

         // TODO(crbug.com/dawn/434): This is just a workaround to make QueryResolve buffer pass the
         // binding group validation when used as an internal resource. Instead the buffer made with
         // QueryResolve usage would implicitly get StorageInternal usage which is only compatible
         // with StorageBufferInternal binding type in BGL, not StorageBuffer binding type.
         if (mUsage & wgpu::BufferUsage::QueryResolve) {
             mUsage |= wgpu::BufferUsage::Storage;
         }
     }

     BufferBase::BufferBase(DeviceBase* device,
                            const BufferDescriptor* descriptor,
                            ObjectBase::ErrorTag tag)
         : ObjectBase(device, tag), mSize(descriptor->size), mState(BufferState::Unmapped) {
         if (descriptor->mappedAtCreation) {
             mState = BufferState::MappedAtCreation;
             mMapOffset = 0;
             mMapSize = mSize;
         }
     }

     BufferBase::~BufferBase() {
         if (mState == BufferState::Mapped) {
             ASSERT(!IsError());
             CallMapCallback(mLastMapID, WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
         }
     }

     // static
     BufferBase* BufferBase::MakeError(DeviceBase* device, const BufferDescriptor* descriptor) {
         return new ErrorBuffer(device, descriptor);
     }

     uint64_t BufferBase::GetSize() const {
         ASSERT(!IsError());
         return mSize;
     }

     wgpu::BufferUsage BufferBase::GetUsage() const {
         ASSERT(!IsError());
         return mUsage;
     }

     MaybeError BufferBase::MapAtCreation() {
         DAWN_TRY(MapAtCreationInternal());

         DeviceBase* device = GetDevice();
         if (device->IsToggleEnabled(Toggle::LazyClearResourceOnFirstUse)) {
             memset(GetMappedRange(0, mSize), uint8_t(0u), mSize);
             SetIsDataInitialized();
             device->IncrementLazyClearCountForTesting();
         } else if (device->IsToggleEnabled(Toggle::NonzeroClearResourcesOnCreationForTesting)) {
             memset(GetMappedRange(0, mSize), uint8_t(1u), mSize);
         }

         return {};
     }

     MaybeError BufferBase::MapAtCreationInternal() {
         ASSERT(!IsError());
         mState = BufferState::MappedAtCreation;
         mMapOffset = 0;
         mMapSize = mSize;

         // 0-sized buffers are not supposed to be written to, Return back any non-null pointer.
         // Handle 0-sized buffers first so we don't try to map them in the backend.
         if (mSize == 0) {
             return {};
         }

         // Mappable buffers don't use a staging buffer and are just as if mapped through MapAsync.
         if (IsCPUWritableAtCreation()) {
             DAWN_TRY(MapAtCreationImpl());
         } else {
             // If any of these fail, the buffer will be deleted and replaced with an
             // error buffer.
             // TODO(crbug.com/dawn/828): Suballocate and reuse memory from a larger staging buffer
             // so we don't create many small buffers.
             DAWN_TRY_ASSIGN(mStagingBuffer, GetDevice()->CreateStagingBuffer(GetSize()));
         }

         return {};
     }

     MaybeError BufferBase::ValidateCanUseOnQueueNow() const {
         ASSERT(!IsError());

         switch (mState) {
             case BufferState::Destroyed:
                 return DAWN_VALIDATION_ERROR("Destroyed buffer used in a submit");
             case BufferState::Mapped:
             case BufferState::MappedAtCreation:
                 return DAWN_VALIDATION_ERROR("Buffer used in a submit while mapped");
             case BufferState::Unmapped:
                 return {};
         }
     }

     void BufferBase::CallMapCallback(MapRequestID mapID, WGPUBufferMapAsyncStatus status) {
         ASSERT(!IsError());
         if (mMapCallback != nullptr && mapID == mLastMapID) {
             // Tag the callback as fired before firing it, otherwise it could fire a second time if
             // for example buffer.Unmap() is called inside the application-provided callback.
             WGPUBufferMapCallback callback = mMapCallback;
             mMapCallback = nullptr;

             if (GetDevice()->IsLost()) {
                 callback(WGPUBufferMapAsyncStatus_DeviceLost, mMapUserdata);
             } else {
                 callback(status, mMapUserdata);
             }
         }
     }

     void BufferBase::APIMapAsync(wgpu::MapMode mode,
                                  size_t offset,
                                  size_t size,
                                  WGPUBufferMapCallback callback,
                                  void* userdata) {
         // Handle the defaulting of size required by WebGPU, even if in webgpu_cpp.h it is not
         // possible to default the function argument (because there is the callback later in the
         // argument list)
         if (size == 0 && offset < mSize) {
             size = mSize - offset;
         }

         WGPUBufferMapAsyncStatus status;
         if (GetDevice()->ConsumedError(ValidateMapAsync(mode, offset, size, &status))) {
             if (callback) {
                 callback(status, userdata);
             }
             return;
         }
         ASSERT(!IsError());

         mLastMapID++;
         mMapMode = mode;
         mMapOffset = offset;
         mMapSize = size;
         mMapCallback = callback;
         mMapUserdata = userdata;
         mState = BufferState::Mapped;

         if (GetDevice()->ConsumedError(MapAsyncImpl(mode, offset, size))) {
             CallMapCallback(mLastMapID, WGPUBufferMapAsyncStatus_DeviceLost);
             return;
         }
         std::unique_ptr<MapRequestTask> request =
             std::make_unique<MapRequestTask>(this, mLastMapID);
         GetDevice()->GetQueue()->TrackTask(std::move(request),
                                            GetDevice()->GetPendingCommandSerial());
     }

     void* BufferBase::APIGetMappedRange(size_t offset, size_t size) {
         return GetMappedRange(offset, size, true);
     }

     const void* BufferBase::APIGetConstMappedRange(size_t offset, size_t size) {
         return GetMappedRange(offset, size, false);
     }

     void* BufferBase::GetMappedRange(size_t offset, size_t size, bool writable) {
         if (!CanGetMappedRange(writable, offset, size)) {
             return nullptr;
         }

         if (mStagingBuffer != nullptr) {
             return static_cast<uint8_t*>(mStagingBuffer->GetMappedPointer()) + offset;
         }
         if (mSize == 0) {
             return reinterpret_cast<uint8_t*>(intptr_t(0xCAFED00D));
         }
         uint8_t* start = static_cast<uint8_t*>(GetMappedPointerImpl());
         return start == nullptr ? nullptr : start + offset;
     }

     void BufferBase::APIDestroy() {
         if (IsError()) {
             // It is an error to call Destroy() on an ErrorBuffer, but we still need to reclaim the
             // fake mapped staging data.
             static_cast<ErrorBuffer*>(this)->ClearMappedData();
             mState = BufferState::Destroyed;
         }
         if (GetDevice()->ConsumedError(ValidateDestroy())) {
             return;
         }
         ASSERT(!IsError());

         if (mState == BufferState::Mapped) {
             UnmapInternal(WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
         } else if (mState == BufferState::MappedAtCreation) {
             if (mStagingBuffer != nullptr) {
                 mStagingBuffer.reset();
             } else if (mSize != 0) {
                 ASSERT(IsCPUWritableAtCreation());
                 UnmapInternal(WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
             }
         }

         DestroyInternal();
     }

     MaybeError BufferBase::CopyFromStagingBuffer() {
         ASSERT(mStagingBuffer);
         if (GetSize() == 0) {
             return {};
         }

         DAWN_TRY(GetDevice()->CopyFromStagingToBuffer(mStagingBuffer.get(), 0, this, 0, GetSize()));

         DynamicUploader* uploader = GetDevice()->GetDynamicUploader();
         uploader->ReleaseStagingBuffer(std::move(mStagingBuffer));

         return {};
     }

     void BufferBase::APIUnmap() {
         Unmap();
     }

     void BufferBase::Unmap() {
         UnmapInternal(WGPUBufferMapAsyncStatus_UnmappedBeforeCallback);
     }

     void BufferBase::UnmapInternal(WGPUBufferMapAsyncStatus callbackStatus) {
         if (IsError()) {
             // It is an error to call Unmap() on an ErrorBuffer, but we still need to reclaim the
             // fake mapped staging data.
             static_cast<ErrorBuffer*>(this)->ClearMappedData();
             mState = BufferState::Unmapped;
         }
         if (GetDevice()->ConsumedError(ValidateUnmap())) {
             return;
         }
         ASSERT(!IsError());

         if (mState == BufferState::Mapped) {
             // A map request can only be called once, so this will fire only if the request wasn't
             // completed before the Unmap.
             // Callbacks are not fired if there is no callback registered, so this is correct for
             // mappedAtCreation = true.
             CallMapCallback(mLastMapID, callbackStatus);
             UnmapImpl();

             mMapCallback = nullptr;
             mMapUserdata = 0;

         } else if (mState == BufferState::MappedAtCreation) {
             if (mStagingBuffer != nullptr) {
                 GetDevice()->ConsumedError(CopyFromStagingBuffer());
             } else if (mSize != 0) {
                 ASSERT(IsCPUWritableAtCreation());
                 UnmapImpl();
             }
         }

         mState = BufferState::Unmapped;
     }

     MaybeError BufferBase::ValidateMap(wgpu::BufferUsage requiredUsage,
                                        WGPUBufferMapAsyncStatus* status) const {
         *status = WGPUBufferMapAsyncStatus_DeviceLost;
         DAWN_TRY(GetDevice()->ValidateIsAlive());

         *status = WGPUBufferMapAsyncStatus_Error;
         DAWN_TRY(GetDevice()->ValidateObject(this));

         switch (mState) {
             case BufferState::Mapped:
             case BufferState::MappedAtCreation:
                 return DAWN_VALIDATION_ERROR("Buffer is already mapped");
             case BufferState::Destroyed:
                 return DAWN_VALIDATION_ERROR("Buffer is destroyed");
             case BufferState::Unmapped:
                 break;
         }

         if (!(mUsage & requiredUsage)) {
             return DAWN_VALIDATION_ERROR("Buffer needs the correct map usage bit");
         }

         *status = WGPUBufferMapAsyncStatus_Success;
         return {};
     }

     MaybeError BufferBase::ValidateMapAsync(wgpu::MapMode mode,
                                             size_t offset,
                                             size_t size,
                                             WGPUBufferMapAsyncStatus* status) const {
         *status = WGPUBufferMapAsyncStatus_DeviceLost;
         DAWN_TRY(GetDevice()->ValidateIsAlive());

         *status = WGPUBufferMapAsyncStatus_Error;
         DAWN_TRY(GetDevice()->ValidateObject(this));

         if (offset % 8 != 0) {
             return DAWN_VALIDATION_ERROR("offset must be a multiple of 8");
         }

         if (size % 4 != 0) {
             return DAWN_VALIDATION_ERROR("size must be a multiple of 4");
         }

         if (uint64_t(offset) > mSize || uint64_t(size) > mSize - uint64_t(offset)) {
             return DAWN_VALIDATION_ERROR("size + offset must fit in the buffer");
         }

         switch (mState) {
             case BufferState::Mapped:
             case BufferState::MappedAtCreation:
                 return DAWN_VALIDATION_ERROR("Buffer is already mapped");
             case BufferState::Destroyed:
                 return DAWN_VALIDATION_ERROR("Buffer is destroyed");
             case BufferState::Unmapped:
                 break;
         }

         bool isReadMode = mode & wgpu::MapMode::Read;
         bool isWriteMode = mode & wgpu::MapMode::Write;
         if (!(isReadMode ^ isWriteMode)) {
             return DAWN_VALIDATION_ERROR("Exactly one of Read or Write mode must be set");
         }

         if (mode & wgpu::MapMode::Read) {
             if (!(mUsage & wgpu::BufferUsage::MapRead)) {
                 return DAWN_VALIDATION_ERROR("The buffer must have the MapRead usage");
             }
         } else {
             ASSERT(mode & wgpu::MapMode::Write);

             if (!(mUsage & wgpu::BufferUsage::MapWrite)) {
                 return DAWN_VALIDATION_ERROR("The buffer must have the MapWrite usage");
             }
         }

         *status = WGPUBufferMapAsyncStatus_Success;
         return {};
     }

     bool BufferBase::CanGetMappedRange(bool writable, size_t offset, size_t size) const {
         if (offset % 8 != 0 || size % 4 != 0) {
             return false;
         }

         if (size > mMapSize || offset < mMapOffset) {
             return false;
         }

         size_t offsetInMappedRange = offset - mMapOffset;
         if (offsetInMappedRange > mMapSize - size) {
             return false;
         }

         // Note that:
         //
         //   - We don't check that the device is alive because the application can ask for the
         //     mapped pointer before it knows, and even Dawn knows, that the device was lost, and
         //     still needs to work properly.
         //   - We don't check that the object is alive because we need to return mapped pointers
         //     for error buffers too.

         switch (mState) {
             // Writeable Buffer::GetMappedRange is always allowed when mapped at creation.
             case BufferState::MappedAtCreation:
                 return true;

             case BufferState::Mapped:
                 ASSERT(bool(mMapMode & wgpu::MapMode::Read) ^
                        bool(mMapMode & wgpu::MapMode::Write));
                 return !writable || (mMapMode & wgpu::MapMode::Write);

             case BufferState::Unmapped:
             case BufferState::Destroyed:
                 return false;
         }
     }

     MaybeError BufferBase::ValidateUnmap() const {
         DAWN_TRY(GetDevice()->ValidateIsAlive());
         DAWN_TRY(GetDevice()->ValidateObject(this));

         switch (mState) {
             case BufferState::Mapped:
             case BufferState::MappedAtCreation:
                 // A buffer may be in the Mapped state if it was created with mappedAtCreation
                 // even if it did not have a mappable usage.
                 return {};
             case BufferState::Unmapped:
                 return DAWN_VALIDATION_ERROR("Buffer is unmapped");
             case BufferState::Destroyed:
                 return DAWN_VALIDATION_ERROR("Buffer is destroyed");
         }
     }

     MaybeError BufferBase::ValidateDestroy() const {
         DAWN_TRY(GetDevice()->ValidateObject(this));
         return {};
     }

     void BufferBase::DestroyInternal() {
         if (mState != BufferState::Destroyed) {
             DestroyImpl();
         }
         mState = BufferState::Destroyed;
     }

     void BufferBase::OnMapRequestCompleted(MapRequestID mapID, WGPUBufferMapAsyncStatus status) {
         CallMapCallback(mapID, status);
     }

     bool BufferBase::IsDataInitialized() const {
         return mIsDataInitialized;
     }

     void BufferBase::SetIsDataInitialized() {
         mIsDataInitialized = true;
     }

     bool BufferBase::IsFullBufferRange(uint64_t offset, uint64_t size) const {
         return offset == 0 && size == GetSize();
     }
 }  // namespace dawn_native
	// Copyright 2017 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.

	#include "dawn_native/Buffer.h"

	#include "common/Alloc.h"
	#include "common/Assert.h"
	#include "dawn_native/Commands.h"
	#include "dawn_native/Device.h"
	#include "dawn_native/DynamicUploader.h"
	#include "dawn_native/ErrorData.h"
	#include "dawn_native/Queue.h"
	#include "dawn_native/ValidationUtils_autogen.h"

	#include <cstdio>
	#include <cstring>
	#include <utility>

	namespace dawn_native {

	namespace {
	struct MapRequestTask : QueueBase::TaskInFlight {
	MapRequestTask(Ref<BufferBase> buffer, MapRequestID id)
	: buffer(std::move(buffer)), id(id) {
	}
	void Finish() override {
	buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_Success);
	}
	void HandleDeviceLoss() override {
	buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_DeviceLost);
	}
	~MapRequestTask() override = default;

	private:
	Ref<BufferBase> buffer;
	MapRequestID id;
	};

	class ErrorBuffer final : public BufferBase {
	public:
	ErrorBuffer(DeviceBase* device, const BufferDescriptor* descriptor)
	: BufferBase(device, descriptor, ObjectBase::kError) {
	if (descriptor->mappedAtCreation) {
	// Check that the size can be used to allocate an mFakeMappedData. A malloc(0)
	// is invalid, and on 32bit systems we should avoid a narrowing conversion that
	// would make size = 1 << 32 + 1 allocate one byte.
	bool isValidSize =
	descriptor->size != 0 &&
	descriptor->size < uint64_t(std::numeric_limits<size_t>::max());

	if (isValidSize) {
	mFakeMappedData =
	std::unique_ptr<uint8_t[]>(AllocNoThrow<uint8_t>(descriptor->size));
	}
	}
	}

	void ClearMappedData() {
	mFakeMappedData.reset();
	}

	private:
	bool IsCPUWritableAtCreation() const override {
	UNREACHABLE();
	}

	MaybeError MapAtCreationImpl() override {
	UNREACHABLE();
	}

	MaybeError MapAsyncImpl(wgpu::MapMode mode, size_t offset, size_t size) override {
	UNREACHABLE();
	}
	void* GetMappedPointerImpl() override {
	return mFakeMappedData.get();
	}
	void UnmapImpl() override {
	UNREACHABLE();
	}
	void DestroyImpl() override {
	UNREACHABLE();
	}

	std::unique_ptr<uint8_t[]> mFakeMappedData;
	};

	} // anonymous namespace

	MaybeError ValidateBufferDescriptor(DeviceBase, const BufferDescriptor descriptor) {
	if (descriptor->nextInChain != nullptr) {
	return DAWN_VALIDATION_ERROR("nextInChain must be nullptr");
	}

	DAWN_TRY(ValidateBufferUsage(descriptor->usage));

	wgpu::BufferUsage usage = descriptor->usage;

	const wgpu::BufferUsage kMapWriteAllowedUsages =
	wgpu::BufferUsage::MapWrite \| wgpu::BufferUsage::CopySrc;
	if (usage & wgpu::BufferUsage::MapWrite && (usage & kMapWriteAllowedUsages) != usage) {
	return DAWN_VALIDATION_ERROR("Only CopySrc is allowed with MapWrite");
	}

	const wgpu::BufferUsage kMapReadAllowedUsages =
	wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::CopyDst;
	if (usage & wgpu::BufferUsage::MapRead && (usage & kMapReadAllowedUsages) != usage) {
	return DAWN_VALIDATION_ERROR("Only CopyDst is allowed with MapRead");
	}

	if (descriptor->mappedAtCreation && descriptor->size % 4 != 0) {
	return DAWN_VALIDATION_ERROR("size must be aligned to 4 when mappedAtCreation is true");
	}

	return {};
	}

	// Buffer

	BufferBase::BufferBase(DeviceBase* device, const BufferDescriptor* descriptor)
	: ObjectBase(device),
	mSize(descriptor->size),
	mUsage(descriptor->usage),
	mState(BufferState::Unmapped) {
	// Add readonly storage usage if the buffer has a storage usage. The validation rules in
	// ValidateSyncScopeResourceUsage will make sure we don't use both at the same time.
	if (mUsage & wgpu::BufferUsage::Storage) {
	mUsage \|= kReadOnlyStorageBuffer;
	}

	// TODO(crbug.com/dawn/434): This is just a workaround to make QueryResolve buffer pass the
	// binding group validation when used as an internal resource. Instead the buffer made with
	// QueryResolve usage would implicitly get StorageInternal usage which is only compatible
	// with StorageBufferInternal binding type in BGL, not StorageBuffer binding type.
	if (mUsage & wgpu::BufferUsage::QueryResolve) {
	mUsage \|= wgpu::BufferUsage::Storage;
	}
	}

	BufferBase::BufferBase(DeviceBase* device,
	const BufferDescriptor* descriptor,
	ObjectBase::ErrorTag tag)
	: ObjectBase(device, tag), mSize(descriptor->size), mState(BufferState::Unmapped) {
	if (descriptor->mappedAtCreation) {
	mState = BufferState::MappedAtCreation;
	mMapOffset = 0;
	mMapSize = mSize;
	}
	}

	BufferBase::~BufferBase() {
	if (mState == BufferState::Mapped) {
	ASSERT(!IsError());
	CallMapCallback(mLastMapID, WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
	}
	}

	// static
	BufferBase* BufferBase::MakeError(DeviceBase* device, const BufferDescriptor* descriptor) {
	return new ErrorBuffer(device, descriptor);
	}

	uint64_t BufferBase::GetSize() const {
	ASSERT(!IsError());
	return mSize;
	}

	wgpu::BufferUsage BufferBase::GetUsage() const {
	ASSERT(!IsError());
	return mUsage;
	}

	MaybeError BufferBase::MapAtCreation() {
	DAWN_TRY(MapAtCreationInternal());

	DeviceBase* device = GetDevice();
	if (device->IsToggleEnabled(Toggle::LazyClearResourceOnFirstUse)) {
	memset(GetMappedRange(0, mSize), uint8_t(0u), mSize);
	SetIsDataInitialized();
	device->IncrementLazyClearCountForTesting();
	} else if (device->IsToggleEnabled(Toggle::NonzeroClearResourcesOnCreationForTesting)) {
	memset(GetMappedRange(0, mSize), uint8_t(1u), mSize);
	}

	return {};
	}

	MaybeError BufferBase::MapAtCreationInternal() {
	ASSERT(!IsError());
	mState = BufferState::MappedAtCreation;
	mMapOffset = 0;
	mMapSize = mSize;

	// 0-sized buffers are not supposed to be written to, Return back any non-null pointer.
	// Handle 0-sized buffers first so we don't try to map them in the backend.
	if (mSize == 0) {
	return {};
	}

	// Mappable buffers don't use a staging buffer and are just as if mapped through MapAsync.
	if (IsCPUWritableAtCreation()) {
	DAWN_TRY(MapAtCreationImpl());
	} else {
	// If any of these fail, the buffer will be deleted and replaced with an
	// error buffer.
	// TODO(crbug.com/dawn/828): Suballocate and reuse memory from a larger staging buffer
	// so we don't create many small buffers.
	DAWN_TRY_ASSIGN(mStagingBuffer, GetDevice()->CreateStagingBuffer(GetSize()));
	}

	return {};
	}

	MaybeError BufferBase::ValidateCanUseOnQueueNow() const {
	ASSERT(!IsError());

	switch (mState) {
	case BufferState::Destroyed:
	return DAWN_VALIDATION_ERROR("Destroyed buffer used in a submit");
	case BufferState::Mapped:
	case BufferState::MappedAtCreation:
	return DAWN_VALIDATION_ERROR("Buffer used in a submit while mapped");
	case BufferState::Unmapped:
	return {};
	}
	}

	void BufferBase::CallMapCallback(MapRequestID mapID, WGPUBufferMapAsyncStatus status) {
	ASSERT(!IsError());
	if (mMapCallback != nullptr && mapID == mLastMapID) {
	// Tag the callback as fired before firing it, otherwise it could fire a second time if
	// for example buffer.Unmap() is called inside the application-provided callback.
	WGPUBufferMapCallback callback = mMapCallback;
	mMapCallback = nullptr;

	if (GetDevice()->IsLost()) {
	callback(WGPUBufferMapAsyncStatus_DeviceLost, mMapUserdata);
	} else {
	callback(status, mMapUserdata);
	}
	}
	}

	void BufferBase::APIMapAsync(wgpu::MapMode mode,
	size_t offset,
	size_t size,
	WGPUBufferMapCallback callback,
	void* userdata) {
	// Handle the defaulting of size required by WebGPU, even if in webgpu_cpp.h it is not
	// possible to default the function argument (because there is the callback later in the
	// argument list)
	if (size == 0 && offset < mSize) {
	size = mSize - offset;
	}

	WGPUBufferMapAsyncStatus status;
	if (GetDevice()->ConsumedError(ValidateMapAsync(mode, offset, size, &status))) {
	if (callback) {
	callback(status, userdata);
	}
	return;
	}
	ASSERT(!IsError());

	mLastMapID++;
	mMapMode = mode;
	mMapOffset = offset;
	mMapSize = size;
	mMapCallback = callback;
	mMapUserdata = userdata;
	mState = BufferState::Mapped;

	if (GetDevice()->ConsumedError(MapAsyncImpl(mode, offset, size))) {
	CallMapCallback(mLastMapID, WGPUBufferMapAsyncStatus_DeviceLost);
	return;
	}
	std::unique_ptr<MapRequestTask> request =
	std::make_unique<MapRequestTask>(this, mLastMapID);
	GetDevice()->GetQueue()->TrackTask(std::move(request),
	GetDevice()->GetPendingCommandSerial());
	}

	void* BufferBase::APIGetMappedRange(size_t offset, size_t size) {
	return GetMappedRange(offset, size, true);
	}

	const void* BufferBase::APIGetConstMappedRange(size_t offset, size_t size) {
	return GetMappedRange(offset, size, false);
	}

	void* BufferBase::GetMappedRange(size_t offset, size_t size, bool writable) {
	if (!CanGetMappedRange(writable, offset, size)) {
	return nullptr;
	}

	if (mStagingBuffer != nullptr) {
	return static_cast<uint8_t*>(mStagingBuffer->GetMappedPointer()) + offset;
	}
	if (mSize == 0) {
	return reinterpret_cast<uint8_t*>(intptr_t(0xCAFED00D));
	}
	uint8_t* start = static_cast<uint8_t*>(GetMappedPointerImpl());
	return start == nullptr ? nullptr : start + offset;
	}

	void BufferBase::APIDestroy() {
	if (IsError()) {
	// It is an error to call Destroy() on an ErrorBuffer, but we still need to reclaim the
	// fake mapped staging data.
	static_cast<ErrorBuffer*>(this)->ClearMappedData();
	mState = BufferState::Destroyed;
	}
	if (GetDevice()->ConsumedError(ValidateDestroy())) {
	return;
	}
	ASSERT(!IsError());

	if (mState == BufferState::Mapped) {
	UnmapInternal(WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
	} else if (mState == BufferState::MappedAtCreation) {
	if (mStagingBuffer != nullptr) {
	mStagingBuffer.reset();
	} else if (mSize != 0) {
	ASSERT(IsCPUWritableAtCreation());
	UnmapInternal(WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
	}
	}

	DestroyInternal();
	}

	MaybeError BufferBase::CopyFromStagingBuffer() {
	ASSERT(mStagingBuffer);
	if (GetSize() == 0) {
	return {};
	}

	DAWN_TRY(GetDevice()->CopyFromStagingToBuffer(mStagingBuffer.get(), 0, this, 0, GetSize()));

	DynamicUploader* uploader = GetDevice()->GetDynamicUploader();
	uploader->ReleaseStagingBuffer(std::move(mStagingBuffer));

	return {};
	}

	void BufferBase::APIUnmap() {
	Unmap();
	}

	void BufferBase::Unmap() {
	UnmapInternal(WGPUBufferMapAsyncStatus_UnmappedBeforeCallback);
	}

	void BufferBase::UnmapInternal(WGPUBufferMapAsyncStatus callbackStatus) {
	if (IsError()) {
	// It is an error to call Unmap() on an ErrorBuffer, but we still need to reclaim the
	// fake mapped staging data.
	static_cast<ErrorBuffer*>(this)->ClearMappedData();
	mState = BufferState::Unmapped;
	}
	if (GetDevice()->ConsumedError(ValidateUnmap())) {
	return;
	}
	ASSERT(!IsError());

	if (mState == BufferState::Mapped) {
	// A map request can only be called once, so this will fire only if the request wasn't
	// completed before the Unmap.
	// Callbacks are not fired if there is no callback registered, so this is correct for
	// mappedAtCreation = true.
	CallMapCallback(mLastMapID, callbackStatus);
	UnmapImpl();

	mMapCallback = nullptr;
	mMapUserdata = 0;

	} else if (mState == BufferState::MappedAtCreation) {
	if (mStagingBuffer != nullptr) {
	GetDevice()->ConsumedError(CopyFromStagingBuffer());
	} else if (mSize != 0) {
	ASSERT(IsCPUWritableAtCreation());
	UnmapImpl();
	}
	}

	mState = BufferState::Unmapped;
	}

	MaybeError BufferBase::ValidateMap(wgpu::BufferUsage requiredUsage,
	WGPUBufferMapAsyncStatus* status) const {
	*status = WGPUBufferMapAsyncStatus_DeviceLost;
	DAWN_TRY(GetDevice()->ValidateIsAlive());

	*status = WGPUBufferMapAsyncStatus_Error;
	DAWN_TRY(GetDevice()->ValidateObject(this));

	switch (mState) {
	case BufferState::Mapped:
	case BufferState::MappedAtCreation:
	return DAWN_VALIDATION_ERROR("Buffer is already mapped");
	case BufferState::Destroyed:
	return DAWN_VALIDATION_ERROR("Buffer is destroyed");
	case BufferState::Unmapped:
	break;
	}

	if (!(mUsage & requiredUsage)) {
	return DAWN_VALIDATION_ERROR("Buffer needs the correct map usage bit");
	}

	*status = WGPUBufferMapAsyncStatus_Success;
	return {};
	}

	MaybeError BufferBase::ValidateMapAsync(wgpu::MapMode mode,
	size_t offset,
	size_t size,
	WGPUBufferMapAsyncStatus* status) const {
	*status = WGPUBufferMapAsyncStatus_DeviceLost;
	DAWN_TRY(GetDevice()->ValidateIsAlive());

	*status = WGPUBufferMapAsyncStatus_Error;
	DAWN_TRY(GetDevice()->ValidateObject(this));

	if (offset % 8 != 0) {
	return DAWN_VALIDATION_ERROR("offset must be a multiple of 8");
	}

	if (size % 4 != 0) {
	return DAWN_VALIDATION_ERROR("size must be a multiple of 4");
	}

	if (uint64_t(offset) > mSize \|\| uint64_t(size) > mSize - uint64_t(offset)) {
	return DAWN_VALIDATION_ERROR("size + offset must fit in the buffer");
	}

	switch (mState) {
	case BufferState::Mapped:
	case BufferState::MappedAtCreation:
	return DAWN_VALIDATION_ERROR("Buffer is already mapped");
	case BufferState::Destroyed:
	return DAWN_VALIDATION_ERROR("Buffer is destroyed");
	case BufferState::Unmapped:
	break;
	}

	bool isReadMode = mode & wgpu::MapMode::Read;
	bool isWriteMode = mode & wgpu::MapMode::Write;
	if (!(isReadMode ^ isWriteMode)) {
	return DAWN_VALIDATION_ERROR("Exactly one of Read or Write mode must be set");
	}

	if (mode & wgpu::MapMode::Read) {
	if (!(mUsage & wgpu::BufferUsage::MapRead)) {
	return DAWN_VALIDATION_ERROR("The buffer must have the MapRead usage");
	}
	} else {
	ASSERT(mode & wgpu::MapMode::Write);

	if (!(mUsage & wgpu::BufferUsage::MapWrite)) {
	return DAWN_VALIDATION_ERROR("The buffer must have the MapWrite usage");
	}
	}

	*status = WGPUBufferMapAsyncStatus_Success;
	return {};
	}

	bool BufferBase::CanGetMappedRange(bool writable, size_t offset, size_t size) const {
	if (offset % 8 != 0 \|\| size % 4 != 0) {
	return false;
	}

	if (size > mMapSize \|\| offset < mMapOffset) {
	return false;
	}

	size_t offsetInMappedRange = offset - mMapOffset;
	if (offsetInMappedRange > mMapSize - size) {
	return false;
	}

	// Note that:
	//
	// - We don't check that the device is alive because the application can ask for the
	// mapped pointer before it knows, and even Dawn knows, that the device was lost, and
	// still needs to work properly.
	// - We don't check that the object is alive because we need to return mapped pointers
	// for error buffers too.

	switch (mState) {
	// Writeable Buffer::GetMappedRange is always allowed when mapped at creation.
	case BufferState::MappedAtCreation:
	return true;

	case BufferState::Mapped:
	ASSERT(bool(mMapMode & wgpu::MapMode::Read) ^
	bool(mMapMode & wgpu::MapMode::Write));
	return !writable \|\| (mMapMode & wgpu::MapMode::Write);

	case BufferState::Unmapped:
	case BufferState::Destroyed:
	return false;
	}
	}

	MaybeError BufferBase::ValidateUnmap() const {
	DAWN_TRY(GetDevice()->ValidateIsAlive());
	DAWN_TRY(GetDevice()->ValidateObject(this));

	switch (mState) {
	case BufferState::Mapped:
	case BufferState::MappedAtCreation:
	// A buffer may be in the Mapped state if it was created with mappedAtCreation
	// even if it did not have a mappable usage.
	return {};
	case BufferState::Unmapped:
	return DAWN_VALIDATION_ERROR("Buffer is unmapped");
	case BufferState::Destroyed:
	return DAWN_VALIDATION_ERROR("Buffer is destroyed");
	}
	}

	MaybeError BufferBase::ValidateDestroy() const {
	DAWN_TRY(GetDevice()->ValidateObject(this));
	return {};
	}

	void BufferBase::DestroyInternal() {
	if (mState != BufferState::Destroyed) {
	DestroyImpl();
	}
	mState = BufferState::Destroyed;
	}

	void BufferBase::OnMapRequestCompleted(MapRequestID mapID, WGPUBufferMapAsyncStatus status) {
	CallMapCallback(mapID, status);
	}

	bool BufferBase::IsDataInitialized() const {
	return mIsDataInitialized;
	}

	void BufferBase::SetIsDataInitialized() {
	mIsDataInitialized = true;
	}

	bool BufferBase::IsFullBufferRange(uint64_t offset, uint64_t size) const {
	return offset == 0 && size == GetSize();
	}
	} // namespace dawn_native