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/Assert.h"
 #include "dawn_native/Device.h"
 #include "dawn_native/DynamicUploader.h"
 #include "dawn_native/ValidationUtils_autogen.h"

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

 namespace dawn_native {

     namespace {

         class ErrorBuffer : public BufferBase {
           public:
             ErrorBuffer(DeviceBase* device) : BufferBase(device, ObjectBase::kError) {
             }

             static ErrorBuffer* MakeMapped(DeviceBase* device,
                                            uint64_t size,
                                            uint8_t** mappedPointer) {
                 ASSERT(mappedPointer != nullptr);

                 ErrorBuffer* buffer = new ErrorBuffer(device);
                 buffer->mFakeMappedData =
                     std::unique_ptr<uint8_t[]>(new (std::nothrow) uint8_t[size]);
                 *mappedPointer = buffer->mFakeMappedData.get();

                 return buffer;
             }

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

           private:
             bool IsMapWritable() const override {
                 UNREACHABLE();
                 return false;
             }

             MaybeError MapAtCreationImpl(uint8_t** mappedPointer) override {
                 UNREACHABLE();
                 return {};
             }

             MaybeError SetSubDataImpl(uint32_t start, uint32_t count, const void* data) override {
                 UNREACHABLE();
                 return {};
             }
             MaybeError MapReadAsyncImpl(uint32_t serial) override {
                 UNREACHABLE();
                 return {};
             }
             MaybeError MapWriteAsyncImpl(uint32_t serial) override {
                 UNREACHABLE();
                 return {};
             }
             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");
         }

         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
         // PassResourceUsageTracker::ValidateUsages will make sure we don't use both at the same
         // time.
         if (mUsage & wgpu::BufferUsage::Storage) {
             mUsage |= kReadOnlyStorage;
         }
     }

     BufferBase::BufferBase(DeviceBase* device, ObjectBase::ErrorTag tag)
         : ObjectBase(device, tag), mState(BufferState::Unmapped) {
     }

     BufferBase::~BufferBase() {
         if (mState == BufferState::Mapped) {
             ASSERT(!IsError());
             CallMapReadCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
             CallMapWriteCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
         }
     }

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

     // static
     BufferBase* BufferBase::MakeErrorMapped(DeviceBase* device,
                                             uint64_t size,
                                             uint8_t** mappedPointer) {
         return ErrorBuffer::MakeMapped(device, size, mappedPointer);
     }


     MaybeError BufferBase::MapAtCreation(uint8_t** mappedPointer) {
         ASSERT(!IsError());
         ASSERT(mappedPointer != nullptr);

         mState = BufferState::Mapped;

         if (IsMapWritable()) {
             DAWN_TRY(MapAtCreationImpl(mappedPointer));
             ASSERT(*mappedPointer != nullptr);
             return {};
         }

         // If any of these fail, the buffer will be deleted and replaced with an
         // error buffer.
         // TODO(enga): Suballocate and reuse memory from a larger staging buffer so we don't create
         // many small buffers.
         DAWN_TRY_ASSIGN(mStagingBuffer, GetDevice()->CreateStagingBuffer(GetSize()));

         ASSERT(mStagingBuffer->GetMappedPointer() != nullptr);
         *mappedPointer = reinterpret_cast<uint8_t*>(mStagingBuffer->GetMappedPointer());

         return {};
     }

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

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

     void BufferBase::CallMapReadCallback(uint32_t serial,
                                          WGPUBufferMapAsyncStatus status,
                                          const void* pointer,
                                          uint32_t dataLength) {
         ASSERT(!IsError());
         if (mMapReadCallback != nullptr && serial == mMapSerial) {
             ASSERT(mMapWriteCallback == nullptr);
             // 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.
             WGPUBufferMapReadCallback callback = mMapReadCallback;
             mMapReadCallback = nullptr;
             callback(status, pointer, dataLength, mMapUserdata);
         }
     }

     void BufferBase::CallMapWriteCallback(uint32_t serial,
                                           WGPUBufferMapAsyncStatus status,
                                           void* pointer,
                                           uint32_t dataLength) {
         ASSERT(!IsError());
         if (mMapWriteCallback != nullptr && serial == mMapSerial) {
             ASSERT(mMapReadCallback == nullptr);
             // 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.
             WGPUBufferMapWriteCallback callback = mMapWriteCallback;
             mMapWriteCallback = nullptr;
             callback(status, pointer, dataLength, mMapUserdata);
         }
     }

     void BufferBase::SetSubData(uint32_t start, uint32_t count, const void* data) {
         if (GetDevice()->ConsumedError(ValidateSetSubData(start, count))) {
             return;
         }
         ASSERT(!IsError());

         if (GetDevice()->ConsumedError(SetSubDataImpl(start, count, data))) {
             return;
         }
     }

     void BufferBase::MapReadAsync(WGPUBufferMapReadCallback callback, void* userdata) {
         if (GetDevice()->ConsumedError(ValidateMap(wgpu::BufferUsage::MapRead))) {
             callback(WGPUBufferMapAsyncStatus_Error, nullptr, 0, userdata);
             return;
         }
         ASSERT(!IsError());

         ASSERT(mMapWriteCallback == nullptr);

         // TODO(cwallez@chromium.org): what to do on wraparound? Could cause crashes.
         mMapSerial++;
         mMapReadCallback = callback;
         mMapUserdata = userdata;
         mState = BufferState::Mapped;

         if (GetDevice()->ConsumedError(MapReadAsyncImpl(mMapSerial))) {
             return;
         }
     }

     MaybeError BufferBase::SetSubDataImpl(uint32_t start, uint32_t count, const void* data) {
         DynamicUploader* uploader = GetDevice()->GetDynamicUploader();

         UploadHandle uploadHandle;
         DAWN_TRY_ASSIGN(uploadHandle,
                         uploader->Allocate(count, GetDevice()->GetPendingCommandSerial()));
         ASSERT(uploadHandle.mappedBuffer != nullptr);

         memcpy(uploadHandle.mappedBuffer, data, count);

         DAWN_TRY(GetDevice()->CopyFromStagingToBuffer(
             uploadHandle.stagingBuffer, uploadHandle.startOffset, this, start, count));

         return {};
     }

     void BufferBase::MapWriteAsync(WGPUBufferMapWriteCallback callback, void* userdata) {
         if (GetDevice()->ConsumedError(ValidateMap(wgpu::BufferUsage::MapWrite))) {
             callback(WGPUBufferMapAsyncStatus_Error, nullptr, 0, userdata);
             return;
         }
         ASSERT(!IsError());

         ASSERT(mMapReadCallback == nullptr);

         // TODO(cwallez@chromium.org): what to do on wraparound? Could cause crashes.
         mMapSerial++;
         mMapWriteCallback = callback;
         mMapUserdata = userdata;
         mState = BufferState::Mapped;

         if (GetDevice()->ConsumedError(MapWriteAsyncImpl(mMapSerial))) {
             return;
         }
     }

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

         if (mState == BufferState::Mapped) {
             if (mStagingBuffer == nullptr) {
                 Unmap();
             }
             mStagingBuffer.reset();
         }
         DestroyInternal();
     }

     MaybeError BufferBase::CopyFromStagingBuffer() {
         ASSERT(mStagingBuffer);
         DAWN_TRY(GetDevice()->CopyFromStagingToBuffer(mStagingBuffer.get(), 0, this, 0, GetSize()));

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

         return {};
     }

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

         if (mStagingBuffer != nullptr) {
             GetDevice()->ConsumedError(CopyFromStagingBuffer());
         } else {
             // 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
             // CreateBufferMapped.
             CallMapReadCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
             CallMapWriteCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
             UnmapImpl();
         }
         mState = BufferState::Unmapped;
         mMapReadCallback = nullptr;
         mMapWriteCallback = nullptr;
         mMapUserdata = 0;
     }

     MaybeError BufferBase::ValidateSetSubData(uint32_t start, uint32_t count) const {
         DAWN_TRY(GetDevice()->ValidateObject(this));

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

         if (count > GetSize()) {
             return DAWN_VALIDATION_ERROR("Buffer subdata with too much data");
         }

         // Metal requests buffer to buffer copy size must be a multiple of 4 bytes on macOS
         if (count % 4 != 0) {
             return DAWN_VALIDATION_ERROR("Buffer subdata size must be a multiple of 4 bytes");
         }

         // Metal requests offset of buffer to buffer copy must be a multiple of 4 bytes on macOS
         if (start % 4 != 0) {
             return DAWN_VALIDATION_ERROR("Start position must be a multiple of 4 bytes");
         }

         // Note that no overflow can happen because we already checked for GetSize() >= count
         if (start > GetSize() - count) {
             return DAWN_VALIDATION_ERROR("Buffer subdata out of range");
         }

         if (!(mUsage & wgpu::BufferUsage::CopyDst)) {
             return DAWN_VALIDATION_ERROR("Buffer needs the CopyDst usage bit");
         }

         return {};
     }

     MaybeError BufferBase::ValidateMap(wgpu::BufferUsage requiredUsage) const {
         DAWN_TRY(GetDevice()->ValidateObject(this));

         switch (mState) {
             case BufferState::Mapped:
                 return DAWN_VALIDATION_ERROR("Buffer 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");
         }

         return {};
     }

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

         switch (mState) {
             case BufferState::Mapped:
                 // A buffer may be in the Mapped state if it was created with CreateBufferMapped
                 // even if it did not have a mappable usage.
                 return {};
             case BufferState::Unmapped:
                 if ((mUsage & (wgpu::BufferUsage::MapRead | wgpu::BufferUsage::MapWrite)) == 0) {
                     return DAWN_VALIDATION_ERROR("Buffer does not have map usage");
                 }
                 return {};
             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;
     }

 }  // 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/Assert.h"
	#include "dawn_native/Device.h"
	#include "dawn_native/DynamicUploader.h"
	#include "dawn_native/ValidationUtils_autogen.h"

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

	namespace dawn_native {

	namespace {

	class ErrorBuffer : public BufferBase {
	public:
	ErrorBuffer(DeviceBase* device) : BufferBase(device, ObjectBase::kError) {
	}

	static ErrorBuffer* MakeMapped(DeviceBase* device,
	uint64_t size,
	uint8_t** mappedPointer) {
	ASSERT(mappedPointer != nullptr);

	ErrorBuffer* buffer = new ErrorBuffer(device);
	buffer->mFakeMappedData =
	std::unique_ptr<uint8_t[]>(new (std::nothrow) uint8_t[size]);
	*mappedPointer = buffer->mFakeMappedData.get();

	return buffer;
	}

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

	private:
	bool IsMapWritable() const override {
	UNREACHABLE();
	return false;
	}

	MaybeError MapAtCreationImpl(uint8_t** mappedPointer) override {
	UNREACHABLE();
	return {};
	}

	MaybeError SetSubDataImpl(uint32_t start, uint32_t count, const void* data) override {
	UNREACHABLE();
	return {};
	}
	MaybeError MapReadAsyncImpl(uint32_t serial) override {
	UNREACHABLE();
	return {};
	}
	MaybeError MapWriteAsyncImpl(uint32_t serial) override {
	UNREACHABLE();
	return {};
	}
	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");
	}

	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
	// PassResourceUsageTracker::ValidateUsages will make sure we don't use both at the same
	// time.
	if (mUsage & wgpu::BufferUsage::Storage) {
	mUsage \|= kReadOnlyStorage;
	}
	}

	BufferBase::BufferBase(DeviceBase* device, ObjectBase::ErrorTag tag)
	: ObjectBase(device, tag), mState(BufferState::Unmapped) {
	}

	BufferBase::~BufferBase() {
	if (mState == BufferState::Mapped) {
	ASSERT(!IsError());
	CallMapReadCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
	CallMapWriteCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
	}
	}

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

	// static
	BufferBase* BufferBase::MakeErrorMapped(DeviceBase* device,
	uint64_t size,
	uint8_t** mappedPointer) {
	return ErrorBuffer::MakeMapped(device, size, mappedPointer);
	}


	MaybeError BufferBase::MapAtCreation(uint8_t** mappedPointer) {
	ASSERT(!IsError());
	ASSERT(mappedPointer != nullptr);

	mState = BufferState::Mapped;

	if (IsMapWritable()) {
	DAWN_TRY(MapAtCreationImpl(mappedPointer));
	ASSERT(*mappedPointer != nullptr);
	return {};
	}

	// If any of these fail, the buffer will be deleted and replaced with an
	// error buffer.
	// TODO(enga): Suballocate and reuse memory from a larger staging buffer so we don't create
	// many small buffers.
	DAWN_TRY_ASSIGN(mStagingBuffer, GetDevice()->CreateStagingBuffer(GetSize()));

	ASSERT(mStagingBuffer->GetMappedPointer() != nullptr);
	mappedPointer = reinterpret_cast<uint8_t>(mStagingBuffer->GetMappedPointer());

	return {};
	}

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

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

	void BufferBase::CallMapReadCallback(uint32_t serial,
	WGPUBufferMapAsyncStatus status,
	const void* pointer,
	uint32_t dataLength) {
	ASSERT(!IsError());
	if (mMapReadCallback != nullptr && serial == mMapSerial) {
	ASSERT(mMapWriteCallback == nullptr);
	// 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.
	WGPUBufferMapReadCallback callback = mMapReadCallback;
	mMapReadCallback = nullptr;
	callback(status, pointer, dataLength, mMapUserdata);
	}
	}

	void BufferBase::CallMapWriteCallback(uint32_t serial,
	WGPUBufferMapAsyncStatus status,
	void* pointer,
	uint32_t dataLength) {
	ASSERT(!IsError());
	if (mMapWriteCallback != nullptr && serial == mMapSerial) {
	ASSERT(mMapReadCallback == nullptr);
	// 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.
	WGPUBufferMapWriteCallback callback = mMapWriteCallback;
	mMapWriteCallback = nullptr;
	callback(status, pointer, dataLength, mMapUserdata);
	}
	}

	void BufferBase::SetSubData(uint32_t start, uint32_t count, const void* data) {
	if (GetDevice()->ConsumedError(ValidateSetSubData(start, count))) {
	return;
	}
	ASSERT(!IsError());

	if (GetDevice()->ConsumedError(SetSubDataImpl(start, count, data))) {
	return;
	}
	}

	void BufferBase::MapReadAsync(WGPUBufferMapReadCallback callback, void* userdata) {
	if (GetDevice()->ConsumedError(ValidateMap(wgpu::BufferUsage::MapRead))) {
	callback(WGPUBufferMapAsyncStatus_Error, nullptr, 0, userdata);
	return;
	}
	ASSERT(!IsError());

	ASSERT(mMapWriteCallback == nullptr);

	// TODO(cwallez@chromium.org): what to do on wraparound? Could cause crashes.
	mMapSerial++;
	mMapReadCallback = callback;
	mMapUserdata = userdata;
	mState = BufferState::Mapped;

	if (GetDevice()->ConsumedError(MapReadAsyncImpl(mMapSerial))) {
	return;
	}
	}

	MaybeError BufferBase::SetSubDataImpl(uint32_t start, uint32_t count, const void* data) {
	DynamicUploader* uploader = GetDevice()->GetDynamicUploader();

	UploadHandle uploadHandle;
	DAWN_TRY_ASSIGN(uploadHandle,
	uploader->Allocate(count, GetDevice()->GetPendingCommandSerial()));
	ASSERT(uploadHandle.mappedBuffer != nullptr);

	memcpy(uploadHandle.mappedBuffer, data, count);

	DAWN_TRY(GetDevice()->CopyFromStagingToBuffer(
	uploadHandle.stagingBuffer, uploadHandle.startOffset, this, start, count));

	return {};
	}

	void BufferBase::MapWriteAsync(WGPUBufferMapWriteCallback callback, void* userdata) {
	if (GetDevice()->ConsumedError(ValidateMap(wgpu::BufferUsage::MapWrite))) {
	callback(WGPUBufferMapAsyncStatus_Error, nullptr, 0, userdata);
	return;
	}
	ASSERT(!IsError());

	ASSERT(mMapReadCallback == nullptr);

	// TODO(cwallez@chromium.org): what to do on wraparound? Could cause crashes.
	mMapSerial++;
	mMapWriteCallback = callback;
	mMapUserdata = userdata;
	mState = BufferState::Mapped;

	if (GetDevice()->ConsumedError(MapWriteAsyncImpl(mMapSerial))) {
	return;
	}
	}

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

	if (mState == BufferState::Mapped) {
	if (mStagingBuffer == nullptr) {
	Unmap();
	}
	mStagingBuffer.reset();
	}
	DestroyInternal();
	}

	MaybeError BufferBase::CopyFromStagingBuffer() {
	ASSERT(mStagingBuffer);
	DAWN_TRY(GetDevice()->CopyFromStagingToBuffer(mStagingBuffer.get(), 0, this, 0, GetSize()));

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

	return {};
	}

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

	if (mStagingBuffer != nullptr) {
	GetDevice()->ConsumedError(CopyFromStagingBuffer());
	} else {
	// 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
	// CreateBufferMapped.
	CallMapReadCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
	CallMapWriteCallback(mMapSerial, WGPUBufferMapAsyncStatus_Unknown, nullptr, 0u);
	UnmapImpl();
	}
	mState = BufferState::Unmapped;
	mMapReadCallback = nullptr;
	mMapWriteCallback = nullptr;
	mMapUserdata = 0;
	}

	MaybeError BufferBase::ValidateSetSubData(uint32_t start, uint32_t count) const {
	DAWN_TRY(GetDevice()->ValidateObject(this));

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

	if (count > GetSize()) {
	return DAWN_VALIDATION_ERROR("Buffer subdata with too much data");
	}

	// Metal requests buffer to buffer copy size must be a multiple of 4 bytes on macOS
	if (count % 4 != 0) {
	return DAWN_VALIDATION_ERROR("Buffer subdata size must be a multiple of 4 bytes");
	}

	// Metal requests offset of buffer to buffer copy must be a multiple of 4 bytes on macOS
	if (start % 4 != 0) {
	return DAWN_VALIDATION_ERROR("Start position must be a multiple of 4 bytes");
	}

	// Note that no overflow can happen because we already checked for GetSize() >= count
	if (start > GetSize() - count) {
	return DAWN_VALIDATION_ERROR("Buffer subdata out of range");
	}

	if (!(mUsage & wgpu::BufferUsage::CopyDst)) {
	return DAWN_VALIDATION_ERROR("Buffer needs the CopyDst usage bit");
	}

	return {};
	}

	MaybeError BufferBase::ValidateMap(wgpu::BufferUsage requiredUsage) const {
	DAWN_TRY(GetDevice()->ValidateObject(this));

	switch (mState) {
	case BufferState::Mapped:
	return DAWN_VALIDATION_ERROR("Buffer 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");
	}

	return {};
	}

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

	switch (mState) {
	case BufferState::Mapped:
	// A buffer may be in the Mapped state if it was created with CreateBufferMapped
	// even if it did not have a mappable usage.
	return {};
	case BufferState::Unmapped:
	if ((mUsage & (wgpu::BufferUsage::MapRead \| wgpu::BufferUsage::MapWrite)) == 0) {
	return DAWN_VALIDATION_ERROR("Buffer does not have map usage");
	}
	return {};
	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;
	}

	} // namespace dawn_native