src/dawn_wire/client/Buffer.cpp - dawn - Git at Google

 // Copyright 2019 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_wire/client/Buffer.h"

 #include "dawn_wire/BufferConsumer_impl.h"
 #include "dawn_wire/WireCmd_autogen.h"
 #include "dawn_wire/client/Client.h"
 #include "dawn_wire/client/Device.h"

 namespace dawn_wire { namespace client {

     // static
     WGPUBuffer Buffer::Create(Device* device, const WGPUBufferDescriptor* descriptor) {
         Client* wireClient = device->client;

         bool mappable =
             (descriptor->usage & (WGPUBufferUsage_MapRead | WGPUBufferUsage_MapWrite)) != 0 ||
             descriptor->mappedAtCreation;
         if (mappable && descriptor->size >= std::numeric_limits<size_t>::max()) {
             device->InjectError(WGPUErrorType_OutOfMemory, "Buffer is too large for map usage");
             return device->CreateErrorBuffer();
         }

         std::unique_ptr<MemoryTransferService::WriteHandle> writeHandle = nullptr;
         void* writeData = nullptr;
         size_t writeHandleCreateInfoLength = 0;

         // If the buffer is mapped at creation, create a write handle that will represent the
         // mapping of the whole buffer.
         if (descriptor->mappedAtCreation) {
             // Create the handle.
             writeHandle.reset(
                 wireClient->GetMemoryTransferService()->CreateWriteHandle(descriptor->size));
             if (writeHandle == nullptr) {
                 device->InjectError(WGPUErrorType_OutOfMemory, "Buffer mapping allocation failed");
                 return device->CreateErrorBuffer();
             }

             // Open the handle, it may fail by returning a nullptr in writeData.
             size_t writeDataLength = 0;
             std::tie(writeData, writeDataLength) = writeHandle->Open();
             if (writeData == nullptr) {
                 device->InjectError(WGPUErrorType_OutOfMemory, "Buffer mapping allocation failed");
                 return device->CreateErrorBuffer();
             }
             ASSERT(writeDataLength == descriptor->size);

             // Get the serialization size of the write handle.
             writeHandleCreateInfoLength = writeHandle->SerializeCreateSize();
         }

         // Create the buffer and send the creation command.
         auto* bufferObjectAndSerial = wireClient->BufferAllocator().New(wireClient);
         Buffer* buffer = bufferObjectAndSerial->object.get();
         buffer->mDevice = device;
         buffer->mDeviceIsAlive = device->GetAliveWeakPtr();
         buffer->mSize = descriptor->size;

         DeviceCreateBufferCmd cmd;
         cmd.deviceId = device->id;
         cmd.descriptor = descriptor;
         cmd.result = ObjectHandle{buffer->id, bufferObjectAndSerial->generation};
         cmd.handleCreateInfoLength = writeHandleCreateInfoLength;
         cmd.handleCreateInfo = nullptr;

         wireClient->SerializeCommand(
             cmd, writeHandleCreateInfoLength, [&](SerializeBuffer* serializeBuffer) {
                 if (descriptor->mappedAtCreation) {
                     char* writeHandleBuffer;
                     WIRE_TRY(
                         serializeBuffer->NextN(writeHandleCreateInfoLength, &writeHandleBuffer));
                     // Serialize the WriteHandle into the space after the command.
                     writeHandle->SerializeCreate(writeHandleBuffer);

                     // Set the buffer state for the mapping at creation. The buffer now owns the
                     // write handle..
                     buffer->mWriteHandle = std::move(writeHandle);
                     buffer->mMappedData = writeData;
                     buffer->mMapOffset = 0;
                     buffer->mMapSize = buffer->mSize;
                 }
                 return WireResult::Success;
             });
         return ToAPI(buffer);
     }

     // static
     WGPUBuffer Buffer::CreateError(Device* device) {
         auto* allocation = device->client->BufferAllocator().New(device->client);
         allocation->object->mDevice = device;
         allocation->object->mDeviceIsAlive = device->GetAliveWeakPtr();

         DeviceCreateErrorBufferCmd cmd;
         cmd.self = ToAPI(device);
         cmd.result = ObjectHandle{allocation->object->id, allocation->generation};
         device->client->SerializeCommand(cmd);

         return ToAPI(allocation->object.get());
     }

     Buffer::~Buffer() {
         // Callbacks need to be fired in all cases, as they can handle freeing resources
         // so we call them with "DestroyedBeforeCallback" status.
         for (auto& it : mRequests) {
             if (it.second.callback) {
                 it.second.callback(WGPUBufferMapAsyncStatus_DestroyedBeforeCallback, it.second.userdata);
             }
         }
         mRequests.clear();

         FreeMappedData(true);
     }

     void Buffer::CancelCallbacksForDisconnect() {
         for (auto& it : mRequests) {
             if (it.second.callback) {
                 it.second.callback(WGPUBufferMapAsyncStatus_DeviceLost, it.second.userdata);
             }
         }
         mRequests.clear();
     }

     void Buffer::MapAsync(WGPUMapModeFlags mode,
                           size_t offset,
                           size_t size,
                           WGPUBufferMapCallback callback,
                           void* userdata) {
         if (client->IsDisconnected()) {
             return callback(WGPUBufferMapAsyncStatus_DeviceLost, userdata);
         }

         // Handle the defaulting of size required by WebGPU.
         if (size == 0 && offset < mSize) {
             size = mSize - offset;
         }

         bool isReadMode = mode & WGPUMapMode_Read;
         bool isWriteMode = mode & WGPUMapMode_Write;

         // Step 1. Do early validation of READ ^ WRITE because the server rejects mode = 0.
         if (!(isReadMode ^ isWriteMode)) {
             if (!mDeviceIsAlive.expired()) {
                 mDevice->InjectError(WGPUErrorType_Validation,
                                      "MapAsync mode must be exactly one of Read or Write");
             }
             if (callback != nullptr) {
                 callback(WGPUBufferMapAsyncStatus_Error, userdata);
             }
             return;
         }

         // Step 2. Create the request structure that will hold information while this mapping is
         // in flight.
         uint32_t serial = mRequestSerial++;
         ASSERT(mRequests.find(serial) == mRequests.end());

         Buffer::MapRequestData request = {};
         request.callback = callback;
         request.userdata = userdata;
         request.size = size;
         request.offset = offset;

         // Step 2a: Create the read / write handles for this request.
         if (isReadMode) {
             request.readHandle.reset(client->GetMemoryTransferService()->CreateReadHandle(size));
             if (request.readHandle == nullptr) {
                 if (!mDeviceIsAlive.expired()) {
                     mDevice->InjectError(WGPUErrorType_OutOfMemory,
                                          "Failed to create buffer mapping");
                 }
                 callback(WGPUBufferMapAsyncStatus_Error, userdata);
                 return;
             }
         } else {
             ASSERT(isWriteMode);
             request.writeHandle.reset(client->GetMemoryTransferService()->CreateWriteHandle(size));
             if (request.writeHandle == nullptr) {
                 if (!mDeviceIsAlive.expired()) {
                     mDevice->InjectError(WGPUErrorType_OutOfMemory,
                                          "Failed to create buffer mapping");
                 }
                 callback(WGPUBufferMapAsyncStatus_Error, userdata);
                 return;
             }
         }

         // Step 3. Serialize the command to send to the server.
         BufferMapAsyncCmd cmd;
         cmd.bufferId = this->id;
         cmd.requestSerial = serial;
         cmd.mode = mode;
         cmd.offset = offset;
         cmd.size = size;
         cmd.handleCreateInfo = nullptr;

         // Step 3a. Fill the handle create info in the command.
         if (isReadMode) {
             cmd.handleCreateInfoLength = request.readHandle->SerializeCreateSize();
             client->SerializeCommand(
                 cmd, cmd.handleCreateInfoLength, [&](SerializeBuffer* serializeBuffer) {
                     char* readHandleBuffer;
                     WIRE_TRY(serializeBuffer->NextN(cmd.handleCreateInfoLength, &readHandleBuffer));
                     request.readHandle->SerializeCreate(readHandleBuffer);
                     return WireResult::Success;
                 });
         } else {
             ASSERT(isWriteMode);
             cmd.handleCreateInfoLength = request.writeHandle->SerializeCreateSize();
             client->SerializeCommand(
                 cmd, cmd.handleCreateInfoLength, [&](SerializeBuffer* serializeBuffer) {
                     char* writeHandleBuffer;
                     WIRE_TRY(
                         serializeBuffer->NextN(cmd.handleCreateInfoLength, &writeHandleBuffer));
                     request.writeHandle->SerializeCreate(writeHandleBuffer);
                     return WireResult::Success;
                 });
         }

         // Step 4. Register this request so that we can retrieve it from its serial when the server
         // sends the callback.
         mRequests[serial] = std::move(request);
     }

     bool Buffer::OnMapAsyncCallback(uint32_t requestSerial,
                                     uint32_t status,
                                     uint64_t readInitialDataInfoLength,
                                     const uint8_t* readInitialDataInfo) {
         auto requestIt = mRequests.find(requestSerial);
         if (requestIt == mRequests.end()) {
             return false;
         }

         auto request = std::move(requestIt->second);
         // Delete the request before calling the callback otherwise the callback could be fired a
         // second time. If, for example, buffer.Unmap() is called inside the callback.
         mRequests.erase(requestIt);

         auto FailRequest = [&request]() -> bool {
             if (request.callback != nullptr) {
                 request.callback(WGPUBufferMapAsyncStatus_DeviceLost, request.userdata);
             }
             return false;
         };

         bool isRead = request.readHandle != nullptr;
         bool isWrite = request.writeHandle != nullptr;
         ASSERT(isRead != isWrite);

         // Take into account the client-side status of the request if the server says it is a success.
         if (status == WGPUBufferMapAsyncStatus_Success) {
             status = request.clientStatus;
         }

         size_t mappedDataLength = 0;
         const void* mappedData = nullptr;
         if (status == WGPUBufferMapAsyncStatus_Success) {
             if (mReadHandle || mWriteHandle) {
                 // Buffer is already mapped.
                 return FailRequest();
             }

             if (isRead) {
                 if (readInitialDataInfoLength > std::numeric_limits<size_t>::max()) {
                     // This is the size of data deserialized from the command stream, which must be
                     // CPU-addressable.
                     return FailRequest();
                 }

                 // The server serializes metadata to initialize the contents of the ReadHandle.
                 // Deserialize the message and return a pointer and size of the mapped data for
                 // reading.
                 if (!request.readHandle->DeserializeInitialData(
                         readInitialDataInfo, static_cast<size_t>(readInitialDataInfoLength),
                         &mappedData, &mappedDataLength)) {
                     // Deserialization shouldn't fail. This is a fatal error.
                     return FailRequest();
                 }
                 ASSERT(mappedData != nullptr);

             } else {
                 // Open the WriteHandle. This returns a pointer and size of mapped memory.
                 // On failure, |mappedData| may be null.
                 std::tie(mappedData, mappedDataLength) = request.writeHandle->Open();

                 if (mappedData == nullptr) {
                     return FailRequest();
                 }
             }

             // The MapAsync request was successful. The buffer now owns the Read/Write handles
             // until Unmap().
             mReadHandle = std::move(request.readHandle);
             mWriteHandle = std::move(request.writeHandle);
         }

         mMapOffset = request.offset;
         mMapSize = request.size;
         mMappedData = const_cast<void*>(mappedData);
         if (request.callback) {
             request.callback(static_cast<WGPUBufferMapAsyncStatus>(status), request.userdata);
         }

         return true;
     }

     void* Buffer::GetMappedRange(size_t offset, size_t size) {
         if (!IsMappedForWriting() || !CheckGetMappedRangeOffsetSize(offset, size)) {
             return nullptr;
         }
         return static_cast<uint8_t*>(mMappedData) + (offset - mMapOffset);
     }

     const void* Buffer::GetConstMappedRange(size_t offset, size_t size) {
         if (!(IsMappedForWriting() || IsMappedForReading()) ||
             !CheckGetMappedRangeOffsetSize(offset, size)) {
             return nullptr;
         }
         return static_cast<uint8_t*>(mMappedData) + (offset - mMapOffset);
     }

     void Buffer::Unmap() {
         // Invalidate the local pointer, and cancel all other in-flight requests that would
         // turn into errors anyway (you can't double map). This prevents race when the following
         // happens, where the application code would have unmapped a buffer but still receive a
         // callback:
         //   - Client -> Server: MapRequest1, Unmap, MapRequest2
         //   - Server -> Client: Result of MapRequest1
         //   - Unmap locally on the client
         //   - Server -> Client: Result of MapRequest2
         if (mWriteHandle) {
             // Writes need to be flushed before Unmap is sent. Unmap calls all associated
             // in-flight callbacks which may read the updated data.
             ASSERT(mReadHandle == nullptr);

             // Get the serialization size of metadata to flush writes.
             size_t writeFlushInfoLength = mWriteHandle->SerializeFlushSize();

             BufferUpdateMappedDataCmd cmd;
             cmd.bufferId = id;
             cmd.writeFlushInfoLength = writeFlushInfoLength;
             cmd.writeFlushInfo = nullptr;

             client->SerializeCommand(
                 cmd, writeFlushInfoLength, [&](SerializeBuffer* serializeBuffer) {
                     char* writeHandleBuffer;
                     WIRE_TRY(serializeBuffer->NextN(writeFlushInfoLength, &writeHandleBuffer));

                     // Serialize flush metadata into the space after the command.
                     // This closes the handle for writing.
                     mWriteHandle->SerializeFlush(writeHandleBuffer);
                     return WireResult::Success;
                 });
         }

         FreeMappedData(false);

         // Tag all mapping requests still in flight as unmapped before callback.
         for (auto& it : mRequests) {
             if (it.second.clientStatus == WGPUBufferMapAsyncStatus_Success) {
                 it.second.clientStatus = WGPUBufferMapAsyncStatus_UnmappedBeforeCallback;
             }
         }

         BufferUnmapCmd cmd;
         cmd.self = ToAPI(this);
         client->SerializeCommand(cmd);
     }

     void Buffer::Destroy() {
         // Remove the current mapping.
         FreeMappedData(true);

         // Tag all mapping requests still in flight as destroyed before callback.
         for (auto& it : mRequests) {
             if (it.second.clientStatus == WGPUBufferMapAsyncStatus_Success) {
                 it.second.clientStatus = WGPUBufferMapAsyncStatus_DestroyedBeforeCallback;
             }
         }

         BufferDestroyCmd cmd;
         cmd.self = ToAPI(this);
         client->SerializeCommand(cmd);
     }

     bool Buffer::IsMappedForReading() const {
         return mReadHandle != nullptr;
     }

     bool Buffer::IsMappedForWriting() const {
         return mWriteHandle != nullptr;
     }

     bool Buffer::CheckGetMappedRangeOffsetSize(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;
         return offsetInMappedRange <= mMapSize - size;
     }

     void Buffer::FreeMappedData(bool destruction) {
 #if defined(DAWN_ENABLE_ASSERTS)
         // When in "debug" mode, 0xCA-out the mapped data when we free it so that in we can detect
         // use-after-free of the mapped data. This is particularly useful for WebGPU test about the
         // interaction of mapping and GC.
         if (mMappedData && destruction) {
             memset(mMappedData, 0xCA, mMapSize);
         }
 #endif  // defined(DAWN_ENABLE_ASSERTS)

         mMapOffset = 0;
         mMapSize = 0;
         mWriteHandle = nullptr;
         mReadHandle = nullptr;
         mMappedData = nullptr;
     }

 }}  // namespace dawn_wire::client
	// Copyright 2019 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_wire/client/Buffer.h"

	#include "dawn_wire/BufferConsumer_impl.h"
	#include "dawn_wire/WireCmd_autogen.h"
	#include "dawn_wire/client/Client.h"
	#include "dawn_wire/client/Device.h"

	namespace dawn_wire { namespace client {

	// static
	WGPUBuffer Buffer::Create(Device* device, const WGPUBufferDescriptor* descriptor) {
	Client* wireClient = device->client;

	bool mappable =
	(descriptor->usage & (WGPUBufferUsage_MapRead \| WGPUBufferUsage_MapWrite)) != 0 \|\|
	descriptor->mappedAtCreation;
	if (mappable && descriptor->size >= std::numeric_limits<size_t>::max()) {
	device->InjectError(WGPUErrorType_OutOfMemory, "Buffer is too large for map usage");
	return device->CreateErrorBuffer();
	}

	std::unique_ptr<MemoryTransferService::WriteHandle> writeHandle = nullptr;
	void* writeData = nullptr;
	size_t writeHandleCreateInfoLength = 0;

	// If the buffer is mapped at creation, create a write handle that will represent the
	// mapping of the whole buffer.
	if (descriptor->mappedAtCreation) {
	// Create the handle.
	writeHandle.reset(
	wireClient->GetMemoryTransferService()->CreateWriteHandle(descriptor->size));
	if (writeHandle == nullptr) {
	device->InjectError(WGPUErrorType_OutOfMemory, "Buffer mapping allocation failed");
	return device->CreateErrorBuffer();
	}

	// Open the handle, it may fail by returning a nullptr in writeData.
	size_t writeDataLength = 0;
	std::tie(writeData, writeDataLength) = writeHandle->Open();
	if (writeData == nullptr) {
	device->InjectError(WGPUErrorType_OutOfMemory, "Buffer mapping allocation failed");
	return device->CreateErrorBuffer();
	}
	ASSERT(writeDataLength == descriptor->size);

	// Get the serialization size of the write handle.
	writeHandleCreateInfoLength = writeHandle->SerializeCreateSize();
	}

	// Create the buffer and send the creation command.
	auto* bufferObjectAndSerial = wireClient->BufferAllocator().New(wireClient);
	Buffer* buffer = bufferObjectAndSerial->object.get();
	buffer->mDevice = device;
	buffer->mDeviceIsAlive = device->GetAliveWeakPtr();
	buffer->mSize = descriptor->size;

	DeviceCreateBufferCmd cmd;
	cmd.deviceId = device->id;
	cmd.descriptor = descriptor;
	cmd.result = ObjectHandle{buffer->id, bufferObjectAndSerial->generation};
	cmd.handleCreateInfoLength = writeHandleCreateInfoLength;
	cmd.handleCreateInfo = nullptr;

	wireClient->SerializeCommand(
	cmd, writeHandleCreateInfoLength, [&](SerializeBuffer* serializeBuffer) {
	if (descriptor->mappedAtCreation) {
	char* writeHandleBuffer;
	WIRE_TRY(
	serializeBuffer->NextN(writeHandleCreateInfoLength, &writeHandleBuffer));
	// Serialize the WriteHandle into the space after the command.
	writeHandle->SerializeCreate(writeHandleBuffer);

	// Set the buffer state for the mapping at creation. The buffer now owns the
	// write handle..
	buffer->mWriteHandle = std::move(writeHandle);
	buffer->mMappedData = writeData;
	buffer->mMapOffset = 0;
	buffer->mMapSize = buffer->mSize;
	}
	return WireResult::Success;
	});
	return ToAPI(buffer);
	}

	// static
	WGPUBuffer Buffer::CreateError(Device* device) {
	auto* allocation = device->client->BufferAllocator().New(device->client);
	allocation->object->mDevice = device;
	allocation->object->mDeviceIsAlive = device->GetAliveWeakPtr();

	DeviceCreateErrorBufferCmd cmd;
	cmd.self = ToAPI(device);
	cmd.result = ObjectHandle{allocation->object->id, allocation->generation};
	device->client->SerializeCommand(cmd);

	return ToAPI(allocation->object.get());
	}

	Buffer::~Buffer() {
	// Callbacks need to be fired in all cases, as they can handle freeing resources
	// so we call them with "DestroyedBeforeCallback" status.
	for (auto& it : mRequests) {
	if (it.second.callback) {
	it.second.callback(WGPUBufferMapAsyncStatus_DestroyedBeforeCallback, it.second.userdata);
	}
	}
	mRequests.clear();

	FreeMappedData(true);
	}

	void Buffer::CancelCallbacksForDisconnect() {
	for (auto& it : mRequests) {
	if (it.second.callback) {
	it.second.callback(WGPUBufferMapAsyncStatus_DeviceLost, it.second.userdata);
	}
	}
	mRequests.clear();
	}

	void Buffer::MapAsync(WGPUMapModeFlags mode,
	size_t offset,
	size_t size,
	WGPUBufferMapCallback callback,
	void* userdata) {
	if (client->IsDisconnected()) {
	return callback(WGPUBufferMapAsyncStatus_DeviceLost, userdata);
	}

	// Handle the defaulting of size required by WebGPU.
	if (size == 0 && offset < mSize) {
	size = mSize - offset;
	}

	bool isReadMode = mode & WGPUMapMode_Read;
	bool isWriteMode = mode & WGPUMapMode_Write;

	// Step 1. Do early validation of READ ^ WRITE because the server rejects mode = 0.
	if (!(isReadMode ^ isWriteMode)) {
	if (!mDeviceIsAlive.expired()) {
	mDevice->InjectError(WGPUErrorType_Validation,
	"MapAsync mode must be exactly one of Read or Write");
	}
	if (callback != nullptr) {
	callback(WGPUBufferMapAsyncStatus_Error, userdata);
	}
	return;
	}

	// Step 2. Create the request structure that will hold information while this mapping is
	// in flight.
	uint32_t serial = mRequestSerial++;
	ASSERT(mRequests.find(serial) == mRequests.end());

	Buffer::MapRequestData request = {};
	request.callback = callback;
	request.userdata = userdata;
	request.size = size;
	request.offset = offset;

	// Step 2a: Create the read / write handles for this request.
	if (isReadMode) {
	request.readHandle.reset(client->GetMemoryTransferService()->CreateReadHandle(size));
	if (request.readHandle == nullptr) {
	if (!mDeviceIsAlive.expired()) {
	mDevice->InjectError(WGPUErrorType_OutOfMemory,
	"Failed to create buffer mapping");
	}
	callback(WGPUBufferMapAsyncStatus_Error, userdata);
	return;
	}
	} else {
	ASSERT(isWriteMode);
	request.writeHandle.reset(client->GetMemoryTransferService()->CreateWriteHandle(size));
	if (request.writeHandle == nullptr) {
	if (!mDeviceIsAlive.expired()) {
	mDevice->InjectError(WGPUErrorType_OutOfMemory,
	"Failed to create buffer mapping");
	}
	callback(WGPUBufferMapAsyncStatus_Error, userdata);
	return;
	}
	}

	// Step 3. Serialize the command to send to the server.
	BufferMapAsyncCmd cmd;
	cmd.bufferId = this->id;
	cmd.requestSerial = serial;
	cmd.mode = mode;
	cmd.offset = offset;
	cmd.size = size;
	cmd.handleCreateInfo = nullptr;

	// Step 3a. Fill the handle create info in the command.
	if (isReadMode) {
	cmd.handleCreateInfoLength = request.readHandle->SerializeCreateSize();
	client->SerializeCommand(
	cmd, cmd.handleCreateInfoLength, [&](SerializeBuffer* serializeBuffer) {
	char* readHandleBuffer;
	WIRE_TRY(serializeBuffer->NextN(cmd.handleCreateInfoLength, &readHandleBuffer));
	request.readHandle->SerializeCreate(readHandleBuffer);
	return WireResult::Success;
	});
	} else {
	ASSERT(isWriteMode);
	cmd.handleCreateInfoLength = request.writeHandle->SerializeCreateSize();
	client->SerializeCommand(
	cmd, cmd.handleCreateInfoLength, [&](SerializeBuffer* serializeBuffer) {
	char* writeHandleBuffer;
	WIRE_TRY(
	serializeBuffer->NextN(cmd.handleCreateInfoLength, &writeHandleBuffer));
	request.writeHandle->SerializeCreate(writeHandleBuffer);
	return WireResult::Success;
	});
	}

	// Step 4. Register this request so that we can retrieve it from its serial when the server
	// sends the callback.
	mRequests[serial] = std::move(request);
	}

	bool Buffer::OnMapAsyncCallback(uint32_t requestSerial,
	uint32_t status,
	uint64_t readInitialDataInfoLength,
	const uint8_t* readInitialDataInfo) {
	auto requestIt = mRequests.find(requestSerial);
	if (requestIt == mRequests.end()) {
	return false;
	}

	auto request = std::move(requestIt->second);
	// Delete the request before calling the callback otherwise the callback could be fired a
	// second time. If, for example, buffer.Unmap() is called inside the callback.
	mRequests.erase(requestIt);

	auto FailRequest = [&request]() -> bool {
	if (request.callback != nullptr) {
	request.callback(WGPUBufferMapAsyncStatus_DeviceLost, request.userdata);
	}
	return false;
	};

	bool isRead = request.readHandle != nullptr;
	bool isWrite = request.writeHandle != nullptr;
	ASSERT(isRead != isWrite);

	// Take into account the client-side status of the request if the server says it is a success.
	if (status == WGPUBufferMapAsyncStatus_Success) {
	status = request.clientStatus;
	}

	size_t mappedDataLength = 0;
	const void* mappedData = nullptr;
	if (status == WGPUBufferMapAsyncStatus_Success) {
	if (mReadHandle \|\| mWriteHandle) {
	// Buffer is already mapped.
	return FailRequest();
	}

	if (isRead) {
	if (readInitialDataInfoLength > std::numeric_limits<size_t>::max()) {
	// This is the size of data deserialized from the command stream, which must be
	// CPU-addressable.
	return FailRequest();
	}

	// The server serializes metadata to initialize the contents of the ReadHandle.
	// Deserialize the message and return a pointer and size of the mapped data for
	// reading.
	if (!request.readHandle->DeserializeInitialData(
	readInitialDataInfo, static_cast<size_t>(readInitialDataInfoLength),
	&mappedData, &mappedDataLength)) {
	// Deserialization shouldn't fail. This is a fatal error.
	return FailRequest();
	}
	ASSERT(mappedData != nullptr);

	} else {
	// Open the WriteHandle. This returns a pointer and size of mapped memory.
	// On failure, \|mappedData\| may be null.
	std::tie(mappedData, mappedDataLength) = request.writeHandle->Open();

	if (mappedData == nullptr) {
	return FailRequest();
	}
	}

	// The MapAsync request was successful. The buffer now owns the Read/Write handles
	// until Unmap().
	mReadHandle = std::move(request.readHandle);
	mWriteHandle = std::move(request.writeHandle);
	}

	mMapOffset = request.offset;
	mMapSize = request.size;
	mMappedData = const_cast<void*>(mappedData);
	if (request.callback) {
	request.callback(static_cast<WGPUBufferMapAsyncStatus>(status), request.userdata);
	}

	return true;
	}

	void* Buffer::GetMappedRange(size_t offset, size_t size) {
	if (!IsMappedForWriting() \|\| !CheckGetMappedRangeOffsetSize(offset, size)) {
	return nullptr;
	}
	return static_cast<uint8_t*>(mMappedData) + (offset - mMapOffset);
	}

	const void* Buffer::GetConstMappedRange(size_t offset, size_t size) {
	if (!(IsMappedForWriting() \|\| IsMappedForReading()) \|\|
	!CheckGetMappedRangeOffsetSize(offset, size)) {
	return nullptr;
	}
	return static_cast<uint8_t*>(mMappedData) + (offset - mMapOffset);
	}

	void Buffer::Unmap() {
	// Invalidate the local pointer, and cancel all other in-flight requests that would
	// turn into errors anyway (you can't double map). This prevents race when the following
	// happens, where the application code would have unmapped a buffer but still receive a
	// callback:
	// - Client -> Server: MapRequest1, Unmap, MapRequest2
	// - Server -> Client: Result of MapRequest1
	// - Unmap locally on the client
	// - Server -> Client: Result of MapRequest2
	if (mWriteHandle) {
	// Writes need to be flushed before Unmap is sent. Unmap calls all associated
	// in-flight callbacks which may read the updated data.
	ASSERT(mReadHandle == nullptr);

	// Get the serialization size of metadata to flush writes.
	size_t writeFlushInfoLength = mWriteHandle->SerializeFlushSize();

	BufferUpdateMappedDataCmd cmd;
	cmd.bufferId = id;
	cmd.writeFlushInfoLength = writeFlushInfoLength;
	cmd.writeFlushInfo = nullptr;

	client->SerializeCommand(
	cmd, writeFlushInfoLength, [&](SerializeBuffer* serializeBuffer) {
	char* writeHandleBuffer;
	WIRE_TRY(serializeBuffer->NextN(writeFlushInfoLength, &writeHandleBuffer));

	// Serialize flush metadata into the space after the command.
	// This closes the handle for writing.
	mWriteHandle->SerializeFlush(writeHandleBuffer);
	return WireResult::Success;
	});
	}

	FreeMappedData(false);

	// Tag all mapping requests still in flight as unmapped before callback.
	for (auto& it : mRequests) {
	if (it.second.clientStatus == WGPUBufferMapAsyncStatus_Success) {
	it.second.clientStatus = WGPUBufferMapAsyncStatus_UnmappedBeforeCallback;
	}
	}

	BufferUnmapCmd cmd;
	cmd.self = ToAPI(this);
	client->SerializeCommand(cmd);
	}

	void Buffer::Destroy() {
	// Remove the current mapping.
	FreeMappedData(true);

	// Tag all mapping requests still in flight as destroyed before callback.
	for (auto& it : mRequests) {
	if (it.second.clientStatus == WGPUBufferMapAsyncStatus_Success) {
	it.second.clientStatus = WGPUBufferMapAsyncStatus_DestroyedBeforeCallback;
	}
	}

	BufferDestroyCmd cmd;
	cmd.self = ToAPI(this);
	client->SerializeCommand(cmd);
	}

	bool Buffer::IsMappedForReading() const {
	return mReadHandle != nullptr;
	}

	bool Buffer::IsMappedForWriting() const {
	return mWriteHandle != nullptr;
	}

	bool Buffer::CheckGetMappedRangeOffsetSize(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;
	return offsetInMappedRange <= mMapSize - size;
	}

	void Buffer::FreeMappedData(bool destruction) {
	#if defined(DAWN_ENABLE_ASSERTS)
	// When in "debug" mode, 0xCA-out the mapped data when we free it so that in we can detect
	// use-after-free of the mapped data. This is particularly useful for WebGPU test about the
	// interaction of mapping and GC.
	if (mMappedData && destruction) {
	memset(mMappedData, 0xCA, mMapSize);
	}
	#endif // defined(DAWN_ENABLE_ASSERTS)

	mMapOffset = 0;
	mMapSize = 0;
	mWriteHandle = nullptr;
	mReadHandle = nullptr;
	mMappedData = nullptr;
	}

	}} // namespace dawn_wire::client