Function createFakeDevice

examples/acceptance/data-store-append.ts:20–69

* Minimal fake GPUDevice for Node.js acceptance tests. * Implements only the subset of GPUDevice needed for createDataStore.

()

 * Implements only the subset of GPUDevice needed for createDataStore.
 */
function createFakeDevice(): GPUDevice {
  const buffers = new Map<GPUBuffer, { size: number; data: ArrayBuffer }>();

  // Expose WebGPU constants needed by createDataStore
  const GPUBufferUsage = {
    VERTEX: 0x20,
    COPY_DST: 0x08,
  };

  const device: GPUDevice = {
    limits: {
      maxBufferSize: 1024 * 1024 * 1024, // 1GB
    },
    createBuffer: (descriptor: GPUBufferDescriptor): GPUBuffer => {
      const size = descriptor.size ?? 0;
      const data = new ArrayBuffer(size);
      const buffer = {
        destroy: () => {
          buffers.delete(buffer as GPUBuffer);
        },
      } as GPUBuffer;
      buffers.set(buffer as GPUBuffer, { size, data });
      return buffer;
    },
    queue: {
      writeBuffer: (buffer: GPUBuffer, bufferOffset: number, data: ArrayBuffer | ArrayBufferView, dataOffset?: number, size?: number): void => {
        const entry = buffers.get(buffer);
        if (!entry) throw new Error('Buffer not found');
        
        const source = data instanceof ArrayBuffer ? new Uint8Array(data) : new Uint8Array(data.buffer, data.byteOffset, data.byteLength);
        const target = new Uint8Array(entry.data);
        const actualSize = size ?? source.length;
        const actualDataOffset = dataOffset ?? 0;
        
        if (bufferOffset + actualSize > entry.size) {
          throw new Error(`writeBuffer: offset ${bufferOffset} + size ${actualSize} exceeds buffer size ${entry.size}`);
        }
        
        for (let i = 0; i < actualSize; i++) {
          target[bufferOffset + i] = source[actualDataOffset + i]!;
        }
      },
    },
  } as GPUDevice;

  // Inject GPUBufferUsage into global scope for createDataStore to access
  (globalThis as unknown as { GPUBufferUsage: typeof GPUBufferUsage }).GPUBufferUsage = GPUBufferUsage;

  return device;
}

// Fast path: append without reallocation
{