src/vs/workbench/api/common/extHostFileSystem.ts/ExtHostFileSystem/$write
class ExtHostFileSystem:	$write(handle: number, fd: number, pos: number, data: VSBuffer): Promise<number> {
		const provider = this._getFsProvider(handle);
		if (!provider.write) {
			throw new Error('FileSystemProvider does not implement "write"');
		}
		return Promise.resolve(provider.write(fd, pos, data.buffer, 0, data.byteLength));
	}