src/vs/workbench/services/userData/common/fileUserDataProvider.ts/FileUserDataProvider/read
class FileUserDataProvider:	read(fd: number, pos: number, data: Uint8Array, offset: number, length: number): Promise<number> {
		if (hasOpenReadWriteCloseCapability(this.fileSystemProvider)) {
			return this.fileSystemProvider.read(fd, pos, data, offset, length);
		}
		throw new Error('not supported');
	}