(('deflate)
           (lambda (block)
             (prepend-type-byte
              1
              (blob->u8vector/shared
               (string->blob
                (z3:encode-buffer
                 (blob->string
                  (u8vector->blob/shared block))))))))

          (('lzma)
           (lambda (block)
             (prepend-type-byte
              2
              (blob->u8vector/shared
               (lzma:compress
                (u8vector->blob/shared block))))))