Slightly optimize copy-mem by aligning the buffer.

(defconstant +buffer-size+ 8192)

(deftype word () 'sb-vm:word)

(deftype signed-word () 'sb-vm:signed-word)

(defun allocate-buffer ()

  (sb-sys:sap-int

   (sb-alien:alien-sap

    (sb-alien:make-alien char (+ +buffer-size+ 3)))))

    (sb-alien:make-alien char

                         ;; alignment

                         (+ +buffer-size+

                            (1- sb-vm:n-word-bytes))))))

(defstruct (input-stream

            (:predicate nil))

(declaim (inline copy-mem))

(defun copy-mem (from to length)

  (declare (word length))

  (let ((words-end (sb-ext:truly-the word

                                     (- length

                                        (rem length sb-vm:n-word-bytes)))))

    (loop for i fixnum by sb-vm:n-word-bytes below words-end

  (loop for i fixnum by sb-vm:n-word-bytes to length

        do (setf (sb-sys:sap-ref-word to i)

                   (sb-sys:sap-ref-word from i)))

    (loop for i fixnum from words-end below length

          do (setf (sb-sys:sap-ref-8 to i)

                   (sb-sys:sap-ref-8 from i)))))

                 (sb-sys:sap-ref-word from i))))

(declaim (inline read-ascii-string-optimized))

(defun read-ascii-string-optimized (length string stream)