guile/test-suite/tests/bytevectors.test

;;;; bytevectors.test --- R6RS bytevectors. -*- mode: scheme; coding: utf-8; -*-
;;;;
;;;; Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
;;;; Ludovic Courtès
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;; 
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;;; Lesser General Public License for more details.
;;;; 
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

(define-module (test-bytevector)
  :use-module (test-suite lib)
  :use-module (system base compile)
  :use-module (rnrs bytevectors))

;;; Some of the tests in here are examples taken from the R6RS Standard
;;; Libraries document.


(with-test-prefix/c&e "2.2 General Operations"

  (pass-if "native-endianness"
    (not (not (memq (native-endianness) '(big little)))))

  (pass-if "make-bytevector"
    (and (bytevector? (make-bytevector 20))
         (bytevector? (make-bytevector 20 3))))

  (pass-if "bytevector-length"
    (= (bytevector-length (make-bytevector 20)) 20))

  (pass-if "bytevector=?"
    (and (bytevector=? (make-bytevector 20 7)
                       (make-bytevector 20 7))
         (not (bytevector=? (make-bytevector 20 7)
                            (make-bytevector 20 0)))))

  (pass-if "bytevector-copy! overlapping"
    ;; See <http://debbugs.gnu.org/10070>.
    (let ((b (u8-list->bytevector '(1 2 3 4 5 6 7 8))))
      (bytevector-copy! b 0 b 3 4)
      (bytevector->u8-list b)
      (bytevector=? b #vu8(1 2 3 1 2 3 4 8)))))


(with-test-prefix/c&e "2.3 Operations on Bytes and Octets"

  (pass-if "bytevector-{u8,s8}-ref"
    (equal? '(-127 129 -1 255)
            (let ((b1 (make-bytevector 16 -127))
                  (b2 (make-bytevector 16 255)))
              (list (bytevector-s8-ref b1 0)
                    (bytevector-u8-ref b1 0)
                    (bytevector-s8-ref b2 0)
                    (bytevector-u8-ref b2 0)))))

  (pass-if "bytevector-{u8,s8}-set!"
    (equal? '(-126 130 -10 246)
            (let ((b (make-bytevector 16 -127)))

              (bytevector-s8-set! b 0 -126)
              (bytevector-u8-set! b 1 246)

              (list (bytevector-s8-ref b 0)
                    (bytevector-u8-ref b 0)
                    (bytevector-s8-ref b 1)
                    (bytevector-u8-ref b 1)))))

  (pass-if "bytevector->u8-list"
    (let ((lst '(1 2 3 128 150 255)))
      (equal? lst
              (bytevector->u8-list
               (let ((b (make-bytevector 6)))
                 (for-each (lambda (i v)
                             (bytevector-u8-set! b i v))
                           (iota 6)
                           lst)
                 b)))))

  (pass-if "u8-list->bytevector"
    (let ((lst '(1 2 3 128 150 255)))
      (equal? lst
              (bytevector->u8-list (u8-list->bytevector lst)))))

  (pass-if "bytevector-uint-{ref,set!} [small]"
    (let ((b (make-bytevector 15)))
      (bytevector-uint-set! b 0 #x1234
                            (endianness little) 2)
      (equal? (bytevector-uint-ref b 0 (endianness big) 2)
              #x3412)))

  (pass-if "bytevector-uint-set! [large]"
    (let ((b (make-bytevector 16)))
      (bytevector-uint-set! b 0 (- (expt 2 128) 3)
                            (endianness little) 16)
      (equal? (bytevector->u8-list b)
              '(253 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 255))))

  (pass-if "bytevector-uint-{ref,set!} [large]"
    (let ((b (make-bytevector 120)))
      (bytevector-uint-set! b 0 (- (expt 2 128) 3)
                            (endianness little) 16)
      (equal? (bytevector-uint-ref b 0 (endianness little) 16)
              #xfffffffffffffffffffffffffffffffd)))

  (pass-if "bytevector-sint-ref [small]"
    (let ((b (u8-list->bytevector '(#xff #xf0 #xff))))
      (equal? (bytevector-sint-ref b 0 (endianness big) 2)
              (bytevector-sint-ref b 1 (endianness little) 2)
              -16)))

  (pass-if "bytevector-sint-ref [large]"
    (let ((b (make-bytevector 50)))
      (bytevector-uint-set! b 0 (- (expt 2 128) 3)
                            (endianness little) 16)
      (equal? (bytevector-sint-ref b 0 (endianness little) 16)
              -3)))

  (pass-if "bytevector-sint-set! [small]"
    (let ((b (make-bytevector 3)))
      (bytevector-sint-set! b 0 -16 (endianness big) 2)
      (bytevector-sint-set! b 1 -16 (endianness little) 2)
      (equal? (bytevector->u8-list b)
	      '(#xff #xf0 #xff))))

  (pass-if "equal?"
    (let ((bv1 (u8-list->bytevector (iota 123)))
          (bv2 (u8-list->bytevector (iota 123))))
      (equal? bv1 bv2))))


(with-test-prefix/c&e "2.4 Operations on Integers of Arbitrary Size"

  (pass-if "bytevector->sint-list"
    (let ((b (u8-list->bytevector '(1 2 3 255 1 2 1 2))))
      (equal? (bytevector->sint-list b (endianness little) 2)
              '(513 -253 513 513))))

  (pass-if "bytevector->uint-list"
    (let ((b (u8-list->bytevector '(2 1 255 3 2 1 2 1))))
      (equal? (bytevector->uint-list b (endianness big) 2)
              '(513 65283 513 513))))

  (pass-if "bytevector->uint-list [empty]"
    (let ((b (make-bytevector 0)))
      (null? (bytevector->uint-list b (endianness big) 2))))

  (pass-if-exception "bytevector->sint-list [out-of-range]"
    exception:out-of-range
    (bytevector->sint-list (make-bytevector 6) (endianness little) 8))

  (pass-if "bytevector->sint-list [off-by-one]"
    (equal? (bytevector->sint-list (make-bytevector 31 #xff)
                                   (endianness little) 8)
            '(-1 -1 -1)))

  (pass-if "{sint,uint}-list->bytevector"
    (let ((b1 (sint-list->bytevector '(513 -253 513 513)
                                     (endianness little) 2))
          (b2 (uint-list->bytevector '(513 65283 513 513)
                                     (endianness little) 2))
          (b3 (u8-list->bytevector '(1 2 3 255 1 2 1 2))))
      (and (bytevector=? b1 b2)
           (bytevector=? b2 b3))))

  (pass-if "sint-list->bytevector [limits]"
           (bytevector=? (sint-list->bytevector '(-32768 32767)
                                                (endianness big) 2)
                         (let ((bv (make-bytevector 4)))
                           (bytevector-u8-set! bv 0 #x80)
                           (bytevector-u8-set! bv 1 #x00)
                           (bytevector-u8-set! bv 2 #x7f)
                           (bytevector-u8-set! bv 3 #xff)
                           bv)))

  (pass-if-exception "sint-list->bytevector [out-of-range]"
    exception:out-of-range
    (sint-list->bytevector (list 0 0 (expt 2 16)) (endianness big)
                           2))

  (pass-if-exception "uint-list->bytevector [out-of-range]"
    exception:out-of-range
    (uint-list->bytevector '(0 -1) (endianness big) 2)))


(with-test-prefix/c&e "2.5 Operations on 16-Bit Integers"

  (pass-if "bytevector-u16-ref"
    (let ((b (u8-list->bytevector
              '(255 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 253))))
      (and (equal? (bytevector-u16-ref b 14 (endianness little))
                   #xfdff)
           (equal? (bytevector-u16-ref b 14 (endianness big))
                   #xfffd))))

  (pass-if "bytevector-s16-ref"
    (let ((b (u8-list->bytevector
              '(255 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 253))))
      (and (equal? (bytevector-s16-ref b 14 (endianness little))
                   -513)
           (equal? (bytevector-s16-ref b 14 (endianness big))
                   -3))))

  (pass-if "bytevector-s16-ref [unaligned]"
    (let ((b (u8-list->bytevector '(#xff #xf0 #xff))))
      (equal? (bytevector-s16-ref b 1 (endianness little))
	      -16)))

  (pass-if "bytevector-{u16,s16}-ref"
    (let ((b (make-bytevector 2)))
      (bytevector-u16-set! b 0 44444 (endianness little))
      (and (equal? (bytevector-u16-ref b 0 (endianness little))
                   44444)
           (equal? (bytevector-s16-ref b 0 (endianness little))
                   (- 44444 65536)))))

  (pass-if "bytevector-native-{u16,s16}-{ref,set!}"
    (let ((b (make-bytevector 2)))
      (bytevector-u16-native-set! b 0 44444)
      (and (equal? (bytevector-u16-native-ref b 0)
                   44444)
           (equal? (bytevector-s16-native-ref b 0)
                   (- 44444 65536)))))

  (pass-if "bytevector-s16-{ref,set!} [unaligned]"
    (let ((b (make-bytevector 3)))
      (bytevector-s16-set! b 1 -77 (endianness little))
      (equal? (bytevector-s16-ref b 1 (endianness little))
	      -77))))


(with-test-prefix/c&e "2.6 Operations on 32-bit Integers"

  (pass-if "bytevector-u32-ref"
    (let ((b (u8-list->bytevector
              '(255 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 253))))
      (and (equal? (bytevector-u32-ref b 12 (endianness little))
                   #xfdffffff)
           (equal? (bytevector-u32-ref b 12 (endianness big))
                   #xfffffffd))))

  (pass-if "bytevector-s32-ref"
    (let ((b (u8-list->bytevector
              '(255 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 253))))
      (and (equal? (bytevector-s32-ref b 12 (endianness little))
                   -33554433)
           (equal? (bytevector-s32-ref b 12 (endianness big))
                   -3))))

  (pass-if "bytevector-{u32,s32}-ref"
    (let ((b (make-bytevector 4)))
      (bytevector-u32-set! b 0 2222222222 (endianness little))
      (and (equal? (bytevector-u32-ref b 0 (endianness little))
                   2222222222)
           (equal? (bytevector-s32-ref b 0 (endianness little))
                   (- 2222222222 (expt 2 32))))))

  (pass-if "bytevector-{u32,s32}-native-{ref,set!}"
    (let ((b (make-bytevector 4)))
      (bytevector-u32-native-set! b 0 2222222222)
      (and (equal? (bytevector-u32-native-ref b 0)
                   2222222222)
           (equal? (bytevector-s32-native-ref b 0)
                   (- 2222222222 (expt 2 32)))))))


(with-test-prefix/c&e "2.7 Operations on 64-bit Integers"

  (pass-if "bytevector-u64-ref"
    (let ((b (u8-list->bytevector
              '(255 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 253))))
      (and (equal? (bytevector-u64-ref b 8 (endianness little))
                   #xfdffffffffffffff)
           (equal? (bytevector-u64-ref b 8 (endianness big))
                   #xfffffffffffffffd))))

  (pass-if "bytevector-s64-ref"
    (let ((b (u8-list->bytevector
              '(255 255 255 255 255 255 255 255
                255 255 255 255 255 255 255 253))))
      (and (equal? (bytevector-s64-ref b 8 (endianness little))
                   -144115188075855873)
           (equal? (bytevector-s64-ref b 8 (endianness big))
                   -3))))

  (pass-if "bytevector-{u64,s64}-ref"
    (let ((b (make-bytevector 8))
          (big 9333333333333333333))
      (bytevector-u64-set! b 0 big (endianness little))
      (and (equal? (bytevector-u64-ref b 0 (endianness little))
                   big)
           (equal? (bytevector-s64-ref b 0 (endianness little))
                   (- big (expt 2 64))))))

  (pass-if "bytevector-{u64,s64}-native-{ref,set!}"
    (let ((b (make-bytevector 8))
          (big 9333333333333333333))
      (bytevector-u64-native-set! b 0 big)
      (and (equal? (bytevector-u64-native-ref b 0)
                   big)
           (equal? (bytevector-s64-native-ref b 0)
                   (- big (expt 2 64))))))

  (pass-if "ref/set! with zero"
     (let ((b (make-bytevector 8)))
       (bytevector-s64-set! b 0 -1 (endianness big))
       (bytevector-u64-set! b 0  0 (endianness big))
       (= 0 (bytevector-u64-ref b 0 (endianness big))))))


(with-test-prefix/c&e "2.8 Operations on IEEE-754 Representations"

  (pass-if "bytevector-ieee-single-native-{ref,set!}"
    (let ((b (make-bytevector 4))
          (number 3.00))
      (bytevector-ieee-single-native-set! b 0 number)
      (equal? (bytevector-ieee-single-native-ref b 0)
              number)))

  (pass-if "bytevector-ieee-single-{ref,set!}"
    (let ((b (make-bytevector 8))
          (number 3.14))
      (bytevector-ieee-single-set! b 0 number (endianness little))
      (bytevector-ieee-single-set! b 4 number (endianness big))
      (equal? (bytevector-ieee-single-ref b 0 (endianness little))
              (bytevector-ieee-single-ref b 4 (endianness big)))))

  (pass-if "bytevector-ieee-single-{ref,set!} [unaligned]"
    (let ((b (make-bytevector 9))
          (number 3.14))
      (bytevector-ieee-single-set! b 1 number (endianness little))
      (bytevector-ieee-single-set! b 5 number (endianness big))
      (equal? (bytevector-ieee-single-ref b 1 (endianness little))
              (bytevector-ieee-single-ref b 5 (endianness big)))))

  (pass-if "bytevector-ieee-double-native-{ref,set!}"
    (let ((b (make-bytevector 8))
          (number 3.14))
      (bytevector-ieee-double-native-set! b 0 number)
      (equal? (bytevector-ieee-double-native-ref b 0)
              number)))

  (pass-if "bytevector-ieee-double-{ref,set!}"
    (let ((b (make-bytevector 16))
          (number 3.14))
      (bytevector-ieee-double-set! b 0 number (endianness little))
      (bytevector-ieee-double-set! b 8 number (endianness big))
      (equal? (bytevector-ieee-double-ref b 0 (endianness little))
              (bytevector-ieee-double-ref b 8 (endianness big))))))



;; Default to the C locale for the following tests.
(setlocale LC_ALL "C")


(with-test-prefix "2.9 Operations on Strings"

  (pass-if "string->utf8"
    (let* ((str  "hello, world")
           (utf8 (string->utf8 str)))
      (and (bytevector? utf8)
           (= (bytevector-length utf8)
              (string-length str))
           (equal? (string->list str)
                   (map integer->char (bytevector->u8-list utf8))))))

  (pass-if "string->utf8 [latin-1]"
    (let* ((str  "hé, ça va bien ?")
           (utf8 (string->utf8 str)))
      (and (bytevector? utf8)
           (= (bytevector-length utf8)
              (+ 2 (string-length str))))))

  (pass-if "string->utf16"
    (let* ((str   "hello, world")
           (utf16 (string->utf16 str)))
      (and (bytevector? utf16)
           (= (bytevector-length utf16)
              (* 2 (string-length str)))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf16
                                               (endianness big) 2))))))

  (pass-if "string->utf16 [little]"
    (let* ((str   "hello, world")
           (utf16 (string->utf16 str (endianness little))))
      (and (bytevector? utf16)
           (= (bytevector-length utf16)
              (* 2 (string-length str)))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf16
                                               (endianness little) 2))))))


  (pass-if "string->utf32"
    (let* ((str   "hello, world")
           (utf32 (string->utf32 str)))
      (and (bytevector? utf32)
           (= (bytevector-length utf32)
              (* 4 (string-length str)))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf32
                                               (endianness big) 4))))))

  (pass-if "string->utf32 [Greek]"
    (let* ((str   "Ἄνεμοι")
           (utf32 (string->utf32 str)))
      (and (bytevector? utf32)
           (equal? (bytevector->uint-list utf32 (endianness big) 4)
                   '(#x1f0c #x3bd #x3b5 #x3bc #x3bf #x3b9)))))

  (pass-if "string->utf32 [little]"
    (let* ((str   "hello, world")
           (utf32 (string->utf32 str (endianness little))))
      (and (bytevector? utf32)
           (= (bytevector-length utf32)
              (* 4 (string-length str)))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf32
                                               (endianness little) 4))))))

  (pass-if "utf8->string"
    (let* ((utf8  (u8-list->bytevector (map char->integer
                                            (string->list "hello, world"))))
           (str   (utf8->string utf8)))
      (and (string? str)
           (= (string-length str)
              (bytevector-length utf8))
           (equal? (string->list str)
                   (map integer->char (bytevector->u8-list utf8))))))

  (pass-if "utf8->string [latin-1]"
    (let* ((utf8  (string->utf8 "hé, ça va bien ?"))
           (str   (utf8->string utf8)))
      (and (string? str)
           (= (string-length str)
              (- (bytevector-length utf8) 2)))))

  (pass-if "utf16->string"
    (let* ((utf16  (uint-list->bytevector (map char->integer
                                               (string->list "hello, world"))
                                          (endianness big) 2))
           (str   (utf16->string utf16)))
      (and (string? str)
           (= (* 2 (string-length str))
              (bytevector-length utf16))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf16 (endianness big)
                                               2))))))

  (pass-if "utf16->string [little]"
    (let* ((utf16  (uint-list->bytevector (map char->integer
                                               (string->list "hello, world"))
                                          (endianness little) 2))
           (str   (utf16->string utf16 (endianness little))))
      (and (string? str)
           (= (* 2 (string-length str))
              (bytevector-length utf16))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf16 (endianness little)
                                               2))))))
  (pass-if "utf32->string"
    (let* ((utf32  (uint-list->bytevector (map char->integer
                                               (string->list "hello, world"))
                                          (endianness big) 4))
           (str   (utf32->string utf32)))
      (and (string? str)
           (= (* 4 (string-length str))
              (bytevector-length utf32))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf32 (endianness big)
                                               4))))))

  (pass-if "utf32->string [little]"
    (let* ((utf32  (uint-list->bytevector (map char->integer
                                               (string->list "hello, world"))
                                          (endianness little) 4))
           (str   (utf32->string utf32 (endianness little))))
      (and (string? str)
           (= (* 4 (string-length str))
              (bytevector-length utf32))
           (equal? (string->list str)
                   (map integer->char
                        (bytevector->uint-list utf32 (endianness little)
                                               4)))))))



(with-test-prefix "Datum Syntax"

  (pass-if "empty"
    (equal? (with-input-from-string "#vu8()" read)
            (make-bytevector 0)))

  (pass-if "simple"
    (equal? (with-input-from-string "#vu8(1 2 3   4 5)" read)
            (u8-list->bytevector '(1 2 3 4 5))))

  (pass-if ">127"
    (equal? (with-input-from-string "#vu8(0 255 127 128)" read)
            (u8-list->bytevector '(0 255 127 128))))

  (pass-if "self-evaluating?"
    (self-evaluating? (make-bytevector 1)))

  (pass-if "self-evaluating"
    (equal? (eval (with-input-from-string "#vu8(1 2 3 4 5)" read)
                  (current-module))
            (u8-list->bytevector '(1 2 3 4 5))))

  (pass-if "quoted"
    (equal? (eval (with-input-from-string "'#vu8(1 2 3 4 5)" read)
                  (current-module))
            (u8-list->bytevector '(1 2 3 4 5))))

  (pass-if "literal simple"
    (equal? #vu8(1 2 3   4 5)
            (u8-list->bytevector '(1 2 3 4 5))))

  (pass-if "literal >127"
    (equal? #vu8(0 255 127 128)
            (u8-list->bytevector '(0 255 127 128))))

  (pass-if "literal quoted"
    (equal? '#vu8(1 2 3   4 5)
            (u8-list->bytevector '(1 2 3 4 5))))

  (pass-if-exception "incorrect prefix"
    exception:read-error
    (with-input-from-string "#vi8(1 2 3)" read))

  (pass-if-exception "extraneous space"
    exception:read-error
    (with-input-from-string "#vu8 (1 2 3)" read))

  (pass-if-exception "negative integers"
    exception:wrong-type-arg
    (with-input-from-string "#vu8(-1 -2 -3)" read))

  (pass-if-exception "out-of-range integers"
    exception:wrong-type-arg
    (with-input-from-string "#vu8(0 256)" read)))


(with-test-prefix "Generalized Vectors"

  (pass-if "generalized-vector?"
    (generalized-vector? #vu8(1 2 3)))

  (pass-if "generalized-vector-length"
    (equal? (iota 16)
            (map generalized-vector-length
                 (map make-bytevector (iota 16)))))

  (pass-if "generalized-vector-ref"
    (let ((bv #vu8(255 127)))
      (and (= 255 (generalized-vector-ref bv 0))
           (= 127 (generalized-vector-ref bv 1)))))

  (pass-if-exception "generalized-vector-ref [index out-of-range]"
    exception:out-of-range
    (let ((bv #vu8(1 2)))
      (generalized-vector-ref bv 2)))

  (pass-if "generalized-vector-set!"
    (let ((bv (make-bytevector 2)))
      (generalized-vector-set! bv 0 255)
      (generalized-vector-set! bv 1 77)
      (equal? '(255 77)
              (bytevector->u8-list bv))))

  (pass-if-exception "generalized-vector-set! [index out-of-range]"
    exception:out-of-range
    (let ((bv (make-bytevector 2)))
      (generalized-vector-set! bv 2 0)))

  (pass-if-exception "generalized-vector-set! [value out-of-range]"
    exception:out-of-range
    (let ((bv (make-bytevector 2)))
      (generalized-vector-set! bv 0 256)))

  (pass-if "array-type"
    (eq? 'vu8 (array-type #vu8())))

  (pass-if "array-contents"
    (let ((bv (u8-list->bytevector (iota 10))))
      (eq? bv (array-contents bv))))

  (pass-if "array-ref"
    (let ((bv (u8-list->bytevector (iota 10))))
      (equal? (iota 10)
              (map (lambda (i) (array-ref bv i))
                   (iota 10)))))

  (pass-if "array-set!"
    (let ((bv (make-bytevector 10)))
      (for-each (lambda (i)
                  (array-set! bv i i))
                (iota 10))
      (equal? (iota 10)
              (bytevector->u8-list bv))))

  (pass-if "make-typed-array"
    (let ((bv (make-typed-array 'vu8 77 33)))
      (equal? bv (u8-list->bytevector (make-list 33 77)))))

  (pass-if-exception "make-typed-array [out-of-range]"
    exception:out-of-range
    (make-typed-array 'vu8 256 77)))


(with-test-prefix "uniform-array->bytevector"

  (pass-if "bytevector"
    (let ((bv #vu8(0 1 128 255)))
      (equal? bv (uniform-array->bytevector bv))))

  (pass-if "empty bitvector"
    (let ((bv (uniform-array->bytevector (make-bitvector 0))))
      (equal? bv #vu8())))

  (pass-if "bitvector < 8"
    (let ((bv (uniform-array->bytevector (make-bitvector 4 #t))))
      (= (bytevector-length bv) 1)))

  (pass-if "bitvector == 8"
    (let ((bv (uniform-array->bytevector (make-bitvector 8 #t))))
      (= (bytevector-length bv) 1)))

  (pass-if "bitvector > 8"
    (let ((bv (uniform-array->bytevector (make-bitvector 9 #t))))
      (= (bytevector-length bv) 2))))