Bytevector

Write a bytevector

Given a file named “main.scm” with:

(import (scheme base))

(write-bytevector #u8(65 66 67))

When I successfully run stak main.scm

Then the stdout should contain exactly “ABC”.

Get a length of a bytevector

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (if (= (bytevector-length <value>) <length>) 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Examples

value	length
#u8()	0
#u8(0)	1
#u8(0 0)	2
#u8(0 0 0)	3

Reference a value in a bytevector

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (bytevector-u8-ref <vector> <index>))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Examples

vector	index
#u8(65)	0
#u8(65 66)	0
#u8(66 65)	1
#u8(65 66 66)	0
#u8(66 65 66)	1
#u8(66 66 65)	2

Set a value in a bytevector

Given a file named “main.scm” with:

(import (scheme base))

(define xs (bytevector <values>))

(bytevector-u8-set! xs <index> <value>)

(write-u8 (if (equal? xs #u8(<result>)) 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Examples

values	index	value	result
0	0	1	1
0 1	0	2	2 1
0 1	1	2	0 2
0 1 2	0	3	3 1 2
0 1 2	1	3	0 3 2
0 1 2	2	3	0 1 3

Append bytevectors

Given a file named “main.scm” with:

(import (scheme base) (srfi 1))

(define xs (bytevector-append <values>))

(for-each
  (lambda (index)
    (write-u8 (bytevector-u8-ref xs index)))
  (iota (bytevector-length xs)))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

values	output
#u8()
#u8() #u8()
#u8(65)	A
#u8(65) #u8(66)	AB
#u8(65) #u8(66) #u8(67)	ABC
#u8(65) #u8(66 67) #u8(68 69 70)	ABCDEF

Copy a bytevector

Given a file named “main.scm” with:

(import (scheme base) (srfi 1))

(define xs (bytevector-copy <value>))

(for-each
  (lambda (index)
    (write-u8 (bytevector-u8-ref xs index)))
  (iota (bytevector-length xs)))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

value	output
#u8()
#u8(65)	A
#u8(65 66)	AB
#u8(65 66 67)	ABC

Copy a bytevector in place

Given a file named “main.scm” with:

(import (scheme base) (srfi 1))

(define xs (bytevector <values>))

(bytevector-copy! xs <arguments>)

(for-each
  (lambda (index)
    (write-u8 (+ 65 (bytevector-u8-ref xs index))))
  (iota (bytevector-length xs)))

When I successfully run stak main.scm

Then the stdout should contain exactly “<output>”.

Examples

values	arguments	output
	0 #u8()
0 1 2	0 #u8(3 4 5)	DEF
0 1 2	1 #u8(3 4)	ADE
0 1 2	2 #u8(3)	ABD
0 1 2 3 4	1 #u8(5 6 7)	AFGHE
0 1 2 3	1 #u8(4 5 6 7) 1	AFGH
0 1 2 3	1 #u8(4 5 6 7) 1 3	AFGD

Large bytevector

Reference an element

Given a file named “main.scm” with:

(import (scheme base) (scheme write))

(write (bytevector-u8-ref (make-bytevector <length> 42) <index>))

When I successfully run stak main.scm

Then the stdout should contain exactly “42”.

Examples

length	index
1	0
2	0
2	1
3	0
3	1
3	2
8	0
8	1
8	6
8	7
9	0
9	1
9	7
9	8
64	63
65	64
512	511
513	512
4096	4095
4097	4096

Use a bytevector literal

Given a file named “main.scm” with:

(import (scheme base) (scheme write))

(define xs (include "./value.scm"))

(write (bytevector-u8-ref xs <index>))

And a file named “write.scm” with:

(import (scheme base) (scheme write) (srfi 1))

(write
  (apply
    bytevector
    (map
      (lambda (x) (remainder x 256))
      (iota <length>))))

And I run the following script:

stak write.scm > value.scm

When I successfully run stak main.scm

Then the stdout should contain exactly “<index>”.

Examples

length	index
1	0
2	0
2	1
512	0
512	1
512	254
512	255
4096	0
4096	1
4096	254
4096	255
8192	0
8192	1
8192	254
8192	255