Port

Check if a value is a port

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (if (port? <expression>) 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Examples

expression
(current-input-port)
(current-output-port)

Check if a value is an input port

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (if (input-port? (current-input-port)) 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Check if a value is an output port

Given a file named “main.scm” with:

(import (scheme base))

(write-u8 (if (output-port? <expression>) 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Examples

expression
(current-output-port)
(current-error-port)

Check if an input port is open or not

Given a file named “main.scm” with:

(import (scheme base) (scheme file))

(define port <expression>)

(write-u8 (if (input-port-open? port) 65 66))
(close-input-port port)
(write-u8 (if (input-port-open? port) 65 66))

And a file named “foo.txt” with:

When I successfully run stak main.scm

Then the stdout should contain exactly “AB”.

Examples

expression
(open-input-file “foo.txt”)
(open-input-string “foo”)

Check if an output port is open or not

Given a file named “main.scm” with:

(import (scheme base) (scheme file))

(define port <expression>)

(write-u8 (if (output-port-open? port) 65 66))
(close-output-port port)
(write-u8 (if (output-port-open? port) 65 66))

And a file named “foo.txt” with:

When I successfully run stak main.scm

Then the stdout should contain exactly “AB”.

Examples

expression
(open-output-file “foo.txt”)
(open-output-string)

Preserve pending input order after peeking

Given a file named “main.scm” with:

(import (scheme base))

(define port (open-input-string "<input>"))
(peek-char port)
(peek-u8 port)
(write-u8 (if (= (read-u8 port) <first-byte>) 65 66))

When I successfully run stak main.scm

Then the stdout should contain exactly “A”.

Examples

input	first-byte
éx	195
😄x	240

Preserve pending input order when peeking a character

Given a file named “main.scm” with:

(import (scheme base) (stak io))

(define port
  (make-port
    (lambda () #f)
    #f
    #f
    (lambda () #f)
    '(195 169 120)))

(peek-char port)

(for-each
  (lambda (expected)
    (write-u8 (if (= (read-u8 port) expected) 65 66)))
  '(195 169 120))

When I successfully run stak main.scm

Then the stdout should contain exactly “AAA”.

Read from a string port

Given a file named “main.scm” with:

(import (scheme base))

(call-with-port
  (open-input-string "<string>")
  (lambda (port)
    (parameterize ((current-input-port port))
      (do ((x (read-u8) (read-u8)))
        ((eof-object? x) #f)
        (write-u8 x)))))

When I successfully run stak main.scm

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

Examples

string
ABC
あ
😄
—

Write to a string port

Given a file named “main.scm” with:

(import (scheme base))

(call-with-port
  (open-output-string)
  (lambda (port)
    (parameterize ((current-output-port port))
      (for-each write-u8 '(<bytes>)))
    (let ((xs (get-output-string port)))
      (unless (= (string-length xs) <length>)
        (error "invalid length"))
      (write-string xs))))

When I successfully run stak main.scm

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

Examples

bytes	output	length
65 66 67	ABC	3
227 129 130	あ	1
240 159 152 132	😄	1

Read from a bytevector port

Given a file named “main.scm” with:

(import (scheme base))

(call-with-port
  (open-input-bytevector #u8(65 66 67))
  (lambda (port)
    (parameterize ((current-input-port port))
      (do ((x (read-u8) (read-u8)))
        ((eof-object? x) #f)
        (write-u8 x)))))

When I successfully run stak main.scm.

Write to a bytevector port

Given a file named “main.scm” with:

(import (scheme base))

(call-with-port
  (open-output-bytevector)
  (lambda (port)
    (parameterize ((current-output-port port))
      (for-each write-u8 '(<bytes>)))
    (let ((xs (get-output-bytevector port)))
      (unless (= (bytevector-length xs) <length>)
        (error "invalid length"))
      (write-bytevector xs))))

When I successfully run stak main.scm

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

Examples

bytes	output	length
65	A	1
65 66	AB	2
65 66 67	ABC	3