30 lines
934 B
Scheme
30 lines
934 B
Scheme
(module file-box mzscheme
|
|
(require (lib "serialize.ss")
|
|
(lib "contract.ss"))
|
|
|
|
(define-serializable-struct internal-file-box (path))
|
|
(define file-box? internal-file-box?)
|
|
|
|
(define (file-box path default)
|
|
(define fb (make-internal-file-box path))
|
|
(unless (file-box-set? fb)
|
|
(file-box-set! fb default))
|
|
fb)
|
|
|
|
(define (file-box-set? fb)
|
|
(with-handlers ([exn? (lambda _ #f)])
|
|
(file-unbox fb)
|
|
#t))
|
|
|
|
(define (file-unbox fb)
|
|
(deserialize (call-with-input-file (internal-file-box-path fb) read)))
|
|
(define (file-box-set! fb v)
|
|
(with-output-to-file (internal-file-box-path fb) (lambda () (write (serialize v))) 'replace))
|
|
|
|
(provide/contract
|
|
[file-box? (any/c . -> . boolean?)]
|
|
[file-box (path? any/c . -> . file-box?)]
|
|
[file-unbox (file-box? . -> . any/c)]
|
|
[file-box-set? (file-box? . -> . boolean?)]
|
|
[file-box-set! (file-box? any/c . -> . void)]))
|