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