typesetting/pitfall/fontkit/prep.rkt

#lang fontkit/racket
(require restructure)
(provide (all-defined-out))
#|
approximates
https://github.com/mbutterick/fontkit/blob/master/src/tables/prep.js
|#

(define-subclass RStruct (Rprep))

(define prep (make-object Rprep
               (dictify
                'controlValueProgram (make-object RArray uint8))))

(test-module
 (require "directory.rkt")
 (define ip (open-input-file charter-path))
 (define dir (directory-decode ip))
 (define offset (· dir tables prep offset))
 (define len (· dir tables prep length))
 (check-equal? offset 4512)
 (check-equal? len 78)
 (set-port-position! ip 0)
 (define table-bytes #"\270\0\0+\0\272\0\1\0\1\0\2+\1\272\0\2\0\1\0\2+\1\277\0\2\0C\0007\0+\0\37\0\23\0\0\0\b+\0\277\0\1\0\200\0i\0R\0;\0#\0\0\0\b+\0\272\0\3\0\5\0\a+\270\0\0 E}i\30D")
 (check-equal? table-bytes (peek-bytes len offset ip))
 (define ds (make-object RDecodeStream (peek-bytes len offset ip)))
 (check-equal? (hash-ref (send prep decode ds) 'controlValueProgram) '(184
  0
  0
  43
  0
  186
  0
  1
  0
  1
  0
  2
  43
  1
  186
  0
  2
  0
  1
  0
  2
  43
  1
  191
  0
  2
  0
  67
  0
  55
  0
  43
  0
  31
  0
  19
  0
  0
  0
  8
  43
  0
  191
  0
  1
  0
  128
  0
  105
  0
  82
  0
  59
  0
  35
  0
  0
  0
  8
  43
  0
  186
  0
  3
  0
  5
  0
  7
  43
  184
  0
  0
  32
  69
  125
  105
  24
  68)))