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71 lines
2.7 KiB
Racket
71 lines
2.7 KiB
Racket
#lang racket/base
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(require xenomorph
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"tables.rkt"
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racket/dict
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sugar/unstable/dict
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racket/string)
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(provide (all-defined-out))
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#|
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https://github.com/mbutterick/fontkit/blob/master/src/tables/directory.js
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|#
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(define table-entry (x:struct
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'tag (x:symbol #:length 4)
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'checkSum uint32be
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'offset (x:pointer #:offset-type uint32be
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#:type 'void
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#:relative-to 'global)
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'length uint32be))
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;; for stupid tags like 'cvt '
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(define (symbol-replace sym this that)
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(string->symbol (string-replace (if (string? sym) sym (symbol->string sym)) this that)))
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(define (escape-tag tag) (symbol-replace tag " " "_"))
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(define (unescape-tag tag) (symbol-replace tag "_" " "))
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(define (directory-post-decode this-res)
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(define new-tables-val (mhash))
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(for ([table (in-list (hash-ref this-res 'tables))])
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(hash-set! new-tables-val (escape-tag (hash-ref table 'tag)) table))
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(dict-set! this-res 'tables new-tables-val)
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this-res)
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(define (directory-pre-encode this-val)
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(define tables (for/list ([(tag table) (in-hash (hash-ref this-val 'tables))])
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(define table-codec (hash-ref table-codecs tag))
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(mhash 'tag (unescape-tag tag)
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'checkSum 0
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'offset (x:void-pointer table-codec table)
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'length (size table-codec table))))
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(define numTables (length tables))
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(define searchRange (* (floor (log numTables 2)) 16))
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(hash-set*! this-val
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'tag 'true
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'numTables numTables
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'tables tables
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'searchRange searchRange
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'entrySelector (floor (/ searchRange (log 2)))
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'rangeShift (- (* numTables 16) searchRange))
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this-val)
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(define Directory (x:struct #:pre-encode directory-pre-encode
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#:post-decode directory-post-decode
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'tag (x:symbol #:length 4)
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'numTables uint16be
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'searchRange uint16be
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'entrySelector uint16be
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'rangeShift uint16be
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'tables (x:array #:type table-entry #:length 'numTables)))
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(define (directory-decode ip [options (mhash)])
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(decode Directory ip))
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(define (file-directory-decode ps)
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(directory-decode (open-input-file ps)))
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#;(test-module
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(define ip (open-input-file charter-path))
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(define decoded-dir (deserialize (read (open-input-file charter-directory-path))))
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(check-equal? (directory-decode ip) decoded-dir)) |