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287 lines
12 KiB
Racket
287 lines
12 KiB
Racket
#lang fontkit/racket
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(require restructure)
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(provide (all-defined-out))
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(define 16bit-style 0)
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(define 32bit-style 1)
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(define max-32-bit-value #xffff)
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#|
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approximates
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https://github.com/mbutterick/fontkit/blob/master/src/tables/loca.js
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|#
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(define-subclass VersionedStruct (Rloca)
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(define/override (process res stream)
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;; in `restructure` `process` method, `res` is aliased as `this`
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;;
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(when (= 16bit-style (· res version))
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;; in a 16bits-style loca table, actual 32bit offset values are divided by 2 (to fit into 16 bits)
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;; so we re-inflate them.
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(hash-update! res 'offsets (λ (offsets) (map (curry * 2) offsets)))))
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(define/override (preEncode this-val stream)
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;; this = val to be encoded
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(loca-preEncode this-val stream)))
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;; make "static method"
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(define (loca-preEncode this-val . args)
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;; this = val to be encoded
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(unless (hash-has-key? this-val 'version)
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(hash-set! this-val 'version (if (> (last (· this-val offsets)) max-32-bit-value)
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32bit-style
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16bit-style))
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(when (= 16bit-style (· this-val version))
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(hash-update! this-val 'offsets (λ (offsets) (map (curryr / 2) offsets))))))
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(define loca (make-object Rloca
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(λ (parent) (hash-ref (send parent _getTable 'head) 'indexToLocFormat))
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(dictify
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0 (dictify 'offsets (+Array uint16be))
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1 (dictify 'offsets (+Array uint32be))
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)))
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(test-module
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(require racket/serialize)
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(define ip (open-input-file charter-path))
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(define dir (deserialize (read (open-input-file charter-directory-path))))
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(define offset (· dir tables loca offset))
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(define len (· dir tables loca length))
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(check-equal? offset 38692)
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(check-equal? len 460)
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(set-port-position! ip 0)
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(define ds (+DecodeStream (peek-bytes len offset ip)))
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(define table-data (send loca decode ds #:version 0))
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(check-equal? (length (· table-data offsets)) 230)
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(check-equal? (· table-data offsets) '(0
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0
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0
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136
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296
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500
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864
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1168
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1548
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1628
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1716
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1804
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1944
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2048
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2128
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2176
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2256
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2312
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2500
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2596
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2788
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3052
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3168
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3396
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3624
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3732
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4056
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4268
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4424
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4564
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4640
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4728
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4804
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5012
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5384
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5532
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5808
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6012
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6212
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6456
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6672
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6916
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7204
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7336
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7496
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7740
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7892
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8180
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8432
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8648
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8892
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9160
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9496
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9764
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9936
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10160
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10312
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10536
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10780
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10992
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11148
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11216
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11272
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11340
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11404
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11444
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11524
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11820
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12044
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12216
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12488
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12728
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12932
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13324
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13584
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13748
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13924
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14128
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14232
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14592
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14852
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15044
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15336
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15588
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15776
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16020
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16164
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16368
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16520
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16744
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16984
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17164
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17320
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17532
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17576
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17788
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17896
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18036
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18284
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18552
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18616
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18988
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19228
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19512
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19712
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19796
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19976
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20096
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20160
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20224
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20536
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20836
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20876
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21000
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21200
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21268
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21368
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21452
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21532
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21720
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21908
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22036
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22244
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22664
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22872
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22932
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22992
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23088
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23220
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23268
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23372
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23440
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23600
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23752
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23868
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23988
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24084
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24184
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24224
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24548
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24788
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25012
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25292
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25716
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25884
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26292
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26396
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26540
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26796
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27172
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27488
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27512
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27536
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27560
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27584
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27912
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27936
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27960
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27984
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28008
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28032
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28056
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28080
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28104
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28128
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28152
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28176
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28200
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28224
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28248
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28272
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28296
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28320
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28344
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28368
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28392
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28416
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28440
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28464
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28488
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28512
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28536
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28560
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28968
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28992
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29016
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29040
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29064
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29088
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29112
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29136
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29160
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29184
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29208
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29232
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29256
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29280
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29304
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29328
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29352
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29376
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29400
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29424
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29448
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29472
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29496
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29520
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29824
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30164
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30220
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30652
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30700
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30956
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31224
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31248
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31332
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31488
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31636
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31916
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32104
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32176
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32484
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32744
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32832
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32956
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33248
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33664
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33884
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34048
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34072)))
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