From 2d9c09c03691e4310c6ee946e5c05b5d21d18123 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 9 Jun 2017 07:51:51 -0700
Subject: [PATCH] next: unify helper modules

---
 pitfall/pitfall/directory.rkt  | 31 +++++++++++++++++++------------
 pitfall/pitfall/helper.rkt     |  1 +
 pitfall/restructure/array.rkt  | 13 ++++++++-----
 pitfall/restructure/helper.rkt |  3 +++
 pitfall/restructure/utils.rkt  |  2 +-
 5 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/pitfall/pitfall/directory.rkt b/pitfall/pitfall/directory.rkt
index d08f991a..9750170c 100644
--- a/pitfall/pitfall/directory.rkt
+++ b/pitfall/pitfall/directory.rkt
@@ -3,21 +3,28 @@
 
 (provide (all-defined-out))
 
+#|
+https://github.com/mbutterick/fontkit/blob/master/src/tables/directory.js
+|#
 
 (define TableEntry (make-object RStruct
-                     (list (cons 'tag (make-object RString 4))
-                           (cons 'checkSum uint32be)
-                           (cons 'offset uint32be)
-                           (cons 'length uint32be))))
+                     (dictify 'tag (make-object RString 4)
+                              'checkSum uint32be
+                              'offset uint32be
+                              'length uint32be)))
 
-(define Directory (make-object RStruct
-                    (list (cons 'tag (make-object RString 4))
-                          (cons 'numTables uint16be)
-                          (cons 'searchRange uint16be)
-                          (cons 'entrySelector uint16be)
-                          (cons 'rangeShift uint16be)
-                          ;; todo next: derive the `14` from 'numTables
-                          (cons 'tables (make-object RArray TableEntry 14)))))
+(define-subclass RStruct (RDirectory)
+  (super-new)
+  (define/public (process)
+    'boom))
+
+(define Directory (make-object RDirectory
+                    (dictify 'tag (make-object RString 4)
+                             'numTables uint16be
+                             'searchRange uint16be
+                             'entrySelector uint16be
+                             'rangeShift uint16be
+                             'tables (make-object RArray TableEntry 'numTables))))
 
 (module+ test
   (require rackunit)
diff --git a/pitfall/pitfall/helper.rkt b/pitfall/pitfall/helper.rkt
index dae1798b..7d6ab462 100644
--- a/pitfall/pitfall/helper.rkt
+++ b/pitfall/pitfall/helper.rkt
@@ -47,6 +47,7 @@
 (define-hashifier mhash make-hash)
 (define-hashifier mhasheq make-hasheq)
 (define-hashifier mhasheqv make-hasheqv)
+(define (dictify . xs) (listify xs))
 
 (module+ test
   (check-equal? (mhash 'k "v") (make-hash (list (cons 'k "v"))))) 
diff --git a/pitfall/restructure/array.rkt b/pitfall/restructure/array.rkt
index 269c99dc..72e6ffcb 100644
--- a/pitfall/restructure/array.rkt
+++ b/pitfall/restructure/array.rkt
@@ -8,12 +8,15 @@ https://github.com/mbutterick/restructure/blob/master/src/Array.coffee
 |#
 
 (define-subclass RStreamcoder (RArray type [length #f] [lengthType 'count])
-  
-         
+          
   (define/augment (decode stream [parent #f])
-    (caseq lengthType
-           [(count) (for/list ([i (in-range length)])
-                              (send type decode stream this))]))
+    (let ([length (if length
+                      (resolveLength length stream parent)
+                      (send stream length))])
+    
+      (caseq lengthType
+             [(count) (for/list ([i (in-range length)])
+                                (send type decode stream this))])))
 
   (define/public (size) (unfinished))
 
diff --git a/pitfall/restructure/helper.rkt b/pitfall/restructure/helper.rkt
index 9eb77d7b..a25dcf49 100644
--- a/pitfall/restructure/helper.rkt
+++ b/pitfall/restructure/helper.rkt
@@ -72,6 +72,9 @@
 (define-hashifier mhasheq make-hasheq)
 (define-hashifier mhasheqv make-hasheqv)
 
+(provide dictify)
+(define (dictify . xs) (listify xs))
+
 (define (port-position port)
   (define-values (l c p) (port-next-location port))
   p)
diff --git a/pitfall/restructure/utils.rkt b/pitfall/restructure/utils.rkt
index 90c57374..5b2a8c1d 100644
--- a/pitfall/restructure/utils.rkt
+++ b/pitfall/restructure/utils.rkt
@@ -6,6 +6,6 @@
   (cond
     [(number? length) length]
     [(procedure? length) (length parent)]
-    [(and parent (string? length) (· parent length))]
+    [(and parent (symbol? length) (hash-ref parent length))] ; treat as key into RStruct parent
     [(and stream (is-a? length Number) (send length decode stream))]
     [else (raise-argument-error 'resolveLength "fixed-size item" length)]))
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