bug in encoding empty glyf table

pitfall/fontkit/glyf.rkt

@@ -0,0 +1,23 @@
+#lang fontkit/racket
+(require restructure)
+(provide (all-defined-out))
+#|
+approximates
+https://github.com/mbutterick/fontkit/blob/master/src/tables/glyf.js
+|#
+
+(define-subclass Struct (Rglyf))
+
+(define glyf (+Array (+Buffer)))
+
+(test-module
+ (define ip (open-input-file charter-path))
+ (define dir (deserialize (read (open-input-file charter-directory-path))))
+ (define offset (· dir tables glyf offset))
+ (define len (· dir tables glyf length))
+ (check-equal? offset 4620)
+ (check-equal? len 34072)
+ (set-port-position! ip 0)
+ (define table-bytes (peek-bytes len offset ip))
+ (define ds (+DecodeStream table-bytes))
+ )

pitfall/fontkit/subset.rkt

@@ -91,9 +91,8 @@ https://github.com/mbutterick/fontkit/blob/master/src/subset/TTFSubset.js
                 'loca (· this loca)
                 'maxp maxp
                 'cvt (send (· this font) _getTable 'cvt)
-                ;; todo: cvt
                 'prep (send (· this font) _getTable 'prep)
-                ;; 'glyf (· this glyf)
+                'glyf (· this glyf)
                 'hmtx (· this hmtx)
                 'fpgm (send (· this font) _getTable 'fpgm)
                 )))

pitfall/fontkit/tables.rkt

@@ -9,4 +9,4 @@
                     (test-module (require (submod TABLE-ID-STRING test) ...))
                     (define ID (make-hasheq (map cons (list 'TABLE-ID ...) (list TABLE-ID ...)))))))
 
-(define-table-decoders table-decoders maxp hhea head loca prep fpgm hmtx cvt)
+(define-table-decoders table-decoders maxp hhea head loca prep fpgm hmtx cvt glyf)

pitfall/restructure/buffer.rkt

@@ -0,0 +1,36 @@
+#lang restructure/racket
+(require "number.rkt" "utils.rkt")
+(provide (all-defined-out))
+
+#|
+approximates
+https://github.com/mbutterick/restructure/blob/master/src/Buffer.coffee
+|#
+
+(define-subclass RestructureBase (Buffer [_length #f])
+  (define/override (decode stream [parent #f])
+    (define len (resolveLength _length stream parent))
+    (send stream readBuffer len))
+
+  (define/override (size [val #f] [parent #f])
+    (when val (unless (bytes? val)
+                (raise-argument-error 'Buffer:size "bytes" val)))
+    (if val
+        (bytes-length val)
+        (resolveLength _length val parent)))
+
+  (define/override (encode stream buf parent)
+    (when (Number? _length)
+      (send _length encode stream (bytes-length buf)))
+    (send stream writeBuffer buf)))
+
+
+#;(test-module
+ (require "stream.rkt")
+ (define stream (+DecodeStream #"\2BCDEF"))
+ (define S (+String uint8 'utf8))
+ (check-equal? (send S decode stream) "BC")
+ (define os (+EncodeStream))
+ (send S encode os "Mike")
+ (check-equal? (send os dump) #"\4Mike")
+ (check-equal? (send (+String) size "foobar") 6))

pitfall/restructure/main.rkt

@@ -5,4 +5,5 @@
      "string.rkt"
      "array.rkt"
      "bitfield.rkt"
-     "stream.rkt")
+     "stream.rkt"
+     "buffer.rkt")

pitfall/restructure/stream.rkt

@@ -34,7 +34,10 @@ https://github.com/mbutterick/restructure/blob/master/src/EncodeStream.coffee
   (define/public-final (write val)
     (unless (bytes? val)
       (raise-argument-error 'EncodeStream:write "bytes" val))
-    (void (write-bytes val (· this _port)))))
+    (void (write-bytes val (· this _port))))
+
+  (define/public-final (writeBuffer buffer)
+    (write buffer)))
 
 (test-module
  (define es (+EncodeStream))
@@ -83,7 +86,10 @@ https://github.com/mbutterick/restructure/blob/master/src/DecodeStream.coffee
     (define bytes-remaining (- length (port-position _port)))
     (when (> count bytes-remaining)
       (raise-argument-error 'DecodeStream:read (format "byte count not more than bytes remaining = ~a" bytes-remaining) count))
-    (read-bytes count _port)))
+    (read-bytes count _port))
+
+  (define/public-final (readBuffer count)
+    (read count)))
 
 (test-module
  (define ds (+DecodeStream #"ABCD"))

pitfall/restructure/utils.rkt

@@ -8,4 +8,4 @@
     [(procedure? len) (len parent)]
     [(and parent (symbol? len) (hash-ref parent len))] ; treat as key into RStruct parent
     [(and stream (Number? len) (send len decode stream))]
-    [else (raise-argument-error 'resolveLength "fixed-size item" len)]))
+    [else (raise-argument-error 'resolveLength "not a fixed size" len)]))