escapableRe & byteSwap

pitfall/pitfall/kit/buffer.rkt

@@ -0,0 +1,25 @@
+#lang br
+
+;; nodejs Buffer object = Racket byte string
+
+(define Buffer
+  (class object%
+    (super-new)
+
+    (init-field [bstr #""])
+
+    (define/public (isBuffer x)
+      (is-a? x Buffer))
+
+    (define/public (length)
+      (bytes-length bstr))))
+
+(define isBuffer (generic Buffer isBuffer))
+
+
+(module+ test
+  (require rackunit)
+  (define good-buffer (make-object Buffer #"foo"))
+  (check-true (send-generic good-buffer isBuffer good-buffer))
+  (check-false (send-generic (new Buffer) isBuffer "foo")))
+

pitfall/pitfall/kit/object.rkt

@@ -1,18 +1,38 @@
-#lang br
-
-(define (string-slice str length)
-  (let loop ([length length])
-     (if (negative? length)
-         (loop (+ (string-length str) length))
-         (substring str length (string-length str))))) 
+#lang at-exp br
 
 (define PDFObject
   (class object%
     (super-new)
 
+    (define (string-slice str length)
+      (if (negative? length)
+          (string-slice str (+ (string-length str) length))
+          (substring str length)))
+
     (define/public (pad str length)
       (define newstr (string-append (string-join (make-list (add1 length) "") "0") str))
-      (string-slice newstr (- length)))))
+      (string-slice newstr (- length)))
+
+    (define escaped-chars '(#\newline #\return #\tab #\backspace #\page #\( #\) #\\))
+    (define escaped-char-strings '("\\n" "\\r" "\\t" "\\b" "\\f" "\\(" "\\)" "\\\\"))
+    
+    (field [escapableRe
+            (regexp (format "[~a]" (regexp-quote (list->string escaped-chars))))])
+
+    (field [escapable (for/hash ([k (in-list escaped-chars)]
+                                 [v (in-list escaped-char-strings)])
+                                (values (string k) v))])
+
+    ; Convert little endian UTF-16 to big endian
+    (define/public (swapBytes buff)
+      (define bufflen (bytes-length buff))
+      (when (odd? bufflen)
+        (raise-argument-error 'swapBytes "even number of bytes" (bytes-length buff)))
+      (define newbuff (make-bytes bufflen))
+      (for ([bidx (in-range 0 bufflen 2)])
+           (bytes-set! newbuff bidx (bytes-ref buff (add1 bidx)))
+           (bytes-set! newbuff (add1 bidx) (bytes-ref buff bidx)))
+      newbuff)))
 
 
 (module+ test
@@ -22,4 +42,12 @@
   (check-equal? (send o pad "foobar" 0) "foobar")
   (check-equal? (send o pad "foobar" 3) "bar")
   (check-equal? (send o pad "foobar" 6) "foobar")
-  (check-equal? (send o pad "foobar" 10) "0000foobar"))
+  (check-equal? (send o pad "foobar" 10) "0000foobar")
+
+  (check-equal? (regexp-replace* (get-field escapableRe o) "foo\nba\nr" "x") "fooxbaxr")
+  (check-equal? (regexp-replace* (get-field escapableRe o) "foo\fba\tr" "x") "fooxbaxr")
+  
+  (check-equal? (regexp-replace* (get-field escapableRe o) "foo\nba\tr" (λ (c) (hash-ref (get-field escapable o) c))) "foo\\nba\\tr")
+
+  (check-equal? (send o swapBytes #"foobar") #"ofbora"))
+