1 files changed, 11 insertions(+), 19 deletions(-)

M decode.rkt

@@ 11,15 11,13 @@
       res
       (error "Unexpected EOF")))
 
-; read n bytes from port into buf. n is inferred from the length of buf
-(define (read-n-bytes buf port)
-  (define n (bytes-length buf))
-  (let loop ([cur 0])
-    (if (= cur n)
-        buf
-        (begin
-          (bytes-set! buf cur (expect-byte port))
-          (loop (add1 cur))))))
+; read exactly n bytes, or throw
+(define (read-n-bytes n port)
+  (let* ([bytes (read-bytes n port)]
+         [len   (if (eof-object? bytes) 0 (bytes-length bytes))])
+    (if (= len n)
+      bytes
+      (error "Unexpected EOF: Expected ~a bytes, got ~a" n len))))
 
 (define (read-argument port major additional)
   (if (< additional 24)


@@ 78,8 76,7 @@
                             (lambda () (cbor-read config port)) ; TODO disallow indefinites in the chunks, and also check that they are actually bytestrings
                             (lambda (strs)
                               (bytes->immutable-bytes (apply bytes-append (reverse strs)))))
-      (let ([buf (make-bytes payload-len)])
-        (bytes->immutable-bytes (read-n-bytes buf port)))))
+      (bytes->immutable-bytes (read-n-bytes payload-len port))))
 
 (define (cbor-read-string config port additional)
   (define payload-len (read-argument port 3 additional))


@@ 88,8 85,7 @@
                             (lambda () (cbor-read config port)) ; TODO disallow indefinites in the chunks, and also check that they are actually strings
                             (lambda (strs)
                               (apply string-append-immutable (reverse strs))))
-      (let ([buf (make-bytes payload-len)])
-        (read-n-bytes buf port)
+      (let ([buf (read-n-bytes payload-len port)])
         (string->immutable-string (bytes->string/utf-8 buf)))))
 
 (define (cbor-read-list config port additional)


@@ 173,13 169,9 @@
                        (arithmetic-shift (expect-byte port) 8)
                        (expect-byte port)))]
         [(26)
-         (define buf (bytes 0 0 0 0))
-         (read-n-bytes buf port)
-         (floating-point-bytes->real buf #t)]
+         (floating-point-bytes->real (read-n-bytes 4 port) #t)]
         [(27)
-         (define buf (bytes 0 0 0 0 0 0 0 0))
-         (read-n-bytes buf port)
-         (floating-point-bytes->real buf #t)]
+         (floating-point-bytes->real (read-n-bytes 8 port) #t)]
         [(28 29 30) (error "Additional information ~a is reserved in major type 7" additional)]
         [(31) (error "Unexpected break code")]))) ; We handle break explicitly in deserialization of lists of things, so it should never appear here.