Fix read-whitespaces behavior

1 files changed, 19 insertions, 8 deletions

diff --git a/pnm/read.scm b/pnm/read.scm
index 5cfec94..e3cb84b 100644
--- a/pnm/read.scm
+++ b/pnm/read.scm
@@ -49,8 +49,11 @@
             (unexpected-char-error))
           n))
       (define (read-whitespaces*)
-        (when (eof-object? (read-whitespaces in))
-          (unexpected-eof-error)))
+        (let ((result (read-whitespaces in)))
+          (when (eof-object? result)
+            (unexpected-eof-error))
+          (unless result
+            (error "(pnm read) image-read: Unexpected character (expected whitespace)"))))
 
       (let ((magic-number (read-magic-number*)))
         (read-whitespaces*)
@@ -105,11 +108,22 @@
         (cond ((eof-object? u8) (eof-object))
               ((newline? u8)
                (read-u8 in)
-               (read-whitespaces in))
+               (skip-whitespace in))
               (else
                (read-u8 in)
                (read-comment in)))))
 
+    (define (skip-whitespace in)
+      (let ((u8 (peek-u8 in)))
+        (cond ((eof-object? u8) #t)
+              ((whitespace? u8)
+               (read-u8 in)
+               (skip-whitespace in))
+              ((comment? u8)
+               (read-u8 in)
+               (read-comment in))
+              (else #t))))
+
     (define (digit? u8)
       (and (<= 48 u8)
            (<= u8 57)))
@@ -134,11 +148,8 @@
         (cond ((eof-object? u8) (eof-object))
               ((whitespace? u8)
                (read-u8 in)
-               (read-whitespaces in))
-              ((comment? u8)
-               (read-u8 in)
-               (read-comment in))
-              (else #t))))
+               (skip-whitespace in))
+              (else #f))))
 
     (define (read-number in)
       (call-with-current-continuation