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Bitmap/Read a PPM file: Difference between revisions
m
→{{header|Common Lisp}}
Line 274:
(defun read-ppm-file-header (file)
(with-open-file (s file :direction :input)
(do ((failure-count 0 (1+ failure-count))
(if (> (length t1) 0)
▲ (tokens nil (cons (read-header-chars s) tokens)))
tokens))))
((>= (length tokens) 4) (values (nreverse tokens)
(file-position s)))
(when (>= failure-count 10)
(error (format nil "File ~a does not seem to be a proper ppm file - maybe too many comment lines" file)))
(when (=
(when (not (or (string= (first tokens) "P6") (string= (first tokens) "P3")))
(error (format nil "File ~a is not a ppm file - wrong magic-number. Read ~a instead of P6 or P3 " file (first tokens))))))))
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