removebom.scm

(use srfi-13)
(use gauche.test)

(define (starts-with? str prefix)
  (let ((str-len (string-length str))
        (prefix-len (string-length prefix)))
    (if (> str-len prefix-len)
        (string=? (substring str 0 prefix-len) prefix)
        #f)))

(define (remove-bom path)
  (let* ((bom (string #xEF #xBB #xBF))
         (content (slurp path)))
    (if (starts-with? content bom)
        (let ((new-content (substring content (string-length bom))))
          (spit path new-content)))))

(define (walk path)
  (if (file-directory? path)
      (do-directory path walk)
      (if (string-suffix? ".java" path)
          (remove-bom path))))

(define (test-remove-bom path)
  (let ((file (open path "wb")))
    (write-string (string #xEF #xBB #xBF) file)
    (write-string "hello" file)
    (close file))
  (remove-bom path)
  (let ((content (slurp path)))
    (assert-string= content "hello")))

(define-test-group remove-bom
  (test-remove-bom "bom.txt"))

(run-tests)