Add io wrapper handling UTF-8 BOM.

src/util-io.scm

@@ -0,0 +1,55 @@
+;;
+;; util-io.scm
+;;
+;; Special IO extensions to deal with weird stuff.
+;;
+;; ISC License
+;;
+;; Copyright 2023 Brmlab, z.s.
+;; Dominik Pantůček <dominik.pantucek@trustica.cz>
+;;
+;; Permission to use, copy, modify, and/or distribute this software
+;; for any purpose with or without fee is hereby granted, provided
+;; that the above copyright notice and this permission notice appear
+;; in all copies.
+;; 
+;; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+;; WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+;; WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+;; AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
+;; CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+;; OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+;; NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+;; CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+;;
+
+(declare (unit util-io))
+
+(module
+ util-io
+ (
+  read-lines/no-bom
+  )
+
+ (import scheme
+	 (chicken io))
+
+ ;; If given string begins with UTF-8 BOM, it is removed.
+ (define (remove-optional-bom str)
+   (if (< (string-length str) 3)
+       str
+       (let ((maybe-bom (substring str 0 3)))
+	 (if (string=? maybe-bom "\xEF\xBB\xBF")
+	     (substring str 3)
+	     str))))
+
+ ;; Reads lines from given input port, discarding BOM at the beginning
+ ;; of the first line if there is any.
+ (define (read-lines/no-bom ip)
+   (let ((lines (read-lines ip)))
+     (if (null? lines)
+	 lines
+	 (cons (remove-optional-bom (car lines))
+	       (cdr lines)))))
+
+ )