Load versions of libraries.

private/utils.rkt

@@ -14,6 +14,8 @@
            until
            build-lib-path
            get-lib
+           linux-lib-versions
+           ffmpeg-lib-versions
            do-for
            dbg-sound
            info-sound
@@ -165,11 +167,27 @@
 
   (define valid-ffmpeg-versions
     (make-hash (list (list 'avutil 58 60 "libavutil")
-                      (list 'avcodec 60 62 "libavcodec")
-                      (list 'avformat 60 62 "libavformat")
-                      (list 'swresample 4 6 "libswresample")
-                      ))
-    )
+                     (list 'avcodec 60 62 "libavcodec")
+                     (list 'avformat 60 62 "libavformat")
+                     (list 'swresample 4 6 "libswresample"))))
+
+  (define (versions-high-to-low from until)
+    (let loop ((n from) (acc '(#f)))
+      (if (> n until)
+          acc
+          (loop (+ n 1) (cons (number->string n) acc)))))
+
+  (define (ffmpeg-lib-versions kind)
+    (case (system-type 'os)
+      [(linux)
+       (let ((v (hash-ref valid-ffmpeg-versions kind)))
+         (versions-high-to-low (car v) (cadr v)))]
+      [else '(#f)]))
+
+  (define (linux-lib-versions versions [default '(#f)])
+    (case (system-type 'os)
+      [(linux) versions]
+      [else default]))
 
   (define (version-str kind)
     (let ((v (hash-ref valid-ffmpeg-versions kind)))