* flac support

* taglib support
It is possible to play some music already.

libflac/flac-definitions.rkt

@@ -0,0 +1,99 @@
+(module flac-definitions racket/base
+  
+  (provide flac-stream-info
+           make-flac-stream-info
+           flac-stream-info->string
+           
+           flac-handle
+           make-flac-handle
+           flac-handle-ffi-decoder-handler
+           flac-handle-stream-info
+           set-flac-handle-stream-info!
+           flac-handle-cb-stream-info
+           set-flac-handle-cb-stream-info!
+           flac-handle-cb-audio
+           set-flac-handle-cb-audio!
+
+           flac-handle->string
+
+           flac-sample-rate
+           flac-channels
+           flac-bits-per-sample
+           flac-total-samples
+           flac-duration
+           )
+
+  (define-struct flac-stream-info
+    (min-blocksize max-blocksize
+     min-framesize max-framesize
+     sample-rate
+     channels
+     bits-per-sample
+     total-samples
+     ))
+
+  (define (flac-stream-info->string si)
+    (format "sample-rate: ~a, channels: ~a, bits-per-sample: ~a, total-samples: ~a"
+            (flac-stream-info-sample-rate si)
+            (flac-stream-info-channels si)
+            (flac-stream-info-bits-per-sample si)
+            (flac-stream-info-total-samples si)))
+
+  (define (flac-sample-rate h)
+    (let ((si (flac-handle-stream-info h)))
+      (if (eq? si #f)
+          #f
+          (flac-stream-info-sample-rate si))))
+
+  (define (flac-channels h)
+    (let ((si (flac-handle-stream-info h)))
+      (if (eq? si #f)
+          #f
+          (flac-stream-info-channels si))))
+
+  (define (flac-bits-per-sample h)
+    (let ((si (flac-handle-stream-info h)))
+      (if (eq? si #f)
+          #f
+          (flac-stream-info-bits-per-sample si))))
+
+  (define (flac-total-samples h)
+    (let ((si (flac-handle-stream-info h)))
+      (if (eq? si #f)
+          #f
+          (flac-stream-info-total-samples si))))
+
+  (define (flac-handle->string h)
+    (let* ((si (flac-handle-stream-info h))
+           (ffi (flac-handle-ffi-decoder-handler h))
+           (ff  (ffi 'file)))
+      (string-append
+       (if (eq? ff #f)
+           "no flac file available\n"
+           (format "Flac File: ~a\n" ff))
+       (if (eq? si #f)
+           "no stream info available\n"
+           (string-append
+             (format "Stream Info: ~a\n" (flac-stream-info->string si))
+             (format "Duration in seconds: ~a\n" (flac-duration h))))
+       )))
+
+  (define (flac-duration h)
+    (let* ((si (flac-handle-stream-info h)))
+      (if (eq? si #f)
+          #f
+          (let* ((total-samples (flac-stream-info-total-samples si))
+                 (sample-rate (flac-stream-info-sample-rate si)))
+            (inexact->exact (round (/ total-samples sample-rate)))))))
+
+  (define-struct flac-handle
+    (
+     ffi-decoder-handler
+     [cb-stream-info #:auto #:mutable]
+     [cb-audio #:auto #:mutable]
+     [stream-info #:auto #:mutable]
+     )
+     #:auto-value #f
+    )
+
+  ); end of module