-typedef int avwCallbackIoRead(void *, unsigned char *, int);
-typedef fs_offset_t avwCallbackIoSeek(void *, fs_offset_t, int);
-typedef fs_offset_t avwCallbackIoSeekSize(void *);
+typedef int avwCallbackIoRead(void *, uint8_t *, int);
+typedef uint64_t avwCallbackIoSeek(void *, uint64_t, int);
+typedef uint64_t avwCallbackIoSeekSize(void *);