diff --git a/demo/cat.c b/demo/cat.c
index 4a42191..a95eebc 100644
--- a/demo/cat.c
+++ b/demo/cat.c
@@ -42,7 +42,7 @@ int main(int argc, char **argv)
         return 1;
     }
 
-    res = file->lstat(file, &info);
+    res = iso_file_source_lstat(file, &info);
     if (res < 0) {
         fprintf(stderr, "Can't stat file, err = %d\n", res);
         return 1;
@@ -53,19 +53,19 @@ int main(int argc, char **argv)
         return 1;
     } else {
         char buf[1024];
-        res = file->open(file);
+        res = iso_file_source_open(file);
         if (res < 0) {
             fprintf(stderr, "Can't open file, err = %d\n", res);
             return 1;
         }
-        while ((res = file->read(file, buf, 1024)) > 0) {
+        while ((res = iso_file_source_read(file, buf, 1024)) > 0) {
             fwrite(buf, 1, res, stdout);
         }
         if (res < 0) {
             fprintf(stderr, "Error reading, err = %d\n", res);
             return 1;
         }
-        file->close(file);
+        iso_file_source_close(file);
     }
     
     iso_file_source_unref(file);
diff --git a/demo/lsl.c b/demo/lsl.c
index 6dae4c1..17659f7 100644
--- a/demo/lsl.c
+++ b/demo/lsl.c
@@ -56,16 +56,16 @@ print_file_src(IsoFileSource *file)
 {
     struct stat info;
     char *name;
-    file->lstat(file, &info);
+    iso_file_source_lstat(file, &info);
     print_type(info.st_mode);
     print_permissions(info.st_mode);
     printf(" {%ld,%ld} ", (long)info.st_dev, (long)info.st_ino);
-    name = file->get_name(file);
+    name = iso_file_source_get_name(file);
     printf(" %s", name);
     free(name);
     if (S_ISLNK(info.st_mode)) {
         char buf[PATH_MAX];
-        file->readlink(file, buf, PATH_MAX);
+        iso_file_source_readlink(file, buf, PATH_MAX);
         printf(" -> %s\n", buf);
     }
     printf("\n");
@@ -97,25 +97,25 @@ int main(int argc, char **argv)
         return 1;
     }
 
-    res = dir->lstat(dir, &info);
+    res = iso_file_source_lstat(dir, &info);
     if (res < 0) {
         fprintf(stderr, "Can't stat file, err = %d\n", res);
         return 1;
     }
 
     if (S_ISDIR(info.st_mode)) {
-        res = dir->open(dir);
+        res = iso_file_source_open(dir);
         if (res < 0) {
             fprintf(stderr, "Can't open file, err = %d\n", res);
             return 1;
         }
 
-        while (dir->readdir(dir, &file) == 1) {
+        while (iso_file_source_readdir(dir, &file) == 1) {
             print_file_src(file);
             iso_file_source_unref(file);
         }
 
-        res = dir->close(dir);
+        res = iso_file_source_close(dir);
         if (res < 0) {
             fprintf(stderr, "Can't close file, err = %d\n", res);
             return 1;
diff --git a/src/builder.c b/src/builder.c
index d1dd79a..3af4adf 100644
--- a/src/builder.c
+++ b/src/builder.c
@@ -43,7 +43,7 @@ int default_create_file(IsoNodeBuilder *builder, IsoImage *image,
         return ISO_NULL_POINTER;
     }
     
-    res = src->stat(src, &info);
+    res = iso_file_source_stat(src, &info);
     if (res < 0) {
         return res;
     }
@@ -65,7 +65,7 @@ int default_create_file(IsoNodeBuilder *builder, IsoImage *image,
     /* fill node fields */
     node->node.refcount = 1;
     node->node.type = LIBISO_FILE;
-    node->node.name = strdup(src->get_name(src));
+    node->node.name = strdup(iso_file_source_get_name(src));
     node->node.mode = S_IFREG | (info.st_mode & ~S_IFMT);
     node->node.uid = info.st_uid;
     node->node.gid = info.st_gid;
@@ -96,13 +96,13 @@ int default_create_node(IsoNodeBuilder *builder, IsoImage *image,
         return ISO_NULL_POINTER;
     }
     
-    name = src->get_name(src);
+    name = iso_file_source_get_name(src);
     
     /* get info about source */
     if (image->recOpts->follow_symlinks) {
-        result = src->stat(src, &info);
+        result = iso_file_source_stat(src, &info);
     } else {
-        result = src->lstat(src, &info);
+        result = iso_file_source_lstat(src, &info);
     }
     if (result < 0) {
         return result;
@@ -149,7 +149,7 @@ int default_create_node(IsoNodeBuilder *builder, IsoImage *image,
             char dest[PATH_MAX];
             IsoSymlink *link;
             
-            result = src->readlink(src, dest, PATH_MAX);
+            result = iso_file_source_readlink(src, dest, PATH_MAX);
             if (result < 0) {
                 return result;
             }
diff --git a/src/fs_local.c b/src/fs_local.c
index 7211422..9adfa9f 100644
--- a/src/fs_local.c
+++ b/src/fs_local.c
@@ -381,7 +381,7 @@ void lfs_free(IsoFileSource *src)
 
     /* close the file if it is already openned */
     if (data->openned) {
-        src->close(src);
+        src->class->close(src);
     }
 
     free(data->path);
@@ -389,6 +389,20 @@ void lfs_free(IsoFileSource *src)
     iso_filesystem_unref(lfs);
 }
 
+IsoFileSourceIface lfs_class = {
+    lfs_get_path,
+    lfs_get_name,
+    lfs_lstat,
+    lfs_stat,
+    lfs_open,
+    lfs_close,
+    lfs_read,
+    lfs_readdir,
+    lfs_readlink,
+    lfs_get_filesystem,
+    lfs_free
+};
+
 /**
  * 
  * @return
@@ -435,17 +449,7 @@ int iso_file_source_new_lfs(const char *path, IsoFileSource **src)
 
     lfs_src->refcount = 1;
     lfs_src->data = data;
-    lfs_src->get_path = lfs_get_path;
-    lfs_src->get_name = lfs_get_name;
-    lfs_src->lstat = lfs_lstat;
-    lfs_src->stat = lfs_stat;
-    lfs_src->open = lfs_open;
-    lfs_src->close = lfs_close;
-    lfs_src->read = lfs_read;
-    lfs_src->readdir = lfs_readdir;
-    lfs_src->readlink = lfs_readlink;
-    lfs_src->get_filesystem = lfs_get_filesystem;
-    lfs_src->free = lfs_free;
+    lfs_src->class = &lfs_class;
     
     /* take a ref to local filesystem */
     iso_filesystem_ref(lfs);
diff --git a/src/fsource.c b/src/fsource.c
index 3bd4480..0c62830 100644
--- a/src/fsource.c
+++ b/src/fsource.c
@@ -22,7 +22,7 @@ void iso_file_source_ref(IsoFileSource *src)
 void iso_file_source_unref(IsoFileSource *src)
 {
 	if (--src->refcount == 0) {
-		src->free(src);
+		src->class->free(src);
 		free(src);
 	}
 }
diff --git a/src/fsource.h b/src/fsource.h
index b433ead..119fc4d 100644
--- a/src/fsource.h
+++ b/src/fsource.h
@@ -69,7 +69,7 @@ struct Iso_Filesystem
     void *data;
 };
 
-struct Iso_File_Source
+typedef struct IsoFileSource_Iface
 {
 
     /**
@@ -231,7 +231,10 @@ struct Iso_File_Source
      * TODO #00004 Add a get_mime_type() function.
      * This can be useful for GUI apps, to choose the icon of the file
      */
-     
+} IsoFileSourceIface;
+
+struct Iso_File_Source {
+    const IsoFileSourceIface *class;
     int refcount;
     void *data;
 };
@@ -239,6 +242,60 @@ struct Iso_File_Source
 void iso_file_source_ref(IsoFileSource *src);
 void iso_file_source_unref(IsoFileSource *src);
 
+/* 
+ * this are just helpers to invoque methods in class
+ */
+extern inline 
+const char* iso_file_source_get_path(IsoFileSource *src) {
+    return src->class->get_path(src);
+}
+
+extern inline 
+char* iso_file_source_get_name(IsoFileSource *src) {
+    return src->class->get_name(src);
+}
+
+extern inline 
+int iso_file_source_lstat(IsoFileSource *src, struct stat *info) {
+    return src->class->lstat(src, info);
+}
+
+extern inline 
+int iso_file_source_stat(IsoFileSource *src, struct stat *info) {
+    return src->class->stat(src, info);
+}
+
+extern inline 
+int iso_file_source_open(IsoFileSource *src) {
+    return src->class->open(src);
+}
+
+extern inline 
+int iso_file_source_close(IsoFileSource *src) {
+    return src->class->close(src);
+}
+
+extern inline 
+int iso_file_source_read(IsoFileSource *src, void *buf, size_t count) {
+    return src->class->read(src, buf, count);
+}
+
+extern inline 
+int iso_file_source_readdir(IsoFileSource *src, IsoFileSource **child)
+{
+    return src->class->readdir(src, child);
+}
+
+extern inline 
+int iso_file_source_readlink(IsoFileSource *src, char *buf, size_t bufsiz) {
+    return src->class->readlink(src, buf, bufsiz);
+}
+
+extern inline 
+IsoFilesystem* iso_file_source_get_filesystem(IsoFileSource *src) {
+    return src->class->get_filesystem(src);
+}
+
 /**
  * Create a new IsoFileSource from a local filesystem path.
  * While this is usually called by corresponding method in IsoFilesystem
diff --git a/src/stream.c b/src/stream.c
index 9abf101..9a48392 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -31,7 +31,7 @@ int fsrc_open(IsoStream *stream)
         return ISO_NULL_POINTER;
     }
     src = ((FSrcStreamData*)stream->data)->src;
-    return src->open(src);
+    return iso_file_source_open(src);
 }
 
 static
@@ -42,7 +42,7 @@ int fsrc_close(IsoStream *stream)
         return ISO_NULL_POINTER;
     }
     src = ((FSrcStreamData*)stream->data)->src;
-    return src->close(src);
+    return iso_file_source_close(src);
 }
 
 static
@@ -62,7 +62,7 @@ int fsrc_read(IsoStream *stream, void *buf, size_t count)
         return ISO_NULL_POINTER;
     }
     src = ((FSrcStreamData*)stream->data)->src;
-    return src->read(src, buf, count);
+    return iso_file_source_read(src, buf, count);
 }
 
 static 
@@ -77,7 +77,7 @@ int fsrc_is_repeatable(IsoStream *stream)
     data = (FSrcStreamData*)stream->data;
     
     /* mode is not cached, this function is only useful for filters */
-    ret = data->src->stat(data->src, &info);
+    ret = iso_file_source_stat(data->src, &info);
     if (ret < 0) {
         return ret; 
     }
@@ -100,7 +100,7 @@ int fsrc_get_id(IsoStream *stream, unsigned int *fs_id, dev_t *dev_id,
     }
     data = (FSrcStreamData*)stream->data;
     
-    fs = data->src->get_filesystem(data->src);
+    fs = iso_file_source_get_filesystem(data->src);
     
     *fs_id = fs->get_id(fs);
     if (fs_id == 0) {
@@ -132,7 +132,7 @@ int iso_file_source_stream_new(IsoFileSource *src, IsoStream **stream)
         return ISO_NULL_POINTER;
     }
     
-    r = src->stat(src, &info);
+    r = iso_file_source_stat(src, &info);
     if (r < 0) {
         return r;
     }
diff --git a/src/tree.c b/src/tree.c
index 7c5c586..0d1d43b 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -313,7 +313,7 @@ int iso_tree_add_node_builder(IsoImage *image, IsoDir *parent,
         *node = NULL;
     }
     
-    name = src->get_name(src);
+    name = iso_file_source_get_name(src);
     
     /* find place where to insert */
     pos = &(parent->children);
@@ -400,24 +400,25 @@ int iso_add_dir_aux(IsoImage *image, IsoDir *parent, IsoFileSource *dir)
     IsoFileSource *file;
     IsoNode **pos;
     
-    result = dir->open(dir);
+    result = iso_file_source_open(dir);
     if (result < 0) {
-        iso_msg_debug(image, "Can't open dir %s", dir->get_path(dir));
+        iso_msg_debug(image, "Can't open dir %s", 
+                      iso_file_source_get_path(dir));
         return result;
     }
     
     builder = image->builder;
     action = 1;
-    while ( (result = dir->readdir(dir, &file)) == 1) {
+    while ( (result = iso_file_source_readdir(dir, &file)) == 1) {
         int flag;
         char *name;
         IsoNode *new;
         
-        iso_msg_debug(image, "Adding file %s", file->get_path(file));
+        iso_msg_debug(image, "Adding file %s", iso_file_source_get_path(file));
         
-        name = file->get_name(file);
+        name = iso_file_source_get_name(file);
         
-        if (check_excludes(image, file->get_path(file))) {
+        if (check_excludes(image, iso_file_source_get_path(file))) {
             action = 2;
         } else if (check_hidden(image, name)) {
             action = 2;
@@ -458,7 +459,7 @@ int iso_add_dir_aux(IsoImage *image, IsoDir *parent, IsoFileSource *dir)
         if (result < 0) {
             
             iso_msg_debug(image, "Error %d when adding file %s", 
-                          result, file->get_path(file));
+                          result, iso_file_source_get_path(file));
             
             if (image->recOpts->report) {
                 action = image->recOpts->report(file, result, flag);
@@ -521,7 +522,7 @@ int iso_add_dir_aux(IsoImage *image, IsoDir *parent, IsoFileSource *dir)
         action = result;
     }
     
-    result = dir->close(dir);
+    result = iso_file_source_close(dir);
     if (result < 0) {
         return result;
     }
@@ -552,7 +553,7 @@ int iso_tree_add_dir_rec(IsoImage *image, IsoDir *parent, const char *dir)
     }
     
     /* we also allow dir path to be a symlink to a dir */
-    result = file->stat(file, &info);
+    result = iso_file_source_stat(file, &info);
     if (result < 0) {
         iso_file_source_unref(file);
         return result;
diff --git a/test/mocked_fsrc.c b/test/mocked_fsrc.c
index a3f2c31..618ad17 100644
--- a/test/mocked_fsrc.c
+++ b/test/mocked_fsrc.c
@@ -171,6 +171,20 @@ void mfs_free(IsoFileSource *src)
     free(data);
 }
 
+IsoFileSourceIface mfs_class = {
+    mfs_get_path,
+    mfs_get_name,
+    mfs_lstat,
+    mfs_stat,
+    mfs_open,
+    mfs_close,
+    mfs_read,
+    mfs_readdir,
+    mfs_readlink,
+    mfs_get_filesystem,
+    mfs_free
+};
+
 /**
  * 
  * @return
@@ -214,17 +228,7 @@ int mocked_file_source_new(IsoFilesystem *fs, const char *path,
 
     mocked_src->refcount = 1;
     mocked_src->data = data;
-    mocked_src->get_path = mfs_get_path;
-    mocked_src->get_name = mfs_get_name;
-    mocked_src->lstat = mfs_lstat;
-    mocked_src->stat = mfs_stat;
-    mocked_src->open = mfs_open;
-    mocked_src->close = mfs_close;
-    mocked_src->read = mfs_read;
-    mocked_src->readdir = mfs_readdir;
-    mocked_src->readlink = mfs_readlink;
-    mocked_src->get_filesystem = mfs_get_filesystem;
-    mocked_src->free = mfs_free;
+    mocked_src->class = &mfs_class;
     
     /* take a ref to filesystem */
     iso_filesystem_ref(fs);