android: add a new file in order to refactor common code between Android vout modules.

Implement a function to load the Native Window API from the Android
library.  This API is needed by current vouts nativewindow and surface
and will also be needed by the opaque vout.
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/video_output/android/utils.c

+/*****************************************************************************
+ * utils.c: shared code between Android vout modules.
+ *****************************************************************************
+ * Copyright (C) 2014 VLC authors and VideoLAN
+ *
+ * Authors: Felix Abecassis <felix.abecassis@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+#include "utils.h"
+#include <dlfcn.h>
+
+void *LoadNativeWindowAPI(native_window_api_t *native)
+{
+    void *p_library = dlopen("libandroid.so", RTLD_NOW);
+    if (!p_library)
+        return NULL;
+
+    native->winFromSurface =
+        (ptr_ANativeWindow_fromSurface)(dlsym(p_library, "ANativeWindow_fromSurface"));
+    native->winRelease =
+        (ptr_ANativeWindow_release)(dlsym(p_library, "ANativeWindow_release"));
+    native->winLock =
+        (ptr_ANativeWindow_lock)(dlsym(p_library, "ANativeWindow_lock"));
+    native->unlockAndPost =
+        (ptr_ANativeWindow_unlockAndPost)(dlsym(p_library, "ANativeWindow_unlockAndPost"));
+
+    if (native->winFromSurface && native->winRelease && native->winLock && native->unlockAndPost)
+        return p_library;
+
+    native->winFromSurface = NULL;
+    native->winRelease = NULL;
+    native->winLock = NULL;
+    native->unlockAndPost = NULL;
+
+    dlclose(p_library);
+    return NULL;
+}

modules/video_output/android/utils.h

+/*****************************************************************************
+ * utils.h: shared code between Android vout modules.
+ *****************************************************************************
+ * Copyright (C) 2014 VLC authors and VideoLAN
+ *
+ * Authors: Felix Abecassis <felix.abecassis@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#include <android/native_window.h>
+#include <jni.h>
+#include <android/native_window_jni.h>
+
+typedef ANativeWindow* (*ptr_ANativeWindow_fromSurface)(JNIEnv*, jobject);
+typedef void (*ptr_ANativeWindow_release)(ANativeWindow*);
+typedef int32_t (*ptr_ANativeWindow_lock)(ANativeWindow*, ANativeWindow_Buffer*, ARect*);
+typedef void (*ptr_ANativeWindow_unlockAndPost)(ANativeWindow*);
+
+typedef struct
+{
+    ptr_ANativeWindow_fromSurface winFromSurface;
+    ptr_ANativeWindow_release winRelease;
+    ptr_ANativeWindow_lock winLock;
+    ptr_ANativeWindow_unlockAndPost unlockAndPost;
+} native_window_api_t;
+
+/* Fill the structure passed as parameter and return a library handle
+   that should be destroyed with dlclose. */
+void *LoadNativeWindowAPI(native_window_api_t *native);