Made the overlay loader code part of the plugin library.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@8813 a1c6a512-1295-4272-9138-f99709370657

apps/plugins/lib/overlay.c

@@ -0,0 +1,106 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Overlay loader
+ *
+ * Copyright (C) 2006 Jens Arnold
+ *
+ * All files in this archive are subject to the GNU General Public License.
+ * See the file COPYING in the source tree root for full license agreement.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#ifndef SIMULATOR
+#include "plugin.h"
+
+/* load and run a plugin linked as an overlay. 
+
+ arguments:
+   rb        = pointer to plugin api, also passed on to the overlay
+   parameter = plugin parameter, passed on to the overlay
+   filename  = overlay file name, absolute path as usual
+   name      = overlay display name
+   
+ result:
+   return value from the overlay
+   
+   As long as a large plugin to be overlayed doesn't use the audiobuffer
+   itself, no adjustments in the plugin source code are necessary to make
+   it work as an overlay, it only needs an adapted linker script.
+   
+   If the overlayed plugin *does* use the audiobuffer itself, it needs 
+   to make sure not to overwrite itself.
+   
+   The linker script for the overlay should use a base address towards the
+   end of the audiobuffer, just low enough to make the overlay fit. */
+
+enum plugin_status run_overlay(struct plugin_api* rb, void* parameter,
+                               unsigned char *filename, unsigned char *name)
+{
+    int fd, readsize;
+    int audiobuf_size;
+    unsigned char *audiobuf;
+    static struct plugin_header header;
+
+    fd = rb->open(filename, O_RDONLY);
+    if (fd < 0)
+    {
+        rb->splash(2*HZ, true, "Can't open %s", filename);
+        return PLUGIN_ERROR;
+    }
+    readsize = rb->read(fd, &header, sizeof(header));
+    rb->close(fd);
+    /* Close for now. Less code than doing it in all error checks.
+     * Would need to seek back anyway. */
+
+    if (readsize != sizeof(header))
+    {
+        rb->splash(2*HZ, true, "Reading %s overlay failed.", name);
+        return PLUGIN_ERROR;
+    }
+    if (header.magic != PLUGIN_MAGIC || header.target_id != TARGET_ID)
+    {
+        rb->splash(2*HZ, true, "%s overlay: Incompatible model.", name);
+        return PLUGIN_ERROR;
+    }
+    if (header.api_version != PLUGIN_API_VERSION) 
+    {
+        rb->splash(2*HZ, true, "%s overlay: Incompatible version.", name);
+        return PLUGIN_ERROR;
+    }
+
+    audiobuf = rb->plugin_get_audio_buffer(&audiobuf_size);
+    if (header.load_addr < audiobuf ||
+        header.end_addr > audiobuf + audiobuf_size)
+    {
+        rb->splash(2*HZ, true, "%s overlay doesn't fit into memory.", name);
+        return PLUGIN_ERROR;
+    }
+    rb->memset(header.load_addr, 0, header.end_addr - header.load_addr);
+
+    fd = rb->open(filename, O_RDONLY);
+    if (fd < 0)
+    {
+        rb->splash(2*HZ, true, "Can't open %s", filename);
+        return PLUGIN_ERROR;
+    }
+    readsize = rb->read(fd, header.load_addr, header.end_addr - header.load_addr);
+    rb->close(fd);
+
+    if (readsize < 0)
+    {
+        rb->splash(2*HZ, true, "Reading %s overlay failed.", name);
+        return PLUGIN_ERROR;
+    }
+    return header.entry_point(rb, parameter);
+}
+#endif