Simplify mpegplayer a bit and use array-based lists rather than linked lists for stream management. Move a couple useful functions to handle pointer arrays from kernel.c into general.c; mpeglayer now makes use of them.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26101 a1c6a512-1295-4272-9138-f99709370657

firmware/general.c

@@ -196,3 +196,40 @@ char *create_datetime_filename(char *buffer, const char *path,
     return buffer;
 }
 #endif /* CONFIG_RTC */
+
+/***
+ ** Compacted pointer lists
+ **
+ ** N-length list requires N+1 elements to ensure NULL-termination.
+ **/
+
+/* Find a pointer in a pointer array. Returns the addess of the element if
+ * found or the address of the terminating NULL otherwise. This can be used
+ * to bounds check and add items. */
+void ** find_array_ptr(void **arr, void *ptr)
+{
+    void *curr;
+    for (curr = *arr; curr != NULL && curr != ptr; curr = *(++arr));
+    return arr;
+}
+
+/* Remove a pointer from a pointer array if it exists. Compacts it so that
+ * no gaps exist. Returns 0 on success and -1 if the element wasn't found. */
+int remove_array_ptr(void **arr, void *ptr)
+{
+    void *curr;
+    arr = find_array_ptr(arr, ptr);
+
+    if (*arr == NULL)
+        return -1;
+
+    /* Found. Slide up following items. */
+    do
+    {
+        void **arr1 = arr + 1;
+        *arr++ = curr = *arr1;
+    }
+    while (curr != NULL);
+
+    return 0;
+}