add RAMFS implementation

components/dfs/filesystems/ramfs/SConscript

@@ -0,0 +1,9 @@
+from building import *
+
+cwd     = GetCurrentDir()
+src     = Glob('*.c')
+CPPPATH = [cwd]
+
+group = DefineGroup('Filesystem', src, depend = ['RT_USING_DFS', 'RT_USING_MEMHEAP'], CPPPATH = CPPPATH)
+
+Return('group')

components/dfs/filesystems/ramfs/dfs_ramfs.h

@@ -0,0 +1,46 @@
+/*
+ * File      : dfs_ramfs.h
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2011, Shanghai Real-Thread Technology Co., Ltd
+ *
+ * All rights reserved.
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2013-04-15     Bernard      the first version
+ * 2013-05-05     Bernard      remove CRC for ramfs persistence
+ */
+
+#ifndef __DFS_ROMFS_H__
+#define __DFS_ROMFS_H__
+
+#include <rtthread.h>
+#include <rtservice.h>
+
+#define RAMFS_NAME_MAX  32
+#define RAMFS_MAGIC		0x0A0A0A0A
+
+struct ramfs_dirent
+{
+    rt_list_t list;
+    char name[RAMFS_NAME_MAX];	/* dirent name */
+    rt_uint8_t* data;
+
+    rt_size_t size;	/* file size */
+};
+
+/**
+ * DFS ramfs object
+ */
+struct dfs_ramfs
+{
+    rt_uint32_t magic;
+
+    struct rt_memheap memheap;
+    struct ramfs_dirent root;
+};
+
+int dfs_ramfs_init(void);
+struct dfs_ramfs* dfs_ramfs_create(rt_uint8_t* pool, rt_size_t size);
+
+#endif