Export file examples to MSH

also:
- change static buffer to dynamiclly allocated buffer.
- replace Chinese comment to English comment in some files.
- add apache-2 license

examples/file/readwrite.c

@@ -1,123 +1,168 @@
 /*
- * 代码清单：文件读写例子
+ * Copyright (c) 2006-2020, RT-Thread Development Team
  *
- * 这个例子演示了如何读写一个文件，特别是写的时候应该如何操作。
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2010-02-10     Bernard      first version
+ * 2020-04-12     Jianjia Ma   add msh cmd
  */
 
 #include <rtthread.h>
-#include <dfs_posix.h> /* 当需要使用文件操作时，需要包含这个头文件 */
+#include <dfs_posix.h>
 
-#define TEST_FN		"/test.dat"
+#define TEST_DATA_LEN     120
 
-/* 测试用的数据和缓冲 */
-static char test_data[120], buffer[120];
-
-/* 文件读写测试 */
+/* file read write test */
 void readwrite(const char* filename)
 {
 	int fd;
 	int index, length;
+	char* test_data;
+	char* buffer;
+	int block_size = TEST_DATA_LEN;
 
-	/* 只写 & 创建 打开 */
-	fd = open(TEST_FN, O_WRONLY | O_CREAT | O_TRUNC, 0);
+	/* open with write only & create */
+	fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0);
 	if (fd < 0)
 	{
 		rt_kprintf("open file for write failed\n");
 		return;
 	}
 
-	/* 准备写入数据 */
-	for (index = 0; index < sizeof(test_data); index ++)
+	test_data = rt_malloc(block_size);
+    if (test_data == RT_NULL)
+    {
+        rt_kprintf("no memory\n");
+        close(fd);
+        return;
+    }
+
+    buffer = rt_malloc(block_size);
+    if (buffer == RT_NULL)
+    {
+        rt_kprintf("no memory\n");
+        close(fd);
+        rt_free(test_data);
+        return;
+    }
+
+	/* prepare some data */
+	for (index = 0; index < block_size; index ++)
 	{
 		test_data[index] = index + 27;
 	}
 
-	/* 写入数据 */
-	length = write(fd, test_data, sizeof(test_data));
-	if (length != sizeof(test_data))
+	/* write to file */
+	length = write(fd, test_data, block_size);
+	if (length != block_size)
 	{
 		rt_kprintf("write data failed\n");
 		close(fd);
-		return;
+		goto __exit;
 	}
 
-	/* 关闭文件 */
+	/* close file */
 	close(fd);
 
-	/* 只写并在末尾添加打开 */
-	fd = open(TEST_FN, O_WRONLY | O_CREAT | O_APPEND, 0);
+	/* reopen the file with append to the end */
+	fd = open(filename, O_WRONLY | O_CREAT | O_APPEND, 0);
 	if (fd < 0)
 	{
 		rt_kprintf("open file for append write failed\n");
-		return;
+		goto __exit;;
 	}
 
-	length = write(fd, test_data, sizeof(test_data));
-	if (length != sizeof(test_data))
+	length = write(fd, test_data, block_size);
+	if (length != block_size)
 	{
 		rt_kprintf("append write data failed\n");
 		close(fd);
-		return;
+		goto __exit;
 	}
-	/* 关闭文件 */
+	/* close the file */
 	close(fd);
 
-	/* 只读打开进行数据校验 */
-	fd = open(TEST_FN, O_RDONLY, 0);
+	/* open the file for data validation. */
+	fd = open(filename, O_RDONLY, 0);
 	if (fd < 0)
 	{
 		rt_kprintf("check: open file for read failed\n");
-		return;
+		goto __exit;
 	}
 
-	/* 读取数据(应该为第一次写入的数据) */
-	length = read(fd, buffer, sizeof(buffer));
-	if (length != sizeof(buffer))
+	/* read the data (should be the data written by the first time ) */
+	length = read(fd, buffer, block_size);
+	if (length != block_size)
 	{
 		rt_kprintf("check: read file failed\n");
 		close(fd);
-		return;
+		goto __exit;
 	}
 
-	/* 检查数据是否正确 */
-	for (index = 0; index < sizeof(test_data); index ++)
+	/* validate */
+	for (index = 0; index < block_size; index ++)
 	{
 		if (test_data[index] != buffer[index])
 		{
 			rt_kprintf("check: check data failed at %d\n", index);
 			close(fd);
-			return;
+			goto __exit;
 		}
 	}
 
-	/* 读取数据(应该为第二次写入的数据) */
-	length = read(fd, buffer, sizeof(buffer));
-	if (length != sizeof(buffer))
+	/* read the data (should be the second time data) */
+	length = read(fd, buffer, block_size);
+	if (length != block_size)
 	{
 		rt_kprintf("check: read file failed\n");
 		close(fd);
-		return;
+		goto __exit;
 	}
 
-	/* 检查数据是否正确 */
-	for (index = 0; index < sizeof(test_data); index ++)
+	/* validate */
+	for (index = 0; index < block_size; index ++)
 	{
 		if (test_data[index] != buffer[index])
 		{
 			rt_kprintf("check: check data failed at %d\n", index);
 			close(fd);
-			return;
+			goto __exit;
 		}
 	}
 
-	/* 检查数据完毕，关闭文件 */
+	/* close the file */
 	close(fd);
-	/* 打印结果 */
-	rt_kprintf("read/write done.\n");
+	/* print result */
+	rt_kprintf("read/write test successful!\n");
+
+__exit:
+    rt_free(test_data);
+    rt_free(buffer);
 }
 
 #ifdef RT_USING_FINSH
 #include <finsh.h>
-/* 输出函数到finsh shell命令行中 */
+/* export to finsh */
 FINSH_FUNCTION_EXPORT(readwrite, perform file read and write test);
-#endif
+
+#ifdef FINSH_USING_MSH
+static void cmd_readwrite(int argc, char *argv[])
+{
+    char* filename;
+
+    if(argc == 2)
+    {
+        filename = argv[1];
+    }
+    else
+    {
+        rt_kprintf("Usage: readwrite [file_path]\n");
+        return;
+    }
+    readwrite(filename);
+}
+FINSH_FUNCTION_EXPORT_ALIAS(cmd_readwrite, __cmd_readwrite, perform file read and write test);
+#endif /* FINSH_USING_MSH */
+#endif /* RT_USING_FINSH */