AP_Filesystem: add simple File I/O example

libraries/AP_Filesystem/examples/File_IO/File_IO.cpp

@@ -0,0 +1,108 @@
+//Simple File I/O example
+
+#include <AP_HAL/AP_HAL.h>
+#include <AP_BoardConfig/AP_BoardConfig.h>
+#include <AP_Filesystem/AP_Filesystem.h>
+#include <stdio.h>
+
+//set according to the data size in file
+#define BUFFER_SIZE 50
+
+const AP_HAL::HAL& hal = AP_HAL::get_HAL();
+
+void setup();
+void loop();
+
+static AP_BoardConfig board_config;
+
+int file_count = 0;
+const char *dir_path = nullptr;
+static void write_file(const char *);
+static void read_file(const char *);
+
+void setup()
+{
+    board_config.init();
+
+    //creating a test directory to store all files
+    dir_path = "./test_dir";
+    hal.console->printf("Creating directory - %s\n", dir_path);
+    int ret = AP::FS().mkdir(dir_path);
+    if (ret == -1) {
+        if (errno == EEXIST) {
+            hal.console->printf("Directory - %s already exist\n", dir_path);
+        } else {
+            hal.console->printf("Failed to create directory %s - %s\n", dir_path, strerror(errno));
+        }
+    }
+}
+
+void loop()
+{
+    //creating 10 files in test directory
+    if (file_count == 10) {
+        hal.console->printf("Finished creating files\n\n");
+        hal.scheduler->delay(1000);
+        return;
+    }
+
+    file_count += 1;
+    char file_path[100];
+    snprintf(file_path, sizeof(file_path), "%s/test_%d.txt", dir_path, file_count);
+    write_file(file_path);
+    hal.scheduler->delay(1000);
+    read_file(file_path);
+    hal.scheduler->delay(1000);
+}
+
+static void write_file(const char *file_path)
+{
+    char write_buf[BUFFER_SIZE];
+
+    //creating or opening a file in write mode
+    const int open_fd = AP::FS().open(file_path, O_WRONLY | O_CREAT | O_TRUNC);
+    if (open_fd == -1) {
+        hal.console->printf("Open %s failed - %s\n", file_path, strerror(errno));
+        return;
+    }
+
+    //writing to file
+    const char *s = "Hello_World";
+    hal.console->printf("Writing to file %s => %s_%d\n", file_path, s, file_count);
+    snprintf(write_buf, sizeof(write_buf), "%s_%d\n", s, file_count);
+    const ssize_t to_write = strlen(write_buf);
+    const ssize_t write_size = AP::FS().write(open_fd, write_buf, to_write);
+    if (write_size == -1 or write_size != to_write) {
+        hal.console->printf("Write failed - %s\n", strerror(errno));
+        return;
+    }
+
+    //closing file after writing
+    AP::FS().close(open_fd);
+}
+
+static void read_file(const char *file_path)
+{
+    char read_buf[BUFFER_SIZE];
+
+    //opening a file in read mode
+    const int open_fd = AP::FS().open(file_path, O_RDONLY);
+    if (open_fd == -1) {
+        hal.console->printf("Open %s failed\n", file_path);
+        return;
+    }
+
+    //reading from file
+    const ssize_t read_size = AP::FS().read(open_fd, read_buf, sizeof(read_buf));
+    if (read_size == -1) {
+        hal.console->printf("Read failed - %s\n", strerror(errno));
+        return;
+    }
+
+    hal.console->printf("Reading from file %s => %s\n", file_path, read_buf);
+
+    //closing file after reading
+    AP::FS().close(open_fd);
+}
+
+AP_HAL_MAIN();

libraries/AP_Filesystem/examples/File_IO/wscript

@@ -0,0 +1,7 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+def build(bld):
+    bld.ap_example(
+        use='ap',
+    )