Rust file code for fgets() code

rust-nuttx-hello_rust_main-fgets.rs

/****************************************************************************
 * apps/examples/hello_rust/hello_rust_main.rs
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Attributes
 ****************************************************************************/

#![no_main]
#![no_std]

/****************************************************************************
 * Uses
 ****************************************************************************/

use core::panic::PanicInfo;

/****************************************************************************
 * Externs
 ****************************************************************************/

extern "C" {
    pub fn printf(format: *const u8, ...) -> i32;
    pub fn puts(s: *const core::ffi::c_char) -> core::ffi::c_int;
    pub fn fgets(
        buf: *mut core::ffi::c_char,
        n: core::ffi::c_int,
        stream: *mut core::ffi::c_void
    ) -> *mut core::ffi::c_char;
    pub fn lib_get_stream(fd: core::ffi::c_int) -> *mut core::ffi::c_void;
}

/****************************************************************************
 * Private functions
 ****************************************************************************/

/****************************************************************************
 * Panic handler (needed for [no_std] compilation)
 ****************************************************************************/

#[panic_handler]
fn panic(_panic: &PanicInfo<_>) -> ! {
    loop {}
}

/****************************************************************************
 * Public functions
 ****************************************************************************/

/****************************************************************************
 * hello_rust_main
 ****************************************************************************/

#[no_mangle]
pub extern "C" fn hello_rust_main(_argc: i32, _argv: *const *const u8) -> i32 {
    /* "Hello, Rust!!" using printf() from libc */

    unsafe {
        printf(b"Hello, Rust!!\n\0" as *const u8);

        printf(b"Please give your output:\n\0" as *const u8);
        let stdin: *mut core::ffi::c_void = lib_get_stream(0);
        let mut buf: [core::ffi::c_char; 256] = [0; 256];
        if !fgets(
            &mut buf[0],
            buf.len() as i32 - 1,
            stdin
        ).is_null() {
            printf(b"You entered...\n\0" as *const u8);
            puts(&buf[0]);
        }
    }

    /* exit with status 0 */
    0
}