lib.rs

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! A bare-metal library supplying functions rustc may lower code to
//!
//! This library is not intended for general use, and is superseded by a system
//! libc if one is available. In a freestanding context, however, common
//! functions such as memset, memcpy, etc are not implemented. This library
//! provides an implementation of these functions which are either required by
//! libcore or called by rustc implicitly.
//!
//! This library is never included by default, and must be manually included if
//! necessary. It is an error to include this library when also linking with
//! the system libc library.

#![no_std]
#![feature(no_std)]
#![cfg_attr(test, feature(core_str_ext, core_slice_ext))]

// This library defines the builtin functions, so it would be a shame for
// LLVM to optimize these function calls to themselves!
#![no_builtins]

#[cfg(test)] #[macro_use] extern crate std;

#[no_mangle]
pub unsafe extern fn memcpy(dest: *mut u8, src: *const u8,
                            n: usize) -> *mut u8 {
    let mut i = 0;
    while i < n {
        *dest.offset(i as isize) = *src.offset(i as isize);
        i += 1;
    }
    return dest;
}

#[no_mangle]
pub unsafe extern fn memmove(dest: *mut u8, src: *const u8,
                             n: usize) -> *mut u8 {
    if src < dest as *const u8 { // copy from end
        let mut i = n;
        while i != 0 {
            i -= 1;
            *dest.offset(i as isize) = *src.offset(i as isize);
        }
    } else { // copy from beginning
        let mut i = 0;
        while i < n {
            *dest.offset(i as isize) = *src.offset(i as isize);
            i += 1;
        }
    }
    return dest;
}

#[no_mangle]
pub unsafe extern fn memset(s: *mut u8, c: i32, n: usize) -> *mut u8 {
    let mut i = 0;
    while i < n {
        *s.offset(i as isize) = c as u8;
        i += 1;
    }
    return s;
}

#[no_mangle]
pub unsafe extern fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
    let mut i = 0;
    while i < n {
        let a = *s1.offset(i as isize);
        let b = *s2.offset(i as isize);
        if a != b {
            return a as i32 - b as i32
        }
        i += 1;
    }
    return 0;
}

#[cfg(test)]
mod test {
    use core::str::StrExt;
    use core::slice::SliceExt;

    use super::{memcmp, memset, memcpy, memmove};

    #[test]
    fn memcmp_single_byte_pointers() {
        unsafe {
            assert_eq!(memcmp(&0xFAu8, &0xFAu8, 1), 0x00);
            assert!(memcmp(&0xEFu8, &0xFEu8, 1) < 0x00);
        }
    }

    #[test]
    fn memcmp_strings() {
        {
            let (x, z) = ("Hello!", "Good Bye.");
            let l = x.len();
            unsafe {
                assert_eq!(memcmp(x.as_ptr(), x.as_ptr(), l), 0);
                assert!(memcmp(x.as_ptr(), z.as_ptr(), l) > 0);
                assert!(memcmp(z.as_ptr(), x.as_ptr(), l) < 0);
            }
        }
        {
            let (x, z) = ("hey!", "hey.");
            let l = x.len();
            unsafe {
                assert!(memcmp(x.as_ptr(), z.as_ptr(), l) < 0);
            }
        }
    }

    #[test]
    fn memset_single_byte_pointers() {
        let mut x: u8 = 0xFF;
        unsafe {
            memset(&mut x, 0xAA, 1);
            assert_eq!(x, 0xAA);
            memset(&mut x, 0x00, 1);
            assert_eq!(x, 0x00);
            x = 0x01;
            memset(&mut x, 0x12, 0);
            assert_eq!(x, 0x01);
        }
    }

    #[test]
    fn memset_array() {
        let mut buffer = [b'X';  100];
        unsafe {
            memset(buffer.as_mut_ptr(), b'#' as i32, buffer.len());
        }
        for byte in buffer.iter() { assert_eq!(*byte, b'#'); }
    }

    #[test]
    fn memcpy_and_memcmp_arrays() {
        let (src, mut dst) = ([b'X';  100], [b'Y';  100]);
        unsafe {
            assert!(memcmp(src.as_ptr(), dst.as_ptr(), 100) != 0);
            let _ = memcpy(dst.as_mut_ptr(), src.as_ptr(), 100);
            assert_eq!(memcmp(src.as_ptr(), dst.as_ptr(), 100), 0);
        }
    }

    #[test]
    fn memmove_overlapping() {
        {
            let mut buffer = [ b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', b'8', b'9' ];
            unsafe {
                memmove(&mut buffer[4], &buffer[0], 6);
                let mut i = 0;
                for byte in b"0123012345".iter() {
                    assert_eq!(buffer[i], *byte);
                    i += 1;
                }
            }
        }
        {
            let mut buffer = [ b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', b'8', b'9' ];
            unsafe {
                memmove(&mut buffer[0], &buffer[4], 6);
                let mut i = 0;
                for byte in b"4567896789".iter() {
                    assert_eq!(buffer[i], *byte);
                    i += 1;
                }
            }
        }
    }
}