#![no_std]
#![no_builtins]
#[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 { let mut i = n;
while i != 0 {
i -= 1;
*dest.offset(i as isize) = *src.offset(i as isize);
}
} else { 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 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;
}
}
}
}
}