use super::*;
use std::cmp;
use std::ptr;
use std::ffi::c_void;

/// Explicitly zero out a byte buffer.
///
/// Essentially `explicit_bzero()`.
#[inline(never)]
pub fn explicit_clear(buffer : &mut[u8]) {
    unsafe {
	std::ptr::write_bytes(buffer.as_mut_ptr() as * mut c_void, 0, buffer.len());

	if cfg!(target_arch = "x86_64") || cfg!(target_arch = "x86") {
            asm!("clflush [{}]", in(reg)buffer.as_mut_ptr());
	} else {
            asm!("")
	}
    }
}

/// Set all bytes of this buffer to a single value.
///
/// Essentially `memset()`.
#[inline] pub fn set(buffer: &mut [u8], to: u8)
{
    unsafe {
	std::ptr::write_bytes(buffer.as_mut_ptr() as *mut c_void, to, buffer.len());
    }
}

/// Zero out this buffer
///
/// Essentially `bzero()`.
#[inline(always)] pub fn clear(buffer: &mut [u8])
{
    set(buffer, 0);
}

/// Copy bytes from one slice to another.
///
/// # Notes
/// The slices can overlap.
#[inline] pub fn memmove(from: &[u8], to: &mut [u8]) -> usize
{
    let len = cmp::min(from.len(), to.len());
    unsafe {
	ptr::copy(from.as_ptr(), to.as_mut_ptr(), len);
    }
    len
}

/// Copy bytes from one slice to another.
///
/// # Notes
/// The slices must *not* overlap.
#[inline] pub fn memcpy(from: &[u8], to: &mut [u8]) -> usize
{
    let len = cmp::min(from.len(), to.len());
    unsafe {
	ptr::copy_nonoverlapping(from.as_ptr(), to.as_mut_ptr(), len);
    }
    len
}