You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
75 lines
2.2 KiB
75 lines
2.2 KiB
use std::io::Write;
|
|
|
|
/// Generate a random frame mask.
|
|
#[inline]
|
|
pub fn generate_mask() -> [u8; 4] {
|
|
rand::random()
|
|
}
|
|
|
|
/// Write data to an output, masking the data in the process
|
|
pub fn write_masked(data: &[u8], output: &mut impl Write, mask: [u8; 4]) {
|
|
write_mask_fast32(data, output, mask)
|
|
}
|
|
|
|
/// A safe unoptimized mask application.
|
|
#[inline]
|
|
fn write_mask_fallback(data: &[u8], output: &mut impl Write, mask: [u8; 4]) {
|
|
for (i, byte) in data.iter().enumerate() {
|
|
output.write(&[*byte ^ mask[i & 3]]).unwrap();
|
|
}
|
|
}
|
|
|
|
/// Faster version of `apply_mask()` which operates on 4-byte blocks.
|
|
#[inline]
|
|
fn write_mask_fast32(data: &[u8], output: &mut impl Write, mask: [u8; 4]) {
|
|
let mask_u32 = u32::from_ne_bytes(mask);
|
|
|
|
let (mut prefix, words, mut suffix) = unsafe { data.align_to::<u32>() };
|
|
write_mask_fallback(&mut prefix, output, mask);
|
|
let head = prefix.len() & 3;
|
|
let mask_u32 = if head > 0 {
|
|
if cfg!(target_endian = "big") {
|
|
mask_u32.rotate_left(8 * head as u32)
|
|
} else {
|
|
mask_u32.rotate_right(8 * head as u32)
|
|
}
|
|
} else {
|
|
mask_u32
|
|
};
|
|
for word in words {
|
|
let bytes = (*word ^ mask_u32).to_ne_bytes();
|
|
output.write(&bytes).unwrap();
|
|
}
|
|
write_mask_fallback(&mut suffix, output, mask_u32.to_ne_bytes());
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
|
|
#[test]
|
|
fn test_apply_mask() {
|
|
let mask = [0x6d, 0xb6, 0xb2, 0x80];
|
|
let unmasked = vec![
|
|
0xf3, 0x00, 0x01, 0x02, 0x03, 0x80, 0x81, 0x82, 0xff, 0xfe, 0x00, 0x17, 0x74, 0xf9,
|
|
0x12, 0x03,
|
|
];
|
|
|
|
for data_len in 0..=unmasked.len() {
|
|
let unmasked = &unmasked[0..data_len];
|
|
// Check masking with different alignment.
|
|
for off in 0..=3 {
|
|
if unmasked.len() < off {
|
|
continue;
|
|
}
|
|
let mut masked = Vec::new();
|
|
write_mask_fallback(&unmasked, &mut masked, mask);
|
|
|
|
let mut masked_fast = Vec::new();
|
|
write_mask_fast32(&unmasked, &mut masked_fast, mask);
|
|
|
|
assert_eq!(masked, masked_fast);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|