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Eliminate some more transmute() (#8879)

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* eliminate some more transmute()

* Address `review comments`

* Make unsafe block smaller
* Use different byte-order than `std`, read words as big endian instead
of little endian!

* Fix IpAddresses nits

* Use `from_be` to work both for big and little endian
* Ipv6 addresses were incorrectly `transmuted`

* remove needless lifetime annotation
This commit is contained in:
Niklas Adolfsson
2018-06-22 13:51:53 +02:00
committed by André Silva
parent 5ae8e8a9ca
commit 0cd1de769b
2 changed files with 22 additions and 31 deletions
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26
ethash/src/compute.rs
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@@ -137,11 +137,11 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
($n:expr, $value:expr) => {{
// We use explicit lifetimes to ensure that val's borrow is invalidated until the
// transmuted val dies.
unsafe fn make_const_array<'a, T, U>(val: &'a mut [T]) -> &'a mut [U; $n] {
unsafe fn make_const_array<T, U>(val: &mut [T]) -> &mut [U; $n] {
use ::std::mem;
debug_assert_eq!(val.len() * mem::size_of::<T>(), $n * mem::size_of::<U>());
mem::transmute(val.as_mut_ptr())
&mut *(val.as_mut_ptr() as *mut [U; $n])
}
make_const_array($value)
@@ -177,7 +177,7 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
ptr::copy_nonoverlapping(header_hash.as_ptr(), out.as_mut_ptr(), header_hash.len());
ptr::copy_nonoverlapping(
mem::transmute(&nonce),
&nonce as *const u64 as *const u8,
out[header_hash.len()..].as_mut_ptr(),
mem::size_of::<u64>(),
);
@@ -266,18 +266,20 @@ fn hash_compute(light: &Light, full_size: usize, header_hash: &H256, nonce: u64)
let mix_hash = buf.compress_bytes;
let value: H256 = unsafe {
let value: H256 = {
// We can interpret the buffer as an array of `u8`s, since it's `repr(C)`.
let read_ptr: *const u8 = mem::transmute(&buf);
let read_ptr: *const u8 = &buf as *const MixBuf as *const u8;
// We overwrite the second half since `keccak_256` has an internal buffer and so allows
// overlapping arrays as input.
let write_ptr: *mut u8 = mem::transmute(&mut buf.compress_bytes);
keccak_256::unchecked(
write_ptr,
buf.compress_bytes.len(),
read_ptr,
buf.half_mix.bytes.len() + buf.compress_bytes.len(),
);
let write_ptr: *mut u8 = &mut buf.compress_bytes as *mut [u8; 32] as *mut u8;
unsafe {
keccak_256::unchecked(
write_ptr,
buf.compress_bytes.len(),
read_ptr,
buf.half_mix.bytes.len() + buf.compress_bytes.len(),
);
}
buf.compress_bytes
};