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Fix bug around single-byte for 0-bits

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This commit is contained in:
Paul Hauner 2019-07-09 20:29:10 +10:00
parent daa8916e6b
commit bb3b3fd8b9
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GPG Key ID: 303E4494BB28068C
2 changed files with 17 additions and 18 deletions
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21
eth2/utils/ssz_types/src/bitfield.rs
View File

@ -82,10 +82,8 @@ impl<N: Unsigned + Clone> Bitfield<BitList<N>> {
/// Returns `None` if `num_bits > N`.
pub fn with_capacity(num_bits: usize) -> Option<Self> {
if num_bits <= N::to_usize() {
let num_bytes = std::cmp::max(bytes_for_bit_len(num_bits), 1);
Some(Self {
bytes: vec![0; num_bytes],
bytes: vec![0; bytes_for_bit_len(num_bits)],
len: num_bits,
_phantom: PhantomData,
})
@ -165,12 +163,9 @@ impl<N: Unsigned + Clone> Bitfield<BitVector<N>> {
///
/// All bits are initialized to `false`.
pub fn new() -> Self {
let num_bits = N::to_usize();
let num_bytes = std::cmp::max(bytes_for_bit_len(num_bits), 1);
Self {
bytes: vec![0; num_bytes],
len: num_bits,
bytes: vec![0; bytes_for_bit_len(Self::capacity())],
len: Self::capacity(),
_phantom: PhantomData,
}
}
@ -285,13 +280,17 @@ impl<T: BitfieldBehaviour> Bitfield<T> {
/// - `bit_len` is not a multiple of 8 and `bytes` contains set bits that are higher than, or
/// equal to `bit_len`.
fn from_raw_bytes(bytes: Vec<u8>, bit_len: usize) -> Option<Self> {
if bytes.len() == 1 && bit_len == 0 && bytes == [0] {
if bit_len == 0 {
if bytes.len() == 1 && bytes == [0] {
// A bitfield with `bit_len` 0 can only be represented by a single zero byte.
Some(Self {
bytes,
len: 0,
_phantom: PhantomData,
})
} else {
None
}
} else if bytes.len() != bytes_for_bit_len(bit_len) || bytes.is_empty() {
// The number of bytes must be the minimum required to represent `bit_len`.
None
@ -299,7 +298,7 @@ impl<T: BitfieldBehaviour> Bitfield<T> {
// Ensure there are no bits higher than `bit_len` that are set to true.
let (mask, _) = u8::max_value().overflowing_shr(8 - (bit_len as u32 % 8));
if (bytes.first().expect("Bytes cannot be empty") & !mask) == 0 {
if (bytes.first().expect("Guarded against empty bytes") & !mask) == 0 {
Some(Self {
bytes,
len: bit_len,
@ -419,7 +418,7 @@ impl<T: BitfieldBehaviour> Bitfield<T> {
///
/// `bit_len == 0` requires a single byte.
fn bytes_for_bit_len(bit_len: usize) -> usize {
(bit_len + 7) / 8
std::cmp::max(1, (bit_len + 7) / 8)
}
/// An iterator over the bits in a `Bitfield`.

2
eth2/utils/ssz_types/src/lib.rs
View File

@ -38,7 +38,7 @@ mod bitfield;
mod fixed_vector;
mod variable_list;
pub use bitfield::{BitList, BitVector, Bitfield, BitfieldBehaviour};
pub use bitfield::{BitList, BitVector, Bitfield};
pub use fixed_vector::FixedVector;
pub use typenum;
pub use variable_list::VariableList;