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fixes bug with serialization logic for boolean bitfield

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should match the python impl
This commit is contained in:
Alex Stokes 2018-12-03 20:45:43 -08:00
parent bedc1abec0
commit 564f13be5f
1 changed files with 25 additions and 24 deletions
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49
beacon_chain/utils/boolean-bitfield/src/lib.rs
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@ -23,6 +23,10 @@ impl BooleanBitfield {
Default::default()
}
pub fn with_capacity(initial_len: usize) -> Self {
Self::from_elem(initial_len, false)
}
/// Create a new bitfield with the given length `initial_len` and all values set to `bit`.
pub fn from_elem(inital_len: usize, bit: bool) -> Self {
Self {
@ -100,25 +104,10 @@ impl default::Default for BooleanBitfield {
}
}
// borrowed from bit_vec crate
fn reverse_bits(byte: u8) -> u8 {
let mut result = 0;
for i in 0..8 {
result = result | ((byte >> i) & 1) << (7 - i);
}
result
}
impl ssz::Encodable for BooleanBitfield {
// ssz_append encodes Self according to the `ssz` spec.
// Note that we have to flip the endianness of the encoding with `reverse_bits` to account for an implementation detail of `bit-vec` crate.
fn ssz_append(&self, s: &mut ssz::SszStream) {
let bytes: Vec<u8> = self
.to_bytes()
.iter()
.map(|&byte| reverse_bits(byte))
.collect();
s.append_vec(&bytes);
s.append_vec(&self.to_bytes())
}
}
@ -134,10 +123,11 @@ impl ssz::Decodable for BooleanBitfield {
} else {
let bytes = &bytes[(index + 4)..(index + len + 4)];
let mut field = BooleanBitfield::from_elem(0, false);
let count = len * 8;
let mut field = BooleanBitfield::with_capacity(count);
for (byte_index, byte) in bytes.iter().enumerate() {
for i in 0..8 {
let bit = byte & (1 << i);
let bit = byte & (128 >> i);
if bit != 0 {
field.set(8 * byte_index + i, true);
}
@ -317,28 +307,39 @@ mod tests {
#[test]
fn test_ssz_encode() {
let field = BooleanBitfield::from_elem(5, true);
let field = create_test_bitfield();
let mut stream = SszStream::new();
stream.append(&field);
assert_eq!(stream.drain(), vec![0, 0, 0, 1, 31]);
assert_eq!(stream.drain(), vec![0, 0, 0, 2, 225, 192]);
let field = BooleanBitfield::from_elem(18, true);
let mut stream = SszStream::new();
stream.append(&field);
assert_eq!(stream.drain(), vec![0, 0, 0, 3, 255, 255, 3]);
assert_eq!(stream.drain(), vec![0, 0, 0, 3, 255, 255, 192]);
}
fn create_test_bitfield() -> BooleanBitfield {
let count = 2 * 8;
let mut field = BooleanBitfield::with_capacity(count);
let indices = &[0, 1, 2, 7, 8, 9];
for &i in indices {
field.set(i, true);
}
field
}
#[test]
fn test_ssz_decode() {
let encoded = vec![0, 0, 0, 1, 31];
let encoded = vec![0, 0, 0, 2, 225, 192];
let (field, _): (BooleanBitfield, usize) = ssz::decode_ssz(&encoded, 0).unwrap();
let expected = BooleanBitfield::from_elem(5, true);
let expected = create_test_bitfield();
assert_eq!(field, expected);
let encoded = vec![0, 0, 0, 3, 255, 255, 3];
let (field, _): (BooleanBitfield, usize) = ssz::decode_ssz(&encoded, 0).unwrap();
let expected = BooleanBitfield::from_elem(18, true);
let expected = BooleanBitfield::from_bytes(&[255, 255, 3]);
assert_eq!(field, expected);
}