diff --git a/boolean-bitfield/src/lib.rs b/boolean-bitfield/src/lib.rs index 0a690bf3d..9c5865f27 100644 --- a/boolean-bitfield/src/lib.rs +++ b/boolean-bitfield/src/lib.rs @@ -6,9 +6,11 @@ * A future implementation should be more efficient, * this is just to get the job done for now. */ +extern crate ssz; + use std::cmp::max; -#[derive(Eq,Clone)] +#[derive(Eq, Clone, Default, Debug)] pub struct BooleanBitfield{ len: usize, vec: Vec @@ -19,15 +21,17 @@ impl BooleanBitfield { pub fn new() -> Self { Self { len: 0, - vec: vec![] + vec: vec![0] } } /// Create a new bitfield of a certain capacity pub fn with_capacity(capacity: usize) -> Self { + let mut vec = Vec::with_capacity(capacity / 8 + 1); + vec.push(0); Self { len: 0, - vec: Vec::with_capacity(capacity / 8 + 1) + vec } } @@ -35,9 +39,9 @@ impl BooleanBitfield { /// /// Will return `true` if the bit has been set to `true` /// without then being set to `False`. - pub fn get_bit(&self, i: &usize) -> bool { - let bit = |i: &usize| *i % 8; - let byte = |i: &usize| *i / 8; + pub fn get_bit(&self, i: usize) -> bool { + let bit = |i: usize| i % 8; + let byte = |i: usize| i / 8; if byte(i) >= self.vec.len() { false @@ -50,24 +54,21 @@ impl BooleanBitfield { /// /// If this bit is larger than the length of the underlying byte /// array it will be extended. - pub fn set_bit(&mut self, i: &usize, to: &bool) { - let bit = |i: &usize| *i % 8; - let byte = |i: &usize| *i / 8; + pub fn set_bit(&mut self, i: usize, to: bool) { + let bit = |i: usize| i % 8; + let byte = |i: usize| i / 8; self.len = max(self.len, i + 1); if byte(i) >= self.vec.len() { self.vec.resize(byte(i) + 1, 0); } - match to { - true => { - self.vec[byte(i)] = - self.vec[byte(i)] | (1 << (bit(i) as u8)) - } - false => { - self.vec[byte(i)] = - self.vec[byte(i)] & !(1 << (bit(i) as u8)) - } + if to { + self.vec[byte(i)] = + self.vec[byte(i)] | (1 << (bit(i) as u8)) + } else { + self.vec[byte(i)] = + self.vec[byte(i)] & !(1 << (bit(i) as u8)) } } @@ -78,6 +79,13 @@ impl BooleanBitfield { /// vector. pub fn len(&self) -> usize { self.len } + /// True if no bits have ever been set. A bit that is set and then + /// unset will still count to the length of the bitfield. + /// + /// Note: this is distinct from the length of the underlying + /// vector. + pub fn is_empty(&self) -> bool { self.len == 0 } + /// Iterate through the underlying vector and count the number of /// true bits. pub fn num_true_bits(&self) -> u64 { @@ -92,6 +100,20 @@ impl BooleanBitfield { count } + /// Iterate through the underlying vector and find the highest + /// set bit. Useful for instantiating a new instance from + /// some set of bytes. + pub fn compute_length(bytes: &[u8]) -> usize { + for byte in (0..bytes.len()).rev() { + for bit in (0..8).rev() { + if byte & (1 << (bit as u8)) != 0 { + return (byte * 8) + bit + } + } + } + 0 + } + /// Clone and return the underlying byte array (`Vec`). pub fn to_be_vec(&self) -> Vec { let mut o = self.vec.clone(); @@ -100,6 +122,17 @@ impl BooleanBitfield { } } +impl<'a> From<&'a [u8]> for BooleanBitfield { + fn from(input: &[u8]) -> Self { + let mut vec = input.to_vec(); + vec.reverse(); + BooleanBitfield { + vec, + len: BooleanBitfield::compute_length(input) + } + } +} + impl PartialEq for BooleanBitfield { fn eq(&self, other: &BooleanBitfield) -> bool { (self.vec == other.vec) & @@ -107,52 +140,132 @@ impl PartialEq for BooleanBitfield { } } +impl ssz::Encodable for BooleanBitfield { + fn ssz_append(&self, s: &mut ssz::SszStream) { + s.append_vec(&self.to_be_vec()); + } +} + +impl ssz::Decodable for BooleanBitfield { + fn ssz_decode(bytes: &[u8], index: usize) + -> Result<(Self, usize), ssz::DecodeError> + { + let len = ssz::decode::decode_length( + bytes, + index, + ssz::LENGTH_BYTES)?; + if (ssz::LENGTH_BYTES + len) > bytes.len() { + return Err(ssz::DecodeError::TooShort); + } + if len == 0 { + Ok((BooleanBitfield::new(), + index + ssz::LENGTH_BYTES)) + } else { + let b = BooleanBitfield::from(&bytes[(index + 4)..(len + 4)]); + let index = index + ssz::LENGTH_BYTES + len; + Ok((b, index)) + } + } +} + #[cfg(test)] mod tests { use super::*; + use ssz::Decodable; + + #[test] + fn test_ssz_encoding() { + let mut b = BooleanBitfield::new(); + b.set_bit(8, true); + + let mut stream = ssz::SszStream::new(); + stream.append(&b); + + assert_eq!(stream.drain(), vec![0, 0, 0, 2, 1, 0]); + } + + #[test] + fn test_ssz_decoding() { + /* + * Correct input + */ + let input = vec![0, 0, 0, 2, 1, 0]; + let (b, i) = BooleanBitfield::ssz_decode(&input, 0).unwrap(); + assert_eq!(i, 6); + assert_eq!(b.num_true_bits(), 1); + assert_eq!(b.get_bit(8), true); + + /* + * Input too long + */ + let mut input = vec![0, 0, 0, 2, 1, 0]; + input.push(42); + let (b, i) = BooleanBitfield::ssz_decode(&input, 0).unwrap(); + assert_eq!(i, 6); + assert_eq!(b.num_true_bits(), 1); + assert_eq!(b.get_bit(8), true); + + /* + * Input too short + */ + let input = vec![0, 0, 0, 2, 1]; + let res = BooleanBitfield::ssz_decode(&input, 0); + assert_eq!(res, Err(ssz::DecodeError::TooShort)); + } + + #[test] + fn test_new_bitfield_len() { + let b = BooleanBitfield::new(); + assert_eq!(b.len(), 0); + assert_eq!(b.to_be_vec(), vec![0]); + + let b = BooleanBitfield::with_capacity(100); + assert_eq!(b.len(), 0); + assert_eq!(b.to_be_vec(), vec![0]); + } #[test] fn test_bitfield_set() { let mut b = BooleanBitfield::new(); - b.set_bit(&0, &false); + b.set_bit(0, false); assert_eq!(b.to_be_vec(), [0]); b = BooleanBitfield::new(); - b.set_bit(&7, &true); + b.set_bit(7, true); assert_eq!(b.to_be_vec(), [128]); - b.set_bit(&7, &false); + b.set_bit(7, false); assert_eq!(b.to_be_vec(), [0]); assert_eq!(b.len(), 8); b = BooleanBitfield::new(); - b.set_bit(&7, &true); - b.set_bit(&0, &true); + b.set_bit(7, true); + b.set_bit(0, true); assert_eq!(b.to_be_vec(), [129]); - b.set_bit(&7, &false); + b.set_bit(7, false); assert_eq!(b.to_be_vec(), [1]); assert_eq!(b.len(), 8); b = BooleanBitfield::new(); - b.set_bit(&8, &true); + b.set_bit(8, true); assert_eq!(b.to_be_vec(), [1, 0]); assert_eq!(b.len(), 9); - b.set_bit(&8, &false); + b.set_bit(8, false); assert_eq!(b.to_be_vec(), [0, 0]); assert_eq!(b.len(), 9); b = BooleanBitfield::new(); - b.set_bit(&15, &true); + b.set_bit(15, true); assert_eq!(b.to_be_vec(), [128, 0]); - b.set_bit(&15, &false); + b.set_bit(15, false); assert_eq!(b.to_be_vec(), [0, 0]); assert_eq!(b.len(), 16); b = BooleanBitfield::new(); - b.set_bit(&8, &true); - b.set_bit(&15, &true); + b.set_bit(8, true); + b.set_bit(15, true); assert_eq!(b.to_be_vec(), [129, 0]); - b.set_bit(&15, &false); + b.set_bit(15, false); assert_eq!(b.to_be_vec(), [1, 0]); assert_eq!(b.len(), 16); } @@ -162,10 +275,10 @@ mod tests { let test_nums = vec![0, 8, 15, 42, 1337]; for i in test_nums { let mut b = BooleanBitfield::new(); - assert_eq!(b.get_bit(&i), false); - b.set_bit(&i, &true); - assert_eq!(b.get_bit(&i), true); - b.set_bit(&i, &true); + assert_eq!(b.get_bit(i), false); + b.set_bit(i, true); + assert_eq!(b.get_bit(i), true); + b.set_bit(i, true); } } @@ -173,14 +286,14 @@ mod tests { fn test_bitfield_num_true_bits() { let mut b = BooleanBitfield::new(); assert_eq!(b.num_true_bits(), 0); - b.set_bit(&15, &true); + b.set_bit(15, true); assert_eq!(b.num_true_bits(), 1); - b.set_bit(&15, &false); + b.set_bit(15, false); assert_eq!(b.num_true_bits(), 0); - b.set_bit(&0, &true); - b.set_bit(&7, &true); - b.set_bit(&8, &true); - b.set_bit(&1337, &true); + b.set_bit(0, true); + b.set_bit(7, true); + b.set_bit(8, true); + b.set_bit(1337, true); assert_eq!(b.num_true_bits(), 4); } }