Start building new bitfield struct

eth2/utils/ssz_types/Cargo.toml

@@ -5,8 +5,6 @@ authors = ["Paul Hauner <paul@paulhauner.com>"]
 edition = "2018"
 
 [dependencies]
-bit_reverse = "0.1"
-bit-vec = "0.5.0"
 cached_tree_hash = { path = "../cached_tree_hash" }
 tree_hash = { path = "../tree_hash" }
 serde = "1.0"

eth2/utils/ssz_types/src/bit_list.rs

@@ -1,6 +1,5 @@
 use super::*;
-use crate::{impl_bitfield_fns, reverse_bit_order, Error};
-use bit_vec::BitVec as Bitfield;
+use crate::{bitfield::Bitfield, impl_bitfield_fns, Error};
 use serde::de::{Deserialize, Deserializer};
 use serde::ser::{Serialize, Serializer};
 use serde_hex::{encode, PrefixedHexVisitor};
@@ -53,7 +52,7 @@ impl<N: Unsigned> BitList<N> {
     /// Create a new, empty BitList.
     pub fn new() -> Self {
         Self {
-            bitfield: Bitfield::default(),
+            bitfield: Bitfield::with_capacity(Self::max_len()),
             _phantom: PhantomData,
         }
     }
@@ -75,18 +74,20 @@ impl<N: Unsigned> BitList<N> {
     pub fn max_len() -> usize {
         N::to_usize()
     }
-
-    /// Create a new bitfield using the supplied `bytes` as input
-    pub fn from_bytes(bytes: &[u8]) -> Result<Self, Error> {
-        Self::validate_length(bytes.len().saturating_mul(8))?;
-
-        Ok(Self {
-            bitfield: Bitfield::from_bytes(&reverse_bit_order(bytes.to_vec())),
-            _phantom: PhantomData,
-        })
-    }
 }
 
+/*
+fn encode_bitfield(bitfield: Bitfield) -> Vec<u8> {
+    // Set the next bit of the bitfield to true.
+    //
+    // SSZ spec:
+    //
+    // An additional leading 1 bit is added so that the length in bits will also be known.
+    bitfield.set(bitfield.len(), true);
+    let bytes = bitfield.to_bytes();
+}
+*/
+
 impl<N: Unsigned + Clone> BitList<N> {
     /// Compute the intersection (binary-and) of this bitfield with another
     ///
@@ -106,7 +107,7 @@ impl<N: Unsigned + Clone> BitList<N> {
     ///
     /// If `self` and `other` have different lengths.
     pub fn intersection_inplace(&mut self, other: &Self) {
-        self.bitfield.intersect(&other.bitfield);
+        self.bitfield.intersection(&other.bitfield);
     }
 
     /// Compute the union (binary-or) of this bitfield with another. Lengths must match.
@@ -154,14 +155,7 @@ impl<N: Unsigned + Clone> BitList<N> {
     }
 }
 
-impl<N: Unsigned> default::Default for BitList<N> {
-    /// Default provides the "empty" bitfield
-    /// Note: the empty bitfield is set to the `0` byte.
-    fn default() -> Self {
-        Self::from_elem(0, false).expect("Zero cannot be larger than the maximum length")
-    }
-}
-
+/*
 #[cfg(test)]
 mod test {
     use super::*;
@@ -451,3 +445,4 @@ mod test {
         assert!(a.difference(&a).is_zero());
     }
 }
+*/

eth2/utils/ssz_types/src/bit_vector.rs

@@ -1,6 +1,5 @@
 use super::*;
-use crate::{impl_bitfield_fns, reverse_bit_order, Error};
-use bit_vec::BitVec as Bitfield;
+use crate::{bitfield::Bitfield, impl_bitfield_fns, Error};
 use serde::de::{Deserialize, Deserializer};
 use serde::ser::{Serialize, Serializer};
 use serde_hex::{encode, PrefixedHexVisitor};
@@ -54,18 +53,6 @@ impl<N: Unsigned> BitVector<N> {
         N::to_usize()
     }
 
-    /// Create a new bitfield using the supplied `bytes` as input
-    pub fn from_bytes(bytes: &[u8]) -> Result<Self, Error> {
-        if Self::capacity() >= 8 && bytes.len() != 1 {
-            Self::validate_length(bytes.len().saturating_mul(8))?;
-        }
-
-        Ok(Self {
-            bitfield: Bitfield::from_bytes(&reverse_bit_order(bytes.to_vec())),
-            _phantom: PhantomData,
-        })
-    }
-
     fn validate_length(len: usize) -> Result<(), Error> {
         let fixed_len = N::to_usize();
 
@@ -113,6 +100,7 @@ mod test {
     }
     */
 
+    /*
     #[test]
     fn new_bitfield() {
         let mut field = BitVector1024::new();
@@ -145,7 +133,6 @@ mod test {
         assert!(bitvec.get(4).is_err());
     }
 
-    /*
     #[test]
     fn from_bytes_bytes_too_long() {
         let bytes = &[0, 0];

eth2/utils/ssz_types/src/bitfield.rs

@@ -0,0 +1,520 @@
+/// A heap-allocated, ordered, fixed-length, collection of `bool` values.
+///
+/// The length of the Bitfield is set at instantiation (i.e., runtime, not compile time).
+///
+/// The internal representation of the bitfield is the same as that required by SSZ - the highest
+/// byte (by `Vec` index) stores the lowest bit-indices and the right-most bit stores the lowest
+/// bit-index. E.g., `vec![0b0000_0010, 0b0000_0001]` has bits `1, 9` set.
+#[derive(Clone, Debug, PartialEq)]
+pub struct Bitfield {
+    bytes: Vec<u8>,
+    len: usize,
+}
+
+impl Bitfield {
+    pub fn with_capacity(num_bits: usize) -> Self {
+        Self {
+            bytes: vec![0; Self::bytes_for_bit_len(num_bits)],
+            len: num_bits,
+        }
+    }
+
+    pub fn set(&mut self, i: usize, value: bool) -> Option<()> {
+        if i < self.len {
+            let byte = {
+                let num_bytes = self.bytes.len();
+                let offset = i / 8;
+                self.bytes
+                    .get_mut(num_bytes - offset - 1)
+                    .expect("Cannot be OOB if less than self.len")
+            };
+
+            if value {
+                *byte |= 1 << (i % 8)
+            } else {
+                *byte &= !(1 << (i % 8))
+            }
+
+            Some(())
+        } else {
+            None
+        }
+    }
+
+    pub fn get(&self, i: usize) -> Option<bool> {
+        if i < self.len {
+            let byte = {
+                let num_bytes = self.bytes.len();
+                let offset = i / 8;
+                self.bytes
+                    .get(num_bytes - offset - 1)
+                    .expect("Cannot be OOB if less than self.len")
+            };
+
+            Some(*byte & 1 << (i % 8) > 0)
+        } else {
+            None
+        }
+    }
+
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+    fn bytes_for_bit_len(bit_len: usize) -> usize {
+        (bit_len + 7) / 8
+    }
+
+    /// Verify that the given `bytes` faithfully represent a bitfield of length `bit_len`.
+    ///
+    /// The only valid `bytes` for `bit_len == 0` is `&[0]`.
+    fn verify_bitfield_bytes(bytes: &[u8], bit_len: usize) -> bool {
+        if bytes.len() == 1 && bit_len == 0 && bytes == &[0] {
+            true // A bitfield with `bit_len` 0 can only be represented by a single zero byte.
+        } else if bytes.len() != Bitfield::bytes_for_bit_len(bit_len) || bytes.is_empty() {
+            false // The number of bytes must be the minimum required to represent `bit_len`.
+        } else {
+            // Ensure there are no bits higher than `bit_len` that are set to true.
+            let (mask, _) = u8::max_value().overflowing_shr(bit_len as u32 % 8);
+            (bytes.last().expect("Bytes cannot be empty") & !mask) == 0
+        }
+    }
+
+    pub fn to_bytes(self) -> Vec<u8> {
+        self.bytes
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        &self.bytes
+    }
+
+    pub fn from_bytes(bytes: Vec<u8>, bit_len: usize) -> Option<Self> {
+        if bytes.len() == 1 && bit_len == 0 && bytes == &[0] {
+            // A bitfield with `bit_len` 0 can only be represented by a single zero byte.
+            Some(Self { bytes, len: 0 })
+        } else if bytes.len() != Bitfield::bytes_for_bit_len(bit_len) || bytes.is_empty() {
+            // The number of bytes must be the minimum required to represent `bit_len`.
+            None
+        } else {
+            // 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 {
+                Some(Self {
+                    bytes,
+                    len: bit_len,
+                })
+            } else {
+                None
+            }
+        }
+    }
+
+    pub fn iter(&self) -> BitIter<'_> {
+        BitIter {
+            bitfield: self,
+            i: 0,
+        }
+    }
+
+    pub fn is_zero(&self) -> bool {
+        !self.bytes.iter().any(|byte| (*byte & u8::max_value()) > 0)
+    }
+
+    pub fn intersection(&self, other: &Self) -> Option<Self> {
+        if self.is_comparable(other) {
+            let mut res = self.clone();
+            res.intersection_inplace(other);
+            Some(res)
+        } else {
+            None
+        }
+    }
+
+    pub fn intersection_inplace(&mut self, other: &Self) -> Option<()> {
+        if self.is_comparable(other) {
+            for i in 0..self.bytes.len() {
+                self.bytes[i] = self.bytes[i] & other.bytes[i];
+            }
+            Some(())
+        } else {
+            None
+        }
+    }
+
+    pub fn union(&self, other: &Self) -> Option<Self> {
+        if self.is_comparable(other) {
+            let mut res = self.clone();
+            res.union_inplace(other);
+            Some(res)
+        } else {
+            None
+        }
+    }
+
+    pub fn union_inplace(&mut self, other: &Self) -> Option<()> {
+        if self.is_comparable(other) {
+            for i in 0..self.bytes.len() {
+                self.bytes[i] = self.bytes[i] | other.bytes[i];
+            }
+            Some(())
+        } else {
+            None
+        }
+    }
+
+    pub fn difference(&self, other: &Self) -> Option<Self> {
+        if self.is_comparable(other) {
+            let mut res = self.clone();
+            res.difference_inplace(other);
+            Some(res)
+        } else {
+            None
+        }
+    }
+
+    pub fn difference_inplace(&mut self, other: &Self) -> Option<()> {
+        if self.is_comparable(other) {
+            for i in 0..self.bytes.len() {
+                self.bytes[i] = self.bytes[i] & !other.bytes[i];
+            }
+            Some(())
+        } else {
+            None
+        }
+    }
+
+    pub fn is_comparable(&self, other: &Self) -> bool {
+        (self.len() == other.len()) && (self.bytes.len() == other.bytes.len())
+    }
+}
+
+pub struct BitIter<'a> {
+    bitfield: &'a Bitfield,
+    i: usize,
+}
+
+impl<'a> Iterator for BitIter<'a> {
+    type Item = bool;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let res = self.bitfield.get(self.i);
+        self.i += 1;
+        res
+    }
+}
+
+/// Provides a common `impl` for structs that wrap a `$name`.
+#[macro_export]
+macro_rules! impl_bitfield_fns {
+    ($name: ident) => {
+        impl<N: Unsigned> $name<N> {
+            pub fn with_capacity(initial_len: usize) -> Result<Self, Error> {
+                Self::validate_length(initial_len)?;
+
+                Self::with_capacity(initial_len)
+            }
+
+            pub fn get(&self, i: usize) -> Result<bool, Error> {
+                if i < N::to_usize() {
+                    match self.bitfield.get(i) {
+                        Some(value) => Ok(value),
+                        None => Err(Error::OutOfBounds {
+                            i,
+                            len: self.bitfield.len(),
+                        }),
+                    }
+                } else {
+                    Err(Error::InvalidLength {
+                        i,
+                        len: N::to_usize(),
+                    })
+                }
+            }
+
+            pub fn set(&mut self, i: usize, value: bool) -> Option<()> {
+                self.bitfield.set(i, value)
+            }
+
+            /// Returns the number of bits in this bitfield.
+            pub fn len(&self) -> usize {
+                self.bitfield.len()
+            }
+
+            /// Returns true if `self.len() == 0`
+            pub fn is_empty(&self) -> bool {
+                self.bitfield.is_empty()
+            }
+
+            /// Returns true if all bits are set to 0.
+            pub fn is_zero(&self) -> bool {
+                self.bitfield.is_zero()
+            }
+
+            /// Returns the number of bytes presently used to store the bitfield.
+            pub fn num_bytes(&self) -> usize {
+                self.bitfield.as_slice().len()
+            }
+
+            /// Returns the number of `1` bits in the bitfield
+            pub fn num_set_bits(&self) -> usize {
+                self.bitfield.iter().filter(|&bit| bit).count()
+            }
+        }
+
+        /*
+        impl<N: Unsigned> Encode for $name<N> {
+            fn is_ssz_fixed_len() -> bool {
+                false
+            }
+
+            fn ssz_append(&self, buf: &mut Vec<u8>) {
+                buf.append(&mut self.bitfield.to_bytes())
+            }
+        }
+
+        impl<N: Unsigned> Decode for $name<N> {
+            fn is_ssz_fixed_len() -> bool {
+                false
+            }
+
+            fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, ssz::DecodeError> {
+                let bitfield =
+                    Bitfield::from_bytes(bytes.to_vec(), bytes.len() * 8).expect("Cannot fail");
+                Ok(Self {
+                    bitfield,
+                    _phantom: PhantomData,
+                })
+                /*
+                $name::from_bytes(bytes)
+                    .map_err(|e| ssz::DecodeError::BytesInvalid(format!("Bitfield {:?}", e)))
+                */
+            }
+        }
+
+        impl<N: Unsigned> Serialize for $name<N> {
+            /// Serde serialization is compliant with the Ethereum YAML test format.
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+            where
+                S: Serializer,
+            {
+                serializer.serialize_str(&encode(self.bitfield.to_bytes()))
+            }
+        }
+
+        impl<'de, N: Unsigned> Deserialize<'de> for $name<N> {
+            /// Serde serialization is compliant with the Ethereum YAML test format.
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+            where
+                D: Deserializer<'de>,
+            {
+                // We reverse the bit-order so that the BitVec library can read its 0th
+                // bit from the end of the hex string, e.g.
+                // "0xef01" => [0xef, 0x01] => [0b1000_0000, 0b1111_1110]
+                let bytes = deserializer.deserialize_str(PrefixedHexVisitor)?;
+                $name::from_bytes(&bytes)
+                    .map_err(|e| serde::de::Error::custom(format!("Bitfield {:?}", e)))
+            }
+        }
+
+        impl<N: Unsigned> tree_hash::TreeHash for $name<N> {
+            fn tree_hash_type() -> tree_hash::TreeHashType {
+                tree_hash::TreeHashType::List
+            }
+
+            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
+                unreachable!("List should never be packed.")
+            }
+
+            fn tree_hash_packing_factor() -> usize {
+                unreachable!("List should never be packed.")
+            }
+
+            fn tree_hash_root(&self) -> Vec<u8> {
+                self.to_bytes().tree_hash_root()
+            }
+        }
+        */
+    };
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn from_bytes() {
+        assert!(Bitfield::from_bytes(vec![0b0000_0000], 0).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_0001], 1).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_0011], 2).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_0111], 3).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_1111], 4).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0001_1111], 5).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0011_1111], 6).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0111_1111], 7).is_some());
+        assert!(Bitfield::from_bytes(vec![0b1111_1111], 8).is_some());
+
+        assert!(Bitfield::from_bytes(vec![0b0000_0001, 0b1111_1111], 9).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_0011, 0b1111_1111], 10).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_0111, 0b1111_1111], 11).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0000_1111, 0b1111_1111], 12).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0001_1111, 0b1111_1111], 13).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0011_1111, 0b1111_1111], 14).is_some());
+        assert!(Bitfield::from_bytes(vec![0b0111_1111, 0b1111_1111], 15).is_some());
+        assert!(Bitfield::from_bytes(vec![0b1111_1111, 0b1111_1111], 16).is_some());
+
+        for i in 0..8 {
+            assert!(Bitfield::from_bytes(vec![], i).is_none());
+            assert!(Bitfield::from_bytes(vec![0b1111_1111], i).is_none());
+            assert!(Bitfield::from_bytes(vec![0b1111_1110, 0b0000_0000], i).is_none());
+        }
+
+        assert!(Bitfield::from_bytes(vec![0b0000_0001], 0).is_none());
+
+        assert!(Bitfield::from_bytes(vec![0b0000_0001], 0).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0000_0011], 1).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0000_0111], 2).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0000_1111], 3).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0001_1111], 4).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0011_1111], 5).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0111_1111], 6).is_none());
+        assert!(Bitfield::from_bytes(vec![0b1111_1111], 7).is_none());
+
+        assert!(Bitfield::from_bytes(vec![0b0000_0001, 0b1111_1111], 8).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0000_0011, 0b1111_1111], 9).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0000_0111, 0b1111_1111], 10).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0000_1111, 0b1111_1111], 11).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0001_1111, 0b1111_1111], 12).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0011_1111, 0b1111_1111], 13).is_none());
+        assert!(Bitfield::from_bytes(vec![0b0111_1111, 0b1111_1111], 14).is_none());
+        assert!(Bitfield::from_bytes(vec![0b1111_1111, 0b1111_1111], 15).is_none());
+    }
+
+    fn test_set_unset(num_bits: usize) {
+        let mut bitfield = Bitfield::with_capacity(num_bits);
+
+        for i in 0..num_bits + 1 {
+            dbg!(i);
+            if i < num_bits {
+                // Starts as false
+                assert_eq!(bitfield.get(i), Some(false));
+                // Can be set true.
+                assert!(bitfield.set(i, true).is_some());
+                assert_eq!(bitfield.get(i), Some(true));
+                // Can be set false
+                assert!(bitfield.set(i, false).is_some());
+                assert_eq!(bitfield.get(i), Some(false));
+            } else {
+                assert_eq!(bitfield.get(i), None);
+                assert!(bitfield.set(i, true).is_none());
+                assert_eq!(bitfield.get(i), None);
+            }
+        }
+    }
+
+    fn test_bytes_round_trip(num_bits: usize) {
+        dbg!(num_bits);
+        for i in 0..num_bits {
+            dbg!(i);
+            let mut bitfield = Bitfield::with_capacity(num_bits);
+            bitfield.set(i, true).unwrap();
+
+            let bytes = bitfield.clone().to_bytes();
+            dbg!(&bytes);
+            assert_eq!(bitfield, Bitfield::from_bytes(bytes, num_bits).unwrap());
+        }
+    }
+
+    #[test]
+    fn set_unset() {
+        for i in 0..8 * 5 {
+            test_set_unset(i)
+        }
+    }
+
+    #[test]
+    fn bytes_round_trip() {
+        for i in 0..8 * 5 {
+            test_bytes_round_trip(i)
+        }
+    }
+
+    #[test]
+    fn to_bytes() {
+        let mut bitfield = Bitfield::with_capacity(9);
+        bitfield.set(0, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0000_0001]);
+        bitfield.set(1, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0000_0011]);
+        bitfield.set(2, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0000_0111]);
+        bitfield.set(3, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0000_1111]);
+        bitfield.set(4, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0001_1111]);
+        bitfield.set(5, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0011_1111]);
+        bitfield.set(6, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b0111_1111]);
+        bitfield.set(7, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0000, 0b1111_1111]);
+        bitfield.set(8, true);
+        assert_eq!(bitfield.clone().to_bytes(), vec![0b0000_0001, 0b1111_1111]);
+    }
+
+    #[test]
+    fn intersection() {
+        let a = Bitfield::from_bytes(vec![0b1100, 0b0001], 16).unwrap();
+        let b = Bitfield::from_bytes(vec![0b1011, 0b1001], 16).unwrap();
+        let c = Bitfield::from_bytes(vec![0b1000, 0b0001], 16).unwrap();
+
+        assert_eq!(a.intersection(&b).unwrap(), c);
+        assert_eq!(b.intersection(&a).unwrap(), c);
+        assert_eq!(a.intersection(&c).unwrap(), c);
+        assert_eq!(b.intersection(&c).unwrap(), c);
+        assert_eq!(a.intersection(&a).unwrap(), a);
+        assert_eq!(b.intersection(&b).unwrap(), b);
+        assert_eq!(c.intersection(&c).unwrap(), c);
+    }
+
+    #[test]
+    fn union() {
+        let a = Bitfield::from_bytes(vec![0b1100, 0b0001], 16).unwrap();
+        let b = Bitfield::from_bytes(vec![0b1011, 0b1001], 16).unwrap();
+        let c = Bitfield::from_bytes(vec![0b1111, 0b1001], 16).unwrap();
+
+        assert_eq!(a.union(&b).unwrap(), c);
+        assert_eq!(b.union(&a).unwrap(), c);
+        assert_eq!(a.union(&a).unwrap(), a);
+        assert_eq!(b.union(&b).unwrap(), b);
+        assert_eq!(c.union(&c).unwrap(), c);
+    }
+
+    #[test]
+    fn difference() {
+        let a = Bitfield::from_bytes(vec![0b1100, 0b0001], 16).unwrap();
+        let b = Bitfield::from_bytes(vec![0b1011, 0b1001], 16).unwrap();
+        let a_b = Bitfield::from_bytes(vec![0b0100, 0b0000], 16).unwrap();
+        let b_a = Bitfield::from_bytes(vec![0b0011, 0b1000], 16).unwrap();
+
+        assert_eq!(a.difference(&b).unwrap(), a_b);
+        assert_eq!(b.difference(&a).unwrap(), b_a);
+        assert!(a.difference(&a).unwrap().is_zero());
+    }
+
+    #[test]
+    fn iter() {
+        let mut bitfield = Bitfield::with_capacity(9);
+        bitfield.set(2, true);
+        bitfield.set(8, true);
+
+        assert_eq!(
+            bitfield.iter().collect::<Vec<bool>>(),
+            vec![false, false, true, false, false, false, false, false, true]
+        );
+    }
+}

eth2/utils/ssz_types/src/impl_bitfield_fns.rs

@@ -1,291 +0,0 @@
-use bit_reverse::LookupReverse;
-
-/// Provides a common `impl` for structs that wrap a `$name`.
-#[macro_export]
-macro_rules! impl_bitfield_fns {
-    ($name: ident) => {
-        impl<N: Unsigned> $name<N> {
-            /// Create a new BitList list with `initial_len` bits all set to `false`.
-            pub fn with_capacity(initial_len: usize) -> Result<Self, Error> {
-                Self::from_elem(initial_len, false)
-            }
-
-            /// Create a new bitfield with the given length `initial_len` and all values set to `bit`.
-            ///
-            /// Note: if `initial_len` is not a multiple of 8, the remaining bits will be set to `false`
-            /// regardless of `bit`.
-            pub fn from_elem(initial_len: usize, bit: bool) -> Result<Self, Error> {
-                // BitVec can panic if we don't set the len to be a multiple of 8.
-                let full_len = ((initial_len + 7) / 8) * 8;
-
-                Self::validate_length(full_len)?;
-
-                let mut bitfield = Bitfield::from_elem(full_len, false);
-
-                if bit {
-                    for i in 0..initial_len {
-                        bitfield.set(i, true);
-                    }
-                }
-
-                Ok(Self {
-                    bitfield,
-                    _phantom: PhantomData,
-                })
-            }
-
-            /// Returns a vector of bytes representing the bitfield
-            pub fn to_bytes(&self) -> Vec<u8> {
-                if self.bitfield.is_empty() {
-                    vec![0] // Empty bitfield should be represented as a zero byte.
-                } else {
-                    reverse_bit_order(self.bitfield.to_bytes().to_vec())
-                }
-            }
-
-            /// Read the value of a bit.
-            ///
-            /// If the index is in bounds, then result is Ok(value) where value is `true` if the
-            /// bit is 1 and `false` if the bit is 0.  If the index is out of bounds, we return an
-            /// error to that extent.
-            pub fn get(&self, i: usize) -> Result<bool, Error> {
-                if i < N::to_usize() {
-                    match self.bitfield.get(i) {
-                        Some(value) => Ok(value),
-                        None => Err(Error::OutOfBounds {
-                            i,
-                            len: self.bitfield.len(),
-                        }),
-                    }
-                } else {
-                    Err(Error::InvalidLength {
-                        i,
-                        len: N::to_usize(),
-                    })
-                }
-            }
-
-            /// Set the value of a bit.
-            ///
-            /// If the index is out of bounds, we expand the size of the underlying set to include
-            /// the new index.  Returns the previous value if there was one.
-            pub fn set(&mut self, i: usize, value: bool) -> Result<(), Error> {
-                match self.get(i) {
-                    Ok(previous) => Some(previous),
-                    Err(Error::OutOfBounds { len, .. }) => {
-                        let new_len = i - len + 1;
-                        self.bitfield.grow(new_len, false);
-                        None
-                    }
-                    Err(e) => return Err(e),
-                };
-
-                self.bitfield.set(i, value);
-
-                Ok(())
-            }
-
-            /// Returns the number of bits in this bitfield.
-            pub fn len(&self) -> usize {
-                self.bitfield.len()
-            }
-
-            /// Returns true if `self.len() == 0`
-            pub fn is_empty(&self) -> bool {
-                self.len() == 0
-            }
-
-            /// Returns true if all bits are set to 0.
-            pub fn is_zero(&self) -> bool {
-                self.bitfield.none()
-            }
-
-            /// Returns the number of bytes required to represent this bitfield.
-            pub fn num_bytes(&self) -> usize {
-                self.to_bytes().len()
-            }
-
-            /// Returns the number of `1` bits in the bitfield
-            pub fn num_set_bits(&self) -> usize {
-                self.bitfield.iter().filter(|&bit| bit).count()
-            }
-        }
-
-        impl<N: Unsigned> cmp::PartialEq for $name<N> {
-            /// Determines equality by comparing the `ssz` encoding of the two candidates.  This
-            /// method ensures that the presence of high-order (empty) bits in the highest byte do
-            /// not exclude equality when they are in fact representing the same information.
-            fn eq(&self, other: &Self) -> bool {
-                ssz::ssz_encode(self) == ssz::ssz_encode(other)
-            }
-        }
-
-        /// Create a new bitfield that is a union of two other bitfields.
-        ///
-        /// For example `union(0101, 1000) == 1101`
-        // TODO: length-independent intersection for BitAnd
-        impl<N: Unsigned + Clone> std::ops::BitOr for $name<N> {
-            type Output = Self;
-
-            fn bitor(self, other: Self) -> Self {
-                let (biggest, smallest) = if self.len() > other.len() {
-                    (&self, &other)
-                } else {
-                    (&other, &self)
-                };
-                let mut new = (*biggest).clone();
-                for i in 0..smallest.len() {
-                    if let Ok(true) = smallest.get(i) {
-                        new.set(i, true)
-                            .expect("Cannot produce bitfield larger than smallest of two given");
-                    }
-                }
-                new
-            }
-        }
-
-        impl<N: Unsigned> Encode for $name<N> {
-            fn is_ssz_fixed_len() -> bool {
-                false
-            }
-
-            fn ssz_append(&self, buf: &mut Vec<u8>) {
-                buf.append(&mut self.to_bytes())
-            }
-        }
-
-        impl<N: Unsigned> Decode for $name<N> {
-            fn is_ssz_fixed_len() -> bool {
-                false
-            }
-
-            fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, ssz::DecodeError> {
-                $name::from_bytes(bytes)
-                    .map_err(|e| ssz::DecodeError::BytesInvalid(format!("Bitfield {:?}", e)))
-            }
-        }
-
-        impl<N: Unsigned> Serialize for $name<N> {
-            /// Serde serialization is compliant with the Ethereum YAML test format.
-            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-            where
-                S: Serializer,
-            {
-                serializer.serialize_str(&encode(self.to_bytes()))
-            }
-        }
-
-        impl<'de, N: Unsigned> Deserialize<'de> for $name<N> {
-            /// Serde serialization is compliant with the Ethereum YAML test format.
-            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-            where
-                D: Deserializer<'de>,
-            {
-                // We reverse the bit-order so that the BitVec library can read its 0th
-                // bit from the end of the hex string, e.g.
-                // "0xef01" => [0xef, 0x01] => [0b1000_0000, 0b1111_1110]
-                let bytes = deserializer.deserialize_str(PrefixedHexVisitor)?;
-                $name::from_bytes(&bytes)
-                    .map_err(|e| serde::de::Error::custom(format!("Bitfield {:?}", e)))
-            }
-        }
-
-        impl<N: Unsigned> tree_hash::TreeHash for $name<N> {
-            fn tree_hash_type() -> tree_hash::TreeHashType {
-                tree_hash::TreeHashType::List
-            }
-
-            fn tree_hash_packed_encoding(&self) -> Vec<u8> {
-                unreachable!("List should never be packed.")
-            }
-
-            fn tree_hash_packing_factor() -> usize {
-                unreachable!("List should never be packed.")
-            }
-
-            fn tree_hash_root(&self) -> Vec<u8> {
-                self.to_bytes().tree_hash_root()
-            }
-        }
-    };
-}
-
-// Reverse the bit order of a whole byte vec, so that the ith bit
-// of the input vec is placed in the (N - i)th bit of the output vec.
-// This function is necessary for converting bitfields to and from YAML,
-// as the BitVec library and the hex-parser use opposing bit orders.
-pub fn reverse_bit_order(mut bytes: Vec<u8>) -> Vec<u8> {
-    bytes.reverse();
-    bytes.into_iter().map(LookupReverse::swap_bits).collect()
-}
-
-/*
-/// Verify that the given `bytes` faithfully represent a bitfield of length `bit_len`.
-///
-/// The only valid `bytes` for `bit_len == 0` is `&[0]`.
-pub fn verify_bitfield_bytes(bytes: &[u8], bit_len: usize) -> bool {
-    if bytes.len() == 1 && bit_len == 0 && bytes == &[0] {
-        true // A bitfield with `bit_len` 0 can only be represented by a single zero byte.
-    } else if bytes.len() != ((bit_len + 7) / 8) || bytes.is_empty() {
-        false // The number of bytes must be the minimum required to represent `bit_len`.
-    } else {
-        // Ensure there are no bits higher than `bit_len` that are set to true.
-        let (mask, _) = u8::max_value().overflowing_shl(8 - (bit_len as u32 % 8));
-        (bytes.last().expect("Bytes cannot be empty") & !mask) == 0
-    }
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn bitfield_bytes_length() {
-        assert!(verify_bitfield_bytes(&[0b0000_0000], 0));
-        assert!(verify_bitfield_bytes(&[0b1000_0000], 1));
-        assert!(verify_bitfield_bytes(&[0b1100_0000], 2));
-        assert!(verify_bitfield_bytes(&[0b1110_0000], 3));
-        assert!(verify_bitfield_bytes(&[0b1111_0000], 4));
-        assert!(verify_bitfield_bytes(&[0b1111_1000], 5));
-        assert!(verify_bitfield_bytes(&[0b1111_1100], 6));
-        assert!(verify_bitfield_bytes(&[0b1111_1110], 7));
-        assert!(verify_bitfield_bytes(&[0b1111_1111], 8));
-
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b0000_0000], 9));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1000_0000], 9));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1100_0000], 10));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1110_0000], 11));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1111_0000], 12));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1111_1000], 13));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1111_1100], 14));
-        assert!(verify_bitfield_bytes(&[0b1111_1111, 0b1111_1110], 15));
-
-        for i in 0..8 {
-            assert!(!verify_bitfield_bytes(&[], i));
-            assert!(!verify_bitfield_bytes(&[0b1111_1111], i));
-            assert!(!verify_bitfield_bytes(&[0b1111_1110, 0b0000_0000], i));
-        }
-
-        assert!(!verify_bitfield_bytes(&[0b1000_0000], 0));
-
-        assert!(!verify_bitfield_bytes(&[0b1000_0000], 0));
-        assert!(!verify_bitfield_bytes(&[0b1100_0000], 1));
-        assert!(!verify_bitfield_bytes(&[0b1110_0000], 2));
-        assert!(!verify_bitfield_bytes(&[0b1111_0000], 3));
-        assert!(!verify_bitfield_bytes(&[0b1111_1000], 4));
-        assert!(!verify_bitfield_bytes(&[0b1111_1100], 5));
-        assert!(!verify_bitfield_bytes(&[0b1111_1110], 6));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111], 7));
-
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1000_0000], 8));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1100_0000], 9));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1110_0000], 10));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1111_0000], 11));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1111_1000], 12));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1111_1100], 13));
-        assert!(!verify_bitfield_bytes(&[0b1111_1111, 0b1111_1110], 14));
-
-        assert!(!verify_bitfield_bytes(&[0b1111_1110], 6));
-    }
-}
-*/

eth2/utils/ssz_types/src/lib.rs

@@ -1,12 +1,10 @@
 #[macro_use]
-mod impl_bitfield_fns;
+mod bitfield;
 mod bit_list;
 mod bit_vector;
 mod fixed_vector;
 mod variable_list;
 
-use impl_bitfield_fns::reverse_bit_order;
-
 pub use bit_list::BitList;
 pub use bit_vector::BitVector;
 pub use fixed_vector::FixedVector;