Add SSZ and fixes for BooleanBitfield

Related to #22

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<u8>
@@ -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 {
+    pub fn get_bit(&self, i: usize) -> bool {
-        let bit = |i: &usize| *i % 8;
+        let bit = |i: usize| i % 8;
-        let byte = |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) {
+    pub fn set_bit(&mut self, i: usize, to: bool) {
-        let bit = |i: &usize| *i % 8;
+        let bit = |i: usize| i % 8;
-        let byte = |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 {
+        if to {
-            true =>  {
+            self.vec[byte(i)] =
-                self.vec[byte(i)] =
+                self.vec[byte(i)] |  (1 << (bit(i) as u8))
-                    self.vec[byte(i)] |  (1 << (bit(i) as u8))
+        } else {
-            }
+            self.vec[byte(i)] =
-            false => {
+                self.vec[byte(i)] & !(1 << (bit(i) as u8))
-                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<u8>`).
     pub fn to_be_vec(&self) -> Vec<u8> {
         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(7, true);
-        b.set_bit(&0, &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(8, true);
-        b.set_bit(&15, &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);
+            assert_eq!(b.get_bit(i), false);
-            b.set_bit(&i, &true);
+            b.set_bit(i, true);
-            assert_eq!(b.get_bit(&i), true);
+            assert_eq!(b.get_bit(i), true);
-            b.set_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(0, true);
-        b.set_bit(&7, &true);
+        b.set_bit(7, true);
-        b.set_bit(&8, &true);
+        b.set_bit(8, true);
-        b.set_bit(&1337, &true);
+        b.set_bit(1337, true);
         assert_eq!(b.num_true_bits(), 4);
     }
 }