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use super::BitsMut;
use storage::BlockType;

/// Bit vector operations that change the length.
pub trait BitsPush: BitsMut {
    /// Adds the given bit to the end of the bit vector.
    fn push_bit(&mut self, value: bool);

    /// Removes and returns the last bit, if any.
    fn pop_bit(&mut self) -> Option<bool>;

    /// Pushes `value` 0 or more times until the size of the bit
    /// vector is block-aligned.
    fn align_block(&mut self, value: bool) {
        while Self::Block::mod_nbits(self.bit_len()) != 0 {
            self.push_bit(value);
        }
    }

    /// Pushes the given block onto the end of the bit vector.
    ///
    /// If the end of the bit vector is not currently block-aligned,
    /// it pads with 0s up to the next block before pushing.
    ///
    /// The default implementation pushes the block one bit at a time;
    /// override it with something more efficient.
    fn push_block(&mut self, mut value: Self::Block) {
        self.align_block(false);

        for _ in 0 .. Self::Block::nbits() {
            self.push_bit(value & Self::Block::one() != Self::Block::zero());
            value = value >> 1;
        }
    }
}

impl BitsPush for Vec<bool> {
    fn push_bit(&mut self, value: bool) {
        self.push(value);
    }

    fn pop_bit(&mut self) -> Option<bool> {
        self.pop()
    }
}