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Module 0x1::bit_vector

Struct BitVector​

struct BitVector has copy, drop, store
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Fields
length: u64
bit_field: vector<bool>

Constants​

The provided index is out of bounds

const EINDEX: u64 = 131072;

An invalid length of bitvector was given

const ELENGTH: u64 = 131073;

The maximum allowed bitvector size

const MAX_SIZE: u64 = 1024;


const WORD_SIZE: u64 = 1;

Function new​

public fun new(length: u64): bit_vector::BitVector
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Implementation
public fun new(length: u64): BitVector {
    assert!(length > 0, ELENGTH);
    assert!(length < MAX_SIZE, ELENGTH);
    let mut counter = 0;
    let mut bit_field = vector::empty();
    while (counter < length) {
        bit_field.push_back(false);
        counter = counter + 1;
    };

    BitVector {
        length,
        bit_field,
    }
}

Function set​

Set the bit at bit_index in the bitvector regardless of its previous state.

public fun set(bitvector: &mut bit_vector::BitVector, bit_index: u64)
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Implementation
public fun set(bitvector: &mut BitVector, bit_index: u64) {
    assert!(bit_index < bitvector.bit_field.length(), EINDEX);
    let x = &mut bitvector.bit_field[bit_index];
    *x = true;
}

Function unset​

Unset the bit at bit_index in the bitvector regardless of its previous state.

public fun unset(bitvector: &mut bit_vector::BitVector, bit_index: u64)
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Implementation
public fun unset(bitvector: &mut BitVector, bit_index: u64) {
    assert!(bit_index < bitvector.bit_field.length(), EINDEX);
    let x = &mut bitvector.bit_field[bit_index];
    *x = false;
}

Function shift_left​

Shift the bitvector left by amount. If amount is greater than the bitvector's length the bitvector will be zeroed out.

public fun shift_left(bitvector: &mut bit_vector::BitVector, amount: u64)
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Implementation
public fun shift_left(bitvector: &mut BitVector, amount: u64) {
    if (amount >= bitvector.length) {
        let len = bitvector.bit_field.length();
        let mut i = 0;
        while (i < len) {
            let elem = &mut bitvector.bit_field[i];
            *elem = false;
            i = i + 1;
        };
    } else {
        let mut i = amount;

        while (i < bitvector.length) {
            if (bitvector.is_index_set(i)) bitvector.set(i - amount)
            else bitvector.unset(i - amount);
            i = i + 1;
        };

        i = bitvector.length - amount;

        while (i < bitvector.length) {
            unset(bitvector, i);
            i = i + 1;
        };
    }
}

Function is_index_set​

Return the value of the bit at bit_index in the bitvector. true represents "1" and false represents a 0

public fun is_index_set(bitvector: &bit_vector::BitVector, bit_index: u64): bool
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Implementation
public fun is_index_set(bitvector: &BitVector, bit_index: u64): bool {
    assert!(bit_index < bitvector.bit_field.length(), EINDEX);
    bitvector.bit_field[bit_index]
}

Function length​

Return the length (number of usable bits) of this bitvector

public fun length(bitvector: &bit_vector::BitVector): u64
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Implementation
public fun length(bitvector: &BitVector): u64 {
    bitvector.bit_field.length()
}

Function longest_set_sequence_starting_at​

Returns the length of the longest sequence of set bits starting at (and including) start_index in the bitvector. If there is no such sequence, then 0 is returned.

public fun longest_set_sequence_starting_at(bitvector: &bit_vector::BitVector, start_index: u64): u64
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Implementation
public fun longest_set_sequence_starting_at(bitvector: &BitVector, start_index: u64): u64 {
    assert!(start_index < bitvector.length, EINDEX);
    let mut index = start_index;

    // Find the greatest index in the vector such that all indices less than it are set.
    while (index < bitvector.length) {
        if (!bitvector.is_index_set(index)) break;
        index = index + 1;
    };

    index - start_index
}