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// Create a bitmap which can represent "bitmap_size" number of blocks 
pub fn bitmap_create(bitmap_size: &mut u64) -> Vec<u8> {
    if *bitmap_size % 8 != 0 {
        *bitmap_size = (*bitmap_size + *bitmap_size % 8) / 8;
    }
    else {
        *bitmap_size = *bitmap_size / 8;
    }
    let mut _bitmap: Vec<u8> = Vec::with_capacity(*bitmap_size as usize);
    for _i in 0..(*bitmap_size) {
        _bitmap.push(0);
    }
    return _bitmap;
}

// Clears the bit corresponding to the block number given by "bitno"
pub fn clear_bit(bitmap: &mut Vec<u8>, bitno: u64) -> i32{
    if bitno > ((bitmap.len() as u64) * 8) {
        return -1;
    }
    let index: u64 = bitno / 8;
    let bit_index: u32 = (bitno % 8) as u32;
    let val: u8 = u8::pow(2, bit_index);
    (* bitmap)[index as usize] = (* bitmap)[index as usize] & !(val);
    return 0;
}

// Sets the bit corresponding to the block number given by "bitno"
pub fn set_bit(bitmap: &mut Vec<u8>, bitno: u64) -> i32{
    if bitno > ((bitmap.len() as u64) * 8) {
        return -1;
    }
    let index: u64 = bitno / 8;
    let bit_index: u32 = (bitno % 8) as u32;
    let val: u8 = u8::pow(2, bit_index);
    (* bitmap)[index as usize] = (* bitmap)[index as usize] | (val);
    return 0;
}

// Fetches the block number of the first occupied block
pub fn get_first_set_bit(bitmap: &mut Vec<u8>) -> i64{
    let mut _val: u8 = 0;
    for index in 0..bitmap.len() {
        for bit_index in 0..8 {
            _val = u8::pow(2, bit_index);
            if (bitmap[index] & _val) > 0 {
                return ((index as u64) * 8 + (bit_index as u64)) as i64;
            }
        }
    }
    return -1;
}

// Fetches the block number of the first free block
pub fn get_first_unset_bit(bitmap: &mut Vec<u8>) -> i64{
    let mut _val: u8 = 0;
    for index in 0..bitmap.len() {
        for bit_index in 0..8 {
            _val = u8::pow(2, bit_index);
            if (bitmap[index] & _val) == 0{
                return ((index as u64) * 8 + (bit_index as u64)) as i64;
            }
        }
    }
    return -1;
}

// Checks the bit status of the bit corresponding to the block number given by "bitno"
pub fn check_bit(bitmap: &mut Vec<u8>, bitno: u64) -> i32 {
    if bitno > ((bitmap.len() as u64) * 8) {
        return -1;
    }
    let index: u64 = bitno / 8;
    let bit_index: u32 = (bitno % 8) as u32;
    return (((bitmap[index as usize] >> bit_index) as u32) & 1) as i32;
}