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use crate::bitops::BitOps;
use num_traits::PrimInt;
use std::mem::size_of;
pub struct Bits {
bits: Vec<Option<bool>>,
size: usize,
}
impl Bits {
pub fn new<T: PrimInt>() -> Self {
let size = Self::bit_size::<T>();
let mut bits: Vec<Option<bool>> = Vec::with_capacity(size);
for _ in 0..size {
bits.push(None);
}
Bits { bits, size }
}
pub fn bit_size<T: PrimInt>() -> usize {
let byte_size = size_of::<T>();
byte_size * 8
}
pub fn get_bit(&self, index: usize) -> Option<bool> {
self.bits[index]
}
pub fn set_bit(&mut self, index: usize, val: bool) {
self.bits[index] = Some(val);
}
pub fn set_bit_within_constrains(
&mut self,
index: usize,
val: bool,
) -> Result<(), &'static str> {
match self.bits[index] {
Some(bit) if bit != val => return Err("Already decided bit value can not be changed!"),
Some(_) => {}
None => self.bits[index] = Some(val),
}
Ok(())
}
pub fn is_bit_decided(&self, index: usize) -> bool {
let bit = self.bits[index];
bit.is_some()
}
pub fn form_zero_padded_number<T: PrimInt>(&self) -> Result<T, &str> {
if Self::bit_size::<T>() < self.size {
return Err("Requested number type has not enough bits to represent the whole number!");
}
let mut number: T = T::zero();
for (index, _) in self.bits.iter().enumerate() {
self.incorporate_bit(index, &mut number);
}
Ok(number)
}
fn incorporate_bit<T: PrimInt + BitOps>(&self, index: usize, number: &mut T) {
let bit = self.bits[index];
match bit {
Some(bit) if bit => {
number.set_bit(index);
}
_ => {}
}
}
}
#[cfg(test)]
mod tests {
use crate::bits::Bits;
#[test]
fn bit_size() {
assert_eq!(8, Bits::bit_size::<u8>());
assert_eq!(16, Bits::bit_size::<u16>());
assert_eq!(32, Bits::bit_size::<u32>());
assert_eq!(64, Bits::bit_size::<u64>());
assert_eq!(128, Bits::bit_size::<u128>());
}
#[test]
fn new_bits_by_default_none() {
let bit_rep = Bits::new::<u64>();
for i in 0..Bits::bit_size::<u64>() {
assert_eq!(
None,
bit_rep.get_bit(i),
"Every bit should be empty in this phase, but the bit with index {} is not!",
i
);
}
}
#[test]
fn get_set_bit() {
let mut bit_rep = Bits::new::<u64>();
assert_eq!(None, bit_rep.get_bit(0));
assert_eq!(None, bit_rep.get_bit(8));
assert_eq!(None, bit_rep.get_bit(63));
let index = 0;
let val = true;
bit_rep.set_bit(index, val);
assert_eq!(Some(val), bit_rep.get_bit(index));
let index = 22;
let val = false;
bit_rep.set_bit(index, val);
assert_eq!(Some(val), bit_rep.get_bit(index));
let index = 63;
let val = false;
bit_rep.set_bit(index, val);
assert_eq!(Some(val), bit_rep.get_bit(index));
let index = 63;
let val = true;
bit_rep.set_bit(index, val);
assert_eq!(Some(val), bit_rep.get_bit(index));
}
#[test]
#[should_panic(expected = "index out of bounds: the len is 64 but the index is 64")]
fn get_bit_index_out_of_range() {
let bit_rep = Bits::new::<u64>();
let index_out_of_range = 64;
bit_rep.get_bit(index_out_of_range);
}
#[test]
#[should_panic(expected = "index out of bounds: the len is 64 but the index is 64")]
fn set_bit_index_out_of_range() {
let mut bit_rep = Bits::new::<u64>();
let index_out_of_range = 64;
bit_rep.set_bit(index_out_of_range, true);
}
#[test]
fn set_bit_within_constrains() {
let mut bit_rep = Bits::new::<u64>();
let index = 2;
assert_eq!(Ok(()), bit_rep.set_bit_within_constrains(index, true));
assert_eq!(Ok(()), bit_rep.set_bit_within_constrains(index, true));
assert_eq!(
Err("Already decided bit value can not be changed!"),
bit_rep.set_bit_within_constrains(index, false)
);
}
#[test]
fn is_bit_decided() {
let mut bit_rep = Bits::new::<u64>();
let index = 0;
assert!(
!bit_rep.is_bit_decided(index),
"Bit hasn't been decided already, so false must be returned!"
);
bit_rep.set_bit(index, true);
assert!(
bit_rep.is_bit_decided(index),
"Bit has been decided already, so true must be returned!"
);
bit_rep.set_bit(index, false);
assert!(
bit_rep.is_bit_decided(index),
"Bit has been decided already, so true must be returned!"
);
}
#[test]
fn form_zero_padded_number() {
let mut bit_rep = Bits::new::<u64>();
bit_rep.set_bit_within_constrains(1, true).unwrap();
bit_rep.set_bit_within_constrains(2, true).unwrap();
bit_rep.set_bit_within_constrains(6, true).unwrap();
assert_eq!(70, bit_rep.form_zero_padded_number::<u64>().unwrap());
}
#[test]
fn form_zero_padded_number_type_error() {
let bit_rep = Bits::new::<u64>();
assert_eq!(
Err("Requested number type has not enough bits to represent the whole number!"),
bit_rep.form_zero_padded_number::<u32>()
);
}
#[test]
fn incorporate_bit() {
let mut bit_rep = Bits::new::<u64>();
bit_rep.set_bit_within_constrains(1, true).unwrap();
bit_rep.set_bit_within_constrains(2, true).unwrap();
let mut number: u64 = 0;
bit_rep.incorporate_bit(1, &mut number);
assert_eq!(2, number);
bit_rep.incorporate_bit(2, &mut number);
assert_eq!(6, number);
bit_rep.incorporate_bit(3, &mut number);
assert_eq!(6, number);
}
}