Trait Checkable

Source

pub trait Checkable: Checkable + Sized {
    // Required methods
    fn write<W: BitWrite + ?Sized>(&self, writer: &mut W) -> Result<()>;
    fn written_bits(&self) -> u32;
}

Expand description

A trait for writable types whose values can be validated

Ordinarily, when writing a value to a stream with a given number of bits, the value must be validated to ensure it will fit within that number of bits.

§Example 1

use bitstream_io::{BitWrite, BitWriter, BigEndian};

let mut w = BitWriter::endian(vec![], BigEndian);

// writing a value of 2 in 1 bit is always an error
// which is checked here at write-time
assert!(w.write::<1, u8>(2).is_err());

But if the value can be checked beforehand, it doesn’t need to be checked at write-time.

§Example 2

use bitstream_io::{BitWrite, BitWriter, BigEndian, CheckedUnsigned};

let mut w = BitWriter::endian(vec![], BigEndian);

// writing a value of 1 in 1 bit is ok
// and we're checking that validity at this stage
let value = CheckedUnsigned::<1, u8>::new_fixed::<1>(1).unwrap();

// because we've pre-validated the value beforehand,
// it doesn't need to be checked again here
// (though the write itself may still fail)
assert!(w.write_checked(value).is_ok());