pub enum BitOrder {
    MostSignificantFirst,
    LeastSignificantFirst,
}
Expand description

Order in which bits are read from a byte

The base-conversion encoding is always little-endian. This means that the least significant byte is always first. However, we can still choose whether, within a byte, this is the most significant or the least significant bit that is first. If the terminology is confusing, testing on an asymmetrical example should be enough to choose the correct value.

Examples

In the following example, we can see that a base with the MostSignificantFirst bit-order has the most significant bit first in the encoded output. In particular, the output is in the same order as the bits in the byte. The opposite happens with the LeastSignificantFirst bit-order. The least significant bit is first and the output is in the reverse order.

use data_encoding::{BitOrder, Specification};
let mut spec = Specification::new();
spec.symbols.push_str("01");
spec.bit_order = BitOrder::MostSignificantFirst;  // default
let msb = spec.encoding().unwrap();
spec.bit_order = BitOrder::LeastSignificantFirst;
let lsb = spec.encoding().unwrap();
assert_eq!(msb.encode(&[0b01010011]), "01010011");
assert_eq!(lsb.encode(&[0b01010011]), "11001010");

Variants§

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MostSignificantFirst

Most significant bit first

This is the most common and most intuitive bit-order. In particular, this is the bit-order used by RFC4648 and thus the usual hexadecimal, base64, base32, base64url, and base32hex encodings. This is the default bit-order when specifying a base.

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LeastSignificantFirst

Least significant bit first

Examples

DNSCurve base32 uses least significant bit first:

use data_encoding::BASE32_DNSCURVE;
assert_eq!(BASE32_DNSCURVE.encode(&[0x64, 0x88]), "4321");
assert_eq!(BASE32_DNSCURVE.decode(b"4321").unwrap(), vec![0x64, 0x88]);

Trait Implementations§

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impl Clone for BitOrder

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fn clone(&self) -> BitOrder

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for BitOrder

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl PartialEq for BitOrder

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fn eq(&self, other: &BitOrder) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl Copy for BitOrder

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impl Eq for BitOrder

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impl StructuralEq for BitOrder

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impl StructuralPartialEq for BitOrder

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.