Trait Flags

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pub trait Flags:
    Default
    + Clone
    + Copy
    + Sized {
    const BIT_SIZE: usize;

    // Required methods
    fn u8_bitmask(&self) -> u8;
    fn from_u8(value: u8) -> Option<Self>;

    // Provided method
    fn from_u8_remove_flags(value: &mut u8) -> Option<Self> { ... }
}

Expand description

Represents metadata to be appended to an object’s serialization.

For example, when serializing elliptic curve points, one can use a Flag to represent whether the serialization is the point at infinity, or whether the y coordinate is positive or not. These bits will be appended to the end of the point’s serialization, or included in a new byte, depending on space available.

This is meant to be provided to CanonicalSerializeWithFlags and CanonicalDeserializeWithFlags

Required Associated Constants§

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const BIT_SIZE: usize

The number of bits required to encode Self. This should be at most 8.

Required Methods§

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fn u8_bitmask(&self) -> u8

Returns a bit mask corresponding to self. For example, if Self contains two variants, there are just two possible bit masks: 0 and 1 << 7.

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fn from_u8(value: u8) -> Option<Self>

Tries to read Self from value. Should return None if the Self::BIT_SIZE most-significant bits of value do not correspond to those generated by u8_bitmask.

That is, this method ignores all but the top Self::BIT_SIZE bits, and decides whether these top bits correspond to a bitmask output by u8_bitmask.

Provided Methods§

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fn from_u8_remove_flags(value: &mut u8) -> Option<Self>

Convenience method that reads Self from value, just like Self::from_u8, but additionally zeroes out the bits corresponding to the resulting flag in value. If Self::from_u8(*value) would return None, then this method should not modify value.