Trait data_encoding::base::Base [−] [src]

pub trait Base {
    fn pad(&self) -> u8;
    fn val(&self, x: u8) -> Option<u8>;

    fn bit(&self) -> usize { ... }
    fn sym(&self, x: u8) -> u8 { ... }
}

Generic interface.

A base implementation needs to define at least its padding pad and its symbol-to-value function val. Its power of two bit and its value-to-symbol function sym are uniquely defined from the pad and val functions. However, for performance reasons, all functions may be defined directly.

Vocabulary

We call ascii a 7-bit code represented as a u8. In other words, any u8 value with most significant bit cleared (or equivalently, any u8 value between 0 and 127 inclusive) is an ascii, and reciprocally.

We call value a b-bit code represented as a u8, where b is the power of two of the base, i.e. 4 for base16 and 6 for base64 for instance. The values for base64 are thus any u8 value from 0 to 63, and similarly the values for base16 are any u8 value from 0 to 15. More generally, values are any u8 value between 0 and 2b - 1 inclusive. Each symbol is uniquely associated to a value.

We call symbol the symbols represented as ascii (as such, only ascii symbols are allowed). For instance, in base64, the symbols are the ascii from A to Z, the ascii from a to z, the ascii from 0 to 9, the ascii +, and the ascii / in value order. And the base16 symbols are the ascii from 0 to 9 and the ascii from A to F.

We call padding the padding represented as ascii (as such, only ascii padding is allowed). For instance, the ascii = is used as the padding for base64 and base16.

Constraints

The base interface comes with invariants which must be satisfied by all implementations. Although it cannot be checked, all implementations must be deterministic, i.e. they never return two different outputs for the same input and they never panic (unless specified otherwise). The other constraints are described in the ValidError enum and may be checked by the valid function. Implementations should also be pure.

Required Methods

Returns the padding.

Returns the value of a symbol.

This function defines what the symbols are, to which value they are associated, and the base size:

  • A symbol is an input that does not return None.
  • The value of a symbol is its associated output.
  • The base size is the number of symbols.

In other words, when val(s) returns:

  • Some(v): s is a symbol with value v.
  • None: s is not a symbol.

Provided Methods

Returns the power of two of the base.

Returns the symbol of a value.

This function must only be called on values.

Panics

May panic when input is not a value.

Implementors