codec

Documentation

Index

• type Codec
  • func (c *Codec) Decode(input string) ([]byte, error)
  • func (c *Codec) Encode(input []byte) (string, error)

Types

type Codec

type Codec struct {

	// Name is the human readable name given to this encoder
	Name string

	// HRP is the Human Readable Prefix to be appended in front of the encoding
	// to disambiguate it from another encoding or as a network or protocol
	// identifier. This can be empty, but more usually this will be used to
	// disambiguate versus other similarly encoded values, such as used on a
	// different cryptocurrency network, or between main and test networks.
	HRP string

	// Charset is the set of characters that the encoder uses. This should match
	// the output encoder, 32 for using base32, 64 for base64, etc.
	//
	// For arbitrary bases, see the following function in the standard library:
	// https://cs.opensource.google/go/go/+/refs/tags/go1.17.7:src/strconv/itoa.go;l=25
	// This function can render up to base36, but by default uses 0-9a-z in its
	// representation, which would either need to be string substituted for
	// non-performance-critical uses or the function above forked to provide a
	// direct encoding to the intended characters used for the encoding, using
	// this charset string as the key. The sequence matters, each character
	// represents the cipher for a given value to be found at a given place in
	// the encoded number.
	Charset string

	// Encode takes an arbitrary length byte input and returns the output as
	// defined for the codec
	Encoder func(input []byte) (output string, err error)

	// Decode takes an encoded string and returns if the encoding is valid and
	// the value passes any check function defined for the type.
	Decoder func(input string) (output []byte, err error)

	// AddCheck is used by Encode to add extra bytes for the checksum to ensure
	// correct input so user does not send to a wrong address by mistake, for
	// example.
	MakeCheck func(input []byte, checkLen int) (output []byte)

	// Check returns whether the check is valid
	Check func(input []byte) (err error)
}

Codec is the collection of elements that creates a Human Readable Binary Transcription Codec

This is an example of the use of a structure definition to encapsulate and logically connect together all of the elements of an implementation, while also permitting this to be used by external code without further dependencies, either through this type, or via the interface defined further down.

It is not "official" idiom, but it's the opinion of the author of this tutorial that return values given in type specifications like this helps the users of the library understand what the return values actually are. Otherwise, the programmer is forced to read the whole function just to spot the names and, even worse, comments explaining what the values are, which are often neglected during debugging, and turn into lies!

func (*Codec) Decode

func (c *Codec) Decode(input string) ([]byte, error)

Decode implements the codecer.Codecer.Decode by calling the provided function, and allows the concrete Codec type to always satisfy the interface, while allowing it to be implemented entirely differently.

Note: this also can be a one liner. Since we name the return values in the type definition and interface, omitting them here makes the line short enough to be a one liner.

func (*Codec) Encode

func (c *Codec) Encode(input []byte) (string, error)

Encode implements the codecer.Codecer.Encode by calling the provided function, and allows the concrete Codec type to always satisfy the interface, while allowing it to be implemented entirely differently.

Note: short functions like this can be one-liners according to gofmt.