shortening

package module

v0.0.0-...-64267dd Latest Latest Go to latest Published: Apr 22, 2019 License: MIT Imports: 2 Imported by: 4

Details

Valid go.mod file
Redistributable license
Tagged version
Stable version
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Repository

github.com/neilvallon/shortening

Links

Open Source Insights

README ¶

Shortening

A bijective base₆₄ encoder for creating short URLs.

Padding significant

Most encoders use decimal bases to convert characters. This can waste space by refusing to use the zero-value in the most significant position.

For example, in base₁₀ the numbers 1, 01, 00001, are all equivalent despite being padded with leading 0's.

This is why non-bijective encoders will skip values such as A and AAA in favor of possibly longer strings.

By using these values we can recover 64^(n-1) IDs of length n.

Length	Radix₆₄	Shortening	difference
1	63	64	1
2	4,032	4,096	64
3	258,048	262,144	4096
4	16,515,072	16,777,216	262,144
5	1,056,964,608	1,073,741,824	16,777,216

Performance

Benchmark	ns/op
Encode64	46.2
Decode64	21.6
Encode32	46.4
Decode32	23.7

go1.12.4 darwin/amd64
Intel Xeon X5675 - 3.06 GHz

References

Wikipedia: Bijective numeration

Documentation ¶

Index ¶

Constants
Variables
func Decode(b []byte) (n uint64, err error)
func Decode32(b []byte) (n uint64, err error)
func Encode(n uint64) []byte
func Encode32(n uint64) []byte

Constants ¶

View Source

const CharSet32 = `ABCDEFGHIJKLMNOPQRSTUVWXYZ234567`

View Source

const CharSet64 = `ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_`

Variables ¶

View Source

var (
	InvalidDecodeLen = errors.New("shortening: invalid decode length")
	InvalidCharacter = errors.New("shortening: invalid decode character")
	Overflow         = errors.New("shortening: uint64 overflow")
)

Functions ¶

func Decode ¶

func Decode(b []byte) (n uint64, err error)

Decode turns a slice of characters back into the original unit64.

Errors are returned for invalid characters or input that would cause an overflow.

func Decode32 ¶

func Decode32(b []byte) (n uint64, err error)

Decode32 turns a slice of characters back into the original unit64.

Errors are returned for invalid characters or input that would cause an overflow.

func Encode ¶

func Encode(n uint64) []byte

Encode turns an uint64 into a slice of characters from 'CharSet64'

func Encode32 ¶

func Encode32(n uint64) []byte

Encode32 turns an uint64 into a slice of characters from 'charSet32'

Types ¶

This section is empty.

Source Files ¶

View all Source files

Directories ¶

Path	Synopsis
examples
server

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