utf8

Documentation

Overview

Package utf8 implements encoding and decoding of UTF-8 coded numbers.

Index

• func Decode(r io.Reader) (x uint64, err error)
• func Encode(w io.Writer, x uint64) error

Functions

func Decode

func Decode(r io.Reader) (x uint64, err error)

Decode decodes a "UTF-8" coded number and returns it.

ref: http://permalink.gmane.org/gmane.comp.audio.compression.flac.devel/3033

Algorithm description:

• read one byte B0 from the stream
• if B0 = 0xxxxxxx then the read value is B0 -> end
• if B0 = 10xxxxxx, the encoding is invalid
• if B0 = 11xxxxxx, set L to the number of leading binary 1s minus 1: B0 = 110xxxxx -> L = 1 B0 = 1110xxxx -> L = 2 B0 = 11110xxx -> L = 3 B0 = 111110xx -> L = 4 B0 = 1111110x -> L = 5 B0 = 11111110 -> L = 6
• assign the bits following the encoding (the x bits in the examples) to a variable R with a magnitude of at least 36 bits
• loop from 1 to L
• left shift R 6 bits
• read B from the stream
• if B does not match 10xxxxxx, the encoding is invalid
• set R = R or <the lower 6 bits from B>
• the read value is R

func Encode

func Encode(w io.Writer, x uint64) error

Encode encodes x as a "UTF-8" coded number.