BitArray

This package provides a bit array structure with sub-byte methods like packing and shifting for arrays of bits of arbitrary length.

This is not useful for set operations. It facilitates encoding data that is not necessarily aligned to 8 bits. It was originally designed to cater to the packed encoding required for the ISO/IEC 20248 digital signature format.

Usage

import (
    "fmt"

    "src.userspace.com.au/bitarray"
)

func main() {
    ba := &bitarray.BitArray{}

    // Add single bits, never truncated
    ba.AddBit(1)
    ba.AddBit(0)
    ba.AddBit(1)
    fmt.Println(ba.Len()) // => 3
    fmt.Printf("%08b\n", ba.Bytes()) // => [10100000]

    // Add with truncated leading padding
    ba.Add(5)
    fmt.Printf("%08b\n", ba.Bytes()) // => [10110100]

    // Add with fixed length
    ba.AddN(5, 10)
    fmt.Printf("%08b\n", ba.Bytes()) // => [10110100 00000101]

    r := bitarray.NewReader(ba)
    var out uint
    r.ReadBits(&out, 16)
    fmt.Printf("%08b\n", out) // => 1011010000000101

    ba.ShiftL(2)
    fmt.Println(ba.String()) // => [11010000 000101--]

    ba2, _ := ba.Slice(9, 6)
    fmt.Println(ba2.String()) // => [000101--]
}