bitfield.go

package main

import (
	"errors"
	"math"
	"strconv"
)

type Bitfield []bool

func (b Bitfield) ToBytes() []byte {
	byteCount := numberOfBytesNeededForNumberOfBits(len(b))
	bitfieldBytes := make([]byte, byteCount)
	for i := 0; i < byteCount; i++ {
		var byteString string
		for y := 0; y < 8; y++ {
			index := (i * 8) + y
			if index < len(b) && b[index] {
				byteString += "1"
			} else {
				byteString += "0"
			}
		}
		bitfieldInt, _ := strconv.ParseInt(byteString, 2, 0)
		bitfieldByte := byte(bitfieldInt)
		bitfieldBytes[i] = bitfieldByte
	}
	return bitfieldBytes
}

func BytesToBitfield(bytes []byte, length int) (bitfield Bitfield, err error) {
	var bitstring string
	byteCount := numberOfBytesNeededForNumberOfBits(length)
	if byteCount != len(bytes) {
		err = errors.New("Length mismatch")
		return
	}
	bitfield = make(Bitfield, length)
	for _, bitfieldByte := range bytes {
		byteString := strconv.FormatUint(uint64(bitfieldByte), 2)
		byteStringMissingBits := 8 - len(byteString)
		if byteStringMissingBits > 0 {
			for i := 0; i < byteStringMissingBits; i++ {
				byteString = "0" + byteString
			}
		}
		bitstring += byteString
	}
	for i, bit := range bitstring {
		if i >= length {
			break
		}
		if string(bit) == "1" {
			bitfield[i] = true
		} else {
			bitfield[i] = false
		}
	}
	return
}

func BitfieldsEqual(a Bitfield, b Bitfield) bool {
	if len(a) != len(b) {
		return false
	}
	for i, _ := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}

func numberOfBytesNeededForNumberOfBits(bitCount int) int {
	count64 := float64(bitCount)
	return int(math.Ceil(count64 / float64(8)))
}