CRC-4 for golang

crc4.go

package crc4

func Checksum(b []byte) uint8 {
        crc := 0xFFFF
        for bI := 0; bI < len(b); bI++ {
                bit := uint8(0x80)
                for bitI := 0; bitI < 8; bitI++ {
                        xorFlag := ((crc & 0x8000) == 0x8000)
                        crc = crc << 1
                        if ((b[bI] & bit) ^ uint8(0xFF)) != uint8(0xFF) {
                                crc = crc + 1
                        }

                        if xorFlag {
                                crc = crc ^ 0x1021
                        }

                        bit = bit >> 1
                }
        }
        return uint8(crc)
}

crc4_test.go

package crc4

import "testing"

func TestChecksum(t *testing.T) {
        gold := []struct {
                Data     []byte
                Checksum uint8
        }{
                {[]byte("apples and bananas"), 224},
                {[]byte(":smiley_face:"), 247},
        }

        for _, i := range gold {
                got := Checksum(i.Data)
                if got != i.Checksum {
                        t.Errorf("expected %d; got %d", i.Checksum, got)
                }
        }
}