day 16 part 1

utils/bits/bits.go

@@ -1,5 +1,7 @@
 package bits
 
+import "fmt"
+
 func GetBitCount(val int) int {
 	count := 0
 	for val != 0 {
@@ -52,3 +54,66 @@ func BitwiseAndA(a ...int) int {
 func ByBitCount(size int) func(int) bool {
 	return func(val int) bool { return GetBitCount(val) == size }
 }
+
+func ToInt(bits []bool) int {
+	intVal := 0
+	for idx := 0; idx < len(bits); idx++ {
+		intVal = intVal << 1
+		if bits[idx] {
+			intVal += 1
+		}
+	}
+	return intVal
+}
+
+func ToStr(bits []bool) string {
+	str := ""
+	for idx := 0; idx < len(bits); idx++ {
+		if bits[idx] {
+			str += "1"
+		} else {
+			str += "0"
+		}
+	}
+	return str
+}
+
+func HexByteToBits(b byte) ([]bool, error) {
+	// just do this manually because i can't be arsed
+	switch b {
+	case byte('0'):
+		return []bool{false, false, false, false}, nil
+	case byte('1'):
+		return []bool{false, false, false, true}, nil
+	case byte('2'):
+		return []bool{false, false, true, false}, nil
+	case byte('3'):
+		return []bool{false, false, true, true}, nil
+	case byte('4'):
+		return []bool{false, true, false, false}, nil
+	case byte('5'):
+		return []bool{false, true, false, true}, nil
+	case byte('6'):
+		return []bool{false, true, true, false}, nil
+	case byte('7'):
+		return []bool{false, true, true, true}, nil
+	case byte('8'):
+		return []bool{true, false, false, false}, nil
+	case byte('9'):
+		return []bool{true, false, false, true}, nil
+	case byte('A'):
+		return []bool{true, false, true, false}, nil
+	case byte('B'):
+		return []bool{true, false, true, true}, nil
+	case byte('C'):
+		return []bool{true, true, false, false}, nil
+	case byte('D'):
+		return []bool{true, true, false, true}, nil
+	case byte('E'):
+		return []bool{true, true, true, false}, nil
+	case byte('F'):
+		return []bool{true, true, true, true}, nil
+	default:
+		return []bool{}, fmt.Errorf("read invalid byte")
+	}
+}

utils/bits/bits_test.go

@@ -26,3 +26,37 @@ func TestByBitCount(t *testing.T) {
 	twoBitFilter := ByBitCount(2)
 	assert.IsTrue(t, twoBitFilter(17 /*10001*/), "should count bits")
 }
+
+func TestHexByteToBits(t *testing.T) {
+	cases := []struct {
+		input  rune
+		output string
+	}{
+		{'0', "0000"},
+		{'1', "0001"},
+		{'2', "0010"},
+		{'3', "0011"},
+		{'4', "0100"},
+		{'5', "0101"},
+		{'6', "0110"},
+		{'7', "0111"},
+		{'8', "1000"},
+		{'9', "1001"},
+		{'A', "1010"},
+		{'B', "1011"},
+		{'C', "1100"},
+		{'D', "1101"},
+		{'E', "1110"},
+		{'F', "1111"},
+	}
+
+	for _, c := range cases {
+		bits, err := HexByteToBits(byte(c.input))
+		if err != nil {
+			t.Logf("Got error from HexByteToBits: %s", err.Error())
+			t.Fail()
+		}
+		bitStr := ToStr(bits)
+		assert.EqualsStr(t, bitStr, c.output, "incorrect value")
+	}
+}