Function Base64Decode

conversion/base64.go:59–83

Base64Decode decodes the received input base64 string into a byte slice. The implementation follows the RFC4648 standard, which is documented at https://datatracker.ietf.org/doc/html/rfc4648#section-4

(input string)

// The implementation follows the RFC4648 standard, which is documented
// at https://datatracker.ietf.org/doc/html/rfc4648#section-4
func Base64Decode(input string) []byte {
	padding := strings.Count(input, "=") // Number of bytes which will be ignored
	var decoded []byte

	// select 4 6-bit input groups, and re-arrange them into 3 8-bit groups
	for i := 0; i < len(input); i += 4 {
		// translate each group into a byte using the static map
		byteInput := [4]byte{
			byte(strings.IndexByte(Alphabet, input[i])),
			byte(strings.IndexByte(Alphabet, input[i+1])),
			byte(strings.IndexByte(Alphabet, input[i+2])),
			byte(strings.IndexByte(Alphabet, input[i+3])),
		}

		group := [3]byte{
			byteInput[0]<<2 + byteInput[1]>>4,
			byteInput[1]<<4 + byteInput[2]>>2,
			byteInput[2]<<6 + byteInput[3],
		}

		decoded = append(decoded, group[:]...)
	}

	return decoded[:len(decoded)-padding]
}