package enc const b64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" func HexToBase64(hex string) string { hb := []byte(hex) b64 := "" for i := 0; i <= len(hb)-3; i = i + 3 { a := fromHexChar(hb[i])<<8 | fromHexChar(hb[i+1])<<4 | fromHexChar(hb[i+2]) b64 += encode(a >> 6) b64 += encode(a & 0b111111) } return b64 } func encode(b uint16) string { return string(b64_table[b]) } // adapted from // https://go.googlesource.com/go/+/refs/tags/go1.15/src/encoding/hex/hex.go#83 func fromHexChar(c byte) uint16 { switch { case '0' <= c && c <= '9': return uint16(c - '0') case 'a' <= c && c <= 'f': return uint16(c - 'a' + 10) } return 0 }