base64DecodeMap kotlin IntArray io encoding ExperimentalEncodingApi native concurrent SharedImmutable base64EncodeMap ByteArray base64UrlDecodeMap base64UrlEncodeMap isInMimeAlphabet Boolean symbol Int SinceKotlin version 1.8 platformCharsToBytes Base64 source CharSequence startIndex endIndex platformEncodeIntoByteArray destination destinationOffset platformEncodeToByteArray platformEncodeToString Stringl                  2(8H  ( 02(2(2(8@H  ( <2(2(2(2(2(8@H  ( 02(2(2(8@H  ( 02(2(2(8@H  ( "8HX  " 8HX " 8HX  " 8HX  0 0 0 0 0 0 0