A 6-bit number can represent 64 possible value.Įach possible value corresponds to an ascii character. To encode, it splits up the three bytes into 4 6-bit numbers. The input is a set of bytes: īase64 uses 4 ascii characters to encode 24-bits (3 bytes) of data. To know the length of the original data, we must understand how Base64 works. Putting binary data inside an xml file, for example, could act weird, but a Base64 string acts just like normal text.Ī base64 string looks like this: TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4= The goal is to make it easier to transfer. Return (3 * (characterCount / 4)) - paddingCount īase64 is a way to encode binary data in ascii data. Var paddingCount = base64string.Substring(characterCount - 2, 2) Var characterCount = base64string.Length Here's a function in C#: public int GetOriginalLengthInBytes(string base64string) To get the length of bytes we use the formula: (3 * (LengthInCharacters / 4)) - (numberOfPaddingCharacters) Sometimes, padding is added in the form of one or two '=' characters. A question was posed today: can I get the exact length in bytes of the input data, if I have a Base64 string?īase64 encodes three bytes to four characters.
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