Dev:EnhancedBase64

There was the necessity to have a base64 encoding of binary objects in many places in YaCy, but a modified version of the standard RFC 1521 Base64 encoding and decoding has been used.

YaCy uses an 'enhanced base 64 encoding' which is based on RFC 1521 Base64 with two exceptions:

• the characters '+' and '/' are replaced by '-' and '_' ('+' by '-' and '/' by '_')
• the trailing fill-up character '=' is omitted

There is a good reason in YaCy to change the RFC 1521 standard:

• the base64 encoding result is used as part of file names, and the characters '+' and '/' are not accepted as file names in all file systems
• the '=' trailing is superfluous and wastes space.

If you want to use the YaCy EnhancedBase64 in other applications or programming languages then you can convert from EnhancedBase64 to RFC 1521 Base64 with the following steps (enhance this!):

String rfc1521 = new String(eb64);
while (rfc1521.length() % 4 != 0) rfc1521 += "=";
rfc1521 = rfc1521.replace('-', '+').replace('_', '/');

If you want to convert from RFC 1521 Base64 to EnhancedBase64, do the following:

String eb64 = new String(rfc1521);
while (eb64.endsWith("=")) eb64 = eb64.substring(0, eb64.length() - 1);
eb64 = eb64.replace('+', '-').replace('/', '_');