31.24 Base 64 Encoding

Base 64 code is used in email to encode a sequence of 8-bit bytes as a longer sequence of ASCII graphic characters. It is defined in Internet RFC¹⁴2045. This section describes the functions for converting to and from this code.

Command: base64-encode-region beg end &optional no-line-break

This function converts the region from beg to end into base 64 code. It returns the length of the encoded text. An error is signaled if a character in the region is multibyte, i.e., in a multibyte buffer the region must contain only characters from the charsets ascii, eight-bit-control and eight-bit-graphic.

Normally, this function inserts newline characters into the encoded text, to avoid overlong lines. However, if the optional argument no-line-break is non-nil, these newlines are not added, so the output is just one long line.

Function: base64-encode-string string &optional no-line-break

This function converts the string string into base 64 code. It returns a string containing the encoded text. As for base64-encode-region, an error is signaled if a character in the string is multibyte.

Normally, this function inserts newline characters into the encoded text, to avoid overlong lines. However, if the optional argument no-line-break is non-nil, these newlines are not added, so the result string is just one long line.

Command: base64-decode-region beg end

This function converts the region from beg to end from base 64 code into the corresponding decoded text. It returns the length of the decoded text.

The decoding functions ignore newline characters in the encoded text.

Function: base64-decode-string string

This function converts the string string from base 64 code into the corresponding decoded text. It returns a unibyte string containing the decoded text.

The decoding functions ignore newline characters in the encoded text.