Base64 for MATLAB

base64.m

function b64 = base64( str )
%BASE64 Encode string (array of chars) into Base64
%   Currently seems to fail for any input > 4 characters. :(
    
    %% Settings
    
    % Valid output codes to choose from.
    base64Chars    = char([65:90, 97:122, 48:57, 43, 47]); % +/ per RFC 2045 et al.
    %base64UrlChars = char([65:90, 97:122, 48:57, 45, 95]); % -_ per RFC 4648 §4
    base64PadChar  = '=';
    
    % Process |x| bits (or |x/8| chars) at once.
    readBufferSize = 4*8; % Multiple of 8
    
    %% Code
    
    charCodes = uint8(str);
    charCount = size(charCodes, 2);
    encLength = ceil(4*charCount / 3);
    padLength = mod(3 - mod(charCount, 3), 3) * 2; % 0, 2, or 4 bits
    %b64Length = encLength + padLength/2;
    
    % Buffer size needs to be divisable by 6.
    %bitBuffer = uint8.empty(0, ceil(readBufferSize/6)*6); 
    bitBuffer = zeros(1, ceil(readBufferSize/6)*6, 'uint8'); 
    readCount = uint8(floor(readBufferSize/8));
    
    b64 = [blanks(encLength), repmat(base64PadChar, 1, padLength/2)];
    
    readIndex  = 0;
    writeIndex = 0;
    
    while readIndex < charCount
        
        % Read buffer.
        for i = 1:readCount
            bufferIndex = (i-1)*8 + 1;
            if readIndex+i > charCount
                bitBuffer(bufferIndex:end) = NaN; %0; % :i*8??
                break;
            end
            bitBuffer(bufferIndex:i*8) = bitget(charCodes(readIndex+i), 8:-1:1);
        end
        
        % Process buffer.
        for i = 1:6:size(bitBuffer, 2)
            writeIndex = writeIndex + 1;
            if writeIndex > encLength
                break;
            end
            b64Code = bin2dec(num2str(bitBuffer(i:i+5))) + 1;
            b64(writeIndex) = base64Chars(b64Code);
        end
        
        % Increment read index.
        readIndex = readIndex + readCount;
        
    end
    
end