Language: JavaScript
Label: safe
CWE: CWE-331 \u2014 Insufficient Entropy
The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others.

Code:
function encode(input) {
    var base64 = '';
    var encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    var bytes = new Uint8Array(input);
    var byteLength = bytes.byteLength;
    var byteRemainder = byteLength % 3;
    var mainLength = byteLength - byteRemainder;
    var a, b, c, d;
    var chunk;
    // Main loop deals with bytes in chunks of 3
    for (var i = 0; i < mainLength; i = i + 3) {
        // Combine the three bytes into a single integer
        chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
        // Use bitmasks to extract 6-bit segments from the triplet
        a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
        b = (chunk & 258048) >> 12; // 258048   = (2^6 - 1) << 12
        c = (chunk & 4032) >> 6; // 4032     = (2^6 - 1) << 6
        d = chunk & 63; // 63       = 2^6 - 1
        // Convert the raw binary segments to the appropriate ASCII encoding
        base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
    }
    // Deal with the remaining bytes and padding
    if (byteRemainder == 1) {
        chunk = bytes[mainLength];
        a = (chunk & 252) >> 2; // 252 = (2^6 - 1) << 2
        // Set the 4 least significant bits to zero
        b = (chunk & 3) << 4; // 3   = 2^2 - 1
        base64 += encodings[a] + encodings[b] + '==';
    }
    else if (byteRemainder == 2) {
        chunk = (bytes[mainLength] << 8) | bytes[mainLength + 1];
        a = (chunk & 64512) >> 10; // 64512 = (2^6 - 1) << 10
        b = (chunk & 1008) >> 4; // 1008  = (2^6 - 1) << 4
        // Set the 2 least significant bits to zero
        c = (chunk & 15) << 2; // 15    = 2^4 - 1
        base64 += encodings[a] + encodings[b] + encodings[c] + '=';
    }
    return base64;
}