private static char[] encodeToChar(byte[] sArr, boolean lineSep) {
        char[] CA = IOUtils.CA;

        // Check special case
        int sLen = sArr != null ? sArr.length : 0;
        if (sLen == 0) {
            return new char[0];
        }

        int eLen = (sLen / 3) * 3; // Length of even 24-bits.
        int cCnt = ((sLen - 1) / 3 + 1) << 2; // Returned character count
        int dLen = cCnt + (lineSep ? (cCnt - 1) / 76 << 1 : 0); // Length of returned array
        char[] dArr = new char[dLen];

        // Encode even 24-bits
        for (int s = 0, d = 0, cc = 0; s < eLen; ) {
            // Copy next three bytes into lower 24 bits of int, paying attension to sign.
            int i = (sArr[s++] & 0xff) << 16 | (sArr[s++] & 0xff) << 8 | (sArr[s++] & 0xff);

            // Encode the int into four chars
            dArr[d++] = CA[(i >>> 18) & 0x3f];
            dArr[d++] = CA[(i >>> 12) & 0x3f];
            dArr[d++] = CA[(i >>> 6) & 0x3f];
            dArr[d++] = CA[i & 0x3f];

            // Add optional line separator
            if (lineSep && ++cc == 19 && d < dLen - 2) {
                dArr[d++] = '\r';
                dArr[d++] = '\n';
                cc = 0;
            }
        }

        // Pad and encode last bits if source isn't even 24 bits.
        int left = sLen - eLen; // 0 - 2.
        if (left > 0) {
            // Prepare the int
            int i = ((sArr[eLen] & 0xff) << 10) | (left == 2 ? ((sArr[sLen - 1] & 0xff) << 2) : 0);

            // Set last four chars
            dArr[dLen - 4] = CA[i >> 12];
            dArr[dLen - 3] = CA[(i >>> 6) & 0x3f];
            dArr[dLen - 2] = left == 2 ? CA[i & 0x3f] : '=';
            dArr[dLen - 1] = '=';
        }
        return dArr;
    }
Encodes a raw byte array into a BASE64 <code>char[]</code> representation i accordance with RFC 2045.

@param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.
@param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>
No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a little faster.
@return A BASE64 encoded array. Never <code>null</code>.
fastjson1-compatible/src/test/java/com/alibaba/fastjson/TestUtils.java