exchange-api/cdut-exchange/src/main/java/com/qmth/cdut/supwisdom/utils/Base64Utils.java

package com.qmth.cdut.supwisdom.utils;

public abstract class Base64Utils {

    private static final byte[] ENC_TAB_BYTES = new byte[64];

    static {
        int j = 0;
        for (byte i = 'A'; i <= 'Z'; i++) {
            ENC_TAB_BYTES[j] = i;
            j++;
        }
        for (byte i = 'a'; i <= 'z'; i++) {
            ENC_TAB_BYTES[j] = i;
            j++;
        }
        for (byte i = '0'; i <= '9'; i++) {
            ENC_TAB_BYTES[j] = i;
            j++;
        }
        ENC_TAB_BYTES[j++] = '+';
        ENC_TAB_BYTES[j] = '/';
    }

    public static String encodeBase64Str(String str) {
        byte[] bytes = StringUtils.getBytes(str);
        return encodeBase64Str(bytes);
    }

    public static String encodeBase64Str(byte[] bytes) {
        byte[] base64Bytes = encodeBase64(bytes);
        return StringUtils.newString(base64Bytes);
    }

    public static byte[] encodeBase64(byte[] bytes) {
        byte[] base64Bytes;
        int modulus = bytes.length % 3;
        if (modulus == 0) {
            base64Bytes = new byte[(4 * bytes.length) / 3];
        } else {
            base64Bytes = new byte[4 * ((bytes.length / 3) + 1)];
        }
        int dataLength = (bytes.length - modulus);
        int a1;
        int a2;
        int a3;
        for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
            a1 = bytes[i] & 0xff;
            a2 = bytes[i + 1] & 0xff;
            a3 = bytes[i + 2] & 0xff;
            base64Bytes[j] = ENC_TAB_BYTES[(a1 >>> 2) & 0x3f];
            base64Bytes[j + 1] = ENC_TAB_BYTES[((a1 << 4) | (a2 >>> 4)) & 0x3f];
            base64Bytes[j + 2] = ENC_TAB_BYTES[((a2 << 2) | (a3 >>> 6)) & 0x3f];
            base64Bytes[j + 3] = ENC_TAB_BYTES[a3 & 0x3f];
        }
        int b1;
        int b2;
        int b3;
        int d1;
        int d2;
        switch (modulus) {
            case 0:
                break;
            case 1:
                d1 = bytes[bytes.length - 1] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = (d1 << 4) & 0x3f;
                base64Bytes[base64Bytes.length - 4] = ENC_TAB_BYTES[b1];
                base64Bytes[base64Bytes.length - 3] = ENC_TAB_BYTES[b2];
                base64Bytes[base64Bytes.length - 2] = '=';
                base64Bytes[base64Bytes.length - 1] = '=';
                break;
            case 2:
                d1 = bytes[bytes.length - 2] & 0xff;
                d2 = bytes[bytes.length - 1] & 0xff;
                b1 = (d1 >>> 2) & 0x3f;
                b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
                b3 = (d2 << 2) & 0x3f;
                base64Bytes[base64Bytes.length - 4] = ENC_TAB_BYTES[b1];
                base64Bytes[base64Bytes.length - 3] = ENC_TAB_BYTES[b2];
                base64Bytes[base64Bytes.length - 2] = ENC_TAB_BYTES[b3];
                base64Bytes[base64Bytes.length - 1] = '=';
                break;
        }
        return base64Bytes;
    }

    private static final byte[] DEC_TAB_BYTES = new byte[128];

    static {
        for (int i = 0; i < 128; i++) {
            DEC_TAB_BYTES[i] = (byte) -1;
        }
        for (int i = 'A'; i <= 'Z'; i++) {
            DEC_TAB_BYTES[i] = (byte) (i - 'A');
        }
        for (int i = 'a'; i <= 'z'; i++) {
            DEC_TAB_BYTES[i] = (byte) (i - 'a' + 26);
        }
        for (int i = '0'; i <= '9'; i++) {
            DEC_TAB_BYTES[i] = (byte) (i - '0' + 52);
        }
        DEC_TAB_BYTES['+'] = 62;
        DEC_TAB_BYTES['/'] = 63;
    }

    public static String decodeBase64Str(String data) {
        byte[] base64Bytes = StringUtils.getBytes(data);
        return decodeBase64Str(base64Bytes);
    }

    public static String decodeBase64Str(byte[] base64Bytes) {
        byte[] bytes = decodeBase64(base64Bytes);
        return StringUtils.newString(bytes);
    }

    public static byte[] decodeBase64(byte[] base64Bytes) {
        byte[] bytes;
        byte b1;
        byte b2;
        byte b3;
        byte b4;
        base64Bytes = discardNonBase64Bytes(base64Bytes);
        if (base64Bytes[base64Bytes.length - 2] == '=') {
            bytes = new byte[(((base64Bytes.length / 4) - 1) * 3) + 1];
        } else if (base64Bytes[base64Bytes.length - 1] == '=') {
            bytes = new byte[(((base64Bytes.length / 4) - 1) * 3) + 2];
        } else {
            bytes = new byte[((base64Bytes.length / 4) * 3)];
        }
        for (int i = 0, j = 0; i < (base64Bytes.length - 4); i += 4, j += 3) {
            b1 = DEC_TAB_BYTES[base64Bytes[i]];
            b2 = DEC_TAB_BYTES[base64Bytes[i + 1]];
            b3 = DEC_TAB_BYTES[base64Bytes[i + 2]];
            b4 = DEC_TAB_BYTES[base64Bytes[i + 3]];
            bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[j + 2] = (byte) ((b3 << 6) | b4);
        }
        if (base64Bytes[base64Bytes.length - 2] == '=') {
            b1 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 4]];
            b2 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 3]];
            bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
        } else if (base64Bytes[base64Bytes.length - 1] == '=') {
            b1 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 4]];
            b2 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 3]];
            b3 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 2]];
            bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
        } else {
            b1 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 4]];
            b2 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 3]];
            b3 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 2]];
            b4 = DEC_TAB_BYTES[base64Bytes[base64Bytes.length - 1]];
            bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
            bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
            bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
        }
        return bytes;
    }

    private static byte[] discardNonBase64Bytes(byte[] datas) {
        byte[] temp = new byte[datas.length];
        int bytesCopied = 0;
        for (byte data : datas) {
            if (isValidBase64Byte(data)) {
                temp[bytesCopied++] = data;
            }
        }
        byte[] newData = new byte[bytesCopied];
        System.arraycopy(temp, 0, newData, 0, bytesCopied);
        return newData;
    }

    private static boolean isValidBase64Byte(byte b) {
        if (b == '=') {
            return true;
        } else if ((b < 0) || (b >= 128)) {
            return false;
        } else if (DEC_TAB_BYTES[b] == -1) {
            return false;
        }
        return true;
    }
}