Android 自用Base64编码类

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/**
 * Created by tab on 2017/10/10
 */
public class Base64Encoder extends FilterOutputStream {

    private static final char[] chars = {'A', 'B', 'C', 'D', 'E', 'F', 'G',
            'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
            'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
            'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
            'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', '+', '/'};

    private int charCount;
    private int carryOver;

    /***
     * Constructs a new Base64 encoder that writes output to the given
     * OutputStream.
     *
     * @param out the output stream
     */
    public Base64Encoder(OutputStream out) {
        super(out);
    }

    /***
     * Writes the given byte to the output stream in an encoded form.
     *
     * @throws IOException if an I/O error occurs
     */
    public void write(int b) throws IOException {
        // Take 24-bits from three octets, translate into four encoded chars
        // Break lines at 76 chars
        // If necessary, pad with 0 bits on the right at the end
        // Use = signs as padding at the end to ensure encodedLength % 4 == 0

        // Remove the sign bit,
        // thanks to Christian Schweingruber <chrigu@lorraine.ch>
        if (b < 0) {
            b += 256;
        }

        // First byte use first six bits, save last two bits
        if (charCount % 3 == 0) {
            int lookup = b >> 2;
            carryOver = b & 3; // last two bits
            out.write(chars[lookup]);
        }
        // Second byte use previous two bits and first four new bits,
        // save last four bits
        else if (charCount % 3 == 1) {
            int lookup = ((carryOver << 4) + (b >> 4)) & 63;
            carryOver = b & 15; // last four bits
            out.write(chars[lookup]);
        }
        // Third byte use previous four bits and first two new bits,
        // then use last six new bits
        else if (charCount % 3 == 2) {
            int lookup = ((carryOver << 2) + (b >> 6)) & 63;
            out.write(chars[lookup]);
            lookup = b & 63; // last six bits
            out.write(chars[lookup]);
            carryOver = 0;
        }
        charCount++;

        // Add newline every 76 output chars (that's 57 input chars)
        if (charCount % 57 == 0) {
            out.write('\n');
        }
    }

    /***
     * Writes the given byte array to the output stream in an encoded form.
     *
     * @param buf the data to be written
     * @param off the start offset of the data
     * @param len the length of the data
     * @throws IOException if an I/O error occurs
     */
    public void write(byte[] buf, int off, int len) throws IOException {
        // This could of course be optimized
        for (int i = 0; i < len; i++) {
            write(buf[off + i]);
        }
    }

    /***
     * Closes the stream, this MUST be called to ensure proper padding is
     * written to the end of the output stream.
     *
     * @throws IOException if an I/O error occurs
     */
    public void close() throws IOException {
        // Handle leftover bytes
        if (charCount % 3 == 1) { // one leftover
            int lookup = (carryOver << 4) & 63;
            out.write(chars[lookup]);
            out.write('=');
            out.write('=');
        } else if (charCount % 3 == 2) { // two leftovers
            int lookup = (carryOver << 2) & 63;
            out.write(chars[lookup]);
            out.write('=');
        }
        super.close();
    }

    /***
     * Returns the encoded form of the given unencoded string. The encoder uses
     * the ISO-8859-1 (Latin-1) encoding to convert the string to bytes. For
     * greater control over the encoding, encode the string to bytes yourself
     * and use encode(byte[]).
     *
     * @param unencoded the string to encode
     * @return the encoded form of the unencoded string
     */
    public static String encode(String unencoded) {
        byte[] bytes = null;
        try {
            bytes = unencoded.getBytes("UTF-8");
        } catch (UnsupportedEncodingException ignored) {
        }
        return encode(bytes);
    }

    /***
     * Returns the encoded form of the given unencoded string.
     *
     * @param bytes the bytes to encode
     * @return the encoded form of the unencoded string
     */
    public static String encode(byte[] bytes) {
        ByteArrayOutputStream out = new ByteArrayOutputStream(
                (int) (bytes.length * 1.37));
        Base64Encoder encodedOut = new Base64Encoder(out);

        try {
            encodedOut.write(bytes);
            encodedOut.close();

            return out.toString("UTF-8");
        } catch (IOException ignored) {
            return null;
        }
    }

    /**
     * file 2 base64
     *
     * @param filename filename
     * @return base64 string
     */
    public static String file2Base64(String filename) {
        File file = new File(filename);
        ULogger.d("filename=" + file.getAbsolutePath());
        FileInputStream fileInputStream = null;
        if (file.exists()) {
            try {
                fileInputStream = new FileInputStream(file);
                int len = (int) file.length();
                byte bytes[] = new byte[len];
                int count, total = 0;
                while ((count = fileInputStream.read(bytes, total, len - total)) > 0) {
                    total += count;
                }
                return Base64.encodeToString(bytes, Base64.DEFAULT);
            } catch (Exception ex) {
                ex.printStackTrace();
            } finally {
                if (fileInputStream != null) {
                    try {
                        fileInputStream.close();
                    } catch (IOException ex) {
                        ex.printStackTrace();
                    }
                }
            }
        }

        return null;
    }


    public static void main(String[] args) throws Exception {
        if (args.length != 1) {
            System.err
                    .println("Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
            return;
        }
        Base64Encoder encoder = null;
        BufferedInputStream in = null;
        try {
            encoder = new Base64Encoder(System.out);
            in = new BufferedInputStream(new FileInputStream(args[0]));

            byte[] buf = new byte[4 * 1024]; // 4K buffer
            int bytesRead;
            while ((bytesRead = in.read(buf)) != -1) {
                encoder.write(buf, 0, bytesRead);
            }
        } finally {
            if (in != null)
                in.close();
            if (encoder != null)
                encoder.close();
        }
    }


}

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