base64.java

JSP实现的在线网络购物系统JAVA程序源码,

package com.comm.util;

import java.io.*;

public class Base64 {
    public Base64() {
    }

    /**
     * returns an array of base64-encoded characters to represent the
     * passed data array.
     *
     * @param data the array of bytes to encode
     * @return base64-coded character array.
     */
    public static char[] encode(byte[] data) {
        char[] out = new char[((data.length + 2) / 3) * 4];
//        LoggerUtil.debug(data.length + " " + out.length + " " +
//            ( (data.length + 2) / 3) * 4);

        //
        // 3 bytes encode to 4 chars.  Output is always an even
        // multiple of 4 characters.
        //
        for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
            boolean quad = false;
            boolean trip = false;

            int val = (0xFF & (int) data[i]);
            val <<= 8;
            if ((i + 1) < data.length) {
                val |= (0xFF & (int) data[i + 1]);
                trip = true;
            }
            val <<= 8;
            if ((i + 2) < data.length) {
                val |= (0xFF & (int) data[i + 2]);
                quad = true;
            }
            out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
            val >>= 6;
            out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
            val >>= 6;
            out[index + 1] = alphabet[val & 0x3F];
            val >>= 6;
            out[index + 0] = alphabet[val & 0x3F];
        }
        return out;
    }

    /**
     * Decodes a BASE-64 encoded stream to recover the original
     * data. White space before and after will be trimmed away,
     * but no other manipulation of the input will be performed.
     *
     * As of version 1.2 this method will properly handle input
     * containing junk characters (newlines and the like) rather
     * than throwing an error. It does this by pre-parsing the
     * input and generating from that a count of VALID input
     * characters.
     **/
    public static byte[] decode(char[] data) {
        // as our input could contain non-BASE64 data (newlines,
        // whitespace of any sort, whatever) we must first adjust
        // our count of USABLE data so that...
        // (a) we don't misallocate the output array, and
        // (b) think that we miscalculated our data length
        //     just because of extraneous throw-away junk

        int tempLen = data.length;
        for (int ix = 0; ix < data.length; ix++) {
            if ((data[ix] > 255) || codes[data[ix]] < 0) {
                --tempLen; // ignore non-valid chars and padding
            }
        }
// calculate required length:
// -- 3 bytes for every 4 valid base64 chars
// -- plus 2 bytes if there are 3 extra base64 chars,
// or plus 1 byte if there are 2 extra.

        int len = (tempLen / 4) * 3;
        if ((tempLen % 4) == 3) {
            len += 2;
        }
        if ((tempLen % 4) == 2) {
            len += 1;

        }
        byte[] out = new byte[len];

        int shift = 0; // # of excess bits stored in accum
        int accum = 0; // excess bits
        int index = 0;

// we now go through the entire array (NOT using the 'tempLen' value)
        for (int ix = 0; ix < data.length; ix++) {
            int value = (data[ix] > 255) ? -1 : codes[data[ix]];

            if (value >= 0) { // skip over non-code
                accum <<= 6; // bits shift up by 6 each time thru
                shift += 6; // loop, with new bits being put in
                accum |= value; // at the bottom.
                if (shift >= 8) { // whenever there are 8 or more shifted in,
                    shift -= 8; // write them out (from the top, leaving any
                    out[index++] = // excess at the bottom for next iteration.
                            (byte) ((accum >> shift) & 0xff);
                }
            }
            // we will also have skipped processing a padding null byte ('=') here;
            // these are used ONLY for padding to an even length and do not legally
            // occur as encoded data. for this reason we can ignore the fact that
            // no index++ operation occurs in that special case: the out[] array is
            // initialized to all-zero bytes to start with and that works to our
            // advantage in this combination.
        }

        // if there is STILL something wrong we just have to throw up now!
        if (index != out.length) {
            throw new Error("Miscalculated data length (wrote " + index +
                            " instead of " + out.length + ")");
        }

        return out;
    }

//
// code characters for values 0..63
//
    private static char[] alphabet =
            "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
            .toCharArray();

//
// lookup table for converting base64 characters to value in range 0..63
//
    private static byte[] codes = new byte[256];
    static {
        for (int i = 0; i < 256; i++) {
            codes[i] = -1;
//            LoggerUtil.debug(i + "&" + codes[i] + " ");
        }
        for (int i = 'A'; i <= 'Z'; i++) {
            codes[i] = (byte) (i - 'A');
//            LoggerUtil.debug(i + "&" + codes[i] + " ");
        }

        for (int i = 'a'; i <= 'z'; i++) {
            codes[i] = (byte) (26 + i - 'a');
//            LoggerUtil.debug(i + "&" + codes[i] + " ");
        }
        for (int i = '0'; i <= '9'; i++) {
            codes[i] = (byte) (52 + i - '0');
//            LoggerUtil.debug(i + "&" + codes[i] + " ");
        }
        codes['+'] = 62;
        codes['/'] = 63;
    }

///////////////////////////////////////////////////
// remainder (main method and helper functions) is
// for testing purposes only, feel free to clip it.
///////////////////////////////////////////////////

    public static void doEncode(String filename) {

        File file = new File(filename);
        if (!file.exists()) {
            System.exit(0);
        }

        else {
            byte[] decoded = readBytes(file);
            char[] encoded = encode(decoded);
            writeChars(file, encoded);
        }
    }

    public static void doDecode(String filename) {

        File file = new File(filename);
        if (!file.exists()) {
            System.exit(0);
        } else {
            char[] encoded = readChars(file);
            byte[] decoded = decode(encoded);
            writeBytes(file, decoded);
        }

    }

    private static byte[] readBytes(File file) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] b = null;
        try {
            InputStream fis = new FileInputStream(file);
            InputStream is = new BufferedInputStream(fis);
            int count = 0;
            byte[] buf = new byte[16384];
            while ((count = is.read(buf)) != -1) {
                if (count > 0) {
                    baos.write(buf, 0, count);
                }
            }
            b = baos.toByteArray();
            baos.close();
            is.close();
        } catch (Exception e) {
            LoggerUtil.error(Base64.class, e);
        }

        return b;
    }

    private static char[] readChars(File file) {
        CharArrayWriter caw = new CharArrayWriter();
        try {
            Reader fr = new FileReader(file);
            Reader in = new BufferedReader(fr);
            int count = 0;
            char[] buf = new char[16384];
            while ((count = in.read(buf)) != -1) {
                if (count > 0) {
                    caw.write(buf, 0, count);
                }
            }
            in.close();
        } catch (Exception e) {
            LoggerUtil.error(Base64.class, e);
        }

        return caw.toCharArray();
    }

    private static void writeBytes(File file, byte[] data) {
        try {
            OutputStream fos = new FileOutputStream(file);
            OutputStream os = new BufferedOutputStream(fos);
            os.write(data);
            os.close();
        } catch (Exception e) {
            LoggerUtil.error(Base64.class, e);
        }
    }

    private static void writeChars(File file, char[] data) {
        try {
            Writer fos = new FileWriter(file);
            Writer os = new BufferedWriter(fos);
            os.write(data);
            os.close();
        } catch (Exception e) {
            LoggerUtil.error(Base64.class, e);
        }
    }

///////////////////////////////////////////////////
// end of test code.
///////////////////////////////////////////////////

}