base64coder.java

JAVA解析MSNP15协议

package jm.framework.msn.util;
/**
 * Base64编码
 * 梦界家园MSNP15
 * @author ISHome
 * @since 0.5.0.1
 * @version 0.1
 */
public class Base64Coder {
    // Mapping table from 6-bit nibbles to Base64 characters.
    private static char[] map1 = new char[64];
    static {
	int i = 0;
	for (char c = 'A'; c <= 'Z'; c++)
	    map1[i++] = c;
	for (char c = 'a'; c <= 'z'; c++)
	    map1[i++] = c;
	for (char c = '0'; c <= '9'; c++)
	    map1[i++] = c;
	map1[i++] = '+';
	map1[i++] = '/';
    }

    // Mapping table from Base64 characters to 6-bit nibbles.
    private static byte[] map2 = new byte[128];
    static {
	for (int i = 0; i < map2.length; i++)
	    map2[i] = -1;
	for (int i = 0; i < 64; i++)
	    map2[map1[i]] = (byte) i;
    }

    /**
     * Encodes a string into Base64 format.
     * No blanks or line breaks are inserted.
     * @param s  a String to be encoded.
     * @return   A String with the Base64 encoded data.
     */
    public static String encodeString(String s) {
	return new String(encode(s.getBytes()));
    }

    /**
     * Encodes a byte array into Base64 format.
     * No blanks or line breaks are inserted.
     * @param in  an array containing the data bytes to be encoded.
     * @return    A character array with the Base64 encoded data.
     */
    public static char[] encode(byte[] in) {
	return encode(in, in.length);
    }

    /**
     * Encodes a byte array into Base64 format.
     * No blanks or line breaks are inserted.
     * @param in   an array containing the data bytes to be encoded.
     * @param iLen number of bytes to process in <code>in</code>.
     * @return     A character array with the Base64 encoded data.
     */
    public static char[] encode(byte[] in, int iLen) {
	int oDataLen = (iLen * 4 + 2) / 3; // output length without padding
	int oLen = ((iLen + 2) / 3) * 4; // output length including padding
	char[] out = new char[oLen];
	int ip = 0;
	int op = 0;
	while (ip < iLen) {
	    int i0 = in[ip++] & 0xff;
	    int i1 = ip < iLen ? in[ip++] & 0xff : 0;
	    int i2 = ip < iLen ? in[ip++] & 0xff : 0;
	    int o0 = i0 >>> 2;
	    int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
	    int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
	    int o3 = i2 & 0x3F;
	    out[op++] = map1[o0];
	    out[op++] = map1[o1];
	    out[op] = op < oDataLen ? map1[o2] : '=';
	    op++;
	    out[op] = op < oDataLen ? map1[o3] : '=';
	    op++;
	}
	return out;
    }

    /**
     * Decodes a string from Base64 format.
     * @param s  a Base64 String to be decoded.
     * @return   A String containing the decoded data.
     * @throws   IllegalArgumentException if the input is not valid Base64 encoded data.
     */
    public static String decodeString(String s) {
	return new String(decode(s));
    }

    /**
     * Decodes a byte array from Base64 format.
     * @param s  a Base64 String to be decoded.
     * @return   An array containing the decoded data bytes.
     * @throws   IllegalArgumentException if the input is not valid Base64 encoded data.
     */
    public static byte[] decode(String s) {
	return decode(s.toCharArray());
    }

    /**
     * Decodes a byte array from Base64 format.
     * No blanks or line breaks are allowed within the Base64 encoded data.
     * @param in  a character array containing the Base64 encoded data.
     * @return    An array containing the decoded data bytes.
     * @throws    IllegalArgumentException if the input is not valid Base64 encoded data.
     */
    public static byte[] decode(char[] in) {
	int iLen = in.length;
	if (iLen % 4 != 0)
	    throw new IllegalArgumentException("Length of Base64 encoded input string is not a multiple of 4.");
	while (iLen > 0 && in[iLen - 1] == '=')
	    iLen--;
	int oLen = (iLen * 3) / 4;
	byte[] out = new byte[oLen];
	int ip = 0;
	int op = 0;
	while (ip < iLen) {
	    int i0 = in[ip++];
	    int i1 = in[ip++];
	    int i2 = ip < iLen ? in[ip++] : 'A';
	    int i3 = ip < iLen ? in[ip++] : 'A';
	    if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
		throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
	    int b0 = map2[i0];
	    int b1 = map2[i1];
	    int b2 = map2[i2];
	    int b3 = map2[i3];
	    if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
		throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
	    int o0 = (b0 << 2) | (b1 >>> 4);
	    int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2);
	    int o2 = ((b2 & 3) << 6) | b3;
	    out[op++] = (byte) o0;
	    if (op < oLen)
		out[op++] = (byte) o1;
	    if (op < oLen)
		out[op++] = (byte) o2;
	}
	return out;
    }
}