mec/mec-util/src/main/java/com/yqh/p2p/utils/codec/NumEncodeUtil.java

package com.yqh.p2p.utils.codec;

/**
 * 62进制数字
 */
public class NumEncodeUtil {
	/**
	 * 62个字母和数字，含大小写
	 */
	public static final char[] N62_CHARS = { '0', '1', '2', '3', '4', '5', '6',
			'7', '8', '9', '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' };
	/**
	 * 36个小写字母和数字
	 */
	public static final char[] N36_CHARS = { '0', '1', '2', '3', '4', '5', '6',
			'7', '8', '9', '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' };
	/**
	 * 长整型用N36表示的最大长度
	 */
	public static final int LONG_N36_LEN = 13;
	/**
	 * 长整型用N62表示的最大长度
	 */
	public static final int LONG_N62_LEN = 11;

	/**
	 * 长整型转换成字符串
	 * 
	 * @param l
	 * @param chars
	 * @return
	 */
	private static StringBuilder longToNBuf(long l, char[] chars) {
		int upgrade = chars.length;
		StringBuilder result = new StringBuilder();
		int last;
		while (l > 0) {
			last = (int) (l % upgrade);
			result.append(chars[last]);
			l /= upgrade;
		}
		return result;
	}

	/**
	 * 长整数转换成N62
	 * 
	 * @param l
	 * @return
	 */
	public static String longToN62(long l) {
		return longToNBuf(l, N62_CHARS).reverse().toString();
	}

	/**
	 * 长整型转换成N36
	 * 
	 * @param l
	 * @return
	 */
	public static String longToN36(long l) {
		return longToNBuf(l, N36_CHARS).reverse().toString();
	}

	/**
	 * 长整数转换成N62
	 * 
	 * @param l
	 * @param length
	 *            如不足length长度，则补足0。
	 * @return
	 */
	public static String longToN62(long l, int length) {
		StringBuilder sb = longToNBuf(l, N62_CHARS);
		for (int i = sb.length(); i < length; i++) {
			sb.append('0');
		}
		return sb.reverse().toString();
	}

	/**
	 * 长整型转换成N36
	 * 
	 * @param l
	 * @param length
	 *            如不足length长度，则补足0。
	 * @return
	 */
	public static String longToN36(long l, int length) {
		StringBuilder sb = longToNBuf(l, N36_CHARS);
		for (int i = sb.length(); i < length; i++) {
			sb.append('0');
		}
		return sb.reverse().toString();
	}

	/**
	 * N62转换成整数
	 * 
	 * @param n62
	 * @return
	 */
	public static long n62ToLong(String n62) {
		return nToLong(n62, N62_CHARS);
	}

	/**
	 * N36转换成整数
	 * 
	 * @param n36
	 * @return
	 */
	public static long n36ToLong(String n36) {
		return nToLong(n36, N36_CHARS);
	}

	private static long nToLong(String s, char[] chars) {
		char[] nc = s.toCharArray();
		long result = 0;
		long pow = 1;
		for (int i = nc.length - 1; i >= 0; i--, pow *= chars.length) {
			int n = findNIndex(nc[i], chars);
			result += n * pow;
		}
		return result;
	}

	private static int findNIndex(char c, char[] chars) {
		for (int i = 0; i < chars.length; i++) {
			if (c == chars[i]) {
				return i;
			}
		}
		throw new RuntimeException("N62(N36)非法字符：" + c);
	}

	public static void main(String[] args) {
		String str = longToN62(13720176797l);
		System.out.println(str);
		System.out.println(n62ToLong(str));
	}
}