transcoderutils.java

memcached JAVA客户端API,应用广泛,运行比较稳定。

// Copyright (c) 2006  Dustin Sallings <[e-mail]>

package net.spy.memcached.transcoders;

/**
 * Utility class for transcoding Java types.
 */
public final class TranscoderUtils {

	private final boolean packZeros;

	/**
	 * Get an instance of TranscoderUtils.
	 *
	 * @param pack if true, remove all zero bytes from the MSB of the packed num
	 */
	public TranscoderUtils(boolean pack) {
		super();
		packZeros=pack;
	}

	public byte[] encodeNum(long l, int maxBytes) {
		byte[] rv=new byte[maxBytes];
		for(int i=0; i<rv.length; i++) {
			int pos=rv.length-i-1;
			rv[pos]=(byte) ((l >> (8 * i)) & 0xff);
		}
		if(packZeros) {
			int firstNon0=0;
			for(;firstNon0<rv.length && rv[firstNon0]==0; firstNon0++) {
				// Just looking for what we can reduce
			}
			if(firstNon0 > 0) {
				byte[] tmp=new byte[rv.length - firstNon0];
				System.arraycopy(rv, firstNon0, tmp, 0, rv.length-firstNon0);
				rv=tmp;
			}
		}
		return rv;
	}

	public byte[] encodeLong(long l) {
		return encodeNum(l, 8);
	}

	public long decodeLong(byte[] b) {
		long rv=0;
		for(byte i : b) {
			rv = (rv << 8) | (i<0?256+i:i);
		}
		return rv;
	}

	public byte[] encodeInt(int in) {
		return encodeNum(in, 4);
	}

	public int decodeInt(byte[] in) {
		assert in.length <= 4
			: "Too long to be an int (" + in.length + ") bytes";
		return (int)decodeLong(in);
	}

	public byte[] encodeByte(byte in) {
		return new byte[]{in};
	}

	public byte decodeByte(byte[] in) {
		assert in.length <= 1 : "Too long for a byte";
		byte rv=0;
		if(in.length == 1) {
			rv=in[0];
		}
		return rv;
	}

	public byte[] encodeBoolean(boolean b) {
		byte[] rv=new byte[1];
		rv[0]=(byte)(b?'1':'0');
		return rv;
	}

	public boolean decodeBoolean(byte[] in) {
		assert in.length == 1 : "Wrong length for a boolean";
		return in[0] == '1';
	}

}