tlv 格式解析

<pre name="code" class="java">/** * 将字符串转换为TLV对象 *  */public abstract class TlvUtils {/** * 将16进制字符串转换为TLV对象列表 * @param hexString * @return */public static List<Tlv> builderTlvList(String hexString) {List<Tlv> tlvs = new ArrayList<Tlv>();int position = 0;while (position != StringUtils.length(hexString)) {String _hexTag = getTag(hexString, position);position += _hexTag.length();LPositon l_position = getLengthAndPosition(hexString, position);int _vl = l_position.get_vL();position = l_position.get_position();String _value = StringUtils.substring(hexString, position, position + _vl * 2);position = position + _value.length();tlvs.add(new Tlv(_hexTag, _vl, _value));}return tlvs;}/** * 将16进制字符串转换为TLV对象MAP * @param hexString * @return */public static Map<String, Tlv> builderTlvMap(String hexString) {Map<String, Tlv> tlvs = new HashMap<String, Tlv>();int position = 0;while (position != hexString.length()) {String _hexTag = getTag(hexString, position);position += _hexTag.length();LPositon l_position = getLengthAndPosition(hexString, position);int _vl = l_position.get_vL();position = l_position.get_position();String _value = hexString.substring(position, position + _vl * 2);position = position + _value.length();tlvs.put(_hexTag, new Tlv(_hexTag, _vl, _value));}return tlvs;}/** * 返回最后的Value的长度 *  * @param hexString * @param position * @return  */private static LPositon getLengthAndPosition(String hexString, int position) {String firstByteString = hexString.substring(position, position + 2);int i = Integer.parseInt(firstByteString, 16);String hexLength = "";if (((i >>> 7) & 1) == 0) {hexLength = hexString.substring(position, position + 2);position = position + 2;} else {// 当最左侧的bit位为1的时候，取得后7bit的值，int _L_Len = i & 127;position = position + 2;hexLength = hexString.substring(position, position + _L_Len * 2);// position表示第一个字节，后面的表示有多少个字节来表示后面的Value值position = position + _L_Len * 2;}return new LPositon(Integer.parseInt(hexLength, 16), position);}/** * 取得子域Tag标签 *  * @param hexString * @param position * @return */private static String getTag(String hexString, int position) {String firstByte = StringUtils.substring(hexString, position, position + 2);int i = Integer.parseInt(firstByte, 16);if ((i & 0x1f) == 0x1f) {return hexString.substring(position, position + 4);} else {return hexString.substring(position, position + 2);}}}

/** * value的长度 */public class LPositon {private int _vL;private int _position;public LPositon(int _vL, int position) {this._vL = _vL;this._position = position;}public int get_vL() {return _vL;}public void set_vL(int _vL) {this._vL = _vL;}public int get_position() {return _position;}public void set_position(int _position) {this._position = _position;}}

TLV：TLV格式数据是指由Tag，Length，Value组成的数据。具体说明如下：

Type和Length的长度固定，一般那是2、4个字节（这里统一采用4个字节）；

Value的长度有Length指定

编码格式：

1.       将类型type转换为网络字节顺序，指针偏移+4

2.       将长度length转换为网络字节顺序，指针偏移+4

3.       若值value数据类型为int、char、short，则将其转换为网络字节顺序，指针偏移+4；若值为字符串类型，写进后，指针偏移+length

……继续处理后面的tlv；

解码格式：（和编码格式相反）

类型(Type)字段是关于标签和编码格式的信息；

长度 (Length)字段定义数值的长度；

内容(Value)字段表示实际的数值。

public class Tlv {


/** 子域Tag标签 */
private String tag;


/** 子域取值的长度 */
private int length;


/** 子域取值 */
private String value;


public Tlv(String tag, int length, String value) {
this.length = length;
this.tag = tag;
this.value = value;
}


public String getTag() {
return tag;
}


public void setTag(String tag) {
this.tag = tag;
}


public int getLength() {
return length;
}


public void setLength(int length) {
this.length = length;
}


public String getValue() {
return value;
}


public void setValue(String value) {
this.value = value;
}


@Override
public String toString() {
return "tag=[" + this.tag + "]," + "length=[" + this.length + "]," + "value=[" + this.value + "]";
}
}

http://my.oschina.net/maxid/blog/206546