/// <summary>
/// 解析指定的字节流。
/// </summary>
public void ParseBytes(byte[] bytes)
{
if (bytes == null || bytes.Length < AleFrame.HeadLength)
{
throw new AleFrameParsingException("无法将指定的字节流解析为AleFrame，长度不够。");
}
int startIndex = 0;
// 包长度
var pktLen = RsspEncoding.ToHostUInt16(bytes, startIndex);
startIndex += AleFrame.SizeofHeadLen;
// 版本
this.Version = bytes[startIndex++];
// 应用类型
this.ApplicationType = bytes[startIndex++];
// 传输序列号
this.SequenceNo = RsspEncoding.ToHostUInt16(bytes, startIndex);
startIndex += 2;
// N/R标志
this.IsNormal = (bytes[startIndex++] == 1);
// 包类型
this.FrameType = (AleFrameType)bytes[startIndex++];
// 校验和
if (this.FrameType != AleFrameType.KAA && this.FrameType != AleFrameType.KANA) // 生命信息不需要校验
{
//var actualCrcValue = BitConverter.ToUInt16(bytes, startIndex);
var actualCrcValue = RsspEncoding.ToHostUInt16(bytes, startIndex);
var expectedCrcValue = CrcTool.CaculateCCITT16(bytes, 0, 8);
if (actualCrcValue != expectedCrcValue)
{
throw new AleFrameParsingException(string.Format("解析Ale协议帧时发生异常，CRC检验不一致，期望值是{0}，实际值是{1}。",
expectedCrcValue, actualCrcValue));
}
}
startIndex += 2;
// 用户数据
var userDataLen = pktLen - (AleFrame.HeadLength - AleFrame.SizeofHeadLen);
if (userDataLen < 0)
{
throw new AleFrameParsingException(string.Format("将字节流解析为ALE帧时发生异常，用户数据长度为负值{0}。", userDataLen));
}
this.UserData = AleUserData.Parse(this.FrameType, bytes, startIndex, startIndex + userDataLen - 1);
}
public AleFrame(byte appType, UInt16 seqNo, bool isNormal, AleUserData userData)
: this()
{
if (userData == null)
{
throw new ArgumentNullException();
}
this.ApplicationType = appType;
this.SequenceNo = seqNo;
this.IsNormal = isNormal;
this.FrameType = userData.FrameType;
this.UserData = userData;
}
public static AleUserData Parse(AleFrameType frameType, byte[] bytes, int startIndex, int endIndex)
{
AleUserData result = null;
if (frameType == AleFrameType.ConnectionRequest)
{
result = new AleConnectionRequest();
}
else if (frameType == AleFrameType.ConnectionConfirm)
{
result = new AleConnectionConfirm();
}
else if (frameType == AleFrameType.DataTransmission)
{
result = new AleDataTransmission();
}
else if (frameType == AleFrameType.Disconnect)
{
result = new AleDisconnect();
}
else if (frameType == AleFrameType.SwitchN2R)
{
result = new AleSwitchN2R();
}
else if (frameType == AleFrameType.SwitchR2N)
{
result = new AleSwitchR2N();
}
else if (frameType == AleFrameType.KANA)
{
result = new AleKeepAliveOnNonActiveLink();
}
else if (frameType == AleFrameType.KAA)
{
result = new AleKeepAliveOnActiveLink();
}
else
{
throw new AleFrameParsingException(string.Format("无法将指定的字节流解析为ALE层的用户数据，类型 = {0}。", frameType));
}
result.ParseBytes(bytes, startIndex, endIndex);
return(result);
}
