How to define the number of bits in record bit variable?-CodePudding

Such as IP header has four bits of data types, how to define in Delphi?

CodePudding user response:

I usually use the collection to simulate this type

 TIP_HEAD_TEST=the packed record 
In case the integer of 
0: (VersionLength: the set of 0.. 7); 
1: (VerLen: Byte); 
end; 

Var 
IPHEAD: TIP_HEAD_TEST; 
The begin 
IPHEAD. VerLen:=$4.//set the IPV4, at the same time, the length of the qing dynasty 0 
IPHEAD. VerLen:=$4 or (nLen SHL 4);//set length and IPV4, at the same time can also be SHL 3, here there seems to be a variable bit 
IPHEAD. VersionLength:=IPHEAD. VersionLength + [2];//only the bit position 1, 2 is set IPV4, other unchanged 
.