Question

So i am working on replacing a legacy app that was written in c++ and i have hit a small issue in mapping a struct used in network communications to c#. Basically the other end on the tcp connection uses the following struct to write dates and i have no idea how to convert the bytes generated by serialising that struct to a c# datetime. Most of it is easy till you get to the “millis” and “second” which are made up of 10 bits and 6 bits respectively so that the 2 bytes is shared between them. I assume you solve this with bit-shifting to read and write the values to a byte array but i have no experience with this.

typedef struct DATE_TIME
{
    USHORT  year;
    UCHAR   month;
    UCHAR   day;
    UCHAR   hour;
    UCHAR   minute;
    USHORT  millis : 10;
    USHORT  second : 6;
}

Code for current attempt to read

ushort Year = br.ReadUInt16();
byte Month = br.ReadByte();
byte Day = br.ReadByte();
byte Hour = br.ReadByte();
byte Minute = br.ReadByte();

ushort secAndMillSec = br.ReadUInt16();
ushort Milliseconds = (ushort)(secAndMillSec >> 6);
ushort Seconds = (ushort)((ushort)(secAndMillSec << 12)>>12);

Code for my first try at a write

 bw.Write(Year);
 bw.Write(Month);
 bw.Write(Day);
 bw.Write(Hour);
 bw.Write(Minute);

 ushort secAndMillSec = (ushort)(Milliseconds << 6);
 secAndMillSec = (ushort)(secAndMillSec + Seconds);
 bw.Write(secAndMillSec);

Again does it look right? So far all the test data i can run it against is empty dates so i am having issues testing myself

Answer 1

Bit fields are not portable across compilers but we can assume that these two fields are in two consequent bytes.

I assume you are receiving a stream from the network, and you are at the point of reading the datetime.

BinaryReader reader = new BinaryReader(networkStream);
int year = reader.ReadUInt16();
int month = reader.ReadByte();
int day = reader.ReadByte();
int hour = reader.ReadByte();
int minute = reader.ReadByte();
int ms = reader.ReadUInt16();
int second = ms >> 10;
int millist = ms & 1023;
DateTime dt = new DateTime(year, month, day, hour, minute, second, millis);