C# Program: Convert 2 Byte Time & 2 Byte Date to DateTime

[Burdzy]

Hi, I am working on writing a .zip file class based on the PKWare Specifications, and in the .zip format, they save the modified time of the file in 2 pieces:
1. 2 bytes for the time
2. 2 bytes for the date.

I am trying to convert that to a C# DateTime datatype, but I can't seem to find any documentation on how to do that. Has anyone done this, and/or show me where to find some documentation on this??

Thanks in Advance!!
-Burdzy

P.S. Here is some Sample Data:
Time:
byte[0] = 91
byte[1] = 161

Date:
byte[2] = 185
byte[3] = 54

Those 4 bytes should be 8:10 PM 5/25/2007

[Plater]

Is there anyway that you can combine them into a single number?
DateTime has various static methods for converting file times and other times to the object.

Also, are you aware that the .net framework has a compression algorithm included?

The Tick values for "8:10 PM 5/25/2007" as byte[8]:
[0] 0
[1] 220
[2] 155
[3] 206
[4] 31
[5] 109
[6] 201
[7] 8

[Burdzy]

Hi Plater,

Thanks for the reply. Are you referring to the System.IO.Compression Class? I believe that only does the Compression/Decompression of the datastream, but does not give you full access to a .zip file such as what files are contained in it, etc.?? That part is what I am trying to implement.



I Found the specifications for the file format that I was working with here: http://msdn2.microsoft.com/en-us/library/ms724247.aspx



From that, I was able to write the following:

 
private void button1_Click(object sender, EventArgs e)
 
{
 
byte[] bTimeDate = { 91, 161, 185, 54 };
 
byte[] bTime = {91, 161};
 
byte[] bDate = {185, 54};
 
MessageBox.Show(GetDateTimeFromDosDateTime(ByteToInt16(bTime), ByteToInt16(bDate)).ToString());
 
MessageBox.Show(GetDateTimeFromDosDateTime(ByteToInt32(bTimeDate)).ToString());
 
}
 
public static DateTime GetDateTimeFromDosDateTime(Int32 i32TimeDate)
 
{
 
Int16 i16Time = (Int16)(i32TimeDate & 0xFFFF);
 
Int16 i16Date = (Int16)((i32TimeDate & 0xFFFF0000) >> 16);
 
return GetDateTimeFromDosDateTime(i16Time, i16Date);
 
}
 
public static DateTime GetDateTimeFromDosDateTime(Int16 i16Time, Int16 i16Date)
 
{
 
int iYear = 0;
 
int iMonth = 1;
 
int iDay = 1;
 
int iHour = 0;
 
int iMinute = 0;
 
int iSecond = 0;
 
iDay = (i16Date & 0x1F);
 
iMonth = ((i16Date & 0x01E0) >> 5);
 
iYear = 1980 + ((i16Date & 0xFE00) >> 9);
 
iSecond = (i16Time & 0x1F) * 2;
 
iMinute = ((i16Time & 0x07E0) >> 5);
 
iHour = ((i16Time & 0x0F800) >> 11);
 
return new DateTime(iYear, iMonth, iDay, iHour, iMinute, iSecond);
 
}
 
public static Int32 ByteToInt32(byte byte0, byte byte1, byte byte2, byte byte3)
 
{
 
return byte0 + byte1 * 256 + byte2 * 256 * 256 + byte3 * 256 * 256 * 256;
 
}
 
public static Int32 ByteToInt32(byte[] convertMe)
 
{
 
return convertMe[0] + convertMe[1] * 256 + convertMe[2] * 256 * 256 + convertMe[3] * 256 * 256 * 256;
 
}
 
public static Int16 ByteToInt16(byte[] convertMe)
 
{
 
return (short)(convertMe[0] + convertMe[1] * 256);
 
}
 
public static Int16 ByteToInt16(byte byte0, byte byte1)
 
{
 
return (short)(byte0 + byte1 * 256);
 
}
 

[Plater]

Looks like it worked, have you tried the BitConverter class? It turns bytes into values for you

i also did the following:

byte[] bdate = new byte[] { 185, 54 };
UInt32 date = BitConverter.ToUInt16(bdate, 0);
UInt32 day = PullPiece(date, 0, 4);// 2^0 -2^4 bits (5bits) make up the day
UInt32 month = PullPiece(date, 5, 8);
UInt32 year =1980+ PullPiece(date, 9, 15);
 
 

public UInt32 PullPiece(UInt32 buffer, int startbit, int endbit)
        {
            UInt32 retval = 0;
            BitArray ender = new BitArray(32);
            BitArray ba = new BitArray(new Int32[] { (Int32)buffer });
            int counter=0;
            for (int i = startbit; i <= endbit; i++)
            {
                ender[counter] = ba[i];
                counter++;
            }
            byte[] interm = new byte[4];
            ender.CopyTo(interm, 0);
            retval = BitConverter.ToUInt32(interm, 0);
            return retval;
        }