Convert 40 bits Date Time Stamped to unix timestamp

Hi.

OS_FILE return the date of a file into Load and Execution Addresses values
40 bits are allocated to the date !

I thaught the code to convert the date to unix timestamp was something like this.

unsigned long long date;
unsigned int mktime;

date = (((unsigned long long)(load_adress & 0x000000ff)) << 32) + (unsigned long long)execute_adresse;
mktime = (unsigned int)(date / 100) - (unsigned int)2208988800;

2208988800 is the number for second between 01/01/1900 and 01/01/1970.
But there’s an error of almost 14 months.

1- does anybody have the correct code to do that
2- the final purpose is to put a file date into a time_t (or struct tm). What is the correct solution to get a file date ?

Thank’s
Etienne

As far as I can tell it looks ok to me.
In my code I’ve subtracted 0×336E996A00 and then divided by 100, so yours looks equivalent.

It’s possible that the casting isn’t working as expected. I usually look at the assembly language and it often becomes clear where the bits are getting dropped.

This won’t explain the discrepancy, but you should not cast to unsigned int when all you have done is divide by 100. The result of (date / 100) will not necessarily fit in 32 bits. So your code would fail about halfway through the 2030s.

Is execute_addresse an int? In C, casting a signed number to a larger type will sign extend the value, even if the type you’re casting to is unsigned.

Jeffrey, You are right

Execute_adresse was an int
So casting it to unsigned long long first cast it to 64bit (so signed 64bit) and then set it unsigned.

Thank’s evetybody.