Simple conversion problem

[Dan203]

OK this is probably the most basic C++ question, but I can't seem to figure it out so I thought I'd ask.

I'm using a 3rd party supplied structure to read data from a file. Some of the members of this structure hold a time value (i.e. hour, minute, second) as a BYTE. Their sample code shows how parse the values as a string using...

sprintf("%2.2X:%2.2X:%2.2X", hour, minute, second);

and that works perfectly. However when I try to use the values in a calculation they're not the same. And even when I use integer values in the sprintf like so...

sprintf("%2.2i:%2.2i:%2.2i", hour, minute, second);

the numbers are wrong. So I'm assuming that the value is stored as a hex value, and that's what's causing the problem. However I'm still pretty green when it comes to C++ and I can't figure out a way to convert this hex value to a proper int so I can use it in a calculation.

Could anyone point me in the right direction?

Thanks,
Dan

[Vanaj]

You can convert each item (hour,min,sec) to a string with sprintf, then convert them to an int or long using atoi(), or atol(). Or if you need to use a different BASE number you can use strtol().

char *hex= "FF";
int num = static_case<int>(strtol(hex,NULL,16));

[JohnyDog]

If i understand the coding correctly, the proper way to convert is

x = ((num / 16) * 10) + (num % 16)

[Dan203]

That worked, thank you.

Jim, your solution worked as well but I thought converting it to a string first then back to an int was kind of inefficient.

Thank you both for the help.

Dan

[Vanaj]

That worked, thank you.

Jim, your solution worked as well but I thought converting it to a string first then back to an int was kind of inefficient.

Thank you both for the help.

Dan

From your code it looked like you were converting it to a string anyway, that is why I did suggest that..

[VladimirF]

That worked, thank you.

WHAT??? What worked? What kind of data is returned to you? What do you mean "as a BYTE"? In a BYTE? How is it encoded? Just a value? You obviously can't have a two-digit value represented as text in one char...
So, if it is a value - it's neither hex nor decimal. It could NOT possibly be formatted correctly with %X spec - you'd get "0A" instead of "10".
I can't imagine what the formula "x = ((num / 16) * 10) + (num % 16)" is supposed to do to a "num"... "11" will be "11", and "17" will become "11"?

[JohnyDog]

VladimirF> i have no idea what the 3rd party struct the OP's using is intended for, but from the code sample he posted it is clear that it is decimal number encoded in hexa in a way so it looks like decimal - eg. 11 is 0x11(=17), 23 is 0x23(=35) and so on.

[VladimirF]

VladimirF> i have no idea what the 3rd party struct the OP's using is intended for, but from the code sample he posted it is clear that it is decimal number encoded in hexa in a way so it looks like decimal - eg. 11 is 0x11(=17), 23 is 0x23(=35) and so on.

I *REALLY* doubt that. Lets wait for the OP to clear it up...

[JohnyDog]

Sure, lets wait Anyway,from the code he got from the documentation shows printing the time as hexadecimal (%X), yet it gives correct (decimal time) results. And he says my formula's working I remember using various hacks when i was writing code for microcontrollers and had to deal with base-10 numbers ...

[Dan203]

Johny is right. The structure I'm using holds data about a DVD from an IFO file. The value is read directly from the IFO and stored as a BYTE variable within the structure. The thing I was saying about the string is that the only place this variable is used in the sample code provided is in a string, so I had no point of reference as to how to convert it to an int that I could use in an actual calculation. Specifically what I was trying to do was figure out the length of a DVD chapter in DirectShow units. However when I had one that was say 30 minutes long it would always get converted to 48, which obviously screwed up what I was trying to do. Johny's code properly converted it to 30 so I could multiply it out like I needed.

Dan