13 character digit string to number

Question

I have a 13 digit string which is milliseconds since 1/1/1970. I need to convert it to a date time. The first step to do that is to get it into a useable number format. At 13 chars it's beyond the limits of ulong and long which have 10 digits max. I'm looking at int64 conversions. What's the best way to get this beast into a number format? I'm using c++ on a windows platform

Example "1382507187943" --> number? -- > datetime?

Thanks!

PART 2

Thank you guys! I am using c++ native. Thank you to poster 2 for the code.

I tried this and it worked as well where str contains the number and is a std::string:

__int64 u = _atoi64( str.c_str() );

PART 3

Actually, the 13 digit number does not fit in strtoul. I did this and got back the correct string.

__int64 u = _atoi64( str.c_str() );

time_t c;
//c = strtoul( "1382507187943", NULL, 0 );
c = u;
time(&c);
std::string s = ctime( &c );

Instead of saying "I'm using c++" buried in your text, add the tag to your question where people can see it, and so that the tagging system here can use it when people search later. You figured out how to use the other three tags, right? — Ken White, Oct 25 '13 at 17:06
Why would you ever get the time in a string like this? The computer has the current time (in secs since 1/1/1970) as an integer already! — Walter, Oct 25 '13 at 17:16
There's a time out for waiting for a useful answer. I used a mix of my answer and poster 2's answer and then poster 3 offered a good answer. How do you mark that? — user2913447, Oct 25 '13 at 17:20
I dunno why they send this time this way. MS are useful but there are other ways to send them. I just have to work with what I have. — user2913447, Oct 25 '13 at 17:22

score 1 · Accepted Answer · answered Oct 25 '13 at 17:03

1

Either use strtull() or lop off the milliseconds yourself.

unsigned long long tms = strtoull("1382507187943", 10, 0);
time_t rawtime = tms/1000;
unsigned ms = tms%1000;

or

char buf[] = "1382507187943";
unsigned ms = strtoul(&buf[10], 10, 0);
buf[10] = '\0';
time_t rawtime = strtoul(buf, 10, 0);

then

struct tm * timeinfo;
time (&rawtime);
timeinfo = localtime (&rawtime);

answered Oct 25 '13 at 17:03

chux - Reinstate Monica

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Note: As `time_t` is usually a _signed_ value, likely better to use `signed long long`, etc. – chux - Reinstate Monica Oct 25 '13 at 17:39

score 0 · Answer 2 · answered Oct 25 '13 at 16:40

If you are using a language that does not have native support for arbitrary precision arithmetic, you will need to add such support. A library such as GMP exposes an API for such math. It is likely that an implementation or binding exists for your language, as long as it is popular.

I created a binding for GMP in C# a while ago and am pretty sure it'll do what you want.

However, it is difficult to answer this question without knowing what language you are using.

score 0 · Answer 3 · edited May 23 '17 at 12:21

0

time_t c;
c = strtoul( "1382507187943", NULL, 0 );
ctime( &c );

solution was from here

edited May 23 '17 at 12:21

Community

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answered Oct 25 '13 at 16:45

aah134

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13 character digit string to number

3 Answers3