Re: Data compression, date range

From:
Ben Pfaff <blp@cs.stanford.edu>
Newsgroups:
comp.lang.c,comp.lang.c++
Date:
Mon, 22 Feb 2010 10:36:28 -0800
Message-ID:
<87wry5kthv.fsf@blp.benpfaff.org>
Kelsey Bjarnason <kbjarnason@gmail.com> writes:

On Mon, 22 Feb 2010 12:09:26 +0100, Branimir Maksimovic wrote:

Kelsey Bjarnason wrote:

On Mon, 22 Feb 2010 10:56:54 +0100, Branimir Maksimovic wrote:

given

const uint64_t maxDateValue = 6074000998ull;

write decode/encode date range functions

uint64_t encodeDate(uint64_t start, uint64_t stop); void
decodeDate(uint64_t blob, uint64_t* start, uint64_t* stop);

Interesting exercise ;)

I'm probably going to regret asking, but if you have a 64-bit integer
type to use, why limit the range that way?

Point is that that's maximum range you can pack in unsigned 64 bit
integer.

According to "bc", 2^64 is 18446744073709551616, or about 3037000500
times larger than the value you selected.

He wants to pack two values in that range 0...6074000998ull into
a 64-bit integer. Otherwise it's just a date, not a date
*range*.
--
char a[]="\n .CJacehknorstu";int putchar(int);int main(void){unsigned long b[]
={0x67dffdff,0x9aa9aa6a,0xa77ffda9,0x7da6aa6a,0xa67f6aaa,0xaa9aa9f6,0x11f6},*p
=b,i=24;for(;p+=!*p;*p/=4)switch(0[p]&3)case 0:{return 0;for(p--;i--;i--)case+
2:{i++;if(i)break;else default:continue;if(0)case 1:putchar(a[i&15]);break;}}}

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