C++ : convert uint64_t to unsigned char array

Question

I need to convert for exemple this number : 281474976710655 to a unsigned char array like this one :

unsigned char value[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

I try to memcpy and other techniques but i didn't get the correct value back, always random hex...

I'm not a c++ developer so thanks to explain if you can.

Thanks a lot, bye !

What values did you expect, and what did you get? And 6 bytes doesn't seem to be the proper length for a 64-bit value. — Bo Persson, Apr 04 '18 at 09:56
Possible duplicate of [C - unsigned int to unsigned char array conversion](https://stackoverflow.com/questions/10319805/c-unsigned-int-to-unsigned-char-array-conversion) — xskxzr, Apr 04 '18 at 10:59
Remember to bear in mind that if you use something like memcpy then the byte order will depend on endianness... — Sean Burton, Apr 04 '18 at 12:13

score 10 · Accepted Answer · answered Apr 04 '18 at 09:57

10

uint64_t x=281474976710655
unsigned char value[sizeof(x)];
std::memcpy(value,&x,sizeof(x));

answered Apr 04 '18 at 09:57

Oliv

1

How do you convert it back to a new uint64_t? – thc Aug 13 '18 at 22:55
1

@thc memcpy(&x, value, sizeof(uint64_t)) – Antwan van Houdt Feb 12 '19 at 08:35

1 Answers1