build a binary string c++

Question

How do I build a binary string in c++?

I want to have it in this format:

  std::string str = signed long (4bytes) "fill out zeros" 0x000 (8bytes) signed long (4bytes)

Note I DO NOT want the viewable binary representation but the actual binary data in the string

IMHO the best thing is to manage a uint8_t* in an explicit way (either by writing the individual bytes by means of bitshifts and explicit endianess or by resorting to unaligned integer load/store), possibly wrapped in a std::array<uint8_t>. — akappa
– akappa, Commented Aug 5, 2012 at 21:58
Though I still need it resulting in a string... Would it work to shift into a char that you later append to the string? — user1432032
– user1432032, Commented Aug 5, 2012 at 22:04
Why do you want this in a std::string? It's not a sequence of characters; it's an arbitrary array of bytes. So use a std::vector<uint8_t>. — Nicol Bolas
– Nicol Bolas, Commented Aug 5, 2012 at 22:07
"Note I DO NOT want the viewable binary representation but the actual binary data in the string" What does this mean? — Code-Apprentice
– Code-Apprentice, Commented Aug 5, 2012 at 22:38
I meant that I don´t want the printable string containing chars of "1" and "0" ("11111100 ... ") but the ascii (11111100) value. — user1432032
– user1432032, Commented Aug 5, 2012 at 22:44

Kerrek SB · Accepted Answer · 2012-08-05 23:30:47Z

3

For your specific application:

std::string data(12, 0);  // construct string of 12 null-bytes

int32_t x, y;  // populate

char const * const p = reinterpret_cast<char const *>(&x);
char const * const q = reinterpret_cast<char const *>(&y);

std::copy(p, p + 4, data.begin()    );
std::copy(q, q + 4, data.begin() + 8);

edited Aug 5, 2012 at 23:30

answered Aug 5, 2012 at 22:44

Kerrek SB

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1 Comment

user1432032 Over a year ago

Thanks! It was something like this I was looking for.

walrii · Accepted Answer · 2012-08-05 22:03:59Z

2

char buffer[1024];
// fill up buffer with whatever
char *end = afterLastChar;
std:string s(buffer, afterLastChar);

answered Aug 5, 2012 at 22:03

walrii

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Comments

Joel Falcou · Accepted Answer · 2012-08-05 22:18:48Z

0

Use std::vector< uint8_t >, this is not a string

answered Aug 5, 2012 at 22:18

Joel Falcou

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