size of binary string

How to get the size of a binary string?
length() and size() both stops at a \0 character.

Code:

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// string::length
#include <iostream>
#include <string>
using namespace std;

int main ()
{
  string str ("Tes\0t string");
  cout << "The length of str is " << str.length() << " characters.\n";
  cout << "The length of str is " << str.size() << " characters.\n";
  return 0;
}

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Quote:

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Originally Posted by Ducky

How to get the size of a binary string?
length() and size() both stops at a \0 character.

Code:

---

// string::length
#include <iostream>
#include <string>
using namespace std;

int main ()
{
  string str ("Tes\0t string");
  cout << "The length of str is " << str.length() << " characters.\n";
  cout << "The length of str is " << str.size() << " characters.\n";
  return 0;
}

---

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Null-terminators don't belong in an std::string. What are you trying to do?

I believe a string can handle binary strings just fine - including a 0 terminator. I'm not completely sure about this, and I think it's "nicer" to use a vector of chars for this, but that's a matter of opinion. Can those who actually know the C++ standard confirm binary strings are legal in the C++ standard (I'm actually 99.9% sure about this though)?

Anyway, the problem with your code is that you use a C-string argument as constructor. And guess how it finds the length of that C-string? By finding a 0-terminator! But you can also pass another argument, being the number of characters in the character array, as such:

Code:

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std::string test("x\x00ab", 4);

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That will create a string with 4 characters.

And to others: what do you think is better for binary strings, vectors or strings, or does it not matter at all? And why do you think so?

The character '\0' has no special meaning to std::string. The problem it is that it does have a special meaning for C-style strings which is what the argument is.

I don't think I'd use a std::string for the storage of a binary string (e.g from a binary file).

Ok, first of all thanks to all of you for your kind help!

I have a function that returns a char* as a binary string of unknown size.
Now i need to write this string to a file but for that first i need to know its size.

First i tried to do it in C but then i thought it's maybe easier in C++.

So maybe i should count it one by one by incrementing a pointer or use a vector?

If your program returns a char* pointing to a buffer of unknown size, then there is nothing you can do.

You have to keep the size around, and that's what a vector does.

Wouldnt this work to get the size?

Code:

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char * binaryStr = RetBinStr(buffer);

while (binaryStr--) { i++; }

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So you think it will stop once the pointer reaches NULL and that is the size of the returned data?

You can test your idea. I'd suppose the result is a crash sooner or later.

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Perhaps the function writes to the passed buffer and the return value points to the end of the range? Yes, in such a case, the length of the binary string would be:

Code:

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char* end = RetBinStr(buffer);
size_t length = end - buffer;

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If that is not so, you can't find out the size any more.

That makes sense, thank you very much Anon!