What container can I use to write binary?

Question

I want to write a c array into a container and i prefer to modify it if possible. I was thinking of using vector but it does seem to have a write(*pchararray, len); function. String looked like the next best thing but that too doesnt have a write function?

Answer 1

Not sure exactly what you mean with your "write" comment but

std::vector<char> charBuffer;

is functionally equivalent to a c char(byte) array

&charBuffer[0]

gives you the contiguous underlying memory.

So now you can do

charBuffer.resize(100);
memcpy(&charBuffer[0], src, charBuffer.size());

Answer 2

You can use a vector. Preallocate the size and then address the first byte: vectors are guarnateed to be contiguous so this is always valid.

std::vector<char> vBuffer;
vBuffer.resize(nLength);
std::copy(pStart, pEnd, &vBuffer[0]);

Answer 3

Given

char myarray[10];

You can use an STL iterator:

vector <char> v;
copy(myarray, myarray + 10, back_inserter(v));

You can use a constructor:

vector <char> v(myarray, myarray + 10);

You can resize and copy:

vector<char> v(10);
copy(myarray, myarray + 10, v.begin());

(and all these work similarly for string)

Thanks to comments/other answers :)

Answer 4

Container selection depends on your usage of the individual elements. If you mean copying a c character array to a conatiner, this is what you can use:

char buf[ n ];
std::vector<char> vc(n); // Thanks to Éric 
std::copy(buf, buf + n, vc.begin());

Answer 5

Vector, string, and many other containers have a "two iterator" constructor for this purpose:

char raw_data[100];
std::vector<char> v(raw_data, raw_data + 100);
std::string s(raw_data, raw_data + 100);

Answer 6

you should prefer using memcpy in this case (since the vector contains a POD type) over using std::copy, it's ALOT faster.

Answer 7

You can use:

string s( pchararray, len );  // constructor

Or:

string s;  s.append( pchararray, len ); // append example.

Or string::insert() if you wanted.

String happily handles null characters ('\0'), provided you specify the length.

See http://www.cplusplus.com/reference/string/string/