I have an unsigned char* c that contains the element 0x1c. How can I add it into an std::vector<unsigned char>vect? I am working in c++.
std::vector<unsigned char>vect; //the vect dimention is dynamic
std::string at="0x1c";
c=(unsigned char*)(at.c_str());
vect[1]=c //error? why?
//The vect dimension is dynamic ONLY if you call push_back
std::vector <std::string> vect;
std::string at="0x1c";
vect.push_back(at);
If you are using C++, use std::string. The above code will copy your "0x1c" string into the vector.
If you try to do
vect[0] = c;
Without first expanding the vector with
vect.resize(1);
You will get segmentation fault because operator[] doesn't expand the the vector dynamically. The initial size of a vector is 0 btw.
UPDATE: According to the OP's comment, here is what he would want: copying a unsigned char * to a std::vector (i.e.copying a C array to a C++ vector)
std::string at = "0x1c";
unsigned char * c = (unsigned char*)(at.c_str());
int string_size = at.size();
std::vector <unsigned char> vect;
// Option 1: Resize the vector before hand and then copy
vect.resize(string_size);
std::copy(c, c+string_size, vect.begin());
// Option 2: You can also do assign
vect.assign(c, c+string_size);
const char* returned by c_str() to an unsigned char* and then call non existent method pushback with that? I don't believe there is a ctor of std::string which takes an unsigned char*![ '0', 'x', '1', 'c']. The OP has not said whether he wants this or a single entry in the vector with the value 0x1c.
c is an unsigned char*. vect is a std::vector<unsigned char>, so it contains unsigned char values. The assignment will fail, as operator [] on std::vector<unsigned char> expects an unsigned char, not a unsigned char *.
You have a hex representation of a character in a string, and you want the character?
easiest:
unsigned char c;
istringstream str(at);
str >> hex >> c; // force the stream to read in as hex
vect.push_back(c);
(I think that should work, have not tested it)
I just reread your question again, this line:
I have an unsigned char* c that contains the element 0x1c
Does this mean that actually your unsigned char* looks like this:
unsigned char c[] = {0x1c}; // i.e. contains 1 byte at position 0 with the value 0x1c?
or my assumption above...
to print the vector out to cout, use a simple for loop, or if you are feeling brave
std::cout << std::ios_base::hex;
std::copy(vect.begin(), vect.end(), std::ostream_iterator<unsigned char>(std::cout, " "));
std::cout << std::endl;
this will print the hex representations of each of the unsigned char values in the vector separated by a space.
vect[1] = *c? I haven't used C++ in a while though.vect[0]rather thanvect[1]if you want to set the first value. Also, what error are you actually getting?