CODEWITHSUNDEEP
c++visual-c++stdstringuint8t
Amir-Mousavi
Amir-Mousavi

Reputation: 4563

c++, convert std::string to uint8_t

in the c++ solution I am working on I have a function that returns a string reference. like const std::string& getData() const {return mData;} and the mData is std::string mData;. now I want to convert it to uint8_t array to pass it to another function pointer.

/* in another header -> typedef uint8_t  U8; */
const std::string& d = frame.getData();
U8 char_array[d.length()];
/* here I want to put the d char by char in char_array*/

the strcpy is deprecated so I am using strcpy_s like strcpy_s(char_array, d);

which of course I get couldn't match type char(&)[_size] against unsigned char[]

and also static or reinterpret casting to char* does not work too.

Upvotes: 0

Views: 4164

Answers (2)

Matthieu Brucher
Matthieu Brucher

Reputation: 22023

Use a vector, what you are writing are VLAs, which is not valid C++ (U8 char_array[d.length()]). then use std::copy.

const std::string& d = frame.getData();
std::vector<U8> char_array(d.length() + 1, 0);

The question is if you need to have the end of string \0 or not, so it's going to be d.length()+1 if you want the last \0. Then:

std::copy(std::begin(d), std::end(d), std::begin(char_array));

Update: Apparently, the goal is to store this vector in another uint8_t[8], if it's a variable named foo, just do:

std::copy(std::begin(d), std::end(d), std::begin(foo));

But check the length first... And pass the structure to populate as a reference. Also get a good C++ book.

Upvotes: 4

Superlokkus
Superlokkus

Reputation: 5069

Update: Since it seems from your comments that you have a compile time constant maximum size, I added a true array version:

#include <string>
#include <vector>
#include <cstdint>
#include <algorithm>
#include <iterator>
#include <array>

struct foo {
    std::string& getData() {return mData;}
    const std::string& getData() const  {return mData;}
    std::vector<uint8_t> get_array() const {
        std::vector<uint8_t> array;
        std::copy(mData.cbegin(), mData.cend(), std::back_inserter(array));
        return array;
    };

    static constexpr size_t max_size = 8u;
    std::array<uint8_t, max_size> get_max_array() const {
        std::array<uint8_t, max_size> array;
        std::copy_n(mData.cbegin(), max_size, array.begin());
        return array;
    }

private:
    std::string mData;
};

Upvotes: 0

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