Question

As the title says I try to convert to byte data type a C++ String of Bytes and count bytes.
The string I get from textbox will contain a series of one byte hexadecimal numbers, but I need to send it as bytes.

char packet_data[200];
HWND hTextBox2 = GetDlgItem(TabOneDlg,IDC_EDIT3);

SendMessageA(hTextBox2, WM_GETTEXT, (WPARAM)200, (LPARAM)packet_data);

That’s how I get the input value (I am using win32 API – unmanaged forms)

EXAMPLE of input string (hex)

AA BB CC DD - 4 bytes !

In SHORT I want to do this :
Got a string containing a textual representation of hexadecimal numbers, and I want to convert each textual representation of the hexadecimal numbers to “normal” numbers.

Answer 1

If you are sure that the hexadecimal numbers are separated by a space (as shown in the question) it is a simple question of extracting them. The simplest way in C++ is by using std::istringstream and the normal input operator >>:

std::istringstream istr(packet_data);
std::vector<uint8_t> data;

uint8_t i;
while (istr >> std::hex >> i)
    data.push_back(i);

After the above code, the vector data will have all data from the string. If you need to e.g. send the data over a socket (or similar) you can use std::vector::data to get a raw pointer to the data (or use &data[0] if the data function doesn’t exist), and the number of bytes is available from std::vector::size.