Getting Hex Through Cin

Getting hex through Cin

I believe in order to use hex you need to do something like this:

cin >> hex >> x;
cout << hex << x; 

you can also replace hex with dec and oct etc.

Reliably get user hex input in C++ with error handling

cin.ignore() will ignore the last character in its internal buffer. You need to use cin.ignore(std::numeric_limits<std::streamsize>::max()) to reset back to the last EOF. Then you can check the next input reliably.

After trying to work this one out (good practice with streams :D), I have come up with a solution

    int startAddr;
    std::cin.exceptions(std::ios_base::failbit);

    while (true) {
        std::cout << "Enter start addr: ";

        try {
            std::cin >> std::hex >> startAddr;
            break;
        } catch(std::exception&) {
            std::cin.clear();
            std::cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n');
            std::cout << "Invalid number\n"; 
        }
    }

This makes use of the ability to set a failbit as an exception for std::iostreams meaning we are guaranteed to catch the error and std::numeric_limits as a more reliable way to clear the buffer

Using C++ hex and cin

The hex manipulator only controls how a value is read - it is always stored using the same internal binary representation. There is no way for a variable to "remember" that it was input in hex.

inputing hex and reading hex with C++

You seem to be intending to read and write one character at a time - cin and cout are both capable of working with integral values and this would be ideal here. Keep in mind that hexadecimal strings do represent numbers! Streams are capable of interpreting them as such. Simply changing the variables v and print to type int will allow you to read in an entire hexadecimal value at once.

For an example:

int value;
cin >> hex >> value;
cout << hex << value;

How to validate hex input with std::cin?

I guess I'd do something like this:

std::getline(cin, your_string);

if (your_string.find_first_not_of("0123456789abcdefABCDEF") != std::string::npos)
    error("Non-hexadecimal input");
else {
    std::istringstream is(your_string);
    is >> std::hex >> address1;
}

There are a lot of variations, but the three steps I'd follow would be:

1. read the whole line,
2. validate it
3. convert if good.

Getting wrong hex value from read function

d0 is a negative 8 bit value in signed char. This is exact the same negative value ffffffd0 in int. For getting "d0" in output, cast the signed char to another unsigned type of the same size (1 byte) then cast the result to int:

hexValue << hex << (int)(unsigned char)buffer[i];
hexValue << hex << (int)(uint8_t)buffer[i];

The first type cast keeps 8 bits in an unsigned type, a positive number, the second cast makes a positive int.

Read file in binary and output in hex std::cin to std::cout

The input stream operator typically requires a separator, you should read a buffer from the file, something like shown here: http://www.cplusplus.com/reference/iostream/istream/read/, then iterate over the contents and print out, you may also want to use showbase to make the hex output prettier...

EDIT: try something like this:

char c;
while(std::cin.get(c))
  ...

How to input hex values instead of chars as input for boost::asio::buffer

That is your solution:

just replace

std::string hex_chars("E8 48 D8 FF FF 8B 0D");

with

std::string hex_chars;
std::getline(std::cin, hex_chars);

P.S. I hope I've understood your question correctly :)

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