C++ hex string to byte array

Question

I'm trying to send a string of hex values through udp,

11 22 33 44 37 4D 58 33 38 4C 30 39 47 35 35 34 31 35 31 04 D7 52 FF 0F 03 43 2D AA

using UdpClient in C++.

What's the best way to convert string^ to array< Byte >^ ?

possible duplicate of How do you convert Byte Array to Hexadecimal String, and vice versa, in C#? (The conversion from C# to its C++/CLI equivalent is trivial.) — Ben Voigt
– Ben Voigt, Commented Jul 8, 2011 at 19:52

Ben Voigt · Accepted Answer · 2011-07-08 20:27:58Z

This works for me, although I haven't tested the error-detection all that well.

ref class Blob
{
    static short* lut;
    static Blob()
    {
        lut = new short['f']();
        for( char c = 0; c < 10; c++ ) lut['0'+c] = 1+c;
        for( char c = 0; c < 6; c++ ) lut['a'+c] = lut['A'+c] = 11+c;
    }
public:
    static bool TryParse(System::String^ s, array<System::Byte>^% arr)
    {
        array<System::Byte>^ results = gcnew array<System::Byte>(s->Length/2);
        int index = 0;
        int accum = 0;
        bool accumReady = false;
        for each (System::Char c in s) {
            if (c == ' ') {
                if (accumReady) {
                    if (accum & ~0xFF) return false;
                    results[index++] = accum;
                    accum = 0;
                }
                accumReady = false;
                continue;
            }
            accum <<= 4;
            accum |= (c <= 'f')? lut[c]-1: -1;
            accumReady = true;
        }
        if (accumReady) {
            if (accum & ~0x00FF) return false;
            results[index++] = accum;
        }
        arr = gcnew array<System::Byte>(index);
        System::Array::Copy(results, arr, index);
        return true;
    }
};

Joel Rondeau · Accepted Answer · 2011-07-08 20:35:36Z

0

If you're trying to send that as ascii bytes, then you probably want System::Text::Encoding::ASCII::GetBytes(String^).

If you want to convert the string to a bunch of bytes first (so first byte sent is 0x11), you'll want to split your string based on whitespace, call Convert::ToByte(String^, 16) on each, and put them into an array to send.

edited Jul 8, 2011 at 20:35

answered Jul 8, 2011 at 19:44

Joel Rondeau

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3 Comments

Ben Voigt Over a year ago

While turning C# into C++/CLI is easy, it's not as simple as just tagging ^ on the end of each type.

Joel Rondeau Over a year ago

Fixed, other than not actually compiling to check.

Ben Voigt Over a year ago

System::String has a capital S. Lowercase string is a C# keyword, and also a native C++ type std::string, but never means .NET String. (Yeah, I know the question got it wrong too.)

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