how to convert a set of hex strings to byte array

Question

I have an input of char *str = "13 00 0A 1B CA 00";

I need an output as BYTE bytes[] = { 0x13, 0x00, 0x0A, 0x1B, 0xCA, 0x00 };

can somebody help with a solution?

sscanf might work, but he may not know the exact number of bytes in the string, so he needs a more dynamic approach. — sean
– sean, Commented Dec 21, 2012 at 16:08
sscanf is not safe, it causes 'buffer overrun'. stackoverflow.com/questions/5873402/… — alex
– alex, Commented Dec 21, 2012 at 16:21

sean · Accepted Answer · 2012-12-21 16:32:49Z

7

You will need to parse out each of the two characters and then convert them into BYTE. This isn't fairly difficult to do.

std::stringstream converter;
std::istringstream ss( "13 00 0A 1B CA 00" );
std::vector<BYTE> bytes;

std::string word;
while( ss >> word )
{
    BYTE temp;
    converter << std::hex << word;
    converter >> temp;
    bytes.push_back( temp );
}

edited Dec 21, 2012 at 16:32

answered Dec 21, 2012 at 16:06

sean

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6 Comments

EvilTeach Over a year ago

Which c++ compiler are you using that has a function named hex_string_to_int in the standard library?

sean Over a year ago

I'm sorry that is not exactly what I ment, I'm going to change that.

Dean Over a year ago

I didn't quite understand this, can you explain in more detail please>

Dean Over a year ago

my strings are "xx xx xx xx" format, will strstream work with the spaces?

evpo Over a year ago

typedef unsigned short BYTE;

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Itsik · Accepted Answer · 2012-12-21 16:23:47Z

2

This answer assumes that the input format is actually 3 chars for each hex BYTE. I used sscanf for simplicity, streams are obviously also an option.

    std::vector<BYTE> bytes;
    char *str = "13 00 0A 1B CA 00";
    std::string input(str);

    size_t count = input.size()/3;
    for (size_t i=0; i < count; i++)
    {           
        std::string numStr = input.substr(i*3, input.find(" "));

        int num=0;
        sscanf(numStr.c_str(), "%x", &num);
        bytes.push_back((BYTE)num);
    }

    // You can access the output as a contiguous array at &bytes[0]
    // or just add the bytes into a pre-allocated buffer you don't want vector

edited Dec 21, 2012 at 16:23

answered Dec 21, 2012 at 16:16

Itsik

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1 Comment

renadeen Over a year ago

Actually count of bytes is (input.size() + 1)/3. Your code will miss last byte in input string.

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