How-To work with hex encoding

Sometimes it is usefult to represent values in hexadecimal encoding, and/or decode hexadecimal values back into binary. This library contains some functions that help here.

Hex encode and decode

Start by hex encoding some input string.

Using hex encoding
 1#include <liberate/string/hexencode.h>
 2
 3using namespace liberate::string;
 4
 5std::string input{"Hello, world!"};
 6
 7// Hexadecimal encoding doubles the number of bytes required.
 8std::vector<char> hex;
 9hex.resize(input.size() * 2);
10
11hexencode(&hex[0], hex.size(), input.c_str(), input.size());

Note

A lot of C++ developers are not aware that this is legal use of vector, which guarantees that its elements are contiguous in memory. Don’t assume this to work with other containers, however.

Of course, we can also make this a tad more convenient.

Using hex encoding (simpler)
1auto hex = hexencode(input.c_str(), input.size());
2// => std::string

Once we have a hex encoded string, we can also decode it.

Using hex decoding
1auto decoded = hexdecode(hex.c_str(), hex.size());
2assert(decoded == input);

See also

Creating hex dumps of some memory buffer

When you work with a lot of binary data, hex encoding a string is not always the easiest way to understand what you are dealing with. On the command line, the hexdump(1) tool may help you. But what to do in code?

Fear not, we can do much the same.

Using hex decoding
1canonical_hexump hd;
2
3std::cerr << hd(buf, bufsize) << std::endl;

The canonical_hexdump formats the contents of the specified buffer much like using hexdump -C would on the CLI. We can also use wide_hexdump for an alternative view.

However, both are just uses of the liberate::string::hexdump struct with specific template parameter values. You can roll your own preferred display instead.

See also