Check if std::string is a valid uuid using boost

Question

I want to check if a given string is a valid UUID using boost.

This is what I have come up with by looking at the documentation on the boost website:

void validate_uuid(const std::string& value)
{
    try
    {
        boost::uuids::string_generator stringGenerator;
        (void)stringGenerator(value);
    }

    catch (const std::exception& ex)
    {
        // ...
    }
}

However, this does not always work.

If I call the function with a string that is too short for a valid UUID, an exception is thrown as expected. But if I call the function with an invalid UUID (e.g. 00000000-0000-0000-0000-00000000000K) no exception is thrown.

Please can someone clarify why this is happening.

Also, I've seen the use of boost::lexical_cast to read a string as a UUID as posted here. I'm wondering if I should follow that approach. Any advice appreciated.

Answer 1

The code you had does nothing in terms of validation. Instead it generates a UUID based on the constant passed (like a hash function).

Looking closer I was mistaken. The missing bit of validation appears to be a check on version:

Live On Coliru

#include <boost/uuid/uuid.hpp>
#include <boost/uuid/uuid_io.hpp>
#include <boost/uuid/string_generator.hpp>
#include <iostream>

bool is_valid_uuid(std::string const& maybe_uuid, boost::uuids::uuid& result) {
    using namespace boost::uuids;

    try {
        result = string_generator()(maybe_uuid); 
        return result.version() != uuid::version_unknown;
    } catch(...) {
        return false;
    }
}

int main() {
    std::string maybe_uuid;
    std::cout << "Enter a UUID: ";

    while (std::cin >> maybe_uuid)
    {
        boost::uuids::uuid result;
        bool is_valid = is_valid_uuid(maybe_uuid, result);
        std::cout << "\n'" << maybe_uuid << "' valid: " << std::boolalpha << is_valid << "\n";

        if (is_valid)
            std::cout << "Parsed value: " << result << "\n";
    }
}

Sample output from Coliru: echo 00000000-0000-{0,4}000-0000-000000000000 $(uuidgen) "{$(uuidgen)}" | ./a.out:

Enter a UUID: 
'00000000-0000-0000-0000-000000000000' valid: false

'00000000-0000-4000-0000-000000000000' valid: true
Parsed value: 00000000-0000-4000-0000-000000000000

'a2c59f5c-6c9b-4800-afb8-282fc5e743cc' valid: true
Parsed value: a2c59f5c-6c9b-4800-afb8-282fc5e743cc

'{82a31d37-6fe4-4b80-b608-c63ec5ecd578}' valid: true
Parsed value: 82a31d37-6fe4-4b80-b608-c63ec5ecd578