nix-super/src/libutil/parser.hh

#pragma once

#include <optional>

namespace nix {

// If `separator` is found, we return the portion of the string before the
// separator, and modify the string argument to contain only the part after the
// separator. Otherwise, wer return `std::nullopt`, and we leave the argument
// string alone.
std::optional<std::string_view> splitPrefix(std::string_view & string, char separator);

std::optional<std::string_view> splitPrefix(std::string_view & string, char separator) {
    auto sepInstance = string.find(separator);

    if (sepInstance != std::string_view::npos) {
        auto prefix = string.substr(0, sepInstance);
        string.remove_prefix(sepInstance+1);
        return prefix;
    }

    return std::nullopt;
}

}