使用Boost program_options指定级别(例如——verbose)

Specifying levels (e.g. --verbose) using Boost program_options

本文关键字：例如 verbose program Boost options 使用      更新时间：2023-10-16

我的一些选项有多个级别，例如"冗长"。我希望我的用户在以下两种等效样式之间进行选择:

// no argument: verbosity of 1
my_program -v
// count the 'v's: verbosity of 4
my_program -vv --something_else XYZ -vv
// specify the value: verbosity of 4
my_program --verbose 3

用Boost program_options库做这件事最简单的方法是什么?

这就是我设想的使用代码的方式。

  1. 我们使用level_value代替正常的program_options::value
  2. 通过option_level<CHAR>(your_value)，其中CHAR是短选项字母，your_value是可选级别，例如，提供

#include <boost/program_options.hpp>
using namespace boost;
using namespace boost::program_options;
int main()  
{
    unsigned verbosity      = 0U;
    unsigned something_else = 0U;
    options_description desc("options");
    desc.add_options()
        ("verbose,v",               
            level_value(option_level<'v'>(&verbosity)),
            "Print more verbose messages at each additional verbosity level.")
        ("something_else,s",
            value<unsigned>(&something_else);
    return 0;
}

行为
# verbosity = 7
test_options -vvvvv --something_else 5 -vv
# final verbosity of 3 overrides
test_options -vvvvv --something_else 5 -v 7 -v 3
# no argument always increments: verbosity = 6
test_options -v 3 --verbose 5 -v
实施

我们需要一些东西来保持水平:

//________________________________________________________________________________________
//  t_option_level
//________________________________________________________________________________________
struct t_option_level {
public:
    unsigned n;
    explicit t_option_level(unsigned n_ = 0):n(n_){}
    t_option_level& inc(unsigned by = 1){n += by; return *this;}
    t_option_level& set(unsigned val){n = val; return *this;}
};
template <typename U>
inline t_option_level* option_level(U* u)
{return reinterpret_cast<t_option_level*>(u);}

增加或设置值的逻辑位于验证器中:

#include <boost/program_options.hpp>
#include <boost/program_options/options_description.hpp>
//________________________________________________________________________________________
// 
//      validate
//________________________________________________________________________________________
template <unsigned SHORT_NAME>
void validate(boost::any& v,
              const std::vector<std::string>& values,
              t_option_level<SHORT_NAME>* /*target_type*/, int)
{
    using namespace boost::program_options;
    // 
    // Get the current value
    // 
    t_option_level<SHORT_NAME> i;
    if (!v.empty())
        i = boost::any_cast<t_option_level<SHORT_NAME>>(v);
    //
    //  Extract any arguments 
    // 
    const std::string& s = validators::get_single_string(values, true);
    if (s.empty())
    {
        v = boost::any(i.inc());
        return;
    }
    char short_name = SHORT_NAME;
    // multiple 'values's
    if (s == std::string(s.length(), short_name))
    {
        v = boost::any(i.inc(s.length() + 1));
        return;
    }
    // match number
    boost::regex r("^(\d+)$");
    // Do regex match and convert the interesting part to 
    // int.
    boost::smatch what;
    if (regex_match(s, what, r)) 
    {
        v = boost::any(i.set(boost::lexical_cast<unsigned>(s)));
        return;
    } 
    else 
    {
        throw validation_error(validation_error::invalid_option_value, """ + s + "" is not a valid argument.");
    }        
}

这提供了program_options::value_semantic覆盖，允许零或一个参数:

template<class T, class charT = char>
class t_level_value : public boost::program_options::typed_value<T, charT>
{
public:
    /** Ctor. The 'store_to' parameter tells where to store
        the value when it's known. The parameter can be NULL. */
    t_level_value(T* store_to)
        : boost::program_options::typed_value<T, charT>(store_to)
    {} 
    unsigned min_tokens() const
    {
        return 0;
    }
    unsigned max_tokens() const 
    {
        return 1;
    }
};
template<class T>
t_level_value<T>*
level_value(T* v)
{
    return new t_level_value<T>(v);
}
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