c++ - 取决于标志位的 Dynamic Spirit 解析器

Question

我正在尝试构建一个解析器来决定是否根据初始位字段的内容解析字段:

rule<Iterator, locals<uint32_t> > r =
    big_dword [_a = _1]
    >> (((_a & 0x01) >> big_dword) | attr(100))
    >> (((_a & 0x10) >> big_dword) | attr(0))
    >> (((_a & 0x80) >> big_qword) | attr(0))
    ;

也就是说，如果设置了 LSB，它只会尝试提取第一个字段，如果没有，它会将默认值 100 公开为属性等，其余字段依此类推。

(来自:spirit-general 列表)

Answer 1

好吧，你让我猜测实际问题。

但我编写了一些具有“告诉”回退值的测试用例。我使用业力来格式化解析结果。为了更好地衡量(检查我自己的理智，真的)我提供了小端和大端测试结果。

希望对您有所帮助:

代码

#include <boost/fusion/adapted.hpp>
#include <boost/tuple/tuple_io.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/karma.hpp>
#include <boost/spirit/include/phoenix.hpp>

namespace qi    = boost::spirit::qi;
namespace karma = boost::spirit::karma;
namespace phx   = boost::phoenix;

template <typename dword_t, typename qword_t, typename Cases>
void test(const dword_t& dword, const qword_t& qword, const Cases& cases)
{
    typedef boost::tuple<uint32_t,uint32_t,uint32_t,uint64_t> attr_t;
    typedef const char* Iterator;
    int count = 0;

    for (auto testcase : cases)
    {
        Iterator f = reinterpret_cast<const char*>(&*testcase.begin());
        Iterator l = reinterpret_cast<const char*>(&*testcase.end());
        Iterator b = f;

        qi::rule<Iterator, attr_t(), qi::locals<uint32_t> > r;

        r %=   dword [ qi::_a = qi::_1 ]
            >> (( qi::eps(qi::_a & 0x01ul) > dword) | qi::attr(0x0123ul ))
            >> (( qi::eps(qi::_a & 0x10ul) > dword) | qi::attr(0x0234ul ))
            >> (( qi::eps(qi::_a & 0x80ul) > qword) | qi::attr(0x0345ull))
            ;

        attr_t data;
        bool ok = qi::parse(f,l,r,data);

        std::cout << std::dec    << "testcase "         << count++ << "\t"
                  << "success: " << std::boolalpha      << ok      << "\t"
                  << "parsed: "  << std::distance(b, f) << (f==l?"(complete)\n":"(incomplete)\n")
                  << "\t"        << std::hex            << data    << "\n";
    }
}

typedef std::vector<uint32_t> Input;

int main()
{
    std::cout << "little endian: ";
    test(qi::dword, qi::qword, std::list<Input> { 
            { 0x11110000u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
            { 0x11110001u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
            { 0x11110010u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
            { 0x11110080u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
            { 0x11110011u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
            { 0x11110081u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
            { 0x11110091u, 0x22220000u, 0x44440000u, 0x88880000u, 0x99990000u, },
        });

    std::cout << "\nbig endian: ";
    test(qi::big_dword, qi::big_qword, std::list<Input> { 
            { 0x00001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
            { 0x01001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
            { 0x10001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
            { 0x80001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
            { 0x11001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
            { 0x81001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
            { 0x91001111u, 0x00002222u, 0x00004444u, 0x00008888u, 0x00009999u, },
        });
}

输出

little endian: testcase 0   success: true   parsed: 4(incomplete)
    (11110000 123 234 345)
testcase 1  success: true   parsed: 8(incomplete)
    (11110001 22220000 234 345)
testcase 2  success: true   parsed: 8(incomplete)
    (11110010 123 22220000 345)
testcase 3  success: true   parsed: 12(incomplete)
    (11110080 123 234 4444000022220000)
testcase 4  success: true   parsed: 12(incomplete)
    (11110011 22220000 44440000 345)
testcase 5  success: true   parsed: 16(incomplete)
    (11110081 22220000 234 8888000044440000)
testcase 6  success: true   parsed: 20(complete)
    (11110091 22220000 44440000 9999000088880000)

big endian: testcase 0  success: true   parsed: 4(incomplete)
    (11110000 123 234 345)
testcase 1  success: true   parsed: 8(incomplete)
    (11110001 22220000 234 345)
testcase 2  success: true   parsed: 8(incomplete)
    (11110010 123 22220000 345)
testcase 3  success: true   parsed: 12(incomplete)
    (11110080 123 234 2222000044440000)
testcase 4  success: true   parsed: 12(incomplete)
    (11110011 22220000 44440000 345)
testcase 5  success: true   parsed: 16(incomplete)
    (11110081 22220000 234 4444000088880000)
testcase 6  success: true   parsed: 20(complete)
    (11110091 22220000 44440000 8888000099990000)