使用 boost-spirit 解析 ipv4 地址

Posted 2023-02-21

【中文标题】使用 boost-spirit 解析 ipv4 地址

【英文标题】：Parsing ipv4 addresses using boost-spirit

【发布时间】：2012-07-03 09:19:01

【问题描述】：

我想使用 boost::spirit 来解析 ipv4 地址。这是我尝试做的：

#include <string>
#include <string.h>
#include <iostream>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>

struct Ipv4  union  uint32_t as_int; uint8_t as_char[4];  raw; ;

Ipv4 make_ipv4(uint8_t i1, uint8_t i2, uint8_t i3, uint8_t i4) 
    Ipv4 ip;
    ip.raw.as_char[0] = i1; ip.raw.as_char[1] = i2;
    ip.raw.as_char[2] = i3; ip.raw.as_char[3] = i4;
    return ip;


namespace qi = boost::spirit::qi;
qi::uint_parser<uint8_t, 10, 1, 3> octet;

struct Ipv4Address : qi::grammar<const char *, Ipv4()> 
    Ipv4Address() : Ipv4Address::base_type(start) 
        start = ( octet >> qi::lit('.') >> octet >> qi::lit('.') >>
                  octet >> qi::lit('.') >> octet
                ) [
                    //qi::_val = make_ipv4(1, 2, 3, 4) // working
                    qi::_val = make_ipv4(qi::_1, qi::_2, qi::_3, qi::_4) // compile error
                ]
        ;
    
    qi::rule<const char *, Ipv4()> start;
 ipv4_address;

int main() 
    Ipv4 ip;
    const char * s = "1.2.3.4";
    bool r = qi::parse(s, s+strlen(s), ipv4_address, ip);
    std::cout << r << " " << (int)ip.raw.as_char[0] << "." <<
                             (int)ip.raw.as_char[1] << "." <<
                             (int)ip.raw.as_char[2] << "." <<
                             (int)ip.raw.as_char[3] << std::endl;

编译时出现以下编译错误：

/tmp/ip.cxx：在构造函数“Ipv4Address::Ipv4Address()”中： /tmp/ip.cxx:26:72：错误：无法转换'const _1_type aka const boost::phoenix::actor >' 到 'uint8_t aka unsigned char' 用于参数 '1' 到 'Ipv4 make_ipv4(uint8_t, uint8_t, uint8_t, uint8_t)'

有什么提示吗？

这是“正确”的做法吗？

【参考方案1】：

语义动作中需要使用bind懒惰绑定函数：

namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
qi::uint_parser<uint8_t, 10, 1, 3> octet;

struct Ipv4Address : qi::grammar<const char *, Ipv4()> 
    Ipv4Address() : Ipv4Address::base_type(start) 
        start = ( octet >> qi::lit('.') >> octet >> qi::lit('.') >>
                  octet >> qi::lit('.') >> octet
                ) [
                    qi::_val = phx::bind(make_ipv4, qi::_1, qi::_2, qi::_3, qi::_4)
                ]
        ;
    
    qi::rule<const char *, Ipv4()> start;
 ipv4_address;

完整样本：

#include <string>
#include <string.h>
#include <iostream>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>

struct Ipv4  union  uint32_t as_int; uint8_t as_char[4];  raw; ;

Ipv4 make_ipv4(uint8_t i1, uint8_t i2, uint8_t i3, uint8_t i4) 
    Ipv4 ip;
    ip.raw.as_char[0] = i1; ip.raw.as_char[1] = i2;
    ip.raw.as_char[2] = i3; ip.raw.as_char[3] = i4;
    return ip;


namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
qi::uint_parser<uint8_t, 10, 1, 3> octet;

struct Ipv4Address : qi::grammar<const char *, Ipv4()> 
    Ipv4Address() : Ipv4Address::base_type(start) 
        start = ( octet >> qi::lit('.') >> octet >> qi::lit('.') >>
                  octet >> qi::lit('.') >> octet
                ) [
                    qi::_val = phx::bind(make_ipv4, qi::_1, qi::_2, qi::_3, qi::_4)
                ]
        ;
    
    qi::rule<const char *, Ipv4()> start;
 ipv4_address;

int main() 
    Ipv4 ip;
    const char * s = "1.2.3.4";
    bool r = qi::parse(s, s+strlen(s), ipv4_address, ip);
    std::cout << r << " " << (int)ip.raw.as_char[0] << "." <<
                             (int)ip.raw.as_char[1] << "." <<
                             (int)ip.raw.as_char[2] << "." <<
                             (int)ip.raw.as_char[3] << std::endl;

【讨论】：

我怎样才能用可选的端口号修改这个优秀的例子。我正在尝试编写一个 CSV 解析器，它接受带有可选端口说明符的 ip 地址，格式为 x.y.z.w:nnnnn，其中 nnnnn 是 1-65535 范围内的小数。

bool r = qi::parse(s, s+strlen(s), ipv4_address >> (":" > qi::uint_parser<uint16_t>() | qi::attr(0u)), ip, port); 会做得很好@johnco3