[英]How to store intermediate values of circular buffer iterator?
我在提升循环缓冲区上使用提升正则表达式,并想“记住”发生匹配的位置,最好的方法是什么? 我尝试了下面的代码,但“end”似乎一直存储相同的值,例如,当我尝试从以前的“end”遍历到最近的“end”时,它不起作用!
boost::circular_buffer<char> cb(2048);
typedef boost::circular_buffer<char>::iterator ccb_iterator;
boost::circular_buffer<ccb_iterator> cbi(4);
//just fill the whole cbi with cb.begin()
cbi.push_back(cb.begin());
cbi.pushback(cb.begin());
cbi.pushback(cb.begin());
cbi.pushback(cb.begin());
typedef regex_iterator<circular_buffer<char>::iterator> circular_regex_iterator;
while (1)
{
//insert new data in circular buffer (omitted)
//basically reads data from file and pushes it back to cb
boost::circular_buffer<char>::iterator start,end;
circular_regex_iterator regexItr(
cb.begin(),
cb.end() ,
re, //expression of the regular expression
boost::match_default | boost::match_partial);
circular_regex_iterator last;
while(regexItr != last)
{
if((*regexItr)[0].matched == false)
{
//partial match
break;
}
else
{
// full match:
start = (*regexItr)[0].first;
end = (*regexItr)[0].second;
//I want to store these "end" positions to to use later so that I can
//traverse the buffer between these positions (matches).
//cbi stores positions of these matches, but this does not seem to work!
cbi.push_back(end);
//for example, cbi[2] --> cbi[3] traversal works only first time this
//loop is run!
}
++regexItr;
}
}
这与其说是试图重构你正在做的事情一样多的答案。 我正在制作一个从字符串初始化的简单循环缓冲区,并通过该缓冲区遍历正则表达式匹配并打印匹配的范围。 一切似乎都很好。
我不建议将范围本身存储在循环缓冲区中; 或者至少范围应该成对存储。
这是我的测试代码:
#include <iostream>
#include <string>
#include <boost/circular_buffer.hpp>
#include <boost/regex.hpp>
#include "prettyprint.hpp"
typedef boost::circular_buffer<char> cb_char;
typedef boost::regex_iterator<cb_char::iterator> cb_char_regex_it;
int main()
{
std::string sample = "Hello 12 Worlds 34 ! 56";
cb_char cbc(8, sample.begin(), sample.end());
std::cout << cbc << std::endl; // (*)
boost::regex expression("\\d+"); // just match numbers
for (cb_char_regex_it m2, m1(cbc.begin(), cbc.end(), expression); m1 != m2; ++m1)
{
const auto & mr = *m1;
std::cout << "--> " << mr << ", range ["
<< std::distance(cbc.begin(), mr[0].first) << ", "
<< std::distance(cbc.begin(), mr[0].second) << "]" << std::endl;
}
}
(这使用 漂亮的打印机打印原始循环缓冲区;您可以删除标记为(*)
的行。)
更新:这是存储匹配项的一种可能方法:
typedef std::pair<std::size_t, std::size_t> match_range;
typedef std::vector<match_range> match_ranges;
/* ... as before ... */
match_ranges ranges;
for (cb_char_regex_it m2, m1(cbc.begin(), cbc.end(), expression); m1 != m2; ++m1)
{
const auto & mr = *m1;
ranges.push_back(match_range(std::distance(cbc.begin(), mr[0].first), std::distance(cbc.begin(), mr[0].second)));
std::cout << "--> " << mr << ", range " << ranges.back() << std::endl;
}
std::cout << "All matching ranges: " << ranges << std::endl;
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