Re: [boost] What else shall I do before reuse a stringstream for date parsing?

Subject: Re: [boost] What else shall I do before reuse a stringstream for date parsing?
From: Bill David (billdavidcn_at_[hidden])
Date: 2009-02-16 04:25:57

2009/2/16 Dmitry Goncharov <dgoncharov_at_[hidden]>

>
>
> Bill David wrote:
>
>> To accelerate date parsing, I have writen a class to encapsulate the date
>> parsing logic as following.
>> But the second call to CDateParser::parseDate(str) always failed to parse
>> the date string. What else shall I do before reuse the stringstream
>> object?
>>
>> #include <stdio.h>
>>
>> #include <iostream>
>> #include <sstream>
>> using namespace std;
>>
>> #include "boost/date_time/posix_time/posix_time.hpp"
>> using namespace boost::gregorian;
>> using namespace boost::posix_time;
>>
>> class CDateParser
>> {
>> public:
>>    static void initialize();
>>    static time_t parseDate(const string& s);
>> private:
>>    static stringstream m_ss; //!< stringstream object used internally for
>> date parsing
>> };
>>
>> stringstream CDateParser::m_ss;
>>
>> time_t CDateParser::parseDate(const string& str)
>> {
>>    ptime p;
>>    m_ss.clear();
>>    m_ss << str;
>>    m_ss >> p;
>>    if (m_ss.fail()) {
>>        cout << "do not understand: " << str << endl;
>>        return 0;
>>    }
>>
>>    tm t = to_tm(p);
>>    return mktime(&t);
>> }
>>
>> void CDateParser::initialize() {
>>    time_input_facet* timefacet = new time_input_facet("%a, %d %b %Y
>> %H:%M:%S %z"); // will be automatically deleted by related locale object
>>    m_ss.imbue(locale(locale::empty(), timefacet));
>> }
>>
>> int main() {
>>    CDateParser::initialize();
>>
>>    string str;
>>    time_t t;
>>
>>    str = "Fri, 18 Jul 2008 11:53:14 GMT";
>>    t = CDateParser::parseDate(str);
>>    cout << ctime(&t) << endl;
>>
>>    str = "Sat, 19 Jul 2008 11:53:14 GMT";
>>    t = CDateParser::parseDate(str);
>>    cout << ctime(&t) << endl;
>> }
>>
>>
>>
>
> You should invoke m_ss.seekg(ios_base::beg) before each parsing.
> Also, be careful with to_tm(). It is buggy. See
> https://svn.boost.org/trac/boost/ticket/1859

But after I do that, both invocations report "do not understand".
And why clear can't rewind it?

>
> BR, Dmitry
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