3. Questions about std::stringstream

Questions about std::stringstream

  • S

    1. How to empty stringstream after I put into it some symbols?
    2. Some funtion needs the start iterator and pass-the-end iterator. How to get these iterators from a stringstream object?
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  • W

    1. How to empty stringstream after I put into it some symbols?

    You could use the heap and simply replace it by a new stringstream. This works perfectly:

    #include <iostream>
#include <string>
#include <sstream>

using namespace std;
int main()
{
    stringstream* s = new stringstream();
    *s << "so what?";
    cout << s->str();

    delete s;
    s = new stringstream();
    cout << s->str();

    return 0;
}
    1. Some funtion needs the start iterator and pass-the-end iterator

    You could use the method str() as shown above and use the iterators of the returned string. Or you try to work with the underlying stringbuf-Object. Here you can read about it:
    http://www.cplusplus.com/reference/iostream/stringbuf/

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  • N

    SAn schrieb:

    1. How to empty stringstream after I put into it some symbols?

    As follows:

    std::stringstream Stream;
Stream.str("");

    SAn schrieb:

    1. Some funtion needs the start iterator and pass-the-end iterator. How to get these iterators from a stringstream object?

    If you just need the Iterators of the std::string , use str() to get the stream's string and access the std::string::iterator .

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  • N

    Wirdbald schrieb:

    You could use the heap and simply replace it by a new stringstream. This works perfectly:

    Oh, and you call that simple? 😉

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  • S

    Other question: how to pass std::string object to the WinAPI function which will write data to it?

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  • N

    SAn schrieb:

    Other question: how to pass std::string object to the WinAPI function which will write data to it?

    Hm, I think you can't do this directly since the internal stuff of std::string is implementation-defined.

    So, you have to go the indirect way about a char -Pointer. Getting a string's Pointer can be done by the member function std::string::c_str() . Note that you get a const char* here, so you have to copy the string.

    Assigning a std::string to a char -Pointer can either be done by operator= , assign() , or the constructor.

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  • W

    I assume that you need to pass a char*. You could do this by copying the whole string via std::string::copy(char* s, size_t n) to a char-array. Or you directly use char*. It depends on what you aim to do with the string.

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  • ?

    http://www.cplusplus.com/reference/

    0
  • W

    Nice. Now I was the first to find the probably more suitable method 😉

    Have a nice day. I should work a little bit now...

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  • S

    Question:

    Will std::basic_stringstream<unsigned int, std::char_traits<unsigned int>, std::allocator<unsigned int> > correctly process UTF32? Will operator>> will convert it to numbers etc. ??

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  • ?

    Der stellt ja immer nur Fragen ohne auf die Antworten einzugehen.

    Allerunterste Schublade. 😡

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  • W
     

    Will std::basic_stringstream<unsigned int, std::char_traits<unsigned int>, std::allocator<unsigned int> > correctly process UTF32?

    Of course. But it will not provide you anything more than simple input-output of 4-byte strings. If you want to do any conversions from or to any encoding you have to implement it by yourself.

    Will operator>> will convert it to numbers

    Nobody knows, I guess. Because it depends on the implementation of that operator that you will have to supply yourself or get from some library.

    Maybe it would be a good idea to post what you are attempting to do. I don't think there are WinAPI-Functions using UCS4-Encoding. Not even utf16. As far as I know windows is uses UCS2 - or did I miss something?

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  • S

    I just sitting here for 4 hours and trying to convert std::vector<unsigned int> containing UTF-32 to the system-default ANSI codepage.

    The only solution I found is:

    1. Convert UTF-32 to UTF-8 using utfcpp.
    2. Convert UTF-8 to UTF-16 using utfcpp or MultiByteToWideChar WinAPI function
    3. Convert UTF-16 to the system-default ANSI codepage by WideCharToMultiByte(CP_ACP,...

    Is there the easier way to do such a conversion???

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  • W

    Of course. You should rather call it UCS4 than UTF32. Both is simply pure unicode, one character per 4-byte value.The Winapi-Function

    int WideCharToMultiByte(
  UINT CodePage, 
  DWORD dwFlags, 
  LPCWSTR lpWideCharStr,
  int cchWideChar, 
  LPSTR lpMultiByteStr, 
  int cbMultiByte,
  LPCSTR lpDefaultChar,    
  LPBOOL lpUsedDefaultChar
);

    takes a pointer to a WCHAR-String as its parameter LPCWSTR. You could copy your 4-byte values to a new WCHAR-array and pass that array to WideCharToMultiByte. If some character doesn't fit into 2 bytes, you won't be able to encode it as ANSI anyway. But you could check for overflows and treat the errors as needed in your context.

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