Re: STL removal algorithm question

From:
"Old Wolf" <oldwolf@inspire.net.nz>
Newsgroups:
comp.lang.c++
Date:
26 Apr 2006 20:38:30 -0700
Message-ID:
<1146109110.815550.323350@t31g2000cwb.googlegroups.com>
Old Wolf wrote:

I recommend this strategy for deleting strings: maintain a
separate container of all your BSTRs.


Let me add that this is only if you decide to stick with the
idea of using a vector of structs of BSTR. My preferred
solution is to work with structs of CComBSTR, or
some other string type; and then generate a struct of BSTR
only when it's needed for a COM interface call; it makes
all of this management crap unnecessary.

When you've finished
with your vector, just destroy the vector normally. Then go
through the separate container and SysFreeString all of them.


Something like this:

struct BstrManager
{
    ~BstrManager() { clear(); }
    void clear()
    {
      for_each(all.begin(), all.end(), SysFreeString);
      all.clear();
    }
    BSTR createString(wchar_t const *s, size_t len)
    {
      BSTR b = SysAllocStringLen(s, len);
      all.push_back(b);
      return b;
    }
    BSTR copyString( BSTR s )
    {
      BSTR b = SysAllocString(s);
      all.push_back(b);
      return b;
    }
    void deleteString( BSTR b )
    {
      std::vector<BSTR>::iterator it = all.find(b);
        if ( it != all.end() ) { SysFreeString(b); all.erase(it); }
    }

  private:
    std::vector<BSTR> all;
};

Then in your code you can go:
  MyStruct m;
  m.somestring = manager.createString(L"Hello", 5);
  m.otherstring = manager.copyString(m.somestring);
  vec.push_back(m);
// ......
  vec.clear();
  manager.clear();

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