using rdbuf()->sputn(...) vs operator<<

Question

I am looking through some legacy code and found that temporary std::string objects are being used liberally throughout the code to convert const char* to force the use of :

inline std::ostream & operator << (std::ostream & s, const std::string & str)

within which str.c_str() is used to effect the call to

template<class _Traits> inline
    basic_ostream<char, _Traits>& __CLRCALL_OR_CDECL operator<<(
        basic_ostream<char, _Traits>& _Ostr,
        const char *_Val)

Weirdly I think this was done because someone created a const char* insertion operator which recursed... Anyway The reason was lost in the dim distant past... I removed it when I noticed exactly what was happening and it all works (AFAIK).

While experimenting with this issue, I redefined operator<<(std::ostream& , const char*) to do the following.

//
// Disclaimer - experiment!!! not enshrined in code.
//
inline std::ostream & operator << (std::ostream & s, const char * str)
{
   //formerly return s << std::string(str);

   if( str ) s.rdbuf()->sputn( str , strlen(str) );
   return s;
}

Question apart from the strlen call (preempting some comments) is there much of a downside to bypassing the insertion operator? (I saw some try catch logic in the operator I'm bypassing and I could place this into the operator above perhaps.)

This functionality already exists (http://en.cppreference.com/w/cpp/io/basic_ostream/operator_ltlt2). I fail to see the motivation behind this question. — R. Martinho Fernandes, Nov 12 '12 at 15:00
@R.MartinhoFernandes I was curious really - I use insertion operators all the time - the operators add a level of indirection and I hadn't considered doing it this way for exactly that reason. — Caribou, Nov 12 '12 at 15:03

score 1 · Accepted Answer · answered Nov 12 '12 at 15:19

1

Stream inserters do formatted input, controlled by a double handful of flags in the stream object. Stuffing characters directly into the output buffer bypasses this formatting, so manipulators like setw won't affect the output.

answered Nov 12 '12 at 15:19

Pete Becker

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Ok, right - I see what you mean. This stuff is basically dumping unformatted text so I didn't think along those lines. - thx – Caribou Nov 12 '12 at 15:21

using rdbuf()->sputn(...) vs operator<<

1 Answers1