Streaming string literals in C++

Question

Let's say that I have some in-house framework for files and streams. I have IOutputStream interface class with write(char const *buffer, size_t size) and flush(). I have a tool, called Printer which can be used with any instance of IOutputStream descendants. Then I have Printer & operator<<(T x) style methods, where T x is the data (or a reference or a pointer to it) to be written.

For example Printer & operator<<(int x) will translate x to string, and will call the referenced output stream's write(...) function for real.

Let's see the problem! Invocation: printer << "appletree";. It calls Printer & operator<<(char const *s). For this kind of usage, I have to call an strlen(s) to determine the size, and after that I can call the final step. This is rather insane since I know the length of appletree at compile time.

Are there any good practice for this? How STL's ostream plays with titerals?

Is the call to `strlen` a performance bottleneck? Personally, I would just take the hit of the `strlen` call to keep your code simple to read (assuming it's not a performance hit). — deanWombourne, Sep 07 '12 at 12:23
See this [answer to another question](http://stackoverflow.com/a/11639305/597607) which shows that sometimes the compiler will be able to compute `strlen("some text")` at compile time. Just call it, and hope for the best. In your case, I bet the printer will be the bottleneck anyway. — Bo Persson, Sep 07 '12 at 12:29

score 6 · Accepted Answer · answered Sep 07 '12 at 12:25

6

Since string literals have type const char(&)[], you could add an overload for them:

template<size_t n>
Printer& operator<<(const char (&cstring)[n]) {
    write(cstring, n - 1);
}

answered Sep 07 '12 at 12:25

mfontanini

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Can you please add a reference where the type of string literals is described? – Notinlist Sep 14 '12 at 08:45
1

@Notinlist there you go: http://msdn.microsoft.com/en-us/library/69ze775t%28v=vs.80%29.aspx – mfontanini Sep 14 '12 at 12:08

score 3 · Answer 2 · answered Sep 07 '12 at 12:25

3

How about

template<std::size_t Size>
Printer& operator << (const char (&s)[Size]);

answered Sep 07 '12 at 12:25

ForEveR

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Streaming string literals in C++

2 Answers2