Output stream help

Hi,

I have implemented the virtual function of the streambuf class
In specification is written that overflow() function is callled when buffer is full.
but i have observed that this function ( overflow() ) is called on writing the each character in output stream e.g. on writing the abc , this function is called three times Why?????
Is the specification wrong or default buffer size is one byte?

Code:

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cout.rdbuf(&DebugStreamBuf);

cout << abc << endl;

int DebugStreamBuf::overflow(int ch)
{
 ...
}

---

It does seem like you need to set the buffer & size using setbuf().

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Mats

what is the default streambuf size? Would you please shortly describe the whole process.

Quote:

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Originally Posted by alibaba786

what is the default streambuf size? Would you please shortly describe the whole process.

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I have never done that - I'm just guessing from the cppreference.

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Mats

matsp is right. You need to set a buffer if you don't want overflow() to be called for every character. How large the buffer is is up to you - but you have to manage it. I guess typical sizes will be about 4k.

It means , if i dont set the buffer size , output stream consider the buffer size . am i right???
Is it specified somewhere??

You actually have to provide the buffer. The size just needs to match the buffer. This is documented in the C++ standard, in the description of basic_streambuf. Although, of course, in standardese.

The best resource for using streams is "Standard C++ IOStreams and Locales", by Langer and Kreft, Addison Wesley.

My question still the same, if i dont set the buffer size , what would be the buffer size?
or by default output stream sets the buffer size = 1 byte???
Is it specified somewhere??

If you don't set a buffer, there is no buffer, so the buffer size is 0. Thus, every character immediately overflows.

Thanks . now i have got the answer ...