istream_iterator & copying files

[Alex Vinokur]

ofstream outfile ("out");
ifstream infile ("in");
istream_iterator<char> iter(infile), eos;

Is it possible to copy 'infile' to 'outfile' using 'iter' and 'eos'?

--
Alex Vinokur
mailto:al****@connect.to
http://mathforum.org/library/view/10978.html

[Rolf Magnus]

Alex Vinokur wrote:

ofstream outfile ("out");
ifstream infile ("in");
istream_iterator<char> iter(infile), eos;

Is it possible to copy 'infile' to 'outfile' using 'iter' and 'eos'?

Yes.

[Alex Vinokur]

"Rolf Magnus" <ra******@t-online.de> wrote in message news:c6*************@news.t-online.com...

Alex Vinokur wrote:

ofstream outfile ("out");
ifstream infile ("in");
istream_iterator<char> iter(infile), eos;

Is it possible to copy 'infile' to 'outfile' using 'iter' and 'eos'?

Yes.

Any sample? Thanks.

--
Alex Vinokur
mailto:al****@connect.to
http://mathforum.org/library/view/10978.html

[Jeff Schwab]

Alex Vinokur wrote:

"Rolf Magnus" <ra******@t-online.de> wrote in message news:c6*************@news.t-online.com...

Alex Vinokur wrote:

ofstream outfile ("out");
ifstream infile ("in");
istream_iterator<char> iter(infile), eos;

Is it possible to copy 'infile' to 'outfile' using 'iter' and 'eos'?

Yes.

Any sample? Thanks.

#include <algorithm>
#include <fstream>
#include <iomanip>
#include <iterator>

int main( )
{
std::ofstream outfile( "out" )
std::ifstream infile( "in" );
std::istream_iterator< char > in( infile ), eos;
std::ostream_iterator< char > out( outfile );

infile >> std::noskipws;

std::copy( in, eos, out );
}

[Alex Vinokur]

"Jeff Schwab" <je******@comcast.net> wrote in message news:ap********************@comcast.com...

Alex Vinokur wrote:

"Rolf Magnus" <ra******@t-online.de> wrote in message news:c6*************@news.t-online.com...

Alex Vinokur wrote:
ofstream outfile ("out");
ifstream infile ("in");
istream_iterator<char> iter(infile), eos;

Is it possible to copy 'infile' to 'outfile' using 'iter' and 'eos'?

Yes.

Any sample? Thanks.

#include <algorithm>
#include <fstream>
#include <iomanip>
#include <iterator>

int main( )
{
std::ofstream outfile( "out" )
std::ifstream infile( "in" );
std::istream_iterator< char > in( infile ), eos;
std::ostream_iterator< char > out( outfile );

infile >> std::noskipws;

std::copy( in, eos, out );
}

Thanks.

The testsuite has been added to C/C++ Performance Tests
(Comparative performance measurement : Copying files)
http://article.gmane.org/gmane.comp.....perfometer/43
http://article.gmane.org/gmane.comp.....perfometer/42

--
Alex Vinokur
mailto:al****@connect.to
http://mathforum.org/library/view/10978.html

[Kevin Goodsell]

Alex Vinokur wrote:

Thanks.

The testsuite has been added to C/C++ Performance Tests
(Comparative performance measurement : Copying files)
http://article.gmane.org/gmane.comp.....perfometer/43
http://article.gmane.org/gmane.comp.....perfometer/42

If you want a fast way to copy files in C++, it should probably look
something like this:

ifstream infile("in", ios::binary);
ofstream outfile("out", ios::binary);
outfile << infile.rdbuf();

The iterator version includes considerable overhead compared to this
version.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[Alex Vinokur]

"Kevin Goodsell" <us*********************@neverbox.com> wrote in message news:5j***************@newsread2.news.pas.earthlin k.net...

Alex Vinokur wrote:

Thanks.

The testsuite has been added to C/C++ Performance Tests
(Comparative performance measurement : Copying files)
http://article.gmane.org/gmane.comp.....perfometer/43
http://article.gmane.org/gmane.comp.....perfometer/42

If you want a fast way to copy files in C++, it should probably look
something like this:

ifstream infile("in", ios::binary);
ofstream outfile("out", ios::binary);
outfile << infile.rdbuf();

The iterator version includes considerable overhead compared to this
version.

[snip]

Thanks.
Binary mode essentially improves performance.

http://article.gmane.org/gmane.comp.....perfometer/45
http://article.gmane.org/gmane.comp.....perfometer/44

--
Alex Vinokur
mailto:al****@connect.to
http://mathforum.org/library/view/10978.html

[Alex Vinokur]

"Jeff Schwab" <je******@comcast.net> wrote in message news:ap********************@comcast.com...
[snip]

#include <algorithm>
#include <fstream>
#include <iomanip>
#include <iterator>

int main( )
{
std::ofstream outfile( "out" )
std::ifstream infile( "in" );
std::istream_iterator< char > in( infile ), eos;
std::ostream_iterator< char > out( outfile );

infile >> std::noskipws;
------------------------------- std::copy( in, eos, out ); Is it possible to that via transform()?
------------------------------- }

--
Alex Vinokur
mailto:al****@connect.to
http://mathforum.org/library/view/10978.html

[tom_usenet]

On Mon, 19 Apr 2004 14:22:26 +0300, "Alex Vinokur"
<al****@big.foot.com> wrote:

ofstream outfile ("out");
ifstream infile ("in");
istream_iterator<char> iter(infile), eos;

Is it possible to copy 'infile' to 'outfile' using 'iter' and 'eos'?

istream_iterator<char> skips whitespace - it uses a formatted read
operation. You should open the files in binary mode, and use the
unformatted iterators:

istreambuf_iterator<char> iter(infile), eos;
ostreambuf_iterator<char> out(outfile);
//make sure serious errors are reported
infile.exceptions(ios_base::bad);
outfile.exceptions(ios_base::bad | ios_base::fail | ios_base::eof);
std::copy(iter, eos, out);

Tom
--
C++ FAQ: http://www.parashift.com/c++-faq-lite/
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html

[tom_usenet]

On Tue, 20 Apr 2004 14:47:57 +0300, "Alex Vinokur"
<al****@big.foot.com> wrote:

-------------------------------

std::copy( in, eos, out );

Is it possible to that via transform()?

std::copy is equivalent to std::transform with the identity function.
So what would be the point of using std::transform where std::copy
suffices?

(if you must:

template <class T>
struct identity
{
T operator(T t) const
{
return t;
}
};

Then
std::transform(in, eos, out, identity<char>());
)

Tom
--
C++ FAQ: http://www.parashift.com/c++-faq-lite/
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html

[Alex Vinokur]

"tom_usenet" <to********@hotmail.com> wrote in message news:vv********************************@4ax.com...

On Tue, 20 Apr 2004 14:47:57 +0300, "Alex Vinokur"
<al****@big.foot.com> wrote:

-------------------------------

std::copy( in, eos, out ); Is it possible to that via transform()?

std::copy is equivalent to std::transform with the identity function.
So what would be the point of using std::transform where std::copy
suffices?

To compare their performances.

(if you must:

template <class T>
struct identity
{
T operator(T t) const
{
return t;
}
};

Then
std::transform(in, eos, out, identity<char>());
)

[snip]

OK.

---------------------------
istreambuf_iterator<char> in(fs_in), eos;
ostreambuf_iterator<char> out(fs_in);
fs_bin_in >> noskipws;

// copy-method
copy (in, eos, out);

// transform-method
struct char_identity
{
char operator()(char ch) const { return ch; }
};
transform(in, eos, out, char_identity());
---------------------------

copy-method and transform-method have almost the same performance.
It seems that copy-method is a bit better, but perhaps is a metering error.
--
Alex Vinokur
mailto:al****@connect.to
http://mathforum.org/library/view/10978.html