best way of copy istream to ostream

[bg]

hi all,

what the best (stl) way of copy input to output using ofstreams/ifstreams

I currently have something like this

ofstream output(output_file_name.c_str(), ios_base::out | ios_base::trunc |
ios_base::binary);
// ... for each file ...
ifstream input(inputname.c_str(),ios_base::in|ios_base::binary);
do
{
// copy chunks of the input to the output
// until theres nothing more to read
input.read(buf, buffsize);
tot = input.gcount();
if(tot>0) output.write(buf,tot);
} while(tot>0);

input.close();

This strikes me as rather clunky and inelegant, there must be a better way,
std::copy? istream iteration ?

Any thoughts appreciated.

TIA

bg

[Pete Becker]

Post by bg
hi all,
what the best (stl) way of copy input to output using ofstreams/ifstreams

Depends on what you mean by that "(stl)" constraint. If you mean
Standard Template Library, then maybe:

copy(istream_iterator<unsigned char>(input), istream_iterator<unsigned
char.(), ostream_iterator<unsigned char>(output, ""));

If it doesn't mean anything, as is often the case, then:

output << input.rdbuf();

[Tom Widmer [VC++ MVP]]

Post by Pete Becker

Post by bg
hi all,
what the best (stl) way of copy input to output using ofstreams/ifstreams

Depends on what you mean by that "(stl)" constraint. If you mean
copy(istream_iterator<unsigned char>(input), istream_iterator<unsigned
char.(), ostream_iterator<unsigned char>(output, ""));

Don't you mean:
copy(
istreambuf_iterator<char>(input),
istreambuf_iterator<char>(),
ostreambuf_iterator<char>(output)
);

Tom

[Pete Becker]

Post by Tom Widmer [VC++ MVP]

Post by Pete Becker
copy(istream_iterator<unsigned char>(input), istream_iterator<unsigned
char.(), ostream_iterator<unsigned char>(output, ""));

copy(
istreambuf_iterator<char>(input),
istreambuf_iterator<char>(),
ostreambuf_iterator<char>(output)
);

That would also work.

[Ulrich Eckhardt]

Post by bg
what the best (stl) way of copy input to output using ofstreams/ifstreams

C++ IOStreams are not part of the STL, you mean the C++ standardlibrary.

Post by bg
ofstream output(output_file_name.c_str(), ios_base::out | ios_base::trunc
| ios_base::binary);

The ios_base::out and the ios_base::trunc are the defaults already.

Post by bg
ifstream input(inputname.c_str(),ios_base::in|ios_base::binary);

The ios_base::in is default, too.

Post by bg
do
{
// copy chunks of the input to the output
// until theres nothing more to read
input.read(buf, buffsize);
tot = input.gcount();
if(tot>0) output.write(buf,tot);
} while(tot>0);

There is an overloaded << operator that takes a streambuffer:

out << in.rdbuf();
// TODO: errorhandling for 'in' and 'out'!

Post by bg
This strikes me as rather clunky and inelegant, there must be a better
way, std::copy? istream iteration ?

The above is probably the shortest and most straightforward way using
IOStreams, but it is still clunky when compared to a platform-specific
solution. The point is that the streams still have to filter each byte
through a complicated IO mechanism, none of which is needed for your job.
I'd only use this as a default implementation for platforms that don't
provide any really straightforward means.

Uli

[bg]

cheers all,

output << input.rdbuff();

was what i was thinking of, and it works a charm to. its just as quick as
are other "OS based" stuff as well.

thanks

bg