Quickest way to load a file into a std::string?
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I seem to remember somebody posting a way of doing this in a couple lines of code using a std::ifstream, a std::istreambuf_iterator, and a std::string
Any takers?
stringstream stream;
copy(istream_iterator<char>(fin), istream_iterator<char>(), ostream_iterator<char>(stream));
string bleh = stream.str();
stringstream::str() returns by value though, so it''s not so quick after all. The fastest way is to first use seek() to find how large the file is, allocate a string large enough and then use copy:
string bleh;
bleh.reserve(filesize);
copy(istream_iterator<char>(fin), istream_iterator<char>(), back_inserter(bleh));
A bit faster still may be this option:
string bleh;
bleh.resize(filesize);
copy(istream_iterator<char>(fin), istream_iterator<char>(), &bleh[0]);
But it has the unfortunate property of assigning values to bleh right before they are overwritten.
copy(istream_iterator<char>(fin), istream_iterator<char>(), ostream_iterator<char>(stream));
string bleh = stream.str();
stringstream::str() returns by value though, so it''s not so quick after all. The fastest way is to first use seek() to find how large the file is, allocate a string large enough and then use copy:
string bleh;
bleh.reserve(filesize);
copy(istream_iterator<char>(fin), istream_iterator<char>(), back_inserter(bleh));
A bit faster still may be this option:
string bleh;
bleh.resize(filesize);
copy(istream_iterator<char>(fin), istream_iterator<char>(), &bleh[0]);
But it has the unfortunate property of assigning values to bleh right before they are overwritten.
Here's another one of my favorites - reads in a text file of integers, separated by whitespace, and prints out a sorted text file of those same integers, separated by new lines.
As for tutorials, well, i'm not really sure where i picked up most of this. There's a book on the stl by austern(or musser) that's quite good.
edit: added paren
[edited by - sjelkjd on August 6, 2003 3:52:00 AM]
multiset<int> myvec(istream_buffer<int>(ifstream("numbers.txt")),istream_buffer());copy(myvec.begin(),myvec.end(),ostream_iterator<int>(ofstream("sorted.txt"),"\n"));As for tutorials, well, i'm not really sure where i picked up most of this. There's a book on the stl by austern(or musser) that's quite good.
edit: added paren
[edited by - sjelkjd on August 6, 2003 3:52:00 AM]
quote:Original post by Anonymous Poster
stringstream stream;
copy(istream_iterator(fin), istream_iterator(), ostream_iterator(stream));
string bleh = stream.str();
This will eat whitespace, whereas istreambuf_iterator will not.
quote:Original post by Anonymous Poster
A bit faster still may be this option:
string bleh;
bleh.resize(filesize);
copy(istream_iterator(fin), istream_iterator(), &bleh[0]);
That &bleh[0] isn''t likely to do anything good as far as correct code is concerned (doesn''t mean it won''t work, of course). You''d better use something like bleh.begin().
quote:Original post by sjelkjd
string myfile(istreambuf_iterator<char>(ifstream("file.txt")),istreambuf_iterator<char>());
So beautiful... *snif*
Can you tell me what happens when the file open fails?
quote:Original post by mputtersSince this is legal:
That &bleh[0] isn''t likely to do anything good as far as correct code is concerned (doesn''t mean it won''t work, of course). You''d better use something like bleh.begin().
bleh[0] = 3;
the character must be returned by reference. Thus taking it''s address is correct there.
String iterators are not guaranteed to be implemented as character pointers though. If the STL implementation doesn''t implement strings as character arrays, then this might not work.
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