public member function
<istream>
explicit istream (streambuf * sb);
Construct object
Constructs an object, assigning initial values to the base class by calling the inherited member
ios::init with
sb as parameter.
Parameters
- sb
- pointer to a streambuf object, which is set as the associated stream buffer for the object.
Return Value
None (constructor).
Example
1 2 3 4 5 6 7 8 9 10 11 12 13
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// istream constructor
#include <iostream>
#include <fstream>
using namespace std;
int main () {
filebuf fb;
fb.open ("test.txt",ios::in);
istream is(&fb);
cout << char(is.get());
fb.close();
return 0;
}
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This code uses a
filebuf object (derived from
streambuf) to open the file
test.txt. The buffer is passed as parameter to the constructor of the
istream object
is, associating it to the stream. Then the first character is read and sent to the standard output stream
cout.
Objects of class
istream are seldom constructed directly. Generally some derived class is used (like the standard ones
ifstream and
istringstream).
Basic template member declaration
( basic_istream<charT,traits> )
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explicit basic_istream ( basic_streambuf<charT,traits>* sb );
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See also
- ios::init
- Initialize object [protected] (protected member function)