istream1.cpp

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#include <fstream>    // for basic_ofstream
#include <iostream>   // for basic_istream, cout
#include <cstdio>     // for tmpnam () and remove ()
 
#include <examples.h>
 
int main ()
{
#ifndef _RWSTD_STRICT_ANSI
 
    // use an extension of this implementation: NULL file name argument
    // creates a temporary file; closing the file stream object or its
    // associated filebuf removes the temporary file
    const char* const fname = 0;
    
#else   // if defined (_RWSTD_STRICT_ANSI)
 
    char fnamebuf [L_tmpnam];
 
    // create a temporary filename
    const char* const fname = std::tmpnam (fnamebuf);
 
    if (!fname)
        return 1;
 
#endif   // _RWSTD_STRICT_ANSI
  
    // typedefs for convenience
    typedef std::basic_istream<char, std::char_traits<char> >         Input;
    typedef std::basic_ofstream<Input::char_type, Input::traits_type> Output;
 
    Input::char_type s [200];
 
    // open a file for read and write operations 
    Output out (fname, std::ios::in | std::ios::out | std::ios::trunc);
 
    // tie the istream object to the ofstream filebuf 
    Input in (out.rdbuf ());
 
    double x = 3.14159;
    int    i = 3;
 
    // output to the file
    out << "He lifted his head and pondered.\n"
        << x << '\n' << i << '\n';
  
    // seek to the beginning of the file
    in.seekg (0);
 
    // read from the file using formatted functions
    in.getline (s, sizeof s);
    in >> x >> i;
 
    // seek to the beginning of the file
    in.seekg (0, std::ios::beg);
 
    // output the all file to the standard output
    std::cout << in.rdbuf ();
 
    // seek to the beginning of the file
    in.seekg (0);
 
    // read the first line in the file
    // "He lifted his head and pondered."
    in.getline (s, sizeof s / 2);
 
    std::cout << s << '\n';
 
    // read the second line in the file
    in.getline (s, sizeof s / 2);
 
    std::cout << s << '\n';
 
    // seek to the beginning of the file
    in.seekg (0);
 
    // read the first line in the file
    // "He lifted his head and pondered."
    in.get (s, sizeof s / 2);
 
    // remove the newline character
    in.ignore ();
 
    std::cout << s << '\n';
 
    // read the second line in the file
    // 3.14159
    in.get (s, sizeof s / 2);
 
    std::cout << s << '\n';
 
    // remove the newline character
    in.ignore ();
 
    // store the current file position   
    const Input::pos_type position = in.tellg ();
 
    out << "\nreplace the int\n";
 
    // move back to the previous saved position
    in.seekg (position);   
 
    // for convenience
    const Input::int_type eof = Input::traits_type::eof ();
 
    // output the remainder of the file
    // this is equivalent to "std::cout << in.rdbuf ();"
    while (!Input::traits_type::eq_int_type (in.peek (), eof))
        std::cout << Input::traits_type::to_char_type (in.get ()); 
 
    std::cout << "\n\n\n";
 
    if (fname) {
        // close the stream before removing the file
        out.close ();
 
        // remove the temporary file (must have a name)
        std::remove (fname);
    }
 
    return 0;
}