/*************************************************************************** * * istream1.cpp - istream example * * $Id: istream1.cpp 550991 2007-06-26 23:58:07Z sebor $ * *************************************************************************** * * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed * with this work for additional information regarding copyright * ownership. The ASF licenses this file to you under the Apache * License, Version 2.0 (the "License"); you may not use this file * except in compliance with the License. You may obtain a copy of * the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or * implied. See the License for the specific language governing * permissions and limitations under the License. * * Copyright 1994-2006 Rogue Wave Software. * **************************************************************************/ #include // for basic_ofstream #include // for basic_istream, cout #include // for tmpnam () and remove () #include 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 > Input; typedef std::basic_ofstream 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; }