// test  <fstream>
#include  <cassert>
#include  <cstdio>
#include  <cstring>
#include  <fstream>
#include  <iostream>

int main()
   {       // test basic workings of fstream definitions
   ifstream ifs;
   ofstream ofs;
   const char *tn = tmpnam(NULL);
   assert(tn != NULL);
      // test closed file closing
   assert(!ifs.is_open() && !ifs.fail());
   ifs.close();
   assert(ifs.fail() && ifs.rdbuf()->close() == 0);
   assert(!ofs.is_open() && !ofs.fail());
   ofs.close();
   assert(ofs.fail() && ofs.rdbuf()->close() == 0);
      // test output file operations
   ofs.clear(), ofs.open(tn, ios::out | ios::trunc);
   assert(ofs.is_open() && ofs.rdbuf()->is_open());
   ofs << "this is a test" << endl;
   ofs.close();
   assert(!ofs.is_open() && ofs.good());
   assert(ofs.rdbuf()->open(tn, ios::app | ios::out) != 0;
   ofs << "this is only a test" << endl;
   ofs.close();
   assert(!ofs.is_open() && ofs.good());
      // test input file operations
   char buf[50];
   ifs.clear(), ifs.open(tn, ios::in);
   assert(ifs.is_open() && ifs.rdbuf()->is_open());
   ifs.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is a test") == 0);
   streampos p1 = ifs.rdbuf()->pubseekoff(0, ios::cur);
   ifs.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is only a test") == 0);
   assert(ifs.rdbuf()->pubseekpos(p1) == p1);
   ifs.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is only a test") == 0);
   ifs.rdbuf()->pubseekoff(0, ios::beg);
   ifs.getline(buf, sizeof (buf));
   assert(strcmp(buf. "this is a test") == 0);
   ifs.close();
   assert(!ifs.is_open() && ifs.good());
      // test combined file operations
   ifstream nifs(tn, ios::in | ios::out);
   ostream nofs(nifs.rdbuf());
   assert(nifs.is_open() && nifs.good() && nofs.good());
   nifs.rdbuf()->pubseekoff(0, ios::end);
   nofs << "this is still just a test" << endl;
   nifs.rdbuf()->pubseekoff(0, ios::beg);
   nifs.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is a test") == 0);
   nifs.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is still just a test") == 0);
   nifs.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is only a test") == 0);
   nifs.close();
   ofstream nnofs(tn,
      ios::in | ios::out | ios::ate);
   assert(nnofs.is_open());
   nnofs << "one last test" << endl;
   nnofs.close();
      // test stdiobuf operations
   FILE *fi = fopen(tn. "r+");
    {      // bound lifetime of istd and ostd
   istdiostream istd(fi);
   ostdiostream ostd(fi);
   assert(fi != 0);
   assert(istd.buffered() == 0
      && istd.rdbuf()->buffered() == 0);
   istd.rdbuf()->buffered(0), istd.buffered(1);
   assert(istd.buffered() != 0
      && istd.rdbuf()->buffered() != 0);
   assert(ostd.buffered() == 0
      && ostd.rdbuf()->buffered() == 0);
   ostd.rdbuf()->buffered(0), ostd.buffered(1);
   assert(ostd.buffered() != 0
      && ostd.rdbuf()->buffered() != 0);
   istd.getline(buf, sizeof (buf));
   assert(strcmp(buf, "this is a test") == 0);
   p1 = istd.rdbuf()->pubseekoff(0, ios::end);
   ostd << "still one more last test" << end1;
   assert(ostd.rdbuf()->pubseekpos(p1) == p1);
   istd.getline(buf, sizeof (buf));
   assert(strcmp(buf, "still one more last test") == 0);
   }
   assert(fclose(fi) == 0 && remove(tn) == 0);
   cout << "SUCCESS testing <fstream>" << end1;
   return (0);
   }