| // 國慶沒事寫著玩的,英文很爛,請把注意力集中在代碼上,呵呵:) // c++基於流的檔案操作使很多C轉過來的程式員在操作檔案時還是選擇了 FILE* // :）其實,C++的流操作檔案也很方便啊 // 下面這個例子就是檔案使用執行個體代碼 #pragma warning(disable:4786)
#include <IOSTREAM>
#include <FSTREAM>
#include <string>
using namespace std;
int main()
{
// using std::cout;
// using std::endl;
cout<<" ********************* C ++ file opration demo ***********************"<<endl;
cout<<"using fstream or ifstream and ofstream"<<endl;
cout<<"fstream derive from istream and ostream, so most of method were defined in"<<endl;
cout<<"istream and ostream"<<endl;
cout<<"By the way, I like C style /"FILE */" indeed. :)"<<endl; // Input file demo
cout<<endl;
cout<<"****Part 1: Input file demo****"<<endl; fstream /*ifstream*/ infile;
// antoher way to declare special class or function in a namespace
using std::string;
string strfilename;
cout<<"Input In FileName:"<<endl;
cin>>strfilename;
infile.open(strfilename.c_str(),ios::in/*openmode*/); // succeed?
if(!infile)
{
cout<<"Cannot open file:"<<strfilename<<endl;
return 1;
} // read a byte
char ch1,ch2;
infile.get(ch1);
ch2 = infile.get(); // read a line
// get(char *,int max_size,char dimiliter) can do the same word as getline()
// but get() doesn't drop the dimiliter,
// use ignore() to drop the dimiliter(the last byte,'/n' by default) char pszLine[1024];
memset(pszLine,0,1024);
infile.getline(pszLine,1024/*read count*/,'/n'/*read until reach '/n'*/); // seek function
// seekg means seek for getting use for input file
infile.seekg(0/*offsize*/,ios_base::beg/*seek from ios_base::beg ios_base::cur ios_base::end*/); // read to a buffer
infile.read(pszLine,1024); // get readed size
int nReadedSize = infile.gcount(); // tell the position also tellg() and tellp()
// tellg() before read() and tellg() after read() then you can get the readed size
// return -1 if eof() turn true
int nCurPos = infile.tellg(); // test end ?
if(infile.eof())
{
cout<<"input file reach file end"<<endl;
} infile.close(); // output file demo
cout<<"****Part 2: Output file demo *****"<<endl; fstream /*ofstream */outfile;
outfile.open("out.txt",ios::out);
if(!outfile)
{
cout<<"Cannot open out file out.txt."<<endl;
return 1;
} // write a byte
char chout = 'a';
outfile.put(chout); // write buffer
outfile.write(pszLine,strlen(pszLine)); // like ifstream ,seekp(),tellp()
outfile.seekp(10,ios_base::beg);
char buffer[] = "seekp and write a buffer";
outfile.write(buffer,strlen(buffer)); nCurPos = outfile.tellp(); outfile.close(); return 0;
} |
