c++中ifstream一次读取整个文件

c++中一次读取整个文件的内容的方法：

1. 读取至char*的情况

std::ifstream t; int length; t.open("file.txt"); // open input file t.seekg(0, std::ios::end); // go to the end length = t.tellg(); // report location (this is the length) t.seekg(0, std::ios::beg); // go back to the beginning buffer = new char[length]; // allocate memory for a buffer of appropriate dimension t.read(buffer, length); // read the whole file into the buffer t.close(); // close file handle // ... do stuff with buffer here ... 

1. 读取至std::string的情况：

第一种方法：

#include   
#include   
#include   
  
std::ifstream t("file.txt"); std::string str((std::istreambuf_iterator<char>(t)), std::istreambuf_iterator<char>()); 

第二种方法：

#include   
#include   
#include   
std::ifstream t("file.txt"); std::stringstream buffer; buffer << t.rdbuf(); std::string contents(buffer.str());

  
  
    
    
    
    
#include
#include
#include
#include
#include
using  namespace  std;
int  main()
{
    ifstream ifs(  "test.cpp"  , ios_base::binary );
    string str;
    std::copy(std::istream_iterator char >(ifs),std::istream_iterator char >(),back_inserter(str) );
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
    cout<

  
  
    
    
    
    
    return  0;
}
  
  
    
    
    
    

  
  
    
    
    
    
#include
#include
#include
using  namespace  std;

int  main ()
{
    ifstream inf( "test.cpp" , ios::binary);

    if (inf)
    {
        ostringstream os;
        os << inf.rdbuf();
        cout << os.str();
    }
    system ( "pause" );
    return  0;
}
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    

  
  
    
    
    
    
include
#include
#include
using  namespace  std;

int  main ()
{
    ifstream inf( "test.cpp" , ios::binary);

    if (inf)
    {
        ostringstream os;
        cout <
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
    }
    system ( "pause" );
    return  0;
}


读出指定字节数，并且包含回车符号等等：
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    
  
  
    
    
    
    

   
   
   
   
     
     
     
     
#include
#include
#include
#include
#include
#include
using  namespace  std;
class  ReadBuffer:unary_function void >
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
{
public :
    string &buffer;
    size_t  length;
    ReadBuffer(string &buf,  size_t  len):buffer(buf),length(len){buffer.reserve(length);}
    void  operator()(  char  c )
    {
        if ( buffer.size()
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
   
   
     
     
     
     
        {
            buffer+=c;
        }
    }
};
int  main()
{
    const  size_t  N=10;
    ifstream infile(  "test.txt" , ios::binary );
    if ( infile.fail() ){  return  0; }
    string buffer;
    istreambuf_iterator< char > bg(infile);
    istreambuf_iterator< char > ed;
    for_each( bg,ed,ReadBuffer(buffer,N) );
    copy( buffer.begin(),buffer.end(), ostream_iterator< char >(cout, "" )  );
    return  0;
}