c++中ifstream一次读取整个文件

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 ...

#include <string>
#include <fstream>
#include <streambuf>

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

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

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