fstream

　　　　　　　　　　　　　　　　用到的关于输入输出fstream流相关的知识 1.两个主要函数： read( )函数 从流中读取字符串的成员函数read 该成员函数一般形式是：read(char* pch, int nCount) 从输入流中读取nCount个字符。当输入流中的字符数小于nCount时，结束读取。经常使用read函数读取二进制数据。 write( )函数 成员函数write()输出一串字符。 该成员函数一般形式是：write（char* pch, int nCount） 其中，pch是指向字符数组的指针; nCount指明从第一个参数中复制输出字符的个数。 2. 文件的随机读写 (1)输出流随机访问函数 　　输出流（output） 随机访问函数有seekp和tellp。 (2)输入流随机访问函数 　　输入流 随机访问函数有seekg和tellg。 3. 获得和设置流指针(get and put stream pointers) 所有输入/输出流对象(i/o streams objects)都有至少一个流指针： ifstream， 类似istream, 有一个被称为get pointer的指针，指向下一个将被读取的元素。 ofstream, 类似 ostream, 有一个指针 p ut pointer ，指向写入下一个元素的位置。 fstream, 类似

Maybe a dummy question, but I need a clear answer to it. Is there any difference at all in the return of any of those functions int FileExists(const std::string& filename) { ifstream file(filename.c_str()); return !!file; } int FileExists(const std::string& filename) { ifstream file(filename.c_str()); return file.is_open(); } So in other words, my question is: does casting the fstream to bool give exactly the same result as fstream::is_open()? No. is_open checks only whether there is an associated file, while a cast to bool also checks whether the file is ready for I/O operations (e.g. the

Java中的IO Java中的IO包含流（Stream）、文件（File）的IO，所有IO类都定义在java.io包中。 一、控制台 IO 1、输入 　　Java的控制台输入由System.in完成。为了获取控制台的输入，可以把System.in封装在一个BufferedReader对象进行操作。样例： 　　　　 BufferedReader bReader = new BufferedReader(new InputeStreamReader(System.in)); 　　然后对bReader对象进行操作。 　　1) bReader.read()： 　　　　从控制台读取一个字符并按照int返回。流读取结束时时候返回-1，并抛出一个IOException。read()函数定义如下： 　　　 　 int read( ) throws IOException 　　2) br.readline() 　　　　从控制台读取一行字符串，返回String类型。readline()函数定义如下： 　　　　String readLine( ) throws IOException 　　 样例： 　　　　char c; 　　　　c = (char)br.read()； 　　　　System.out.printfln(c); 　　　　String str; 　　　　str = br.readline()

I'm implementing a program in C++ using ifstream that must seek in large files (~1TB). However, this fails after reading 2GB. Is there a way to get file positions, even for large files? I compile for a 32-bit windows machine. std::ifstream f; f.open( filename.c_str(), std::ifstream::in | std::ifstream::binary ); while(true) { std::cout << (uint64_t)(f.tellg()) << std::endl; //read data } Since you are compiling on a 32-bit platform, if you use fstream , you are going to get 32-bits access. To access large files, you need to use a platform dependent solution : for windows, use _lseeki64() for

Here's probably a very noobish question for you: How (if at all possible) can I return an ifstream from a function? Basically, I need to obtain the filename of a database from the user, and if the database with that filename does not exist, then I need to create that file for the user. I know how to do that, but only by asking the user to restart the program after creating the file. I wanted to avoid that inconvenience for the user if possible, but the function below does not compile in gcc: ifstream getFile() { string fileName; cout << "Please enter in the name of the file you'd like to open: