C++ Binary File I/OContents. C++ file input and output are typically achieved by using an object of. All three classes are defined in < fstream. Throughout this. page, the term "file stream" will be used when referring to features that. Normally, for binary file i/o you do not use the conventional. It can be done. but that is an advanced topic. Basic Model for File I/O. Istream& read (char* s, streamsize n). // read a file into memory #include <iostream> // std. ifstream::binary).In C++, the file stream classes are designed with the idea that a file. For. convenience, the "array" of bytes stored in a file is indexed from zero. Each open file has two "positions" associated with it. The current reading position, which is the index of the next byte that. This is called the "get pointer" since it points.
The current writing position, which is the index of the byte location where. This is called the "put pointer" since. These two file positions are independent, and either one can point anywhere. Getting The Size of a File. The typical way to get the size of a file is to use the C library function. The size of the file in bytes is in. An error occurred. Note that the second parameter to stat is a pointer. It is your. responsibility to create and manage the memory where stat will. The above example shows the use of a local. A file stream object can be opened in one of two ways. First, you can supply. File ("data. bin", ios: :in | ios: :binary). Alternatively, after a file stream object has been declared, you can call. File. my. File. open ("data. Either approach will work with an ifstream, an ofstream. C++ Binary File IO_IT/计算机_专业资料 暂无评价|0人阅读|0次下载 |举报文档 C++ Binary File IO_IT/计算机_专业资料。c++读写二进制文件. Normally, when manipulating text files, one omits the second parameter. However, in order to manipulate binary files. For read/write access to a file, use an fstream. File. my. File. open ("data. Note: If you are a GNU g++ user (version 2. Because of a bug in the GNU libg++ implementation, the flags will not be. If you are working under Unix, omit the i/o mode. MS- DOS, then use an fstream. This note applies to g++ users only. Reading From a File. 今天一个小错误,卡了两个小时也没找出来。 回来又试了一下,原来需要在in_file(fileName, ios::binary)加上后一个参数 一直没想到这个,是因为记的以前有一句话. To read from an fstream or ifstream object, use the read. This method takes two parameters. The read member function extracts a given number of bytes from. It is your responsibility to create and manage the memory where. The bytes that are read and. If an error occurs while reading (for example, if you read off the end. If that occurs, you. Once a stream goes into an error state, all future. File ("data. bin", ios: :in | ios: :binary). File. read (buffer, 1. File) {. // An error occurred! File. gcount() returns the number of bytes read. File. clear() will reset the stream state. File. read (buffer, 1. Same effect as above. Repositioning the "Get" Pointer. To change the position of the "get" pointer (the file reading position). The basic form of this operation takes a single parameter. A streampos is essentially an unsigned long integer value. When calling seekg be careful of the types of your arguments. BLKSIZE 1. 02. 4. File. seekg (blk_number * BLKSIZE); // Error! The problem above is that files can be relatively large, so streampos. But above, if blk_number is above. BLKSIZE. (both ints), on a PC their product can only be 1. To. correct this, ensure constants used in file positioning are long. You can determine the current get pointer position using "my. File. tellg()". a method with no parameters that returns the index of the get pointer on. There is also a variant of seekg that allows you to specify. Writing To a File. To write to an fstream or ofstream object, use the write. This method takes two parameters. The write member function writes a given number of bytes on the. If the put. pointer is current at the end of the file, the file is extended. If the. put pointer points into the middle of the file, characters in the file. The bytes that are written and not interpreted. If an error occurs while writing (for example, if you run out of disk. Such errors are not as. File ("data. bin", ios: :out | ios: :binary). File. write (buffer, 1. Repositioning the "Put" Pointer. To change the position of the "put" pointer (the file reading position). The basic form of this operation takes a single parameter. A streampos is essentially an unsigned long integer value. You can determine the current put pointer position using "my. File. tellp()". a method with no parameters that returns the index of the put pointer on. There is also a variant of seekp that allows you to specify. Reading and Writing Complex Data. Although the read and write methods accept a char*. You can read or write complex data objects. Data {. int key. Data *y = new Data[1. File ("data. bin", ios: :in | ios: :out | ios: :binary). File. seekp (location. File. write ((char*)& x, sizeof (Data)). File. seekg (0). my. File. read ((char*)y, sizeof (Data) * 1. For all file stream objects, use. File. close(). CS2. Wed Jan 2. 8 1. 99.
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