rdbuf() in c++
The C++ member function rdbuf() provides a pointer to the stream buffer object connected to the input/output stream object. The stream buffer used by the stream object for input/output operations can be retrieved or modified using this method.
Syntax:
streambuf* rdbuf() const; //to obtain or make use of a pointer to the stream buffer
streambuf* rdbuf (streambuf* sb); //To set or modify the object referenced to by sb as the stream buffer, the function immediately sets the bad bit error status flags if sb is a null pointer.
sb-stream buffer
Return values:
- A reference to the filebuf object connected to the stream.
- Even if no file is linked with the buffer, this reference is never NULL. It is a pointer to the private filebuf object.
Let us consider simple program:
#include <iostream>
#include <fstream>
using namespace std;
int main () {
//streambuf pointer
streambuf *psbuf, *backup;
ofstream filestr;
//opening tutorial.txt file
filestr.open ("tutorial.txt");
backup=cout.rdbuf();
psbuf = filestr.rdbuf();
cout.rdbuf(psbuf);
cout << "This is written to the file";
cout.rdbuf(backup);
filestr.close();
return 0;
}
Benefits of rdbuf() in c++:
The C++ rdbuf() method offers several advantages and use cases. Some of the main advantages of rdbuf() are listed below:
- Duplicating stream: Using the rdbuf() function, you can copy the stream buffer from one stream object to another. Managing numerous streams with the same input or output source makes it possible to build many stream objects that share the same underlying stream buffer.
- Low-Level I/O Manipulation: The stream buffer can be accessed at a lower level using the rdbuf() function, allowing you to alter the data or carry out low-level I/O operations directly. When you need precise control over the input/output process or you need to communicate with platform-specific capabilities or other libraries, this can be helpful.
- Stream Redirection: Using rdbuf(), you can reroute a stream object's input/output actions to another stream buffer. This can come in handy when you wish to modify the output or input source, such as reading input from a memory buffer or network socket instead of the standard output stream (cout).
- Customization of Stream Operations: You can alter how input/output stream operations behave by using rdbuf() to access the underlying stream buffer. This enables you to add specialized functionality, such as adjusting the buffering strategy, altering the encoding or formatting, or enhancing the capability of the stream operations.
- Using Custom Stream Buffers in conjunction: You can incorporate unique stream buffer implementations into the fundamental stream infrastructure by acquiring a pointer to the stream buffer using rdbuf(). This allows you to develop unique stream buffer classes that offer specialized functionality or incorporate with external systems or data sources.
By enabling direct access to the fundamental stream buffer, the C++ rdbuf() method offers flexibility and control over the input/output processes. It is a potent tool for complex input/output handling and customization in C++ applications since it allows modification, redirection, and integration with other parts of stream processing.
Important:
- A filebufobject is internally created (or given) when an ifstream object is created. Ifstream looks for the required data in the buffer (using the internal filebuf object) when it is requested for the subsequent bytes. If some of the requested data is not already in the buffer, it is read (again by the filebuf object) into the buffer from the hard drive.
- This enables abstraction and accelerates file operations. A pointer to this internal filebuf object is returned when the function "istream.rdbuf();" is called.
- Not all of the file's contents are necessarily included in the filebuf object that was returned. Almost always, it will only include some things.
- In most situations, it is preferable to let ifstream and ofstream handle the process of reading from and saving to files, respectively. Only in extreme resource-constrained circumstances might it be required to implement their functionality personally.