streambuf::pubseekoff


public member function
streampos pubseekoff ( streamoff off, ios_base::seekdir way, ios_base::openmode which = ios_base::in | ios_base::out );

Set internal position pointer to relative position

Calls protected virtual member seekoff, which sets a new position value for one or both of the internal position pointers.

The parameter which determines which of the position pointers is affected: either the get pointer gptr or the put pointer pptr, or both.

Parameters

off
Offset value. This is relative to the way parameter.
It is a value of type streamoff, which can be implicitly constructed from an integral value.
way
Object of type ios_base::seekdir. It may take any of the following constant values:
valueoffset is relative to...
ios_base::begbeginning of the stream buffer
ios_base::curcurrent position in the stream buffer
ios_base::endend of the stream buffer
which
Determines which of the internal position pointers shall be modified: the input pointer, the output pointer, or both. It is an object of type ios_base::openmode that for this function may take any combination of the following significant constant values:
valueposition pointer affected
ios_base::inModify get pointer position
ios_base::outModify put pointer position


Return Value

The new position value of the modified position pointer.

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
 
// get file size using pubseekoff
#include <iostream>
#include <fstream>
using namespace std;

int main () {

  long size;
  filebuf* pbuf;

  fstream filestr ("test.txt");
  pbuf = filestr.rdbuf();
  size = pbuf->pubseekoff(0,ios_base::end);
  filestr.close();

  cout << "size of file is " << size << endl;

  return 0;
}


This program prints out the size of file test.txt using the value returned by pubseekoff when it repositions the position pointer to the end of the file buffer.

Basic template member declaration

( basic_streambuf<charT,traits> )
1
2
3
 
typedef traits::pos_type pos_type;
typedef traits::off_type off_type;
pos_type pubseekoff (off_type off, ios_base::seekdir way, ios_base which = ios_base::in | ios_base::out );


See also

streambuf::pubseekpos Set internal position pointer to absolute position (public member function)
streambuf::seekoff Set internal position pointer to relative position (virtual protected member function)