Editare

Partajați prin

<ios> typedefs

  • Articol

ios

Supports the ios class from the old iostream library.

typedef basic_ios<char, char_traits<char>> ios;

Remarks

The type is a synonym for class template basic_ios, specialized for elements of type char with default character traits.

streamoff

Supports internal operations.

#ifdef _WIN64
    typedef __int64 streamoff;
#else
    typedef long streamoff;
#endif

Remarks

The type is a signed integer. It describes an object that can store a byte offset in stream positioning operations. Its representation has at least 32 value bits. It isn't necessarily large enough to represent an arbitrary byte position within a stream. The value streamoff(-1) generally indicates an erroneous offset.

streampos

Holds the current position of the buffer pointer or file pointer.

typedef fpos<mbstate_t> streampos;

Remarks

The type is a synonym for fpos< mbstate_t>.

Example

// ios_streampos.cpp
// compile with: /EHsc
#include <iostream>
#include <fstream>

int main( )
{
   using namespace std;

   ofstream x( "iostream.txt" );
   x << "testing";
   streampos y = x.tellp( );
   cout << streamoff( y ) << '\n';
}

7

streamsize

Denotes the size of the stream.

#ifdef _WIN64
    typedef __int64 streamsize;
#else
    typedef int streamsize;
#endif

Remarks

The type is a signed integer that describes an object that can store a count of the number of elements involved in various stream operations. Its representation has at least 16 bits. It isn't necessarily large enough to represent an arbitrary byte position within a stream.

Example

After compiling and running the following program, look at the file test.txt to see the effect of setting streamsize.

// ios_streamsize.cpp
// compile with: /EHsc
#include <iostream>
#include <fstream>

int main( )
{
   using namespace std;
   char a[16] = "any such text";
   ofstream x( "test.txt" );
   streamsize y = 6;
   x.write( a, y );
}

wios

Supports the wios class from the old iostream library.

typedef basic_ios<wchar_t, char_traits<wchar_t>> wios;

Remarks

The type is a synonym for class template basic_ios, specialized for elements of type wchar_t with default character traits.

wstreampos

Holds the current position of the buffer pointer or file pointer.

typedef fpos<mbstate_t> wstreampos;

Remarks

The type is a synonym for fpos< mbstate_t>.

Example

// ios_wstreampos.cpp
// compile with: /EHsc
#include <iostream>
#include <fstream>

int main( )
{
   using namespace std;
   wofstream xw( "wiostream.txt" );
   xw << L"testing";
   wstreampos y = xw.tellp( );
   cout << streamoff( y ) << '\n';
}

7