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Question pertaining to <xiosbase>

base evil (2)
While using Microsoft Visual Studio 2010, there's a class _Iosb within <xiosbase>

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  // TEMPLATE CLASS _Iosb
template<class _Dummy>
	class _Iosb
	{	// define templatized bitmask/enumerated types, instantiate on demand
public:
	enum _Dummy_enum {_Dummy_enum_val = 1};	// don't ask
	enum _Fmtflags
		{	// constants for formatting options
		_Fmtmask = 0xffff, _Fmtzero = 0};

	static const _Fmtflags skipws = (_Fmtflags)_IOSskipws;
	static const _Fmtflags unitbuf = (_Fmtflags)_IOSunitbuf;
	static const _Fmtflags uppercase = (_Fmtflags)_IOSuppercase;
	static const _Fmtflags showbase = (_Fmtflags)_IOSshowbase;
	static const _Fmtflags showpoint = (_Fmtflags)_IOSshowpoint;
	static const _Fmtflags showpos = (_Fmtflags)_IOSshowpos;
	static const _Fmtflags left = (_Fmtflags)_IOSleft;
	static const _Fmtflags right = (_Fmtflags)_IOSright;
	static const _Fmtflags internal = (_Fmtflags)_IOSinternal;
	static const _Fmtflags dec = (_Fmtflags)_IOSdec;
	static const _Fmtflags oct = (_Fmtflags)_IOSoct;
	static const _Fmtflags hex = (_Fmtflags)_IOShex;
	static const _Fmtflags scientific = (_Fmtflags)_IOSscientific;
	static const _Fmtflags fixed = (_Fmtflags)_IOSfixed;

	static const _Fmtflags hexfloat =
		(_Fmtflags)_IOShexfloat;	// added with TR1/

	static const _Fmtflags boolalpha = (_Fmtflags)_IOSboolalpha;
	static const _Fmtflags _Stdio = (_Fmtflags)_IOS_Stdio;
	static const _Fmtflags adjustfield = (_Fmtflags)(_IOSleft
		| _IOSright | _IOSinternal);
	static const _Fmtflags basefield = (_Fmtflags)(_IOSdec
		| _IOSoct | _IOShex);
	static const _Fmtflags floatfield = (_Fmtflags)(_IOSscientific
		| _IOSfixed);

	enum _Iostate
		{	// constants for stream states
		_Statmask = 0x17};

	static const _Iostate goodbit = (_Iostate)0x0;
	static const _Iostate eofbit = (_Iostate)0x1;
	static const _Iostate failbit = (_Iostate)0x2;
	static const _Iostate badbit = (_Iostate)0x4;
	static const _Iostate _Hardfail = (_Iostate)0x10;

	enum _Openmode
		{	// constants for file opening options
		_Openmask = 0xff};

	static const _Openmode in = (_Openmode)0x01;
	static const _Openmode out = (_Openmode)0x02;
	static const _Openmode ate = (_Openmode)0x04;
	static const _Openmode app = (_Openmode)0x08;
	static const _Openmode trunc = (_Openmode)0x10;
	static const _Openmode _Nocreate = (_Openmode)_IOS_Nocreate;
	static const _Openmode _Noreplace = (_Openmode)_IOS_Noreplace;
	static const _Openmode binary = (_Openmode)_IOSbinary;

	enum _Seekdir
		{	// constants for file positioning options
		_Seekmask = 0x3};

	static const _Seekdir beg = (_Seekdir)0;
	static const _Seekdir cur = (_Seekdir)1;
	static const _Seekdir end = (_Seekdir)2;

	enum
		{	// constant for default file opening protection
		_Openprot = _OPENPROT};
	};


The class itself is pretty easy to understand, but after the class the following lines of code are present-

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template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::skipws;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::unitbuf;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::uppercase;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::showbase;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::showpoint;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::showpos;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::left;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::right;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::internal;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::dec;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::oct;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::hex;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::scientific;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::fixed;

template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags
		_Iosb<_Dummy>::hexfloat;	// added with TR1

template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::boolalpha;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::_Stdio;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::adjustfield;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::basefield;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Fmtflags _Iosb<_Dummy>::floatfield;

template<class _Dummy>
	const typename _Iosb<_Dummy>::_Iostate _Iosb<_Dummy>::goodbit;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Iostate _Iosb<_Dummy>::eofbit;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Iostate _Iosb<_Dummy>::failbit;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Iostate _Iosb<_Dummy>::badbit;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Iostate _Iosb<_Dummy>::_Hardfail;

template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::in;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::out;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::ate;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::app;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::trunc;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::_Nocreate;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::_Noreplace;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Openmode _Iosb<_Dummy>::binary;

template<class _Dummy>
	const typename _Iosb<_Dummy>::_Seekdir _Iosb<_Dummy>::beg;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Seekdir _Iosb<_Dummy>::cur;
template<class _Dummy>
	const typename _Iosb<_Dummy>::_Seekdir _Iosb<_Dummy>::end;


What do these lines of code do?

P.S. - I am pretty new to programming and this forum, so if this topic is in the wrong subforum(?) please forgive me.

Thanks,
base evil.
Last edited on
MiiNiPaa (8886)
Judging from underscore followed by capital letter, this is internal class used by implementation and does not intendet to be used by end-user. Looks like it is defines flags you usually access as ios::in, ios::out, ios::ate and others.
base evil (2)
Sorry, I did not word my question properly-

Revised question-

Isn't the definition in the class?(See the first block of code.)

Correct me if I am wrong but isn't the first block Creating the flags?

Then the second block is referring to them, with their type ("_Iosb<_Dummy>") in front? (const typename className::Enum1 className::ObjectWithTypeEnum1;)

The last part of the line "className::ObjectWithTypeEnum1" is referring to the flags created in the class.


As far as I know you don't refer to objects with their type in front of them.
Last edited on
andywestken (4094)
Edit: On re-reading, the post I thought might be interesting (now below), I'm not so sure it's interesting.

- The static const values are being declared and initialized inside the class, but not defined.

- The lines after the class are then defining them but not re-initializing them.

And all these members are enum value (i.e. some sort of integer, depending on what the compiler choses to use.)

Andy

This post might be of interest: Not so interesting post

static variable in the class declaration or definition?
http://stackoverflow.com/questions/11178434/static-variable-in-the-class-declaration-or-definition
Last edited on
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