ISO C++
ctype

# ctype

## Implementation

### Specializations

For the required specialization codecvt<wchar_t, char, mbstate_t> , conversions are made between the internal character set (always UCS4 on GNU/Linux) and whatever the currently selected locale for the LC_CTYPE category implements.

The two required specializations are implemented as follows:

`ctype<char>`

This is simple specialization. Implementing this was a piece of cake.

`ctype<wchar_t>`

This specialization, by specifying all the template parameters, pretty much ties the hands of implementors. As such, the implementation is straightforward, involving mcsrtombs for the conversions between char to wchar_t and wcsrtombs for conversions between wchar_t and char.

Neither of these two required specializations deals with Unicode characters.

## Future

- How to deal with the global locale issue?

- How to deal with different types than char, wchar_t?

- Overlap between codecvt/ctype: narrow/widen

- Mask typedef in codecvt_base, argument types in codecvt. what is know about this type?

- Why mask* argument in codecvt?

- Can this be made (more) generic? is there a simple way to straighten out the configure-time mess that is a by-product of this class?

- Get the ctype<wchar_t>::mask stuff under control. Need to make some kind of static table, and not do lookup every time somebody hits the do_is... functions. Too bad we can't just redefine mask for ctype<wchar_t>

- Rename abstract base class. See if just smash-overriding is a better approach. Clarify, add sanity to naming.

## Bibliography

### The GNU C Library

McGrath
Roland
Drepper
Ulrich
2007
FSF
Chapters 6 Character Set Handling and 7 Locales and Internationalization

### Correspondence

Drepper
Ulrich
2002

### ISO/IEC 14882:1998 Programming languages - C++

1998
ISO

### ISO/IEC 9899:1999 Programming languages - C

1999
ISO

### System Interface Definitions, Issue 6 (IEEE Std. 1003.1-200x)

1999
The Open Group/The Institute of Electrical and Electronics Engineers, Inc.

### The C++ Programming Language, Special Edition

Stroustrup
Bjarne
2000
Addison Wesley, Inc.
Appendix D
Addison Wesley

### Standard C++ IOStreams and Locales

Advanced Programmer's Guide and Reference
Langer
Angelika
Kreft
Klaus
2000
Addison Wesley Longman, Inc.
Addison Wesley Longman