Character Set Names
===================

A typical entry from the IANA character set listing at 
http://www.iana.org/assignments/character-sets is as follows:

Name: ANSI_X3.4-1968                                   [RFC1345,KXS2]
MIBenum: 3
Source: ECMA registry
Alias: iso-ir-6
Alias: ANSI_X3.4-1986
Alias: ISO_646.irv:1991
Alias: ASCII
Alias: ISO646-US
Alias: US-ASCII (preferred MIME name)
Alias: us
Alias: IBM367
Alias: cp367
Alias: csASCII

Based on this, three things are needed:
- A set of valid C++ identifiers that can be used in the charset_t enumeration.
- An ASCII string that should be output when the character set's name must be printed.
- A set of ASCII strings that should be recognised when the character set's name is 
  input.

The following rules are applied:


charset_t enumeration members
-----------------------------

The Name: and all Alias: lines are used.  All punctuation characters are replaced by 
underscores; all adjacent punctuation characters are compressed to one, and any trailing 
punctuation characters are trimmed (?).  Letters are mapped to lower case.  This results 
for the example above in the following:

ansi_x3_4_1968
iso_ir_6
ansi_x3_4_1986
iso_646_irv_1991
ascii
iso646_us
us_ascii
us
ibm367
cp367
csascii

Variants are then produced with underscores omitted [but not underscores that separate 
numbers on both sides]:

ansi_x3_4_1968	ansix3_4_1968
iso_ir_6	iso_ir6	isoir_6	isoir6
ansi_x3_4_1986	ansix3_4_1986
iso_646_irv_1991	iso_646_irv1991	iso_646irv_1991	iso_646irv1991
	iso646_irv_1991	iso646_irv1991	iso646irv_1991	isi646irv1991
ascii
iso646_us	iso646us
us_ascii	usascii
us
ibm367
cp367
csascii


ASCII Output
------------

Two functions convert to ASCII: charset_name uses the string from the Name: line in 
the description (ANSI_X3.4-1968 in this case) and charset_mime_name uses any "preferred 
MIME name" that is specified (US-ASCII in this case).


ASCII Input
-----------

The name is looked up in a similar table to the one used for enumerations above; the 
lookup is insensitive to case and to punctuation.