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source: vbox/trunk/src/libs/libxml2-2.13.2/os400/iconv/README.iconv@ 105448

Last change on this file since 105448 was 105420, checked in by vboxsync, 5 months ago

libxml2-2.12.6: Applied and adjusted our libxml2 changes to 2.12.6. bugref:10730

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1IBM OS/400 implements iconv in an odd way:
2- Type iconv_t is a structure: therefore objects of this type cannot be
3 compared to (iconv_t) -1.
4- Supported character sets names are all of the form IBMCCSIDccsid..., where
5 ccsid is a decimal 5-digit integer identifying an IBM coded character set.
6 In addition, character set names have to be given in EBCDIC.
7 Standard character set names like "UTF-8" are NOT recognized.
8- The prototype of iconv_open() does not declare parameters as const, although
9 they are not altered.
10
11 Since libiconv does not support EBCDIC, use of this package here as a
12replacement is not a solution.
13
14 For these reasons, the code in this directory implements a wrapper to the
15OS/400 iconv implementation. The wrapper performs the following transformations:
16- Type iconv_t is an pointer. Although OS/400 pointers are odd, comparing
17 with (iconv_t) -1 is OK.
18- All IANA character set names are recognized in a coding- and case-insensitive
19 way, providing an equivalent CCSID exists. see
20 http://www.iana.org/assignments/character-sets/character-sets.xhtml
21- All CCSIDs from the association file can be expressed as IBMCCSIDxxxxx where
22 xxxxx is the 5 digit CCSID; no null terminator is required. Alternate codes
23 are of the form ibm-xxx (null-terminated), where xxx is the integer CCSID with
24 leading zeroes stripped.
25- If a IANA BIBenum is defined for a CCSID, the name iana-xxx can be used,
26 where xxx is the integer MIBenum without leading zeroes.
27- In addition, some aliases are also taken from the association file. Examples
28 are: ASCII, EBCDIC, UTF8.
29- Prototype of iconv_open() has const parameters.
30- Character code names can be given in any code.
31
32Character set names to CCSID conversion.
33- http://www.iana.org/assignments/character-sets/character-sets.xhtml provides
34 all IANA registered character set names and aliases associated with a
35 MIBenum, that is a unique character set identifier.
36- A hand-maintained file ccsid_mibenum.xml associates IBM CCSIDs to
37 IANA MBenums.
38- An OS/400 C program (in subdirectory bldcsndfa) generates a deterministic
39 finite automaton from the files mentioned above into a C file for all
40 possible character set name and associating each of them with its
41 corresponding CCSID. This program can only be run on OS/400 since it uses
42 the native iconv support for EBCDIC.
43- Since these operations are tedious and the table generation needs bootstraping
44 with libxml2, the generated automaton is stored within sources and need not
45 be rebuilt at each compilation. However, source is provided here to allow
46 new table generation with conversion tables that were not available at the
47 time of original generation.
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