Oracle 5.0, Reference Manual

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Adding a Character Set
806
a suffix of
general_ci
(general, case insensitive). It is possible for the binary collation to be the
default collation, but usually they are different. The default collation should have a
primary
flag.
The binary collation should have a
binary
flag.
You must assign a unique ID number to each collation, chosen from the range 1 to 254. To find the
maximum of the currently used collation IDs, use this query:
SELECT MAX(ID) FROM INFORMATION_SCHEMA.COLLATIONS;
2. This step depends on whether you are adding a simple or complex character set. A simple
character set requires only a configuration file, whereas a complex character set requires C source
file that defines collation functions, multi-byte functions, or both.
For a simple character set, create a configuration file,
MYSET.xml
, that describes the character
set properties. Create this file in the
sql/share/charsets
directory. You can use a copy of
latin1.xml
as the basis for this file. The syntax for the file is very simple:
• Comments are written as ordinary XML comments (
<!-- text -->
).
• Words within
<map>
array elements are separated by arbitrary amounts of whitespace.
• Each word within
<map>
array elements must be a number in hexadecimal format.
• The
<map>
array element for the
<ctype>
element has 257 words. The other
<map>
array
elements after that have 256 words. See Section 10.3.1, “Character Definition Arrays” .
• For each collation listed in the
<charset>
element for the character set in
Index.xml
,
MYSET.xml
must contain a
<collation>
element that defines the character ordering.
For a complex character set, create a C source file that describes the character set properties and
defines the support routines necessary to properly perform operations on the character set:
• Create the file
ctype-MYSET.c
in the
strings
directory. Look at one of the existing
ctype-
*.c
files (such as
ctype-big5.c
) to see what needs to be defined. The arrays in your file must
have names like
ctype_MYSET
,
to_lower_MYSET
, and so on. These correspond to the arrays
for a simple character set. See Section 10.3.1, “Character Definition Arrays” .
• For each
<collation>
element listed in the
<charset>
element for the character set in
Index.xml
, the
ctype-MYSET.c
file must provide an implementation of the collation.
• If the character set requires string collating functions, see Section 10.3.2, “String Collating
Support for Complex Character Sets” .
• If the character set requires multi-byte character support, see Section 10.3.3, “Multi-Byte
Character Support for Complex Character Sets” .
3. Modify the configuration information. Use the existing configuration information as a guide to adding
information for
MYSYS
. The example here assumes that the character set has default and binary
collations, but more lines are needed if
MYSET
has additional collations.
a. Edit
mysys/charset-def.c
, and “register” the collations for the new character set.
Add these lines to the “declaration” section:
#ifdef HAVE_CHARSET_ MYSET
extern CHARSET_INFO my_charset_ MYSET _general_ci;
extern CHARSET_INFO my_charset_ MYSET _bin;
#endif
Add these lines to the “registration” section:
#ifdef HAVE_CHARSET_ MYSET
add_compiled_collation(&my_charset_ MYSET _general_ci);