Each simple character set has a configuration file located in
the sql/share/charsets
directory. The file
is named
for
MySQL 4.1 and
MYSET
.xml
for
MySQL 4.0 or older.
MYSET
.conf
For MySQL 4.1,
files
use MYSET
.xml<map>
array elements to list
character set properties. <map>
elements appear within these elements:
<ctype>
defines attributes for each
character
<lower>
and
<upper>
list the lowercase and
uppercase characters
<unicode>
maps 8-bit character
values to Unicode values
<collation>
elements indicate
character ordering for comparisons and sorts, one element
per collation (binary collations need no
<map>
element because the character
codes themselves provide the ordering)
For MySQL 4.0 or older,
files
list character set properties using these arrays:
MYSET
.conf
ctype[]
defines attributes for each
character
to_lower[]
and
to_upper[]
list the lowercase and
uppercase characters
sort_order[]
indicates character ordering
for comparisons and sorts
For a complex character set as implemented in a
ctype-
file in the MYSET
.cstrings
directory, there are
corresponding arrays:
ctype_
,
MYSET
[]to_lower_
,
and so forth. Not every complex character set has all of the
arrays. See the existing MYSET
[]ctype-*.c
files
for examples. For MySQL 4.1, see the
CHARSET_INFO.txt
file in the
strings
directory for additional
information.
The ctype
array is indexed by character value
+ 1 and has 257 elements. This is an old legacy convention for
handling EOF
. The other arrays are indexed by
character value and have 256 elements.
ctype
array elements are bit values. Each
element describes the attributes of a single character in the
character set. Each attribute is associated with a bitmask, as
defined in include/m_ctype.h
:
#define _MY_U 01 /* Upper case */ #define _MY_L 02 /* Lower case */ #define _MY_NMR 04 /* Numeral (digit) */ #define _MY_SPC 010 /* Spacing character */ #define _MY_PNT 020 /* Punctuation */ #define _MY_CTR 040 /* Control character */ #define _MY_B 0100 /* Blank */ #define _MY_X 0200 /* heXadecimal digit */
The ctype
value for a given character should
be the union of the applicable bitmask values that describe the
character. For example, 'A'
is an uppercase
character (_MY_U
) as well as a hexadecimal
digit (_MY_X
), so its
ctype
value should be defined like this:
ctype['A'+1] = _MY_U | _MY_X = 01 | 0200 = 0201
The bitmask values in m_ctype.h
are octal
values, but the elements of the ctype
array
in
(or
MYSET
.xml
)
should be written as hexadecimal values.
MYSET
.conf
The lower
and upper
(or
to_lower
and to_upper
)
arrays hold the lowercase and uppercase characters corresponding
to each member of the character set. For example:
lower['A'] should contain 'a' upper['a'] should contain 'A'
Each collation
(or
sort_order
) array is a map indicating how
characters should be ordered for comparison and sorting
purposes. MySQL sorts characters based on the values of this
information. In some cases, this is the same as the
upper
array, which means that sorting is
case-insensitive. For more complicated sorting rules (for
complex character sets), see the discussion of string collating
in Section 9.4.2, “String Collating Support”.
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