Tribblix: manual page: charmap.7

CHARMAP(7) Standards, Environments, and Macros CHARMAP(7)

NAME

charmap - character set description file

DESCRIPTION

A character set description file or charmap defines characteristics
for a coded character set. Other information about the coded
character set may also be in the file. Coded character set character
values are defined using symbolic character names followed by
character encoding values.

The character set description file provides:

o The capability to describe character set attributes (such
as collation order or character classes) independent of
character set encoding, and using only the characters in
the portable character set. This makes it possible to
create generic localedef(1) source files for all codesets
that share the portable character set.

o Standardized symbolic names for all characters in the
portable character set, making it possible to refer to any
such character regardless of encoding.

Symbolic Names

Each symbolic name is included in the file and is mapped to a unique
encoding value (except for those symbolic names that are shown with
identical glyphs). If the control characters commonly associated
with the symbolic names in the following table are supported by the
implementation, the symbolic names and their corresponding encoding
values are included in the file. Some of the encodings associated
with the symbolic names in this table may be the same as characters
in the portable character set table.

+----------------------------------------------+
|<ACK> <DC2> <ENQ> <FS> <IS4> <SOH> |
|<BEL> <DC3> <EOT> <GS> <LF> <STX> |
|<BS> <DC4> <ESC> <HT> <NAK> <SUB> |
|<CAN> <DEL> <ETB> <IS1> <RS> <SYN> |
|<CR> <DLE> <ETX> <IS2> <SI> <US> |
|<DC1> <EM> <FF> <IS3> <SO> <VT> |
+----------------------------------------------+

Declarations

The following declarations can precede the character definitions.
Each must consist of the symbol shown in the following list, starting
in column 1, including the surrounding brackets, followed by one or
more blank characters, followed by the value to be assigned to the
symbol.

<code_set_name>
The name of the coded character set for which the
character set description file is defined.

<mb_cur_max>
The maximum number of bytes in a multi-byte
character. This defaults to 1.

<mb_cur_min>
An unsigned positive integer value that defines
the minimum number of bytes in a character for the
encoded character set.

<escape_char>
The escape character used to indicate that the
characters following will be interpreted in a
special way, as defined later in this section.
This defaults to backslash ('\'), which is the
character glyph used in all the following text and
examples, unless otherwise noted.

<comment_char>
The character that when placed in column 1 of a
charmap line, is used to indicate that the line is
to be ignored. The default character is the number
sign (#).

Format

The character set mapping definitions will be all the lines
immediately following an identifier line containing the string
CHARMAP starting in column 1, and preceding a trailer line containing
the string END CHARMAP starting in column 1. Empty lines and lines
containing a <comment_char> in the first column will be ignored. Each
non-comment line of the character set mapping definition, that is,
between the CHARMAP and END CHARMAP lines of the file), must be in
either of two forms:

"%s %s %s\n",<symbolic-name>,<encoding>,<comments>

or

"%s...%s %s %s\n",<symbolic-name>,<symbolic-name>, <encoding>,\
<comments>

In the first format, the line in the character set mapping definition
defines a single symbolic name and a corresponding encoding. A
character following an escape character is interpreted as itself; for
example, the sequence "<\\\>>" represents the symbolic name "\>"
enclosed between angle brackets.

In the second format, the line in the character set mapping
definition defines a range of one or more symbolic names. In this
form, the symbolic names must consist of zero or more non-numeric
characters, followed by an integer formed by one or more decimal
digits. The characters preceding the integer must be identical in the
two symbolic names, and the integer formed by the digits in the
second symbolic name must be equal to or greater than the integer
formed by the digits in the first name. This is interpreted as a
series of symbolic names formed from the common part and each of the
integers between the first and the second integer, inclusive. As an
example, <j0101>...<j0104> is interpreted as the symbolic names
<j0101>, <j0102>, <j0103>, and <j0104>, in that order.

A character set mapping definition line must exist for all symbolic
names and must define the coded character value that corresponds to
the character glyph indicated in the table, or the coded character
value that corresponds with the control character symbolic name. If
the control characters commonly associated with the symbolic names
are supported by the implementation, the symbolic name and the
corresponding encoding value must be included in the file. Additional
unique symbolic names may be included. A coded character value can be
represented by more than one symbolic name.

The encoding part is expressed as one (for single-byte character
values) or more concatenated decimal, octal or hexadecimal constants
in the following formats:

"%cd%d",<escape_char>,<decimal byte value>

"%cx%x",<escape_char>,<hexadecimal byte value>

"%c%o",<escape_char>,<octal byte value>

Decimal Constants

Decimal constants must be represented by two or three decimal digits,
preceded by the escape character and the lower-case letter d; for
example, \d05, \d97, or \d143. Hexadecimal constants must be
represented by two hexadecimal digits, preceded by the escape
character and the lower-case letter x; for example, \x05, \x61, or
\x8f. Octal constants must be represented by two or three octal
digits, preceded by the escape character; for example, \05, \141, or
\217. In a portable charmap file, each constant must represent an
8-bit byte. Implementations supporting other byte sizes may allow
constants to represent values larger than those that can be
represented in 8-bit bytes, and to allow additional digits in
constants. When constants are concatenated for multi-byte character
values, they must be of the same type, and interpreted in byte order
from first to last with the least significant byte of the multi-byte
character specified by the last constant.

Ranges of Symbolic Names

In lines defining ranges of symbolic names, the encoded value is the
value for the first symbolic name in the range (the symbolic name
preceding the ellipsis). Subsequent symbolic names defined by the
range will have encoding values in increasing order. Bytes are
treated as unsigned octets and carry is propagated between the bytes
as necessary to represent the range. However, because this causes a
null byte in the second or subsequent bytes of a character, such a
declaration should not be specified. For example, the line

<j0101>...<j0104> \d129\d254

is interpreted as:

<j0101> \d129\d254
<j0102> \d129\d255
<j0103> \d130\d00
<j0104> \d130\d01

The expanded declaration of the symbol <j0103> in the above example
is an invalid specification, because it contains a null byte in the
second byte of a character.

The comment is optional.

Width Specification

The following declarations can follow the character set mapping
definitions (after the "END CHARMAP" statement). Each consists of the
keyword shown in the following list, starting in column 1, followed
by the value(s) to be associated to the keyword, as defined below.

WIDTH
A non-negative integer value defining the column
width for the printable character in the coded
character set mapping definitions. Coded character
set character values are defined using symbolic
character names followed by column width values.
Defining a character with more than one WIDTH
produces undefined results. The END WIDTH keyword is
used to terminate the WIDTH definitions. Specifying
the width of a non-printable character in a WIDTH
declaration produces undefined results.

WIDTH_DEFAULT
A non-negative integer value defining the default
column width for any printable character not listed
by one of the WIDTH keywords. If no WIDTH_DEFAULT
keyword is included in the charmap, the default
character width is 1.

Example:

After the "END CHARMAP" statement, a syntax for a width definition
would be:

WIDTH
<A> 1
<B> 1
<C>...<Z> 1
...
<fool>...<foon> 2
...
END WIDTH

In this example, the numerical code point values represented by the
symbols <A> and <B> are assigned a width of 1. The code point values
< C> to <Z> inclusive, that is, <C>, <D>, <E>, and so on, are also
assigned a width of 1. Using <A>...<Z> would have required fewer
lines, but the alternative was shown to demonstrate flexibility. The
keyword WIDTH_DEFAULT could have been added as appropriate.