.\"	$Id: mchars_alloc.3,v 1.4 2016/07/07 19:19:01 schwarze Exp $
.\"
.\" Copyright (c) 2014 Ingo Schwarze <schwarze@openbsd.org>
.\"
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.Dd $Mdocdate: July 7 2016 $
.Dt MCHARS_ALLOC 3
.Os
.Sh NAME
.Nm mchars_alloc ,
.Nm mchars_free ,
.Nm mchars_num2char ,
.Nm mchars_num2uc ,
.Nm mchars_spec2cp ,
.Nm mchars_spec2str ,
.Nm mchars_uc2str
.Nd character table for mandoc
.Sh SYNOPSIS
.In sys/types.h
.In mandoc.h
.Ft void
.Fn mchars_alloc void
.Ft void
.Fn mchars_free void
.Ft char
.Fo mchars_num2char
.Fa "const char *decimal"
.Fa "size_t sz"
.Fc
.Ft int
.Fo mchars_num2uc
.Fa "const char *hexadecimal"
.Fa "size_t sz"
.Fc
.Ft int
.Fo mchars_spec2cp
.Fa "const char *name"
.Fa "size_t sz"
.Fc
.Ft "const char *"
.Fo mchars_spec2str
.Fa "const char *name"
.Fa "size_t sz"
.Fa "size_t *rsz"
.Fc
.Ft "const char *"
.Fn mchars_uc2str "int codepoint"
.Sh DESCRIPTION
These functions translate Unicode character numbers and
.Xr roff 7
character names into glyphs.
See
.Xr mandoc_char 7
for a list of
.Xr roff 7
special characters.
These functions are intended for external use by programs formatting
.Xr mdoc 7
and
.Xr man 7
pages for output, for example the
.Xr mandoc 1
output formatter modules and
.Xr makewhatis 8 .
The
.Fa decimal ,
.Fa hexadecimal ,
.Fa name ,
and
.Fa size
input arguments are usually obtained from the
.Xr mandoc_escape 3
parser function.
.Pp
The function
.Fn mchars_num2char
converts a
.Fa decimal
string representation of a character number consisting of
.Fa sz
digits into a printable ASCII character.
If the input string is non-numeric or does not represent a printable
ASCII character, the NUL character
.Pq Sq \e0
is returned.
For example, the
.Xr mandoc 1
.Fl Tascii ,
.Fl Tutf8 ,
and
.Fl Thtml
output modules use this function to render
.Xr roff 7
.Ic \eN
escape sequences.
.Pp
The function
.Fn mchars_num2uc
converts a
.Fa hexadecimal
string representation of a Unicode codepoint consisting of
.Fa sz
digits into an integer representation.
If the input string is non-numeric or represents an ASCII character,
the NUL character
.Pq Sq \e0
is returned.
For example, the
.Xr mandoc 1
.Fl Tutf8
and
.Fl Thtml
output modules use this function to render
.Xr roff 7
.Ic \e[u Ns Ar XXXX Ns Ic \&]
and
.Ic \eC\(aqu Ns Ar XXXX Ns Ic \(aq
escape sequences.
.Pp
The function
.Fn mchars_alloc
initializes a static
.Vt "struct ohash"
object for subsequent use by the following two lookup functions.
When no longer needed, this object can be destroyed with
.Fn mchars_free .
.Pp
The function
.Fn mchars_spec2cp
looks up a
.Xr roff 7
special character
.Fa name
consisting of
.Fa sz
characters and returns the corresponding Unicode codepoint.
If the
.Ar name
is not recognized, \-1 is returned.
For example, the
.Xr mandoc 1
.Fl Tutf8
and
.Fl Thtml
output modules use this function to render
.Xr roff 7
.Ic \e[ Ns Ar name Ns Ic \&]
and
.Ic \eC\(aq Ns Ar name Ns Ic \(aq
escape sequences.
.Pp
The function
.Fn mchars_spec2str
looks up a
.Xr roff 7
special character
.Fa name
consisting of
.Fa sz
characters and returns an ASCII string representation.
The length of the representation is returned in
.Fa rsz .
In many cases, the meaning of such ASCII representations
is not quite obvious, so using
.Xr roff 7
special characters in documents intended for ASCII rendering
is usually a bad idea.
If the
.Ar name
is not recognized,
.Dv NULL
is returned.
For example,
.Xr makewhatis 8
and the
.Xr mandoc 1
.Fl Tascii
output module use this function to render
.Xr roff 7
.Ic \e[ Ns Ar name Ns Ic \&]
and
.Ic \eC\(aq Ns Ar name Ns Ic \(aq
escape sequences.
.Pp
The function
.Fn mchars_uc2str
performs a reverse lookup of the Unicode
.Fa codepoint
and returns an ASCII string representation, or the string
.Qq <?>
if none is available.
.Sh FILES
These funtions are implemented in the file
.Pa chars.c .
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr mandoc_escape 3 ,
.Xr ohash_init 3 ,
.Xr mandoc_char 7 ,
.Xr roff 7
.Sh HISTORY
These functions and their predecessors have been available since the
following mandoc versions:
.Bl -column "mchars_num2char()" "1.11.3" "chars_num2char()" "1.10.10"
.It Sy function Ta since Ta Sy predecessor Ta since
.It Fn mchars_alloc Ta 1.11.3 Ta Fn ascii2htab Ta 1.5.3
.It Fn mchars_free Ta 1.11.2 Ta Fn asciifree Ta 1.6.0
.It Fn mchars_num2char Ta 1.11.2 Ta Fn chars_num2char Ta 1.10.10
.It Fn mchars_num2uc Ta 1.11.3 Ta \(em Ta \(em
.It Fn mchars_spec2cp Ta 1.11.2 Ta Fn chars_spec2cp Ta 1.10.5
.It Fn mchars_spec2str Ta 1.11.2 Ta Fn a2ascii Ta 1.5.3
.It Fn mchars_uc2str Ta 1.13.2 Ta \(em Ta \(em
.El
.Sh AUTHORS
.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv
.An Ingo Schwarze Aq Mt schwarze@openbsd.org