path: root/mandoc.3

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.\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
.\" Copyright (c) 2010 Ingo Schwarze <schwarze@openbsd.org>
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.Dd $Mdocdate$
.Dt MANDOC 3
.Os
.Sh NAME
.Nm mandoc ,
.Nm man_meta ,
.Nm man_node ,
.Nm mdoc_meta ,
.Nm mdoc_node ,
.Nm mparse_alloc ,
.Nm mparse_free ,
.Nm mparse_readfd ,
.Nm mparse_reset ,
.Nm mparse_result
.Nd mandoc macro compiler library
.Sh SYNOPSIS
.In man.h
.In mdoc.h
.In mandoc.h
.Ft "const struct man_meta *"
.Fo man_meta
.Fa "const struct man *man"
.Fc
.Ft "const struct man_node *"
.Fo man_node
.Fa "const struct man *man"
.Fc
.Ft "const struct mdoc_meta *"
.Fo mdoc_meta
.Fa "const struct mdoc *mdoc"
.Fc
.Ft "const struct mdoc_node *"
.Fo mdoc_node
.Fa "const struct mdoc *mdoc"
.Fc
.Ft void
.Fo mparse_alloc
.Fa "enum mparset type"
.Fa "enum mandoclevel wlevel"
.Fa "mandocmsg msg"
.Fa "void *msgarg"
.Fc
.Ft void
.Fo mparse_free
.Fa "struct mparse *parse"
.Fc
.Ft "enum mandoclevel"
.Fo mparse_readfd
.Fa "struct mparse *parse"
.Fa "int fd"
.Fa "const char *fname"
.Fc
.Ft void
.Fo mparse_reset
.Fa "struct mparse *parse"
.Fc
.Ft void
.Fo mparse_result
.Fa "struct mparse *parse"
.Fa "struct mdoc **mdoc"
.Fa "struct man **man"
.Fc
.Vt extern const char * const * man_macronames;
.Vt extern const char * const * mdoc_argnames;
.Vt extern const char * const * mdoc_macronames;
.Sh DESCRIPTION
The
.Nm mandoc
library parses a
.Ux
manual into an abstract syntax tree (AST).
.Ux
manuals are composed of
.Xr mdoc 7
or
.Xr man 7 ,
and may be mixed with
.Xr roff 7 ,
.Xr tbl 7 ,
and
.Xr eqn 7
invocations.
.Pp
The following describes a general parse sequence:
.Bl -enum
.It
initiate a parsing sequence with
.Fn mparse_alloc ;
.It
parse files or file descriptors with
.Fn mparse_readfd ;
.It
retrieve a parsed syntax tree, if the parse was successful, with
.Fn mparse_result ;
.It
iterate over parse nodes with
.Fn mdoc_node
or
.Fn man_node ;
.It
free all allocated memory with
.Fn mparse_free ,
or invoke
.Fn mparse_reset
and parse new files.
.El
.Sh IMPLEMENTATION NOTES
This section consists of structural documentation for
.Xr mdoc 7
and
.Xr man 7
syntax trees.
.Ss Man Abstract Syntax Tree
This AST is governed by the ontological rules dictated in
.Xr man 7
and derives its terminology accordingly.
.Pp
The AST is composed of
.Vt struct man_node
nodes with element, root and text types as declared by the
.Va type
field.
Each node also provides its parse point (the
.Va line ,
.Va sec ,
and
.Va pos
fields), its position in the tree (the
.Va parent ,
.Va child ,
.Va next
and
.Va prev
fields) and some type-specific data.
.Pp
The tree itself is arranged according to the following normal form,
where capitalised non-terminals represent nodes.
.Pp
.Bl -tag -width "ELEMENTXX" -compact
.It ROOT
\(<- mnode+
.It mnode
\(<- ELEMENT | TEXT | BLOCK
.It BLOCK
\(<- HEAD BODY
.It HEAD
\(<- mnode*
.It BODY
\(<- mnode*
.It ELEMENT
\(<- ELEMENT | TEXT*
.It TEXT
\(<- [[:alpha:]]*
.El
.Pp
The only elements capable of nesting other elements are those with
next-lint scope as documented in
.Xr man 7 .
.Ss Mdoc Abstract Syntax Tree
This AST is governed by the ontological
rules dictated in
.Xr mdoc 7
and derives its terminology accordingly.
.Qq In-line
elements described in
.Xr mdoc 7
are described simply as
.Qq elements .
.Pp
The AST is composed of
.Vt struct mdoc_node
nodes with block, head, body, element, root and text types as declared
by the
.Va type
field.
Each node also provides its parse point (the
.Va line ,
.Va sec ,
and
.Va pos
fields), its position in the tree (the
.Va parent ,
.Va child ,
.Va nchild ,
.Va next
and
.Va prev
fields) and some type-specific data, in particular, for nodes generated
from macros, the generating macro in the
.Va tok
field.
.Pp
The tree itself is arranged according to the following normal form,
where capitalised non-terminals represent nodes.
.Pp
.Bl -tag -width "ELEMENTXX" -compact
.It ROOT
\(<- mnode+
.It mnode
\(<- BLOCK | ELEMENT | TEXT
.It BLOCK
\(<- HEAD [TEXT] (BODY [TEXT])+ [TAIL [TEXT]]
.It ELEMENT
\(<- TEXT*
.It HEAD
\(<- mnode*
.It BODY
\(<- mnode* [ENDBODY mnode*]
.It TAIL
\(<- mnode*
.It TEXT
\(<- [[:printable:],0x1e]*
.El
.Pp
Of note are the TEXT nodes following the HEAD, BODY and TAIL nodes of
the BLOCK production: these refer to punctuation marks.
Furthermore, although a TEXT node will generally have a non-zero-length
string, in the specific case of
.Sq \&.Bd \-literal ,
an empty line will produce a zero-length string.
Multiple body parts are only found in invocations of
.Sq \&Bl \-column ,
where a new body introduces a new phrase.
.Pp
The
.Xr mdoc 7
syntax tree accomodates for broken block structures as well.
The ENDBODY node is available to end the formatting associated
with a given block before the physical end of that block.
It has a non-null
.Va end
field, is of the BODY
.Va type ,
has the same
.Va tok
as the BLOCK it is ending, and has a
.Va pending
field pointing to that BLOCK's BODY node.
It is an indirect child of that BODY node
and has no children of its own.
.Pp
An ENDBODY node is generated when a block ends while one of its child
blocks is still open, like in the following example:
.Bd -literal -offset indent
\&.Ao ao
\&.Bo bo ac
\&.Ac bc
\&.Bc end
.Ed
.Pp
This example results in the following block structure:
.Bd -literal -offset indent
BLOCK Ao
    HEAD Ao
    BODY Ao
        TEXT ao
        BLOCK Bo, pending -> Ao
            HEAD Bo
            BODY Bo
                TEXT bo
                TEXT ac
                ENDBODY Ao, pending -> Ao
                TEXT bc
TEXT end
.Ed
.Pp
Here, the formatting of the
.Sq \&Ao
block extends from TEXT ao to TEXT ac,
while the formatting of the
.Sq \&Bo
block extends from TEXT bo to TEXT bc.
It renders as follows in
.Fl T Ns Cm ascii
mode:
.Pp
.Dl <ao [bo ac> bc] end
.Pp
Support for badly-nested blocks is only provided for backward
compatibility with some older
.Xr mdoc 7
implementations.
Using badly-nested blocks is
.Em strongly discouraged ;
for example, the
.Fl T Ns Cm html
and
.Fl T Ns Cm xhtml
front-ends to
.Xr mandoc 1
are unable to render them in any meaningful way.
Furthermore, behaviour when encountering badly-nested blocks is not
consistent across troff implementations, especially when using  multiple
levels of badly-nested blocks.
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr eqn 7 ,
.Xr man 7 ,
.Xr mdoc 7 ,
.Xr roff 7 ,
.Xr tbl 7
.Sh AUTHORS
The
.Nm
library was written by
.An Kristaps Dzonsons Aq kristaps@bsd.lv .