.\"	$Id: mdoc.3,v 1.33 2009/07/20 13:45:11 kristaps Exp $
.\"
.\" Copyright (c) 2009 Kristaps Dzonsons <kristaps@kth.se>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: July 20 2009 $
.Dt MDOC 3
.Os
.\" SECTION
.Sh NAME
.Nm mdoc_alloc ,
.Nm mdoc_parseln ,
.Nm mdoc_endparse ,
.Nm mdoc_node ,
.Nm mdoc_meta ,
.Nm mdoc_free ,
.Nm mdoc_reset
.Nd mdoc macro compiler library
.\" SECTION
.Sh SYNOPSIS
.Fd #include <mdoc.h>
.Vt extern const char * const * mdoc_macronames;
.Vt extern const char * const * mdoc_argnames;
.Ft "struct mdoc *"
.Fn mdoc_alloc "void *data" "int pflags" "const struct mdoc_cb *cb"
.Ft int
.Fn mdoc_reset "struct mdoc *mdoc"
.Ft void
.Fn mdoc_free "struct mdoc *mdoc"
.Ft int
.Fn mdoc_parseln "struct mdoc *mdoc" "int line" "char *buf"
.Ft "const struct mdoc_node *"
.Fn mdoc_node "const struct mdoc *mdoc"
.Ft "const struct mdoc_meta *"
.Fn mdoc_meta "const struct mdoc *mdoc"
.Ft int
.Fn mdoc_endparse "struct mdoc *mdoc"
.\" SECTION
.Sh DESCRIPTION
The
.Nm mdoc
library parses lines of
.Xr mdoc 7
input (and
.Em only
mdoc) into an abstract syntax tree (AST).
.\" PARAGRAPH
.Pp
In general, applications initiate a parsing sequence with
.Fn mdoc_alloc ,
parse each line in a document with
.Fn mdoc_parseln ,
close the parsing session with
.Fn mdoc_endparse ,
operate over the syntax tree returned by
.Fn mdoc_node
and
.Fn mdoc_meta ,
then free all allocated memory with
.Fn mdoc_free .
The
.Fn mdoc_reset
function may be used in order to reset the parser for another input
sequence.  See the
.Sx EXAMPLES
section for a full example.
.\" PARAGRAPH
.Pp
This section further defines the
.Sx Types ,
.Sx Functions
and
.Sx Variables
available to programmers.  Following that, the
.Sx Abstract Syntax Tree
section documents the output tree.
.\" SUBSECTION
.Ss Types
Both functions (see
.Sx Functions )
and variables (see
.Sx Variables )
may use the following types:
.Bl -ohang -offset "XXXX"
.\" LIST-ITEM
.It Vt struct mdoc
An opaque type defined in
.Pa mdoc.c .
Its values are only used privately within the library.
.\" LIST-ITEM
.It Vt struct mdoc_cb
A set of message callbacks defined in
.Pa mdoc.h .
.\" LIST-ITEM
.It Vt struct mdoc_node
A parsed node.  Defined in
.Pa mdoc.h .
See
.Sx Abstract Syntax Tree
for details.
.El
.\" SUBSECTION
.Ss Functions
Function descriptions follow:
.Bl -ohang -offset "XXXX"
.\" LIST-ITEM
.It Fn mdoc_alloc
Allocates a parsing structure.  The
.Fa data
pointer is passed to callbacks in
.Fa cb ,
which are documented further in the header file.
The
.Fa pflags
arguments are defined in
.Pa mdoc.h .
Returns NULL on failure.  If non-NULL, the pointer must be freed with
.Fn mdoc_free .
.\" LIST-ITEM
.It Fn mdoc_reset
Reset the parser for another parse routine.  After its use,
.Fn mdoc_parseln
behaves as if invoked for the first time.  If it returns 0, memory could
not be allocated.
.\" LIST-ITEM
.It Fn mdoc_free
Free all resources of a parser.  The pointer is no longer valid after
invocation.
.\" LIST-ITEM
.It Fn mdoc_parseln
Parse a nil-terminated line of input.  This line should not contain the
trailing newline.  Returns 0 on failure, 1 on success.  The input buffer
.Fa buf
is modified by this function.
.\" LIST-ITEM
.It Fn mdoc_endparse
Signals that the parse is complete.  Note that if
.Fn mdoc_endparse
is called subsequent to
.Fn mdoc_node ,
the resulting tree is incomplete.  Returns 0 on failure, 1 on success.
.\" LIST-ITEM
.It Fn mdoc_node
Returns the first node of the parse.  Note that if
.Fn mdoc_parseln
or
.Fn mdoc_endparse
return 0, the tree will be incomplete.
.It Fn mdoc_meta
Returns the document's parsed meta-data.  If this information has not
yet been supplied or
.Fn mdoc_parseln
or
.Fn mdoc_endparse
return 0, the data will be incomplete.
.El
.\" SUBSECTION
.Ss Variables
The following variables are also defined:
.Bl -ohang -offset "XXXX"
.\" LIST-ITEM
.It Va mdoc_macronames
An array of string-ified token names.
.\" LIST-ITEM
.It Va mdoc_argnames
An array of string-ified token argument names.
.El
.\" SUBSECTION
.Ss Abstract Syntax Tree
The
.Nm
functions produce an abstract syntax tree (AST) describing input in a
regular form.  It may be reviewed at any time with
.Fn mdoc_nodes ;
however, if called before
.Fn mdoc_endparse ,
or after
.Fn mdoc_endparse
or
.Fn mdoc_parseln
fail, it may be incomplete.
.\" PARAGRAPH
.Pp
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 .
.\" PARAGRAPH
.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 next
and
.Va prev
fields) and some type-specific data.
.\" PARAGRAPH
.Pp
The tree itself is arranged according to the following normal form,
where capitalised non-terminals represent nodes.
.Pp
.Bl -tag -width "ELEMENTXX" -compact -offset "XXXX"
.\" LIST-ITEM
.It ROOT
\(<- mnode+
.It mnode
\(<- BLOCK | ELEMENT | TEXT
.It BLOCK
\(<- (HEAD [TEXT])+ [BODY [TEXT]] [TAIL [TEXT]]
.It BLOCK
\(<- BODY [TEXT] [TAIL [TEXT]]
.It ELEMENT
\(<- TEXT*
.It HEAD
\(<- mnode+
.It BODY
\(<- mnode+
.It TAIL
\(<- mnode+
.It TEXT
\(<- [[:alpha:]]*
.El
.\" PARAGRAPH
.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.
.\" SECTION
.Sh EXAMPLES
The following example reads lines from stdin and parses them, operating
on the finished parse tree with
.Fn parsed .
Note that, if the last line of the file isn't newline-terminated, this
will truncate the file's last character (see
.Xr fgetln 3 ) .
Further, this example does not error-check nor free memory upon failure.
.Bd -literal -offset "XXXX"
struct mdoc *mdoc;
const struct mdoc_node *node;
char *buf;
size_t len;
int line;

line = 1;
mdoc = mdoc_alloc(NULL, 0, NULL);

while ((buf = fgetln(fp, &len))) {
	buf[len - 1] = '\\0';
	if ( ! mdoc_parseln(mdoc, line, buf))
		errx(1, "mdoc_parseln");
	line++;
}

if ( ! mdoc_endparse(mdoc))
	errx(1, "mdoc_endparse");
if (NULL == (node = mdoc_node(mdoc)))
	errx(1, "mdoc_node");

parsed(mdoc, node);
mdoc_free(mdoc);
.Ed
.\" SECTION
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr mdoc 7
.\" SECTION
.Sh AUTHORS
The
.Nm
utility was written by
.An Kristaps Dzonsons Aq kristaps@kth.se .
.\" SECTION
.Sh CAVEATS
.Bl -dash -compact
.\" LIST-ITEM
.It
The
.Sq \&.Xc
and
.Sq \&.Xo
macros aren't handled when used to span lines for the
.Sq \&.It
macro.
.\" LIST-ITEM
.It
The
.Sq \&.Bsx
macro family doesn't yet understand version arguments.
.\" LIST-ITEM
.It
If not given a value, the \-offset argument to
.Sq \&.Bd
and
.Sq \&.Bl
should be the width of
.Qq <string> ;
instead, a value of
.Li 10n
is provided.
.\" LIST-ITEM
.It
Columns widths in
.Sq \&.Bl \-column
should default to width
.Qq <stringx>
if not included.
.El