path: root/man.3

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.\"
.\" Copyright (c) 2009 Kristaps Dzonsons <kristaps@kth.se>
.\"
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.Dd $Mdocdate$
.Dt MAN 3
.Os
.\" SECTION
.Sh NAME
.Nm man_alloc ,
.Nm man_parseln ,
.Nm man_endparse ,
.Nm man_node ,
.Nm man_meta ,
.Nm man_free ,
.Nm man_reset
.Nd man macro compiler library
.\" SECTION
.Sh SYNOPSIS
.Fd #include <man.h>
.Vt extern const char * const * man_macronames;
.Ft "struct man *"
.Fn man_alloc "void *data" "int pflags" "const struct man_cb *cb"
.Ft void
.Fn man_reset "struct man *man"
.Ft void
.Fn man_free "struct man *man"
.Ft int
.Fn man_parseln "struct man *man" "int line" "char *buf"
.Ft "const struct man_node *"
.Fn man_node "struct man *man"
.Ft "const struct man_meta *"
.Fn man_meta "struct man *man"
.Ft int
.Fn man_endparse "struct man *man"
.\" SECTION
.Sh DESCRIPTION
The
.Nm man
library parses lines of 
.Xr man 7
input (and
.Em only
man) into an abstract syntax tree (AST).
.\" PARAGRAPH
.Pp
In general, applications initiate a parsing sequence with
.Fn man_alloc ,
parse each line in a document with 
.Fn man_parseln ,
close the parsing session with
.Fn man_endparse ,
operate over the syntax tree returned by
.Fn man_node 
and
.Fn man_meta ,
then free all allocated memory with
.Fn man_free .
The
.Fn man_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 man
An opaque type defined in
.Pa man.c .
Its values are only used privately within the library.
.\" LIST-ITEM
.It Vt struct man_cb
A set of message callbacks defined in
.Pa man.h .
.\" LIST-ITEM
.It Vt struct man_node
A parsed node.  Defined in
.Pa man.h .
See 
.Sx Abstract Syntax Tree
for details.
.El
.\" SUBSECTION
.Ss Functions
Function descriptions follow:
.Bl -ohang -offset "XXXX"
.\" LIST-ITEM
.It Fn man_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 man.h .
Returns NULL on failure.  If non-NULL, the pointer must be freed with
.Fn man_free .
.\" LIST-ITEM
.It Fn man_reset
Reset the parser for another parse routine.  After its use, 
.Fn man_parseln
behaves as if invoked for the first time.
.\" LIST-ITEM
.It Fn man_free
Free all resources of a parser.  The pointer is no longer valid after
invocation.
.\" LIST-ITEM
.It Fn man_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 man_endparse
Signals that the parse is complete.  Note that if 
.Fn man_endparse
is called subsequent to
.Fn man_node ,
the resulting tree is incomplete.  Returns 0 on failure, 1 on success.
.\" LIST-ITEM
.It Fn man_node
Returns the first node of the parse.  Note that if 
.Fn man_parseln
or
.Fn man_endparse
return 0, the tree will be incomplete.
.It Fn man_meta
Returns the document's parsed meta-data.  If this information has not
yet been supplied or 
.Fn man_parseln
or
.Fn man_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 man_macronames
An array of string-ified token 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 man_nodes ;
however, if called before
.Fn man_endparse ,
or after
.Fn man_endparse 
or
.Fn man_parseln
fail, it may be incomplete.  
.\" PARAGRAPH
.Pp
This AST is governed by the ontological
rules dictated in
.Xr man 7
and derives its terminology accordingly.  
.\" PARAGRAPH
.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.
.\" 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
\(<- ELEMENT | TEXT
.It ELEMENT
\(<- ELEMENT | TEXT*
.It TEXT
\(<- [[:alpha:]]*
.El
.\" PARAGRAPH
.Pp
The only elements capable of nesting other elements are those with
next-lint scope as documented in
.Xr man 7 .
.\" 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 man *man;
struct man_node *node;
char *buf;
size_t len;
int line;

line = 1;
man = man_alloc(NULL, 0, NULL);

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

if ( ! man_endparse(man))
	errx(1, "man_endparse");
if (NULL == (node = man_node(man)))
	errx(1, "man_node");

parsed(man, node);
man_free(man);
.Ed
.\" SECTION
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr man 7
.\" SECTION
.Sh AUTHORS
The
.Nm
utility was written by 
.An Kristaps Dzonsons Aq kristaps@kth.se .