.\"	$Id: mandoc.3,v 1.17 2012/01/13 15:27:14 joerg Exp $
.\"
.\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
.\" Copyright (c) 2010 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" 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: January 13 2012 $
.Dt MANDOC 3
.Os
.Sh NAME
.Nm mandoc ,
.Nm mandoc_escape ,
.Nm man_meta ,
.Nm man_mparse ,
.Nm man_node ,
.Nm mchars_alloc ,
.Nm mchars_free ,
.Nm mchars_num2char ,
.Nm mchars_num2uc ,
.Nm mchars_spec2cp ,
.Nm mchars_spec2str ,
.Nm mdoc_meta ,
.Nm mdoc_node ,
.Nm mparse_alloc ,
.Nm mparse_free ,
.Nm mparse_getkeep ,
.Nm mparse_keep ,
.Nm mparse_readfd ,
.Nm mparse_reset ,
.Nm mparse_result ,
.Nm mparse_strerror ,
.Nm mparse_strlevel
.Nd mandoc macro compiler library
.Sh LIBRARY
.Lb mandoc
.Sh SYNOPSIS
.In man.h
.In mdoc.h
.In mandoc.h
.Ft "enum mandoc_esc"
.Fo mandoc_escape
.Fa "const char **end"
.Fa "const char **start"
.Fa "int *sz"
.Fc
.Ft "const struct man_meta *"
.Fo man_meta
.Fa "const struct man *man"
.Fc
.Ft "const struct mparse *"
.Fo man_mparse
.Fa "const struct man *man"
.Fc
.Ft "const struct man_node *"
.Fo man_node
.Fa "const struct man *man"
.Fc
.Ft "struct mchars *"
.Fn mchars_alloc
.Ft void
.Fn mchars_free "struct mchars *p"
.Ft char
.Fn mchars_num2char "const char *cp" "size_t sz"
.Ft int
.Fn mchars_num2uc "const char *cp" "size_t sz"
.Ft "const char *"
.Fo mchars_spec2str
.Fa "const struct mchars *p"
.Fa "const char *cp"
.Fa "size_t sz"
.Fa "size_t *rsz"
.Fc
.Ft int
.Fo mchars_spec2cp
.Fa "const struct mchars *p"
.Fa "const char *cp"
.Fa "size_t sz"
.Ft "const char *"
.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 void
.Fo mparse_getkeep
.Fa "const struct mparse *parse"
.Fc
.Ft void
.Fo mparse_keep
.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
.Ft "const char *"
.Fo mparse_strerror
.Fa "enum mandocerr"
.Fc
.Ft "const char *"
.Fo mparse_strlevel
.Fa "enum mandoclevel"
.Fc
.Vt extern const char * const * man_macronames;
.Vt extern const char * const * mdoc_argnames;
.Vt extern const char * const * mdoc_macronames;
.Fd "#define ASCII_NBRSP"
.Fd "#define ASCII_HYPH"
.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
.Pp
The
.Nm
library also contains routines for translating character strings into glyphs
.Pq see Fn mchars_alloc
and parsing escape sequences from strings
.Pq see Fn mandoc_escape .
.Sh REFERENCE
This section documents the functions, types, and variables available
via
.In mandoc.h .
.Ss Types
.Bl -ohang
.It Vt "enum mandoc_esc"
An escape sequence classification.
.It Vt "enum mandocerr"
A fatal error, error, or warning message during parsing.
.It Vt "enum mandoclevel"
A classification of an
.Vt "enum mandoclevel"
as regards system operation.
.It Vt "struct mchars"
An opaque pointer to an object allowing for translation between
character strings and glyphs.
See
.Fn mchars_alloc .
.It Vt "enum mparset"
The type of parser when reading input.
This should usually be
.Dv MPARSE_AUTO
for auto-detection.
.It Vt "struct mparse"
An opaque pointer to a running parse sequence.
Created with
.Fn mparse_alloc
and freed with
.Fn mparse_free .
This may be used across parsed input if
.Fn mparse_reset
is called between parses.
.It Vt "mandocmsg"
A prototype for a function to handle fatal error, error, and warning
messages emitted by the parser.
.El
.Ss Functions
.Bl -ohang
.It Fn mandoc_escape
Scan an escape sequence, i.e., a character string beginning with
.Sq \e .
Pass a pointer to the character after the
.Sq \e
as
.Va end ;
it will be set to the supremum of the parsed escape sequence unless
returning
.Dv ESCAPE_ERROR ,
in which case the string is bogus and should be
thrown away.
If not
.Dv ESCAPE_ERROR
or
.Dv ESCAPE_IGNORE ,
.Va start
is set to the first relevant character of the substring (font, glyph,
whatever) of length
.Va sz .
Both
.Va start
and
.Va sz
may be
.Dv NULL .
.It Fn man_meta
Obtain the meta-data of a successful parse.
This may only be used on a pointer returned by
.Fn mparse_result .
.It Fn man_mparse
Get the parser used for the current output.
.It Fn man_node
Obtain the root node of a successful parse.
This may only be used on a pointer returned by
.Fn mparse_result .
.It Fn mchars_alloc
Allocate an
.Vt "struct mchars *"
object for translating special characters into glyphs.
See
.Xr mandoc_char 7
for an overview of special characters.
The object must be freed with
.Fn mchars_free .
.It Fn mchars_free
Free an object created with
.Fn mchars_alloc .
.It Fn mchars_num2char
Convert a character index (e.g., the \eN\(aq\(aq escape) into a
printable ASCII character.
Returns \e0 (the nil character) if the input sequence is malformed.
.It Fn mchars_num2uc
Convert a hexadecimal character index (e.g., the \e[uNNNN] escape) into
a Unicode codepoint.
Returns \e0 (the nil character) if the input sequence is malformed.
.It Fn mchars_spec2cp
Convert a special character into a valid Unicode codepoint.
Returns \-1 on failure or a non-zero Unicode codepoint on success.
.It Fn mchars_spec2str
Convert a special character into an ASCII string.
Returns
.Dv NULL
on failure.
.It Fn mdoc_meta
Obtain the meta-data of a successful parse.
This may only be used on a pointer returned by
.Fn mparse_result .
.It Fn mdoc_node
Obtain the root node of a successful parse.
This may only be used on a pointer returned by
.Fn mparse_result .
.It Fn mparse_alloc
Allocate a parser.
The same parser may be used for multiple files so long as
.Fn mparse_reset
is called between parses.
.Fn mparse_free
must be called to free the memory allocated by this function.
.It Fn mparse_free
Free all memory allocated by
.Fn mparse_alloc .
.It Fn mparse_getkeep
Acquire the keep buffer.
Must follow a call of
.Fn mparse_keep .
.It Fn mparse_keep
Instruct the parser to retain a copy of its parsed input.
This can be acquired with subsequent
.Fn mparse_getkeep
calls.
.It Fn mparse_readfd
Parse a file or file descriptor.
If
.Va fd
is -1,
.Va fname
is opened for reading.
Otherwise,
.Va fname
is assumed to be the name associated with
.Va fd .
This may be called multiple times with different parameters; however,
.Fn mparse_reset
should be invoked between parses.
.It Fn mparse_reset
Reset a parser so that
.Fn mparse_readfd
may be used again.
.It Fn mparse_result
Obtain the result of a parse.
Only successful parses
.Po
i.e., those where
.Fn mparse_readfd
returned less than MANDOCLEVEL_FATAL
.Pc
should invoke this function, in which case one of the two pointers will
be filled in.
.It Fn mparse_strerror
Return a statically-allocated string representation of an error code.
.It Fn mparse_strlevel
Return a statically-allocated string representation of a level code.
.El
.Ss Variables
.Bl -ohang
.It Va man_macronames
The string representation of a man macro as indexed by
.Vt "enum mant" .
.It Va mdoc_argnames
The string representation of a mdoc macro argument as indexed by
.Vt "enum mdocargt" .
.It Va mdoc_macronames
The string representation of a mdoc macro as indexed by
.Vt "enum mdoct" .
.El
.Sh IMPLEMENTATION NOTES
This section consists of structural documentation for
.Xr mdoc 7
and
.Xr man 7
syntax trees and strings.
.Ss Man and Mdoc Strings
Strings may be extracted from mdoc and man meta-data, or from text
nodes (MDOC_TEXT and MAN_TEXT, respectively).
These strings have special non-printing formatting cues embedded in the
text itself, as well as
.Xr roff 7
escapes preserved from input.
Implementing systems will need to handle both situations to produce
human-readable text.
In general, strings may be assumed to consist of 7-bit ASCII characters.
.Pp
The following non-printing characters may be embedded in text strings:
.Bl -tag -width Ds
.It Dv ASCII_NBRSP
A non-breaking space character.
.It Dv ASCII_HYPH
A soft hyphen.
.El
.Pp
Escape characters are also passed verbatim into text strings.
An escape character is a sequence of characters beginning with the
backslash
.Pq Sq \e .
To construct human-readable text, these should be intercepted with
.Fn mandoc_escape
and converted with one of
.Fn mchars_num2char ,
.Fn mchars_spec2str ,
and so on.
.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
\(<- [[:ascii:]]*
.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
\(<- [[:ascii:]]*
.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 accommodates 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 mandoc_char 7 ,
.Xr mdoc 7 ,
.Xr roff 7 ,
.Xr tbl 7
.Sh AUTHORS
The
.Nm
library was written by
.An Kristaps Dzonsons ,
.Mt kristaps@bsd.lv .
