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Make .de1 a symnonym for .de, not .ig as it was before.

The .de1 instructions is a GNU extension not found in traditional roff and
not even in old groff, defined as "define a macro that will be executed with
traditional roff compatibility mode switched off during macro execution".
Since we ran into it in the wild, we have been parsing and ignoring it for
a long time.  Now that we have proper .de support, we can as well use the
contents, even though we don't implement compatibility mode at all.

/*	$Id: roff.c,v 1.18 2010/11/25 23:07:58 schwarze Exp $ */
/*
 * Copyright (c) 2010 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 AUTHORS DISCLAIM ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS 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.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <assert.h>
#include <errno.h>
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "mandoc.h"
#include "roff.h"
#include "libmandoc.h"

#define	RSTACK_MAX	128

#define	ROFF_CTL(c) \
	('.' == (c) || '\'' == (c))

enum	rofft {
	ROFF_am,
	ROFF_ami,
	ROFF_am1,
	ROFF_de,
	ROFF_dei,
	ROFF_de1,
	ROFF_ds,
	ROFF_el,
	ROFF_ie,
	ROFF_if,
	ROFF_ig,
	ROFF_nr,
	ROFF_rm,
	ROFF_so,
	ROFF_tr,
	ROFF_cblock,
	ROFF_ccond, /* FIXME: remove this. */
	ROFF_USERDEF,
	ROFF_MAX
};

enum	roffrule {
	ROFFRULE_ALLOW,
	ROFFRULE_DENY
};


struct	roffstr {
	char		*name; /* key of symbol */
	char		*string; /* current value */
	struct roffstr	*next; /* next in list */
};

struct	roff {
	struct roffnode	*last; /* leaf of stack */
	mandocmsg	 msg; /* err/warn/fatal messages */
	void		*data; /* privdata for messages */
	enum roffrule	 rstack[RSTACK_MAX]; /* stack of !`ie' rules */
	int		 rstackpos; /* position in rstack */
	struct regset	*regs; /* read/writable registers */
	struct roffstr	*first_string; /* user-defined strings & macros */
	const char	*current_string; /* value of last called user macro */
};

struct	roffnode {
	enum rofft	 tok; /* type of node */
	struct roffnode	*parent; /* up one in stack */
	int		 line; /* parse line */
	int		 col; /* parse col */
	char		*name; /* node name, e.g. macro name */
	char		*end; /* end-rules: custom token */
	int		 endspan; /* end-rules: next-line or infty */
	enum roffrule	 rule; /* current evaluation rule */
};

#define	ROFF_ARGS	 struct roff *r, /* parse ctx */ \
			 enum rofft tok, /* tok of macro */ \
		 	 char **bufp, /* input buffer */ \
			 size_t *szp, /* size of input buffer */ \
			 int ln, /* parse line */ \
			 int ppos, /* original pos in buffer */ \
			 int pos, /* current pos in buffer */ \
			 int *offs /* reset offset of buffer data */

typedef	enum rofferr (*roffproc)(ROFF_ARGS);

struct	roffmac {
	const char	*name; /* macro name */
	roffproc	 proc; /* process new macro */
	roffproc	 text; /* process as child text of macro */
	roffproc	 sub; /* process as child of macro */
	int		 flags;
#define	ROFFMAC_STRUCT	(1 << 0) /* always interpret */
	struct roffmac	*next;
};

static	enum rofferr	 roff_block(ROFF_ARGS);
static	enum rofferr	 roff_block_text(ROFF_ARGS);
static	enum rofferr	 roff_block_sub(ROFF_ARGS);
static	enum rofferr	 roff_cblock(ROFF_ARGS);
static	enum rofferr	 roff_ccond(ROFF_ARGS);
static	enum rofferr	 roff_cond(ROFF_ARGS);
static	enum rofferr	 roff_cond_text(ROFF_ARGS);
static	enum rofferr	 roff_cond_sub(ROFF_ARGS);
static	enum rofferr	 roff_ds(ROFF_ARGS);
static	enum roffrule	 roff_evalcond(const char *, int *);
static	void		 roff_freestr(struct roff *);
static	const char	*roff_getstrn(const struct roff *, 
				const char *, size_t);
static	enum rofferr	 roff_line(ROFF_ARGS);
static	enum rofferr	 roff_nr(ROFF_ARGS);
static	int		 roff_res(struct roff *, 
				char **, size_t *, int);
static	void		 roff_setstr(struct roff *,
				const char *, const char *, int);
static	enum rofferr	 roff_so(ROFF_ARGS);
static	enum rofferr	 roff_userdef(ROFF_ARGS);

/* See roff_hash_find() */

#define	ASCII_HI	 126
#define	ASCII_LO	 33
#define	HASHWIDTH	(ASCII_HI - ASCII_LO + 1)

static	struct roffmac	*hash[HASHWIDTH];

static	struct roffmac	 roffs[ROFF_MAX] = {
	{ "am", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "ami", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "am1", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "de", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "dei", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "de1", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "ds", roff_ds, NULL, NULL, 0, NULL },
	{ "el", roff_cond, roff_cond_text, roff_cond_sub, ROFFMAC_STRUCT, NULL },
	{ "ie", roff_cond, roff_cond_text, roff_cond_sub, ROFFMAC_STRUCT, NULL },
	{ "if", roff_cond, roff_cond_text, roff_cond_sub, ROFFMAC_STRUCT, NULL },
	{ "ig", roff_block, roff_block_text, roff_block_sub, 0, NULL },
	{ "nr", roff_nr, NULL, NULL, 0, NULL },
	{ "rm", roff_line, NULL, NULL, 0, NULL },
	{ "so", roff_so, NULL, NULL, 0, NULL },
	{ "tr", roff_line, NULL, NULL, 0, NULL },
	{ ".", roff_cblock, NULL, NULL, 0, NULL },
	{ "\\}", roff_ccond, NULL, NULL, 0, NULL },
	{ NULL, roff_userdef, NULL, NULL, 0, NULL },
};

static	void		 roff_free1(struct roff *);
static	enum rofft	 roff_hash_find(const char *, size_t);
static	void		 roff_hash_init(void);
static	void		 roffnode_cleanscope(struct roff *);
static	void		 roffnode_push(struct roff *, enum rofft,
				const char *, int, int);
static	void		 roffnode_pop(struct roff *);
static	enum rofft	 roff_parse(struct roff *, const char *, int *);
static	int		 roff_parse_nat(const char *, unsigned int *);

/* See roff_hash_find() */
#define	ROFF_HASH(p)	(p[0] - ASCII_LO)

static void
roff_hash_init(void)
{
	struct roffmac	 *n;
	int		  buc, i;

	for (i = 0; i < (int)ROFF_USERDEF; i++) {
		assert(roffs[i].name[0] >= ASCII_LO);
		assert(roffs[i].name[0] <= ASCII_HI);

		buc = ROFF_HASH(roffs[i].name);

		if (NULL != (n = hash[buc])) {
			for ( ; n->next; n = n->next)
				/* Do nothing. */ ;
			n->next = &roffs[i];
		} else
			hash[buc] = &roffs[i];
	}
}


/*
 * Look up a roff token by its name.  Returns ROFF_MAX if no macro by
 * the nil-terminated string name could be found.
 */
static enum rofft
roff_hash_find(const char *p, size_t s)
{
	int		 buc;
	struct roffmac	*n;

	/*
	 * libroff has an extremely simple hashtable, for the time
	 * being, which simply keys on the first character, which must
	 * be printable, then walks a chain.  It works well enough until
	 * optimised.
	 */

	if (p[0] < ASCII_LO || p[0] > ASCII_HI)
		return(ROFF_MAX);

	buc = ROFF_HASH(p);

	if (NULL == (n = hash[buc]))
		return(ROFF_MAX);
	for ( ; n; n = n->next)
		if (0 == strncmp(n->name, p, s) && '\0' == n->name[(int)s])
			return((enum rofft)(n - roffs));

	return(ROFF_MAX);
}


/*
 * Pop the current node off of the stack of roff instructions currently
 * pending.
 */
static void
roffnode_pop(struct roff *r)
{
	struct roffnode	*p;

	assert(r->last);
	p = r->last; 

	if (ROFF_el == p->tok)
		if (r->rstackpos > -1)
			r->rstackpos--;

	r->last = r->last->parent;
	free(p->name);
	free(p->end);
	free(p);
}


/*
 * Push a roff node onto the instruction stack.  This must later be
 * removed with roffnode_pop().
 */
static void
roffnode_push(struct roff *r, enum rofft tok, const char *name,
		int line, int col)
{
	struct roffnode	*p;

	p = mandoc_calloc(1, sizeof(struct roffnode));
	p->tok = tok;
	if (name)
		p->name = mandoc_strdup(name);
	p->parent = r->last;
	p->line = line;
	p->col = col;
	p->rule = p->parent ? p->parent->rule : ROFFRULE_DENY;

	r->last = p;
}


static void
roff_free1(struct roff *r)
{

	while (r->last)
		roffnode_pop(r);
	roff_freestr(r);
}


void
roff_reset(struct roff *r)
{

	roff_free1(r);
}


void
roff_free(struct roff *r)
{

	roff_free1(r);
	free(r);
}


struct roff *
roff_alloc(struct regset *regs, void *data, const mandocmsg msg)
{
	struct roff	*r;

	r = mandoc_calloc(1, sizeof(struct roff));
	r->regs = regs;
	r->msg = msg;
	r->data = data;
	r->rstackpos = -1;
	
	roff_hash_init();
	return(r);
}


/*
 * Pre-filter each and every line for reserved words (one beginning with
 * `\*', e.g., `\*(ab').  These must be handled before the actual line
 * is processed. 
 */
static int
roff_res(struct roff *r, char **bufp, size_t *szp, int pos)
{
	const char	*cp, *cpp, *st, *res;
	int		 i, maxl;
	size_t		 nsz;
	char		*n;

	/* LINTED */
	for (cp = &(*bufp)[pos]; (cpp = strstr(cp, "\\*")); cp++) {
		cp = cpp + 2;
		switch (*cp) {
		case ('('):
			cp++;
			maxl = 2;
			break;
		case ('['):
			cp++;
			maxl = 0;
			break;
		default:
			maxl = 1;
			break;
		}

		st = cp;

		for (i = 0; 0 == maxl || i < maxl; i++, cp++) {
			if ('\0' == *cp)
				return(1); /* Error. */
			if (0 == maxl && ']' == *cp)
				break;
		}

		res = roff_getstrn(r, st, (size_t)i);

		if (NULL == res) {
			cp -= maxl ? 1 : 0;
			continue;
		}

		nsz = *szp + strlen(res) + 1;
		n = mandoc_malloc(nsz);

		*n = '\0';

		strlcat(n, *bufp, (size_t)(cpp - *bufp + 1));
		strlcat(n, res, nsz);
		strlcat(n, cp + (maxl ? 0 : 1), nsz);

		free(*bufp);

		*bufp = n;
		*szp = nsz;
		return(0);
	}

	return(1);
}


enum rofferr
roff_parseln(struct roff *r, int ln, char **bufp, 
		size_t *szp, int pos, int *offs)
{
	enum rofft	 t;
	int		 ppos;

	/*
	 * Run the reserved-word filter only if we have some reserved
	 * words to fill in.
	 */

	if (r->first_string && ! roff_res(r, bufp, szp, pos))
		return(ROFF_REPARSE);

	/*
	 * First, if a scope is open and we're not a macro, pass the
	 * text through the macro's filter.  If a scope isn't open and
	 * we're not a macro, just let it through.
	 */

	if (r->last && ! ROFF_CTL((*bufp)[pos])) {
		t = r->last->tok;
		assert(roffs[t].text);
		return((*roffs[t].text)
				(r, t, bufp, szp, 
				 ln, pos, pos, offs));
	} else if ( ! ROFF_CTL((*bufp)[pos]))
		return(ROFF_CONT);

	/*
	 * If a scope is open, go to the child handler for that macro,
	 * as it may want to preprocess before doing anything with it.
	 */

	if (r->last) {
		t = r->last->tok;
		assert(roffs[t].sub);
		return((*roffs[t].sub)
				(r, t, bufp, szp, 
				 ln, pos, pos, offs));
	}

	/*
	 * Lastly, as we've no scope open, try to look up and execute
	 * the new macro.  If no macro is found, simply return and let
	 * the compilers handle it.
	 */

	ppos = pos;
	if (ROFF_MAX == (t = roff_parse(r, *bufp, &pos)))
		return(ROFF_CONT);

	assert(roffs[t].proc);
	return((*roffs[t].proc)
			(r, t, bufp, szp, 
			 ln, ppos, pos, offs));
}


int
roff_endparse(struct roff *r)
{

	if (NULL == r->last)
		return(1);
	return((*r->msg)(MANDOCERR_SCOPEEXIT, r->data, r->last->line, 
				r->last->col, NULL));
}


/*
 * Parse a roff node's type from the input buffer.  This must be in the
 * form of ".foo xxx" in the usual way.
 */
static enum rofft
roff_parse(struct roff *r, const char *buf, int *pos)
{
	const char	*mac;
	size_t		 maclen;
	enum rofft	 t;

	assert(ROFF_CTL(buf[*pos]));
	(*pos)++;

	while (' ' == buf[*pos] || '\t' == buf[*pos])
		(*pos)++;

	if ('\0' == buf[*pos])
		return(ROFF_MAX);

	mac = buf + *pos;
	maclen = strcspn(mac, " \\\t\0");

	t = (r->current_string = roff_getstrn(r, mac, maclen))
	    ? ROFF_USERDEF : roff_hash_find(mac, maclen);

	*pos += maclen;
	while (buf[*pos] && ' ' == buf[*pos])
		(*pos)++;

	return(t);
}


static int
roff_parse_nat(const char *buf, unsigned int *res)
{
	char		*ep;
	long		 lval;

	errno = 0;
	lval = strtol(buf, &ep, 10);
	if (buf[0] == '\0' || *ep != '\0')
		return(0);
	if ((errno == ERANGE && 
			(lval == LONG_MAX || lval == LONG_MIN)) ||
			(lval > INT_MAX || lval < 0))
		return(0);

	*res = (unsigned int)lval;
	return(1);
}


/* ARGSUSED */
static enum rofferr
roff_cblock(ROFF_ARGS)
{

	/*
	 * A block-close `..' should only be invoked as a child of an
	 * ignore macro, otherwise raise a warning and just ignore it.
	 */

	if (NULL == r->last) {
		if ( ! (*r->msg)(MANDOCERR_NOSCOPE, r->data, ln, ppos, NULL))
			return(ROFF_ERR);
		return(ROFF_IGN);
	}

	switch (r->last->tok) {
	case (ROFF_am):
		/* FALLTHROUGH */
	case (ROFF_ami):
		/* FALLTHROUGH */
	case (ROFF_am1):
		/* FALLTHROUGH */
	case (ROFF_de):
		/* FALLTHROUGH */
	case (ROFF_dei):
		/* FALLTHROUGH */
	case (ROFF_ig):
		break;
	default:
		if ( ! (*r->msg)(MANDOCERR_NOSCOPE, r->data, ln, ppos, NULL))
			return(ROFF_ERR);
		return(ROFF_IGN);
	}

	if ((*bufp)[pos])
		if ( ! (*r->msg)(MANDOCERR_ARGSLOST, r->data, ln, pos, NULL))
			return(ROFF_ERR);

	roffnode_pop(r);
	roffnode_cleanscope(r);
	return(ROFF_IGN);

}


static void
roffnode_cleanscope(struct roff *r)
{

	while (r->last) {
		if (--r->last->endspan < 0)
			break;
		roffnode_pop(r);
	}
}


/* ARGSUSED */
static enum rofferr
roff_ccond(ROFF_ARGS)
{

	if (NULL == r->last) {
		if ( ! (*r->msg)(MANDOCERR_NOSCOPE, r->data, ln, ppos, NULL))
			return(ROFF_ERR);
		return(ROFF_IGN);
	}

	switch (r->last->tok) {
	case (ROFF_el):
		/* FALLTHROUGH */
	case (ROFF_ie):
		/* FALLTHROUGH */
	case (ROFF_if):
		break;
	default:
		if ( ! (*r->msg)(MANDOCERR_NOSCOPE, r->data, ln, ppos, NULL))
			return(ROFF_ERR);
		return(ROFF_IGN);
	}

	if (r->last->endspan > -1) {
		if ( ! (*r->msg)(MANDOCERR_NOSCOPE, r->data, ln, ppos, NULL))
			return(ROFF_ERR);
		return(ROFF_IGN);
	}

	if ((*bufp)[pos])
		if ( ! (*r->msg)(MANDOCERR_ARGSLOST, r->data, ln, pos, NULL))
			return(ROFF_ERR);

	roffnode_pop(r);
	roffnode_cleanscope(r);
	return(ROFF_IGN);
}


/* ARGSUSED */
static enum rofferr
roff_block(ROFF_ARGS)
{
	int		sv;
	size_t		sz;
	char		*name;

	name = NULL;

	if (ROFF_ig != tok) {
		if ('\0' == (*bufp)[pos]) {
			(*r->msg)(MANDOCERR_NOARGS, r->data, ln, ppos, NULL);
			return(ROFF_IGN);
		}
		if (ROFF_de1 == tok)
			tok = ROFF_de;
		if (ROFF_de == tok)
			name = *bufp + pos;
		while ((*bufp)[pos] && ' ' != (*bufp)[pos])
			pos++;
		while (' ' == (*bufp)[pos])
			(*bufp)[pos++] = '\0';
	}

	roffnode_push(r, tok, name, ln, ppos);

	/*
	 * At the beginning of a `de' macro, clear the existing string
	 * with the same name, if there is one.  New content will be
	 * added from roff_block_text() in multiline mode.
	 */
	if (ROFF_de == tok)
		roff_setstr(r, name, NULL, 0);

	if ('\0' == (*bufp)[pos])
		return(ROFF_IGN);

	sv = pos;
	while ((*bufp)[pos] && ' ' != (*bufp)[pos] && 
			'\t' != (*bufp)[pos])
		pos++;

	/*
	 * Note: groff does NOT like escape characters in the input.
	 * Instead of detecting this, we're just going to let it fly and
	 * to hell with it.
	 */

	assert(pos > sv);
	sz = (size_t)(pos - sv);

	if (1 == sz && '.' == (*bufp)[sv])
		return(ROFF_IGN);

	r->last->end = mandoc_malloc(sz + 1);

	memcpy(r->last->end, *bufp + sv, sz);
	r->last->end[(int)sz] = '\0';

	if ((*bufp)[pos])
		if ( ! (*r->msg)(MANDOCERR_ARGSLOST, r->data, ln, pos, NULL))
			return(ROFF_ERR);

	return(ROFF_IGN);
}


/* ARGSUSED */
static enum rofferr
roff_block_sub(ROFF_ARGS)
{
	enum rofft	t;
	int		i, j;

	/*
	 * First check whether a custom macro exists at this level.  If
	 * it does, then check against it.  This is some of groff's
	 * stranger behaviours.  If we encountered a custom end-scope
	 * tag and that tag also happens to be a "real" macro, then we
	 * need to try interpreting it again as a real macro.  If it's
	 * not, then return ignore.  Else continue.
	 */

	if (r->last->end) {
		i = pos + 1;
		while (' ' == (*bufp)[i] || '\t' == (*bufp)[i])
			i++;

		for (j = 0; r->last->end[j]; j++, i++)
			if ((*bufp)[i] != r->last->end[j])
				break;

		if ('\0' == r->last->end[j] && 
				('\0' == (*bufp)[i] ||
				 ' ' == (*bufp)[i] ||
				 '\t' == (*bufp)[i])) {
			roffnode_pop(r);
			roffnode_cleanscope(r);

			if (ROFF_MAX != roff_parse(r, *bufp, &pos))
				return(ROFF_RERUN);
			return(ROFF_IGN);
		}
	}

	/*
	 * If we have no custom end-query or lookup failed, then try
	 * pulling it out of the hashtable.
	 */

	ppos = pos;
	t = roff_parse(r, *bufp, &pos);

	/*
	 * Macros other than block-end are only significant
	 * in `de' blocks; elsewhere, simply throw them away.
	 */
	if (ROFF_cblock != t) {
		if (ROFF_de == tok)
			roff_setstr(r, r->last->name, *bufp + ppos, 1);
		return(ROFF_IGN);
	}

	assert(roffs[t].proc);
	return((*roffs[t].proc)(r, t, bufp, szp, 
				ln, ppos, pos, offs));
}


/* ARGSUSED */
static enum rofferr
roff_block_text(ROFF_ARGS)
{

	if (ROFF_de == tok)
		roff_setstr(r, r->last->name, *bufp + pos, 1);

	return(ROFF_IGN);
}


/* ARGSUSED */
static enum rofferr
roff_cond_sub(ROFF_ARGS)
{
	enum rofft	 t;
	enum roffrule	 rr;

	ppos = pos;
	rr = r->last->rule;

	/* 
	 * Clean out scope.  If we've closed ourselves, then don't
	 * continue. 
	 */

	roffnode_cleanscope(r);

	if (ROFF_MAX == (t = roff_parse(r, *bufp, &pos))) {
		if ('\\' == (*bufp)[pos] && '}' == (*bufp)[pos + 1])
			return(roff_ccond
				(r, ROFF_ccond, bufp, szp,
				 ln, pos, pos + 2, offs));
		return(ROFFRULE_DENY == rr ? ROFF_IGN : ROFF_CONT);
	}

	/*
	 * A denied conditional must evaluate its children if and only
	 * if they're either structurally required (such as loops and
	 * conditionals) or a closing macro.
	 */
	if (ROFFRULE_DENY == rr)
		if ( ! (ROFFMAC_STRUCT & roffs[t].flags))
			if (ROFF_ccond != t)
				return(ROFF_IGN);

	assert(roffs[t].proc);
	return((*roffs[t].proc)(r, t, bufp, szp, 
				ln, ppos, pos, offs));
}


/* ARGSUSED */
static enum rofferr
roff_cond_text(ROFF_ARGS)
{
	char		*ep, *st;
	enum roffrule	 rr;

	rr = r->last->rule;

	/*
	 * We display the value of the text if out current evaluation
	 * scope permits us to do so.
	 */

	/* FIXME: use roff_ccond? */

	st = &(*bufp)[pos];
	if (NULL == (ep = strstr(st, "\\}"))) {
		roffnode_cleanscope(r);
		return(ROFFRULE_DENY == rr ? ROFF_IGN : ROFF_CONT);
	}

	if (ep == st || (ep > st && '\\' != *(ep - 1)))
		roffnode_pop(r);

	roffnode_cleanscope(r);
	return(ROFFRULE_DENY == rr ? ROFF_IGN : ROFF_CONT);
}


static enum roffrule
roff_evalcond(const char *v, int *pos)
{

	switch (v[*pos]) {
	case ('n'):
		(*pos)++;
		return(ROFFRULE_ALLOW);
	case ('e'):
		/* FALLTHROUGH */
	case ('o'):
		/* FALLTHROUGH */
	case ('t'):
		(*pos)++;
		return(ROFFRULE_DENY);
	default:
		break;
	}

	while (v[*pos] && ' ' != v[*pos])
		(*pos)++;
	return(ROFFRULE_DENY);
}


/* ARGSUSED */
static enum rofferr
roff_line(ROFF_ARGS)
{

	return(ROFF_IGN);
}


/* ARGSUSED */
static enum rofferr
roff_cond(ROFF_ARGS)
{
	int		 sv;
	enum roffrule	 rule;

	/* Stack overflow! */

	if (ROFF_ie == tok && r->rstackpos == RSTACK_MAX - 1) {
		(*r->msg)(MANDOCERR_MEM, r->data, ln, ppos, NULL);
		return(ROFF_ERR);
	}

	/* First, evaluate the conditional. */

	if (ROFF_el == tok) {
		/* 
		 * An `.el' will get the value of the current rstack
		 * entry set in prior `ie' calls or defaults to DENY.
	 	 */
		if (r->rstackpos < 0)
			rule = ROFFRULE_DENY;
		else
			rule = r->rstack[r->rstackpos];
	} else
		rule = roff_evalcond(*bufp, &pos);

	sv = pos;

	while (' ' == (*bufp)[pos])
		pos++;

	/*
	 * Roff is weird.  If we have just white-space after the
	 * conditional, it's considered the BODY and we exit without
	 * really doing anything.  Warn about this.  It's probably
	 * wrong.
	 */

	if ('\0' == (*bufp)[pos] && sv != pos) {
		if ((*r->msg)(MANDOCERR_NOARGS, r->data, ln, ppos, NULL))
			return(ROFF_IGN);
		return(ROFF_ERR);
	}

	roffnode_push(r, tok, NULL, ln, ppos);

	r->last->rule = rule;

	if (ROFF_ie == tok) {
		/*
		 * An if-else will put the NEGATION of the current
		 * evaluated conditional into the stack.
		 */
		r->rstackpos++;
		if (ROFFRULE_DENY == r->last->rule)
			r->rstack[r->rstackpos] = ROFFRULE_ALLOW;
		else
			r->rstack[r->rstackpos] = ROFFRULE_DENY;
	}

	/* If the parent has false as its rule, then so do we. */

	if (r->last->parent && ROFFRULE_DENY == r->last->parent->rule)
		r->last->rule = ROFFRULE_DENY;

	/*
	 * Determine scope.  If we're invoked with "\{" trailing the
	 * conditional, then we're in a multiline scope.  Else our scope
	 * expires on the next line.
	 */

	r->last->endspan = 1;

	if ('\\' == (*bufp)[pos] && '{' == (*bufp)[pos + 1]) {
		r->last->endspan = -1;
		pos += 2;
	} 

	/*
	 * If there are no arguments on the line, the next-line scope is
	 * assumed.
	 */

	if ('\0' == (*bufp)[pos])
		return(ROFF_IGN);

	/* Otherwise re-run the roff parser after recalculating. */

	*offs = pos;
	return(ROFF_RERUN);
}


/* ARGSUSED */
static enum rofferr
roff_ds(ROFF_ARGS)
{
	char		*name, *string;

	/*
	 * A symbol is named by the first word following the macro
	 * invocation up to a space.  Its value is anything after the
	 * name's trailing whitespace and optional double-quote.  Thus,
	 *
	 *  [.ds foo "bar  "     ]
	 *
	 * will have `bar  "     ' as its value.
	 */

	name = *bufp + pos;
	if ('\0' == *name)
		return(ROFF_IGN);

	string = name;
	/* Read until end of name. */
	while (*string && ' ' != *string)
		string++;

	/* Nil-terminate name. */
	if (*string)
		*(string++) = '\0';
	
	/* Read past spaces. */
	while (*string && ' ' == *string)
		string++;

	/* Read passed initial double-quote. */
	if (*string && '"' == *string)
		string++;

	/* The rest is the value. */
	roff_setstr(r, name, string, 0);
	return(ROFF_IGN);
}


/* ARGSUSED */
static enum rofferr
roff_nr(ROFF_ARGS)
{
	const char	*key, *val;
	struct reg	*rg;

	key = &(*bufp)[pos];
	rg = r->regs->regs;

	/* Parse register request. */
	while ((*bufp)[pos] && ' ' != (*bufp)[pos])
		pos++;

	/*
	 * Set our nil terminator.  Because this line is going to be
	 * ignored anyway, we can munge it as we please.
	 */
	if ((*bufp)[pos])
		(*bufp)[pos++] = '\0';

	/* Skip whitespace to register token. */
	while ((*bufp)[pos] && ' ' == (*bufp)[pos])
		pos++;

	val = &(*bufp)[pos];

	/* Process register token. */

	if (0 == strcmp(key, "nS")) {
		rg[(int)REG_nS].set = 1;
		if ( ! roff_parse_nat(val, &rg[(int)REG_nS].v.u))
			rg[(int)REG_nS].v.u = 0;
	}

	return(ROFF_IGN);
}


/* ARGSUSED */
static enum rofferr
roff_so(ROFF_ARGS)
{
	char *name;

	(*r->msg)(MANDOCERR_SO, r->data, ln, ppos, NULL);

	name = *bufp + pos;
	if ('/' == *name || strstr(name, "../") || strstr(name, "/..")) {
		(*r->msg)(MANDOCERR_SOPATH, r->data, ln, pos, NULL);
		return(ROFF_ERR);
	}

	*offs = pos;
	return(ROFF_SO);
}


/* ARGSUSED */
static enum rofferr
roff_userdef(ROFF_ARGS)
{
	const char	 *arg[9];
	char		 *cp, *n1, *n2;
	int		  i, quoted, pairs;

	/*
	 * Collect pointers to macro argument strings
	 * and null-terminate them.
	 */
	cp = *bufp + pos;
	for (i = 0; i < 9; i++) {
		/* Quoting can only start with a new word. */
		if ('"' == *cp) {
			quoted = 1;
			cp++;
		} else
			quoted = 0;
		arg[i] = cp;
		for (pairs = 0; '\0' != *cp; cp++) {
			/* Unquoted arguments end at blanks. */
			if (0 == quoted) {
				if (' ' == *cp)
					break;
				continue;
			}
			/* After pairs of quotes, move left. */
			if (pairs)
				cp[-pairs] = cp[0];
			/* Pairs of quotes do not end words, ... */
			if ('"' == cp[0] && '"' == cp[1]) {
				pairs++;
				cp++;
				continue;
			}
			/* ... but solitary quotes do. */
			if ('"' != *cp)
				continue;
			if (pairs)
				cp[-pairs] = '\0';
			*cp = ' ';
			break;
		}
		/* Last argument; the remaining ones are empty strings. */
		if ('\0' == *cp)
			continue;
		/* Null-terminate argument and move to the next one. */
		*cp++ = '\0';
		while (' ' == *cp)
			cp++;
	}

	/*
	 * Expand macro arguments.
	 */
	*szp = 0;
	n1 = cp = mandoc_strdup(r->current_string);
	while (NULL != (cp = strstr(cp, "\\$"))) {
		i = cp[2] - '1';
		if (0 > i || 8 < i) {
			/* Not an argument invocation. */
			cp += 2;
			continue;
		}

		*szp = strlen(n1) - 3 + strlen(arg[i]) + 1;
		n2 = mandoc_malloc(*szp);

		strlcpy(n2, n1, (size_t)(cp - n1 + 1));
		strlcat(n2, arg[i], *szp);
		strlcat(n2, cp + 3, *szp);

		cp = n2 + (cp - n1);
		free(n1);
		n1 = n2;
	}

	/*
	 * Replace the macro invocation
	 * by the expanded macro.
	 */
	free(*bufp);
	*bufp = n1;
	if (0 == *szp)
		*szp = strlen(*bufp) + 1;

	return(*szp && '\n' == (*bufp)[(int)*szp - 2] ?
	   ROFF_REPARSE : ROFF_APPEND);
}

/*
 * Store *string into the user-defined string called *name.
 * In multiline mode, append to an existing entry and append '\n';
 * else replace the existing entry, if there is one.
 * To clear an existing entry, call with (*r, *name, NULL, 0).
 */
static void
roff_setstr(struct roff *r, const char *name, const char *string,
	int multiline)
{
	struct roffstr	 *n;
	char		 *c;
	size_t		  oldch, newch;

	/* Search for an existing string with the same name. */
	n = r->first_string;
	while (n && strcmp(name, n->name))
		n = n->next;

	if (NULL == n) {
		/* Create a new string table entry. */
		n = mandoc_malloc(sizeof(struct roffstr));
		n->name = mandoc_strdup(name);
		n->string = NULL;
		n->next = r->first_string;
		r->first_string = n;
	} else if (0 == multiline) {
		/* In multiline mode, append; else replace. */
		free(n->string);
		n->string = NULL;
	}

	if (NULL == string)
		return;

	/*
	 * One additional byte for the '\n' in multiline mode,
	 * and one for the terminating '\0'.
	 */
	newch = strlen(string) + (multiline ? 2 : 1);
	if (NULL == n->string) {
		n->string = mandoc_malloc(newch);
		*n->string = '\0';
		oldch = 0;
	} else {
		oldch = strlen(n->string);
		n->string = mandoc_realloc(n->string, oldch + newch);
	}

	/* Skip existing content in the destination buffer. */
	c = n->string + oldch;

	/* Append new content to the destination buffer. */
	while (*string) {
		/*
		 * Rudimentary roff copy mode:
		 * Handle escaped backslashes.
		 */
		if ('\\' == *string && '\\' == *(string + 1))
			string++;
		*c++ = *string++;
	}

	/* Append terminating bytes. */
	if (multiline)
		*c++ = '\n';
	*c = '\0';
}


static const char *
roff_getstrn(const struct roff *r, const char *name, size_t len)
{
	const struct roffstr *n;

	n = r->first_string;
	while (n && (strncmp(name, n->name, len) || '\0' != n->name[(int)len]))
		n = n->next;

	return(n ? n->string : NULL);
}


static void
roff_freestr(struct roff *r)
{
	struct roffstr	 *n, *nn;

	for (n = r->first_string; n; n = nn) {
		free(n->name);
		free(n->string);
		nn = n->next;
		free(n);
	}

	r->first_string = NULL;
}