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Fix an infinite loop that could occur during some cases of horizontally
overlapping horizontal spans.  One span would calculate a desired
target width and start preparations for applying it to some columns,
then the other span would overwrite the target width with a different
value and also start preparations for applying that one to some
columns, which could sometimes confuse the code doing the final
distribution to the point of not doing anything at all before
entering the next iteration.

Fix this by making sure the distribution is done step by step, doing
one step at a time rather than allowing multiple steps to conflict.
Specifically, always do the smallest useful step first.  This change
also simplifies the code.  For example, the local "colwidth" array
is no longer needed.

Note that the algorithm still differs from the one implemented in
GNU tbl(1), which appears to not even try to harmonize column widths
but seems to simply distribute the same amount to all constituent
columns, no matter whether their intrinsic width is narrow or wide.
Adopting a GNU-compatible algorithm might allow further simplifiction
in addition to yielding even more similar output, but i do not want
to implement any major changes of the algorithm at this time.

The infinite loop was reported by <Oliver dot Corff at email dot de>.

/*	$Id: out.c,v 1.82 2021/09/07 17:07:58 schwarze Exp $ */
/*
 * Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
 * Copyright (c) 2011, 2014, 2015, 2017, 2018, 2019, 2021
 *               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.
 */
#include "config.h"

#include <sys/types.h>

#include <assert.h>
#include <ctype.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "mandoc_aux.h"
#include "mandoc.h"
#include "tbl.h"
#include "out.h"

struct	tbl_colgroup {
	struct tbl_colgroup	*next;
	size_t			 wanted;
	int			 startcol;
	int			 endcol;
};

static	size_t	tblcalc_data(struct rofftbl *, struct roffcol *,
			const struct tbl_opts *, const struct tbl_dat *,
			size_t);
static	size_t	tblcalc_literal(struct rofftbl *, struct roffcol *,
			const struct tbl_dat *, size_t);
static	size_t	tblcalc_number(struct rofftbl *, struct roffcol *,
			const struct tbl_opts *, const struct tbl_dat *);


/*
 * Parse the *src string and store a scaling unit into *dst.
 * If the string doesn't specify the unit, use the default.
 * If no default is specified, fail.
 * Return a pointer to the byte after the last byte used,
 * or NULL on total failure.
 */
const char *
a2roffsu(const char *src, struct roffsu *dst, enum roffscale def)
{
	char		*endptr;

	dst->unit = def == SCALE_MAX ? SCALE_BU : def;
	dst->scale = strtod(src, &endptr);
	if (endptr == src)
		return NULL;

	switch (*endptr++) {
	case 'c':
		dst->unit = SCALE_CM;
		break;
	case 'i':
		dst->unit = SCALE_IN;
		break;
	case 'f':
		dst->unit = SCALE_FS;
		break;
	case 'M':
		dst->unit = SCALE_MM;
		break;
	case 'm':
		dst->unit = SCALE_EM;
		break;
	case 'n':
		dst->unit = SCALE_EN;
		break;
	case 'P':
		dst->unit = SCALE_PC;
		break;
	case 'p':
		dst->unit = SCALE_PT;
		break;
	case 'u':
		dst->unit = SCALE_BU;
		break;
	case 'v':
		dst->unit = SCALE_VS;
		break;
	default:
		endptr--;
		if (SCALE_MAX == def)
			return NULL;
		dst->unit = def;
		break;
	}
	return endptr;
}

/*
 * Calculate the abstract widths and decimal positions of columns in a
 * table.  This routine allocates the columns structures then runs over
 * all rows and cells in the table.  The function pointers in "tbl" are
 * used for the actual width calculations.
 */
void
tblcalc(struct rofftbl *tbl, const struct tbl_span *sp_first,
    size_t offset, size_t rmargin)
{
	struct roffsu		 su;
	const struct tbl_opts	*opts;
	const struct tbl_span	*sp;
	const struct tbl_dat	*dp;
	struct roffcol		*col;
	struct tbl_colgroup	*first_group, **gp, *g;
	size_t			 ewidth, min1, min2, wanted, width, xwidth;
	int			 done, icol, maxcol, necol, nxcol, quirkcol;

	/*
	 * Allocate the master column specifiers.  These will hold the
	 * widths and decimal positions for all cells in the column.  It
	 * must be freed and nullified by the caller.
	 */

	assert(tbl->cols == NULL);
	tbl->cols = mandoc_calloc((size_t)sp_first->opts->cols,
	    sizeof(struct roffcol));
	opts = sp_first->opts;

	maxcol = -1;
	first_group = NULL;
	for (sp = sp_first; sp != NULL; sp = sp->next) {
		if (sp->pos != TBL_SPAN_DATA)
			continue;

		/*
		 * Account for the data cells in the layout, matching it
		 * to data cells in the data section.
		 */

		gp = &first_group;
		for (dp = sp->first; dp != NULL; dp = dp->next) {
			icol = dp->layout->col;
			while (maxcol < icol + dp->hspans)
				tbl->cols[++maxcol].spacing = SIZE_MAX;
			col = tbl->cols + icol;
			col->flags |= dp->layout->flags;
			if (dp->layout->flags & TBL_CELL_WIGN)
				continue;

			/* Handle explicit width specifications. */

			if (dp->layout->wstr != NULL &&
			    dp->layout->width == 0 &&
			    a2roffsu(dp->layout->wstr, &su, SCALE_EN)
			    != NULL)
				dp->layout->width =
				    (*tbl->sulen)(&su, tbl->arg);
			if (col->width < dp->layout->width)
				col->width = dp->layout->width;
			if (dp->layout->spacing != SIZE_MAX &&
			    (col->spacing == SIZE_MAX ||
			     col->spacing < dp->layout->spacing))
				col->spacing = dp->layout->spacing;

			/*
			 * Calculate an automatic width.
			 * Except for spanning cells, apply it.
			 */

			width = tblcalc_data(tbl,
			    dp->hspans == 0 ? col : NULL,
			    opts, dp,
			    dp->block == 0 ? 0 :
			    dp->layout->width ? dp->layout->width :
			    rmargin ? (rmargin + sp->opts->cols / 2)
			    / (sp->opts->cols + 1) : 0);
			if (dp->hspans == 0)
				continue;

			/*
			 * Build an ordered, singly linked list
			 * of all groups of columns joined by spans,
			 * recording the minimum width for each group.
			 */

			while (*gp != NULL && ((*gp)->startcol < icol ||
			    (*gp)->endcol < icol + dp->hspans))
				gp = &(*gp)->next;
			if (*gp == NULL || (*gp)->startcol > icol ||
                            (*gp)->endcol > icol + dp->hspans) {
				g = mandoc_malloc(sizeof(*g));
				g->next = *gp;
				g->wanted = width;
				g->startcol = icol;
				g->endcol = icol + dp->hspans;
				*gp = g;
			} else if ((*gp)->wanted < width)
				(*gp)->wanted = width;
		}
	}

	/*
	 * The minimum width of columns explicitly specified
	 * in the layout is 1n.
	 */

	if (maxcol < sp_first->opts->cols - 1)
		maxcol = sp_first->opts->cols - 1;
	for (icol = 0; icol <= maxcol; icol++) {
		col = tbl->cols + icol;
		if (col->width < 1)
			col->width = 1;

		/*
		 * Column spacings are needed for span width
		 * calculations, so set the default values now.
		 */

		if (col->spacing == SIZE_MAX || icol == maxcol)
			col->spacing = 3;
	}

	/*
	 * Replace the minimum widths with the missing widths,
	 * and dismiss groups that are already wide enough.
	 */

	gp = &first_group;
	while ((g = *gp) != NULL) {
		done = 0;
		for (icol = g->startcol; icol <= g->endcol; icol++) {
			width = tbl->cols[icol].width;
			if (icol < g->endcol)
				width += tbl->cols[icol].spacing;
			if (g->wanted <= width) {
				done = 1;
				break;
			} else
				(*gp)->wanted -= width;
		}
		if (done) {
			*gp = g->next;
			free(g);
		} else
			gp = &(*gp)->next;
	}

	while (first_group != NULL) {

		/*
		 * Find the smallest and second smallest column width
		 * among the columns which may need expamsion.
		 */

		min1 = min2 = SIZE_MAX;
		for (icol = 0; icol <= maxcol; icol++) {
			width = tbl->cols[icol].width;
			if (min1 > width) {
				min2 = min1;
				min1 = width;
			} else if (min1 < width && min2 > width)
				min2 = width;
		}

		/*
		 * Find the minimum wanted width
		 * for any one of the narrowest columns,
		 * and mark the columns wanting that width.
		 */

		wanted = min2;
		for (g = first_group; g != NULL; g = g->next) {
			necol = 0;
			for (icol = g->startcol; icol <= g->endcol; icol++)
				if (tbl->cols[icol].width == min1)
					necol++;
			if (necol == 0)
				continue;
			width = min1 + (g->wanted - 1) / necol + 1;
			if (width > min2)
				width = min2;
			if (wanted > width)
				wanted = width;
		}

		/* Record the effect of the widening. */

		gp = &first_group;
		while ((g = *gp) != NULL) {
			done = 0;
			for (icol = g->startcol; icol <= g->endcol; icol++) {
				if (tbl->cols[icol].width != min1)
					continue;
				if (g->wanted <= wanted - min1) {
					tbl->cols[icol].width += g->wanted;
					done = 1;
					break;
				}
				tbl->cols[icol].width = wanted;
				g->wanted -= wanted - min1;
			}
			if (done) {
				*gp = g->next;
				free(g);
			} else
				gp = &(*gp)->next;
		}
	}

	/*
	 * Align numbers with text.
	 * Count columns to equalize and columns to maximize.
	 * Find maximum width of the columns to equalize.
	 * Find total width of the columns *not* to maximize.
	 */

	necol = nxcol = 0;
	ewidth = xwidth = 0;
	for (icol = 0; icol <= maxcol; icol++) {
		col = tbl->cols + icol;
		if (col->width > col->nwidth)
			col->decimal += (col->width - col->nwidth) / 2;
		if (col->flags & TBL_CELL_EQUAL) {
			necol++;
			if (ewidth < col->width)
				ewidth = col->width;
		}
		if (col->flags & TBL_CELL_WMAX)
			nxcol++;
		else
			xwidth += col->width;
	}

	/*
	 * Equalize columns, if requested for any of them.
	 * Update total width of the columns not to maximize.
	 */

	if (necol) {
		for (icol = 0; icol <= maxcol; icol++) {
			col = tbl->cols + icol;
			if ( ! (col->flags & TBL_CELL_EQUAL))
				continue;
			if (col->width == ewidth)
				continue;
			if (nxcol && rmargin)
				xwidth += ewidth - col->width;
			col->width = ewidth;
		}
	}

	/*
	 * If there are any columns to maximize, find the total
	 * available width, deducting 3n margins between columns.
	 * Distribute the available width evenly.
	 */

	if (nxcol && rmargin) {
		xwidth += 3*maxcol +
		    (opts->opts & (TBL_OPT_BOX | TBL_OPT_DBOX) ?
		     2 : !!opts->lvert + !!opts->rvert);
		if (rmargin <= offset + xwidth)
			return;
		xwidth = rmargin - offset - xwidth;

		/*
		 * Emulate a bug in GNU tbl width calculation that
		 * manifests itself for large numbers of x-columns.
		 * Emulating it for 5 x-columns gives identical
		 * behaviour for up to 6 x-columns.
		 */

		if (nxcol == 5) {
			quirkcol = xwidth % nxcol + 2;
			if (quirkcol != 3 && quirkcol != 4)
				quirkcol = -1;
		} else
			quirkcol = -1;

		necol = 0;
		ewidth = 0;
		for (icol = 0; icol <= maxcol; icol++) {
			col = tbl->cols + icol;
			if ( ! (col->flags & TBL_CELL_WMAX))
				continue;
			col->width = (double)xwidth * ++necol / nxcol
			    - ewidth + 0.4995;
			if (necol == quirkcol)
				col->width--;
			ewidth += col->width;
		}
	}
}

static size_t
tblcalc_data(struct rofftbl *tbl, struct roffcol *col,
    const struct tbl_opts *opts, const struct tbl_dat *dp, size_t mw)
{
	size_t		 sz;

	/* Branch down into data sub-types. */

	switch (dp->layout->pos) {
	case TBL_CELL_HORIZ:
	case TBL_CELL_DHORIZ:
		sz = (*tbl->len)(1, tbl->arg);
		if (col != NULL && col->width < sz)
			col->width = sz;
		return sz;
	case TBL_CELL_LONG:
	case TBL_CELL_CENTRE:
	case TBL_CELL_LEFT:
	case TBL_CELL_RIGHT:
		return tblcalc_literal(tbl, col, dp, mw);
	case TBL_CELL_NUMBER:
		return tblcalc_number(tbl, col, opts, dp);
	case TBL_CELL_DOWN:
		return 0;
	default:
		abort();
	}
}

static size_t
tblcalc_literal(struct rofftbl *tbl, struct roffcol *col,
    const struct tbl_dat *dp, size_t mw)
{
	const char	*str;	/* Beginning of the first line. */
	const char	*beg;	/* Beginning of the current line. */
	char		*end;	/* End of the current line. */
	size_t		 lsz;	/* Length of the current line. */
	size_t		 wsz;	/* Length of the current word. */
	size_t		 msz;   /* Length of the longest line. */

	if (dp->string == NULL || *dp->string == '\0')
		return 0;
	str = mw ? mandoc_strdup(dp->string) : dp->string;
	msz = lsz = 0;
	for (beg = str; beg != NULL && *beg != '\0'; beg = end) {
		end = mw ? strchr(beg, ' ') : NULL;
		if (end != NULL) {
			*end++ = '\0';
			while (*end == ' ')
				end++;
		}
		wsz = (*tbl->slen)(beg, tbl->arg);
		if (mw && lsz && lsz + 1 + wsz <= mw)
			lsz += 1 + wsz;
		else
			lsz = wsz;
		if (msz < lsz)
			msz = lsz;
	}
	if (mw)
		free((void *)str);
	if (col != NULL && col->width < msz)
		col->width = msz;
	return msz;
}

static size_t
tblcalc_number(struct rofftbl *tbl, struct roffcol *col,
		const struct tbl_opts *opts, const struct tbl_dat *dp)
{
	const char	*cp, *lastdigit, *lastpoint;
	size_t		 intsz, totsz;
	char		 buf[2];

	if (dp->string == NULL || *dp->string == '\0')
		return 0;

	totsz = (*tbl->slen)(dp->string, tbl->arg);
	if (col == NULL)
		return totsz;

	/*
	 * Find the last digit and
	 * the last decimal point that is adjacent to a digit.
	 * The alignment indicator "\&" overrides everything.
	 */

	lastdigit = lastpoint = NULL;
	for (cp = dp->string; cp[0] != '\0'; cp++) {
		if (cp[0] == '\\' && cp[1] == '&') {
			lastdigit = lastpoint = cp;
			break;
		} else if (cp[0] == opts->decimal &&
		    (isdigit((unsigned char)cp[1]) ||
		     (cp > dp->string && isdigit((unsigned char)cp[-1]))))
			lastpoint = cp;
		else if (isdigit((unsigned char)cp[0]))
			lastdigit = cp;
	}

	/* Not a number, treat as a literal string. */

	if (lastdigit == NULL) {
		if (col != NULL && col->width < totsz)
			col->width = totsz;
		return totsz;
	}

	/* Measure the width of the integer part. */

	if (lastpoint == NULL)
		lastpoint = lastdigit + 1;
	intsz = 0;
	buf[1] = '\0';
	for (cp = dp->string; cp < lastpoint; cp++) {
		buf[0] = cp[0];
		intsz += (*tbl->slen)(buf, tbl->arg);
	}

	/*
         * If this number has more integer digits than all numbers
         * seen on earlier lines, shift them all to the right.
	 * If it has fewer, shift this number to the right.
	 */

	if (intsz > col->decimal) {
		col->nwidth += intsz - col->decimal;
		col->decimal = intsz;
	} else
		totsz += col->decimal - intsz;

	/* Update the maximum total width seen so far. */

	if (totsz > col->nwidth)
		col->nwidth = totsz;
	if (col->nwidth > col->width)
		col->width = col->nwidth;
	return totsz;
}