cal: fix signed integer overflow [AddressSanitizer]

[thirdparty/util-linux.git] / misc-utils / cal.c

/*
 * Copyright (c) 1989, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kim Letkeman.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* 1999-02-01   Jean-Francois Bignolles: added option '-m' to display
 *              monday as the first day of the week.
 * 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
 * - added Native Language Support
 *
 * 2000-09-01  Michael Charles Pruznick <dummy@netwiz.net>
 *             Added "-3" option to print prev/next month with current.
 *             Added over-ridable default NUM_MONTHS and "-1" option to
 *             get traditional output when -3 is the default.  I hope that
 *             enough people will like -3 as the default that one day the
 *             product can be shipped that way.
 *
 * 2001-05-07  Pablo Saratxaga <pablo@mandrakesoft.com>
 *             Fixed the bugs with multi-byte charset (zg: cjk, utf-8)
 *             displaying. made the 'month year' ("%s %d") header translatable
 *             so it can be adapted to conventions used by different languages
 *             added support to read "first_weekday" locale information
 *             still to do: support for 'cal_direction' (will require a major
 *             rewrite of the displaying) and proper handling of RTL scripts
 */

#include <sys/types.h>

#include <ctype.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>

#include "c.h"
#include "closestream.h"
#include "colors.h"
#include "nls.h"
#include "mbsalign.h"
#include "strutils.h"

#if defined(HAVE_LIBNCURSES) || defined(HAVE_LIBNCURSESW)
# ifdef HAVE_NCURSES_H
#  include <ncurses.h>
# elif defined(HAVE_NCURSES_NCURSES_H)
#  include <ncurses/ncurses.h>
# endif
# include <term.h>

static void my_setupterm(const char *term, int fildes, int *errret)
{
        setupterm((char *)term, fildes, errret);
}

static void my_putstring(char *s)
{
        putp(s);
}

static const char *my_tgetstr(char *s __attribute__((__unused__)), char *ss)
{
        const char *ret = tigetstr(ss);
        if (!ret || ret == (char *)-1)
                return "";

        return ret;
}

#elif defined(HAVE_LIBTERMCAP)
# include <termcap.h>

static char termbuffer[4096];
static char tcbuffer[4096];
static char *strbuf = termbuffer;

static void my_setupterm(const char *term, int fildes __attribute__((__unused__)), int *errret)
{
        *errret = tgetent(tcbuffer, term);
}

static void my_putstring(char *s)
{
        tputs(s, 1, putchar);
}

static const char *my_tgetstr(char *s, char *ss __attribute__((__unused__)))
{
        const char *ret = tgetstr(s, &strbuf);
        if (!ret)
                return "";

        return ret;
}

#else   /* ! (HAVE_LIBTERMCAP || HAVE_LIBNCURSES || HAVE_LIBNCURSESW) */

static void my_putstring(char *s)
{
        fputs(s, stdout);
}

#endif  /* end of LIBTERMCAP / NCURSES */

#if defined(HAVE_LIBNCURSES) || defined(HAVE_LIBNCURSESW) || defined(HAVE_LIBTERMCAP)
static const char       *term="";
#endif

static const char       *Senter="", *Sexit="";/* enter and exit standout mode */

#include "widechar.h"

/* allow compile-time define to over-ride default */
#ifndef NUM_MONTHS
# define NUM_MONTHS 1
#endif

#if ( NUM_MONTHS != 1 && NUM_MONTHS !=3 )
# error NUM_MONTHS must be 1 or 3
#endif

enum {
        SUNDAY = 0,
        MONDAY,
        TUESDAY,
        WEDNESDAY,
        THURSDAY,
        FRIDAY,
        SATURDAY,
        DAYS_IN_WEEK,
        NONEDAY
};

#define FIRST_WEEKDAY           SATURDAY        /* Jan 1st, 1 was a Saturday */
#define REFORMATION_YEAR        1752            /* Signed-off-by: Lord Chesterfield */
#define REFORMATION_MONTH       9               /* September */
#define FIRST_MISSING_DAY       639799          /* 3 Sep 1752 */
#define NUMBER_MISSING_DAYS     11              /* 11 day correction */
#define YDAY_AFTER_MISSING      258             /* 14th in Sep 1752 */

#define DAYS_IN_YEAR            365             /* the common case, leap years are calculated */
#define MONTHS_IN_YEAR          12
#define DAYS_IN_MONTH           31
#define MAXDAYS                 42              /* slots in a month array */
#define SPACE                   -1              /* used in day array */

#define SMALLEST_YEAR           1

#define DAY_LEN                 3               /* 3 spaces per day */
#define WEEK_LEN                (DAYS_IN_WEEK * DAY_LEN)
#define HEAD_SEP                2
#define MONTH_COLS              3               /* month columns in year view */
#define WNUM_LEN                3

#define TODAY_FLAG              0x400           /* flag day for highlighting */

#define FMT_ST_CHARS 300        /* 90 suffices in most locales */

static const int days_in_month[2][13] = {
        {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
        {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
};

enum {
        WEEK_NUM_DISABLED = 0,
        WEEK_NUM_MASK=0xff,
        WEEK_NUM_ISO=0x100,
        WEEK_NUM_US=0x200,
};

/* utf-8 can have up to 6 bytes per char; and an extra byte for ending \0 */
static char day_headings[(WEEK_LEN + 1) * 6 + 1];

struct cal_request {
        int day;
        int month;
        int32_t year;
        int week;
};

struct cal_control {
        const char *full_month[MONTHS_IN_YEAR]; /* month names */
        int colormode;                  /* day and week number highlight */
        int num_months;                 /* number of months horizontally in print out */
        int weekstart;                  /* day the week starts, often Sun or Mon */
        int weektype;                   /* WEEK_TYPE_{NONE,ISO,US} */
        size_t day_width;               /* day width in characters in printout */
        size_t week_width;              /* 7 * day_width + possible week num */
        int gutter_width;               /* spaces in between horizontal month outputs */
        struct cal_request req;         /* the times user is interested */
        unsigned int    julian:1,       /* julian output */
                        yflag:1,        /* print whole year */
                        header_hint:1;  /* does month name + year need two lines to fit */
};

struct cal_month {
        int days[MAXDAYS];              /* the day numbers, or SPACE */
        int weeks[MAXDAYS / DAYS_IN_WEEK];
        int month;
        int32_t year;
        struct cal_month *next;
};

/* function prototypes */
static int leap_year(int32_t year);
static void headers_init(struct cal_control *ctl);
static void set_consecutive_months(struct cal_month *month, int m, int32_t y);
static void cal_fill_month(struct cal_month *month, const struct cal_control *ctl);
static void cal_output_header(struct cal_month *month, const struct cal_control *ctl);
static void cal_output_months(struct cal_month *month, const struct cal_control *ctl);
static void monthly(const struct cal_control *ctl);
static void monthly3(const struct cal_control *ctl);
static void yearly(const struct cal_control *ctl);
static int day_in_year(int day, int month, int32_t year);
static int day_in_week(int day, int month, int32_t year);
static int week_number(int day, int month, int32_t year, const struct cal_control *ctl);
static int week_to_day(const struct cal_control *ctl);
static int center_str(const char *src, char *dest, size_t dest_size, size_t width);
static void center(const char *str, size_t len, int separate);
static void __attribute__((__noreturn__)) usage(FILE *out);

int main(int argc, char **argv)
{
        struct tm *local_time;
        time_t now;
        int ch;
        static struct cal_control ctl = {
                .weekstart = SUNDAY,
                .num_months = NUM_MONTHS,
                .colormode = UL_COLORMODE_UNDEF,
                .weektype = WEEK_NUM_DISABLED,
                .day_width = DAY_LEN,
                .gutter_width = 2,
                .req.day = 0,
                .req.month = 0
        };

        enum {
                OPT_COLOR = CHAR_MAX + 1
        };

        static const struct option longopts[] = {
                {"one", no_argument, NULL, '1'},
                {"three", no_argument, NULL, '3'},
                {"sunday", no_argument, NULL, 's'},
                {"monday", no_argument, NULL, 'm'},
                {"julian", no_argument, NULL, 'j'},
                {"year", no_argument, NULL, 'y'},
                {"week", optional_argument, NULL, 'w'},
                {"color", optional_argument, NULL, OPT_COLOR},
                {"version", no_argument, NULL, 'V'},
                {"help", no_argument, NULL, 'h'},
                {NULL, 0, NULL, 0}
        };

        setlocale(LC_ALL, "");
        bindtextdomain(PACKAGE, LOCALEDIR);
        textdomain(PACKAGE);
        atexit(close_stdout);

#if defined(HAVE_LIBNCURSES) || defined(HAVE_LIBNCURSESW) || defined(HAVE_LIBTERMCAP)
        if ((term = getenv("TERM"))) {
                int ret;
                my_setupterm(term, STDOUT_FILENO, &ret);
                if (ret > 0) {
                        Senter = my_tgetstr("so","smso");
                        Sexit = my_tgetstr("se","rmso");
                }
        }
#endif

/*
 * The traditional Unix cal utility starts the week at Sunday,
 * while ISO 8601 starts at Monday. We read the start day from
 * the locale database, which can be overridden with the
 * -s (Sunday) or -m (Monday) options.
 */
#if HAVE_DECL__NL_TIME_WEEK_1STDAY
        /*
         * You need to use 2 locale variables to get the first day of the week.
         * This is needed to support first_weekday=2 and first_workday=1 for
         * the rare case where working days span across 2 weeks.
         * This shell script shows the combinations and calculations involved:
         *
         * for LANG in en_US ru_RU fr_FR csb_PL POSIX; do
         *   printf "%s:\t%s + %s -1 = " $LANG $(locale week-1stday first_weekday)
         *   date -d"$(locale week-1stday) +$(($(locale first_weekday)-1))day" +%w
         * done
         *
         * en_US:  19971130 + 1 -1 = 0  #0 = sunday
         * ru_RU:  19971130 + 2 -1 = 1
         * fr_FR:  19971201 + 1 -1 = 1
         * csb_PL: 19971201 + 2 -1 = 2
         * POSIX:  19971201 + 7 -1 = 0
         */
        {
                int wfd;
                union { unsigned int word; char *string; } val;
                val.string = nl_langinfo(_NL_TIME_WEEK_1STDAY);

                wfd = val.word;
                wfd = day_in_week(wfd % 100, (wfd / 100) % 100, wfd / (100 * 100));
                ctl.weekstart = (wfd + *nl_langinfo(_NL_TIME_FIRST_WEEKDAY) - 1) % DAYS_IN_WEEK;
        }
#endif

        while ((ch = getopt_long(argc, argv, "13mjsywVh", longopts, NULL)) != -1)
                switch(ch) {
                case '1':
                        ctl.num_months = 1;             /* default */
                        break;
                case '3':
                        ctl.num_months = 3;
                        break;
                case 's':
                        ctl.weekstart = SUNDAY;         /* default */
                        break;
                case 'm':
                        ctl.weekstart = MONDAY;
                        break;
                case 'j':
                        ctl.julian = 1;
                        ctl.day_width = DAY_LEN + 1;
                        break;
                case 'y':
                        ctl.yflag = 1;
                        break;
                case 'w':
                        if (optarg) {
                                ctl.req.week = strtos32_or_err(optarg,
                                                _("invalid week argument"));
                                if (ctl.req.week < 1 || 53 < ctl.req.week)
                                        errx(EXIT_FAILURE,_("illegal week value: use 1-53"));
                        }
                        ctl.weektype = WEEK_NUM_US;     /* default per weekstart */
                        break;
                case OPT_COLOR:
                        if (optarg)
                                ctl.colormode = colormode_or_err(optarg,
                                                _("unsupported color mode"));
                        break;
                case 'V':
                        printf(UTIL_LINUX_VERSION);
                        return EXIT_SUCCESS;
                case 'h':
                        usage(stdout);
                case '?':
                default:
                        usage(stderr);
                }
        argc -= optind;
        argv += optind;

        if (ctl.weektype) {
                ctl.weektype = ctl.req.week & WEEK_NUM_MASK;
                ctl.weektype |= (ctl.weekstart == MONDAY ? WEEK_NUM_ISO : WEEK_NUM_US);
                ctl.week_width = (ctl.day_width * DAYS_IN_WEEK) + WNUM_LEN;
        } else
                ctl.week_width = ctl.day_width * DAYS_IN_WEEK;

        time(&now);
        local_time = localtime(&now);

        switch(argc) {
        case 3:
                ctl.req.day = strtos32_or_err(*argv++, _("illegal day value"));
                if (ctl.req.day < 1 || DAYS_IN_MONTH < ctl.req.day)
                        errx(EXIT_FAILURE, _("illegal day value: use 1-%d"), DAYS_IN_MONTH);
                /* FALLTHROUGH */
        case 2:
                ctl.req.month = strtos32_or_err(*argv++, _("illegal month value: use 1-12"));
                if (ctl.req.month < 1 || MONTHS_IN_YEAR < ctl.req.month)
                        errx(EXIT_FAILURE, _("illegal month value: use 1-12"));
                /* FALLTHROUGH */
        case 1:
                ctl.req.year = strtos32_or_err(*argv++, _("illegal year value"));
                if (ctl.req.year < SMALLEST_YEAR)
                        errx(EXIT_FAILURE, _("illegal year value: use positive integer"));
                if (ctl.req.year == INT32_MAX)
                        errx(EXIT_FAILURE, _("illegal year value"));
                if (ctl.req.day) {
                        int dm = days_in_month[leap_year(ctl.req.year)][ctl.req.month];
                        if (ctl.req.day > dm)
                                errx(EXIT_FAILURE, _("illegal day value: use 1-%d"), dm);
                        ctl.req.day = day_in_year(ctl.req.day, ctl.req.month, ctl.req.year);
                } else if ((int32_t) (local_time->tm_year + 1900) == ctl.req.year) {
                        ctl.req.day = local_time->tm_yday + 1;
                }
                if (!ctl.req.month && !ctl.req.week) {
                        ctl.req.month = local_time->tm_mon + 1;
                        ctl.yflag = 1;
                }
                break;
        case 0:
                ctl.req.day = local_time->tm_yday + 1;
                ctl.req.year = local_time->tm_year + 1900;
                ctl.req.month = local_time->tm_mon + 1;
                break;
        default:
                usage(stderr);
        }

        if (0 < ctl.req.week) {
                int yday = week_to_day(&ctl);
                int leap = leap_year(ctl.req.year);
                int m = 1;

                if (yday < 1)
                        errx(EXIT_FAILURE, _("illegal week value: year %d "
                                             "doesn't have week %d"),
                                        ctl.req.year, ctl.req.week);
                while (m <= 12 && yday > days_in_month[leap][m])
                        yday -= days_in_month[leap][m++];
                if (m > 12) {
                        /* In some years (e.g. 2010 in ISO mode) it's possible
                         * to have a remnant of week 53 starting the year yet
                         * the year in question ends during 52, in this case
                         * we're assuming that early remnant is being referred
                         * to if 53 is given as argument. */
                        if (ctl.req.week != week_number(31, 12, ctl.req.year - 1, &ctl))
                                errx(EXIT_FAILURE,
                                        _("illegal week value: year %d "
                                          "doesn't have week %d"),
                                        ctl.req.year, ctl.req.week);
                }
                if (!ctl.req.month)
                        ctl.req.month = 12 < m ? 1 : m;
        }

        headers_init(&ctl);

        if (!colors_init(ctl.colormode, "cal")) {
                ctl.req.day = 0;
                ctl.weektype &= ~WEEK_NUM_MASK;
        }

        if (ctl.yflag) {
                if (ctl.julian)
                        ctl.num_months = MONTH_COLS - 1;
                else
                        ctl.num_months = MONTH_COLS;
                ctl.gutter_width = 3;
                yearly(&ctl);
        } else if (ctl.num_months == 1)
                monthly(&ctl);
        else if (ctl.num_months == 3)
                monthly3(&ctl);

        return EXIT_SUCCESS;
}

/* leap year -- account for gregorian reformation in 1752 */
static int leap_year(int32_t year)
{
        if (year <= REFORMATION_YEAR)
                return !(year % 4);
        else
                return ( !(year % 4) && (year % 100) ) || !(year % 400);
}

static void headers_init(struct cal_control *ctl)
{
        size_t i, wd;
        char *cur_dh = day_headings;
        char tmp[FMT_ST_CHARS];
        size_t year_len;

        year_len = snprintf(tmp, sizeof(tmp), "%d", ctl->req.year);

        for (i = 0; i < DAYS_IN_WEEK; i++) {
                size_t space_left;
                wd = (i + ctl->weekstart) % DAYS_IN_WEEK;

                if (i)
                        strcat(cur_dh++, " ");
                space_left = sizeof(day_headings) - (cur_dh - day_headings);

                if (space_left <= (ctl->day_width - 1))
                        break;
                cur_dh += center_str(nl_langinfo(ABDAY_1 + wd), cur_dh,
                                     space_left, ctl->day_width - 1);
        }

        for (i = 0; i < MONTHS_IN_YEAR; i++) {
                ctl->full_month[i] = nl_langinfo(MON_1 + i);
                /* The +1 after year_len is space in between month and year. */
                if (ctl->week_width < strlen(ctl->full_month[i]) + year_len + 1)
                        ctl->header_hint = 1;
        }
}

static void set_consecutive_months(struct cal_month *month, int m, int32_t y)
{
        struct cal_month *i;
        for (i = month; i; i = i->next) {
                i->month = m++;
                i->year = y;
                if (MONTHS_IN_YEAR < m) {
                        m = 1;
                        y++;
                }
        }
}

static void cal_fill_month(struct cal_month *month, const struct cal_control *ctl)
{
        int first_week_day = day_in_week(1, month->month, month->year);
        int month_days;
        int i, j, weeklines = 0;

        if (ctl->julian)
                j = day_in_year(1, month->month, month->year);
        else
                j = 1;
        month_days = j + days_in_month[leap_year(month->year)][month->month];

        /* True when Sunday is not first day in the output week. */
        if (ctl->weekstart) {
                first_week_day -= ctl->weekstart;
                if (first_week_day < 0)
                        first_week_day = DAYS_IN_WEEK - ctl->weekstart;
                month_days += ctl->weekstart - 1;
        }

        /* Fill day array. */
        for (i = 0; i < MAXDAYS; i++) {
                if (0 < first_week_day) {
                        month->days[i] = SPACE;
                        first_week_day--;
                        continue;
                }
                if (j < month_days) {
                        if (month->year == 1752 && month->month == 9 && (j == 3 || j == 247))
                                j += NUMBER_MISSING_DAYS;
                        month->days[i] = j;
                        j++;
                        continue;
                }
                month->days[i] = SPACE;
                weeklines++;
        }

        /* Add week numbers */
        if (ctl->weektype) {
                int weeknum = week_number(1, month->month, month->year, ctl);
                weeklines = MAXDAYS / DAYS_IN_WEEK - weeklines / DAYS_IN_WEEK;
                for (i = 0; i < MAXDAYS / DAYS_IN_WEEK; i++) {
                        if (0 < weeklines)
                                month->weeks[i] = weeknum++;
                        else
                                month->weeks[i] = SPACE;
                        weeklines--;
                        if (52 < weeknum && i == 0)
                                weeknum = week_number(month->days[DAYS_IN_WEEK * (i + 1)], 1, month->year, ctl);
                        else if (52 < weeknum)
                                weeknum = week_number(31, 12, month->year, ctl);
                }
        }
}

static void cal_output_header(struct cal_month *month, const struct cal_control *ctl)
{
        char out[FMT_ST_CHARS];
        struct cal_month *i;

        if (ctl->header_hint || ctl->yflag) {
                for (i = month; i; i = i->next) {
                        sprintf(out, _("%s"), ctl->full_month[i->month - 1]);
                        center(out, ctl->week_width - 1, i->next == NULL ? 0 : ctl->gutter_width);
                }
                if (!ctl->yflag) {
                        my_putstring("\n");
                        for (i = month; i; i = i->next) {
                                sprintf(out, _("%d"), i->year);
                                center(out, ctl->week_width - 1, i->next == NULL ? 0 : ctl->gutter_width);
                        }
                }
        } else {
                for (i = month; i; i = i->next) {
                        sprintf(out, _("%s %d"), ctl->full_month[i->month - 1], i->year);
                        center(out, ctl->week_width - 1, i->next == NULL ? 0 : ctl->gutter_width);
                }
        }
        my_putstring("\n");
        for (i = month; i; i = i->next) {
                if (ctl->weektype) {
                        if (ctl->julian)
                                sprintf(out, "%*s%s", (int)ctl->day_width - 1, "", day_headings);
                        else
                                sprintf(out, "%*s%s", (int)ctl->day_width, "", day_headings);
                        my_putstring(out);
                } else
                        my_putstring(day_headings);
                if (i->next != NULL) {
                        sprintf(out, "%*s", ctl->gutter_width, "");
                        my_putstring(out);
                }
        }
        my_putstring("\n");
}

static void cal_output_months(struct cal_month *month, const struct cal_control *ctl)
{
        char out[FMT_ST_CHARS];
        int reqday, week_line, d;
        int skip;
        struct cal_month *i;

        for (week_line = 0; week_line < MAXDAYS / DAYS_IN_WEEK; week_line++) {
                for (i = month; i; i = i->next) {
                        /* Determine the day that should be highlighted. */
                        reqday = 0;
                        if (i->month == ctl->req.month && i->year == ctl->req.year) {
                                if (ctl->julian)
                                        reqday = ctl->req.day;
                                else
                                        reqday =
                                            ctl->req.day + 1 - day_in_year(1, i->month,
                                                                           i->year);
                        }

                        if (ctl->weektype) {
                                if (0 < i->weeks[week_line]) {
                                        if ((ctl->weektype & WEEK_NUM_MASK) ==
                                            i->weeks[week_line])
                                                sprintf(out, "%s%2d%s", Senter, i->weeks[week_line],
                                                       Sexit);
                                        else
                                                sprintf(out, "%2d", i->weeks[week_line]);
                                } else
                                        sprintf(out, "%2s", "");
                                my_putstring(out);
                                skip = ctl->day_width;
                        } else
                                /* First day of the week is one char narrower than the other days,
                                 * unless week number is printed.  */
                                skip = ctl->day_width - 1;

                        for (d = DAYS_IN_WEEK * week_line;
                             d < DAYS_IN_WEEK * week_line + DAYS_IN_WEEK; d++) {
                                if (0 < i->days[d]) {
                                        if (reqday == i->days[d])
                                                sprintf(out, "%*s%s%*d%s", skip - (ctl->julian ? 3 : 2),
                                                       "", Senter, (ctl->julian ? 3 : 2),
                                                       i->days[d], Sexit);
                                        else
                                                sprintf(out, "%*d", skip, i->days[d]);
                                } else
                                        sprintf(out, "%*s", skip, "");
                                my_putstring(out);
                                if (skip < (int)ctl->day_width)
                                        skip++;
                        }
                        if (i->next != NULL) {
                                sprintf(out, "%*s", ctl->gutter_width, "");
                                my_putstring(out);
                        }
                }
                if (i == NULL) {
                        sprintf(out, "%*s\n", ctl->gutter_width - (ctl->yflag ? 0 : 1), "");
                        my_putstring(out);
                }
        }
}

static void monthly(const struct cal_control *ctl)
{
        struct cal_month month;

        month.month = ctl->req.month;
        month.year = ctl->req.year;
        month.next = NULL;

        cal_fill_month(&month, ctl);

        cal_output_header(&month, ctl);
        cal_output_months(&month, ctl);
}

static void monthly3(const struct cal_control *ctl)
{
        struct cal_month m1, m2, m3, *i;
        int first_month;
        int32_t first_year;

        m1.next = &m2;
        m2.next = &m3;
        m3.next = NULL;

        if (ctl->req.month == 1) {
                first_month = MONTHS_IN_YEAR;
                first_year = ctl->req.year - 1;
        } else {
                first_month = ctl->req.month - 1;
                first_year = ctl->req.year;
        }

        set_consecutive_months(&m1, first_month, first_year);
        for (i = &m1; i; i = i->next)
                cal_fill_month(i, ctl);
        cal_output_header(&m1, ctl);
        cal_output_months(&m1, ctl);
}

static void yearly(const struct cal_control *ctl)
{
        struct cal_month m1, m2, m3, *i;
        int month;
        char out[FMT_ST_CHARS];
        int year_width = 0;

        m1.next = &m2;
        if (ctl->julian)
                m2.next = NULL;
        else {
                m2.next = &m3;
                m3.next = NULL;
        }

        /* year header */
        for (i = &m1; i; i = i->next)
                year_width += ctl->week_width + 1;
        if (ctl->julian)
                year_width--;
        sprintf(out, "%d", ctl->req.year);
        center(out, year_width, 0);
        my_putstring("\n\n");

        for (month = 1; month < MONTHS_IN_YEAR; month += ctl->julian ? 2 : 3) {
                set_consecutive_months(&m1, month, ctl->req.year);
                for (i = &m1; i; i = i->next)
                        cal_fill_month(i, ctl);
                cal_output_header(&m1, ctl);
                cal_output_months(&m1, ctl);
        }
        /* Is empty line at the end year output really needed? */
        my_putstring("\n");
}

/*
 * day_in_year --
 *      return the 1 based day number within the year
 */
static int day_in_year(int day, int month, int32_t year)
{
        int i, leap;

        leap = leap_year(year);
        for (i = 1; i < month; i++)
                day += days_in_month[leap][i];
        return day;
}

/*
 * day_in_week
 *      return the 0 based day number for any date from 1 Jan. 1 to
 *      31 Dec. 9999.  Assumes the Gregorian reformation eliminates
 *      3 Sep. 1752 through 13 Sep. 1752, and returns invalid weekday
 *      during the period of 11 days.
 */
static int day_in_week(int day, int month, int32_t year)
{
        static const int reform[] = {
                SUNDAY, WEDNESDAY, TUESDAY, FRIDAY, SUNDAY, WEDNESDAY,
                FRIDAY, MONDAY, THURSDAY, SATURDAY, TUESDAY, THURSDAY
        };
        static const int old[] = {
                FRIDAY, MONDAY, SUNDAY, WEDNESDAY, FRIDAY, MONDAY,
                WEDNESDAY, SATURDAY, TUESDAY, THURSDAY, SUNDAY, TUESDAY
        };
        if (year != 1753)
                year -= month < 3;
        else
                year -= (month < 3) + 14;
        if (REFORMATION_YEAR < year
            || (year == REFORMATION_YEAR && 9 < month)
            || (year == REFORMATION_YEAR && month == 9 && 13 < day)) {
                long long_year = year;
                return (long_year + (year / 4) - (year / 100) + (year / 400) + reform[month - 1] +
                        day) % 7;
        }
        if (year < REFORMATION_YEAR
            || (year == REFORMATION_YEAR && month < 9)
            || (year == REFORMATION_YEAR && month == 9 && day < 3))
                return (year + year / 4 + old[month - 1] + day) % 7;
        return NONEDAY;
}

/*
 * week_number
 *      return the week number of a given date, 1..53.
 *      Supports ISO-8601 and North American modes.
 *      Day may be given as Julian day of the year mode, in which
 *      case the month is disregarded entirely.
 */
static int week_number(int day, int month, int32_t year, const struct cal_control *ctl)
{
        int fday = 0, yday;
        int wday = day_in_week(1, 1, year);

        if (ctl->weektype & WEEK_NUM_ISO)
                fday = wday + (wday >= FRIDAY ? -2 : 5);
        else
                /* WEEK_NUM_US
                 * - according to gcal, the first Sun is in the first week
                 * - according to wikipedia, the first Sat is in the first week
                 */
                fday = wday + (wday == SUNDAY ? 6 : -1);

        /* For julian dates the month can be set to 1, the global julian
         * variable cannot be relied upon here, because we may recurse
         * internally for 31.12. which would not work. */
        if (day > 31)
                month = 1;

        yday = day_in_year(day,month,year);
        if (year == REFORMATION_YEAR) {
                if (yday >= YDAY_AFTER_MISSING)
                        fday -= NUMBER_MISSING_DAYS;
        }

        /* Last year is last year */
        if (yday + fday < 7)
                return week_number(31, 12, year - 1, ctl);

        /* Or it could be part of the next year.  The reformation year had less
         * days than 365 making this check invalid, but reformation year ended
         * on Sunday and in week 51, so it's ok here. */
        if (ctl->weektype == WEEK_NUM_ISO && yday >= 363
            && day_in_week(day, month, year) >= MONDAY
            && day_in_week(day, month, year) <= WEDNESDAY
            && day_in_week(31, 12, year) >= MONDAY
            && day_in_week(31, 12, year) <= WEDNESDAY)
                return  week_number(1, 1, year + 1, ctl);

        return (yday + fday) / 7;
}

/*
 * week_to_day
 *      return the yday of the first day in a given week inside
 *      the given year. This may be something other than Monday
 *      for ISO-8601 modes. For North American numbering this
 *      always returns a Sunday.
 */
static int week_to_day(const struct cal_control *ctl)
{
        int yday, wday;

        wday = day_in_week(1, 1, ctl->req.year);
        yday = ctl->req.week * 7 - wday;

        if (ctl->weektype & WEEK_NUM_ISO)
                yday -= (wday >= FRIDAY ? -2 : 5);
        else
                yday -= (wday == SUNDAY ? 6 : -1);      /* WEEK_NUM_US */
        if (yday <= 0)
                return 1;

        return yday;
}

/*
 * Center string, handling multibyte characters appropriately.
 * In addition if the string is too large for the width it's truncated.
 * The number of trailing spaces may be 1 less than the number of leading spaces.
 */
static int center_str(const char* src, char* dest,
                      size_t dest_size, size_t width)
{
        return mbsalign(src, dest, dest_size, &width,
                        MBS_ALIGN_CENTER, MBA_UNIBYTE_FALLBACK);
}

static void center(const char *str, size_t len, int separate)
{
        char lineout[FMT_ST_CHARS];

        center_str(str, lineout, ARRAY_SIZE(lineout), len);
        my_putstring(lineout);

        if (separate) {
                snprintf(lineout, sizeof(lineout), "%*s", separate, "");
                my_putstring(lineout);
        }
}

static void __attribute__ ((__noreturn__)) usage(FILE * out)
{
        fputs(USAGE_HEADER, out);
        fprintf(out, _(" %s [options] [[[day] month] year]\n"), program_invocation_short_name);

        fputs(USAGE_SEPARATOR, out);
        fputs(_("Display a calendar, or some part of it.\n"), out);
        fputs(_("Without any arguments, display the current month.\n"), out);

        fputs(USAGE_OPTIONS, out);
        fputs(_(" -1, --one             show only a single month (default)\n"), out);
        fputs(_(" -3, --three           show three months spanning the date\n"), out);
        fputs(_(" -s, --sunday          Sunday as first day of week\n"), out);
        fputs(_(" -m, --monday          Monday as first day of week\n"), out);
        fputs(_(" -j, --julian          output Julian dates\n"), out);
        fputs(_(" -y, --year            show the whole year\n"), out);
        fputs(_(" -w, --week[=<num>]    show US or ISO-8601 week numbers\n"), out);
        fputs(_("     --color[=<when>]  colorize messages (auto, always or never)\n"), out);

        fputs(USAGE_SEPARATOR, out);
        fputs(USAGE_HELP, out);
        fputs(USAGE_VERSION, out);
        fprintf(out, USAGE_MAN_TAIL("cal(1)"));

        exit(out == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
}