]> git.ipfire.org Git - thirdparty/util-linux.git/blobdiff - misc-utils/cal.c
lib/mbalign: fix unsigned integer overflow [AddressSanitizer]
[thirdparty/util-linux.git] / misc-utils / cal.c
index ec8922e4a2e4041b55b36f5ad7277053121c2337..a11136a5ba2f1b2944b59657f718d793f85f9c0d 100644 (file)
@@ -96,18 +96,18 @@ static const char *my_tgetstr(char *s __attribute__((__unused__)), char *ss)
        const char *ret = tigetstr(ss);
        if (!ret || ret == (char *)-1)
                return "";
-       else
-               return ret;
+
+       return ret;
 }
 
 #elif defined(HAVE_LIBTERMCAP)
 # include <termcap.h>
 
-char termbuffer[4096];
-char tcbuffer[4096];
-char *strbuf = termbuffer;
+static char termbuffer[4096];
+static char tcbuffer[4096];
+static char *strbuf = termbuffer;
 
-static void my_setupterm(const char *term, int fildes, int *errret)
+static void my_setupterm(const char *term, int fildes __attribute__((__unused__)), int *errret)
 {
        *errret = tgetent(tcbuffer, term);
 }
@@ -122,8 +122,8 @@ static const char *my_tgetstr(char *s, char *ss __attribute__((__unused__)))
        const char *ret = tgetstr(s, &strbuf);
        if (!ret)
                return "";
-       else
-               return ret;
+
+       return ret;
 }
 
 #else  /* ! (HAVE_LIBTERMCAP || HAVE_LIBNCURSES || HAVE_LIBNCURSESW) */
@@ -135,21 +135,21 @@ static void my_putstring(char *s)
 
 #endif /* end of LIBTERMCAP / NCURSES */
 
+#if defined(HAVE_LIBNCURSES) || defined(HAVE_LIBNCURSESW) || defined(HAVE_LIBTERMCAP)
+static const char      *term="";
+#endif
 
-const char     *term="";
-const char     *Senter="", *Sexit="";/* enter and exit standout mode */
-int            Slen;           /* strlen of Senter+Sexit */
-char           *Hrow;          /* pointer to highlighted row in month */
+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
+# define NUM_MONTHS 1
 #endif
 
 #if ( NUM_MONTHS != 1 && NUM_MONTHS !=3 )
-#error NUM_MONTHS must be 1 or 3
+# error NUM_MONTHS must be 1 or 3
 #endif
 
 enum {
@@ -160,15 +160,16 @@ enum {
        THURSDAY,
        FRIDAY,
        SATURDAY,
-       DAYS_IN_WEEK
+       DAYS_IN_WEEK,
+       NONEDAY
 };
 
 #define        FIRST_WEEKDAY           SATURDAY        /* Jan 1st, 1 was a Saturday */
-#define        REFORMATION_WEEKDAY     THURSDAY        /* after reformation it was Thursday */
 #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
@@ -177,85 +178,95 @@ enum {
 #define        SPACE                   -1              /* used in day array */
 
 #define SMALLEST_YEAR          1
-#define GREATEST_YEAR          9999
 
 #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        J_DAY_LEN               4               /* 4 spaces per day */
-#define        J_WEEK_LEN              (DAYS_IN_WEEK * J_DAY_LEN)
-#define        J_HEAD_SEP              2
-#define J_MONTH_COLS           2
+#define WNUM_LEN                3
 
 #define TODAY_FLAG             0x400           /* flag day for highlighting */
 
-#define FMT_ST_LINES 8
 #define FMT_ST_CHARS 300       /* 90 suffices in most locales */
-struct fmt_st
-{
-  char s[FMT_ST_LINES][FMT_ST_CHARS];
-};
 
-static int days_in_month[2][13] = {
+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},
 };
 
-/* September 1752 is special, and has static assignments for both date
- * and Julian representations.  */
- int d_sep1752[MAXDAYS / 2] = {
-       SPACE,  SPACE,  1,      2,      14,     15,     16,
-       17,     18,     19,     20,     21,     22,     23,
-       24,     25,     26,     27,     28,     29,     30
-}, j_sep1752[MAXDAYS / 2] = {
-       SPACE,  SPACE,  245,    246,    258,    259,    260,
-       261,    262,    263,    264,    265,    266,    267,
-       268,    269,    270,    271,    272,    273,    274
-}, empty[MAXDAYS] = {
-       SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,
-       SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,
-       SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,
-       SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,
-       SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,
-       SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE,  SPACE
+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 */
-char day_headings[J_WEEK_LEN * 6 + 1];
-/* weekstart = 1  =>   "  M  Tu   W  Th   F   S   S " */
-const char *full_month[MONTHS_IN_YEAR];
+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 */
+};
 
-/* 0 => sunday, 1 => monday */
-int weekstart = SUNDAY;
-int julian;
+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(int year);
-static int centuries_since_1700(int year, int centuries);
-static int leap_years_since_year_1(int year);
-char * ascii_day(char *, int);
-int center_str(const char* src, char* dest, size_t dest_size, size_t width);
-void center(const char *, size_t, int);
-void day_array(int, int, int, int *);
-int day_in_week(int, int, int);
-int day_in_year(int, int, int);
-void yearly(int, int, int);
-void do_monthly(int, int, int, struct fmt_st*);
-void monthly(int, int, int);
-void monthly3(int, int, int);
-static void __attribute__ ((__noreturn__)) usage(FILE * out);
-void headers_init(int);
-
-int
-main(int argc, char **argv) {
+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, day = 0, month = 0, year = 0, yflag = 0;
-       int num_months = NUM_MONTHS;
-       int colormode = UL_COLORMODE_AUTO;
+       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
@@ -268,6 +279,7 @@ main(int argc, char **argv) {
                {"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'},
@@ -286,7 +298,6 @@ main(int argc, char **argv) {
                if (ret > 0) {
                        Senter = my_tgetstr("so","smso");
                        Sexit = my_tgetstr("se","rmso");
-                       Slen = strlen(Senter) + strlen(Sexit);
                }
        }
 #endif
@@ -322,37 +333,44 @@ main(int argc, char **argv) {
 
                wfd = val.word;
                wfd = day_in_week(wfd % 100, (wfd / 100) % 100, wfd / (100 * 100));
-               weekstart = (wfd + *nl_langinfo(_NL_TIME_FIRST_WEEKDAY) - 1) % DAYS_IN_WEEK;
+               ctl.weekstart = (wfd + *nl_langinfo(_NL_TIME_FIRST_WEEKDAY) - 1) % DAYS_IN_WEEK;
        }
 #endif
 
-       while ((ch = getopt_long(argc, argv, "13mjsyVh", longopts, NULL)) != -1)
+       while ((ch = getopt_long(argc, argv, "13mjsywVh", longopts, NULL)) != -1)
                switch(ch) {
                case '1':
-                       num_months = 1;         /* default */
+                       ctl.num_months = 1;             /* default */
                        break;
                case '3':
-                       num_months = 3;
+                       ctl.num_months = 3;
                        break;
                case 's':
-                       weekstart = SUNDAY;     /* default */
+                       ctl.weekstart = SUNDAY;         /* default */
                        break;
                case 'm':
-                       weekstart = MONDAY;
+                       ctl.weekstart = MONDAY;
                        break;
                case 'j':
-                       julian = 1;
+                       ctl.julian = 1;
+                       ctl.day_width = DAY_LEN + 1;
                        break;
                case 'y':
-                       yflag = 1;
+                       ctl.yflag = 1;
                        break;
-               case OPT_COLOR:
+               case 'w':
                        if (optarg) {
-                               char *p = *optarg == '=' ? optarg + 1 : optarg;
-                               colormode = colormode_from_string(p);
-                               if (colormode < 0)
-                                       errx(EXIT_FAILURE, _("unsupported color mode: '%s'"), p);
+                               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);
@@ -366,60 +384,106 @@ main(int argc, char **argv) {
        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:
-               day = strtos32_or_err(*argv++, _("illegal day value"));
-               if (day < 1 || DAYS_IN_MONTH < day)
+               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:
-               month = strtos32_or_err(*argv++, _("illegal month value: use 1-12"));
-               if (month < 1 || MONTHS_IN_YEAR < month)
+               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:
-               year = strtos32_or_err(*argv++, _("illegal year value: use 1-9999"));
-               if (year < SMALLEST_YEAR || GREATEST_YEAR < year)
-                       errx(EXIT_FAILURE, _("illegal year value: use 1-9999"));
-               if (day) {
-                       int dm = days_in_month[leap_year(year)][month];
-                       if (day > dm)
+               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);
-                       day = day_in_year(day, month, year);
-               } else if ((local_time->tm_year + 1900) == year) {
-                       day = local_time->tm_yday + 1;
+                       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;
                }
-               if (!month)
-                       yflag=1;
                break;
        case 0:
-               day = local_time->tm_yday + 1;
-               year = local_time->tm_year + 1900;
-               month = local_time->tm_mon + 1;
+               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);
        }
-       headers_init(julian);
 
-       if (!colors_init(colormode))
-               day = 0;
+       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 (yflag)
-               yearly(day, year, julian);
-       else if (num_months == 1)
-               monthly(day, month, year);
-       else if (num_months == 3)
-               monthly3(day, month, year);
+       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(int year)
+static int leap_year(int32_t year)
 {
        if (year <= REFORMATION_YEAR)
                return !(year % 4);
@@ -427,244 +491,291 @@ static int leap_year(int year)
                return ( !(year % 4) && (year % 100) ) || !(year % 400);
 }
 
-/* number of centuries since 1700 */
-static int centuries_since_1700(int year, int n)
-{
-       if (year < REFORMATION_YEAR)
-               return 0;
-       else
-               return ((year / (100 * n)) - ((REFORMATION_YEAR / 100) / n));
-}
-
-/* number of leap years between year 1 and this year, not inclusive */
-static int leap_years_since_year_1(int year)
+static void headers_init(struct cal_control *ctl)
 {
-       return (year / 4 - centuries_since_1700(year, 1) +
-               centuries_since_1700(year, 4));
-}
-
-void headers_init(int julian)
-{
-       int i, wd, spaces = julian ? J_DAY_LEN - 1 : DAY_LEN - 1;
+       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++) {
-               ssize_t space_left;
-               wd = (i + weekstart) % DAYS_IN_WEEK;
+               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 <= spaces)
+               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, spaces);
+               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++)
-               full_month[i] = nl_langinfo(MON_1 + i);
+       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;
+       }
 }
 
-void
-do_monthly(int day, int month, int year, struct fmt_st *out) {
-       int col, row, days[MAXDAYS];
-       char *p, lineout[FMT_ST_CHARS];
-       int width = (julian ? J_WEEK_LEN : WEEK_LEN) - 1;
-
-       day_array(day, month, year, days);
-
-       /*
-        * %s is the month name, %d the year number.
-        * you can change the order and/or add something here; eg for
-        * Basque the translation should be: "%2$dko %1$s", and
-        * the Vietnamese should be "%s na(m %d", etc.
-        */
-       snprintf(lineout, sizeof(lineout), _("%s %d"),
-                       full_month[month - 1], year);
-       center_str(lineout, out->s[0], ARRAY_SIZE(out->s[0]), width);
-
-       snprintf(out->s[1], FMT_ST_CHARS, "%s", day_headings);
-       for (row = 0; row < DAYS_IN_WEEK - 1; row++) {
-               int has_hl = 0;
-               for (col = 0, p = lineout; col < DAYS_IN_WEEK; col++) {
-                       int xd = days[row * DAYS_IN_WEEK + col];
-                       if (xd != SPACE && (xd & TODAY_FLAG))
-                               has_hl = 1;
-                       p = ascii_day(p, xd);
+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++;
                }
-               *p = '\0';
-               snprintf(out->s[row+2], FMT_ST_CHARS, "%s", lineout);
-               if (has_hl)
-                       Hrow = out->s[row+2];
        }
 }
 
-void
-monthly(int day, int month, int year) {
-       int i;
-       struct fmt_st out;
+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;
 
-       do_monthly(day, month, year, &out);
-       for (i = 0; i < FMT_ST_LINES; i++) {
-               my_putstring(out.s[i]);
-               my_putstring("\n");
+       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);
+               }
        }
 }
 
-void
-monthly3(int day, int month, int year) {
-       char lineout[FMT_ST_CHARS];
-       int i;
-       int width;
-       struct fmt_st out_prev;
-       struct fmt_st out_curm;
-       struct fmt_st out_next;
-       int prev_month, prev_year;
-       int next_month, next_year;
-
-       if (month == 1) {
-               prev_month = MONTHS_IN_YEAR;
-               prev_year  = year - 1;
+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 {
-               prev_month = month - 1;
-               prev_year  = year;
+               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);
+               }
        }
-       if (month == MONTHS_IN_YEAR) {
-               next_month = 1;
-               next_year  = year + 1;
-       } else {
-               next_month = month + 1;
-               next_year  = year;
+       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");
+}
 
-       do_monthly(day, prev_month, prev_year, &out_prev);
-       do_monthly(day, month,      year,      &out_curm);
-       do_monthly(day, next_month, next_year, &out_next);
+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);
+                       }
 
-       width = (julian ? J_WEEK_LEN : WEEK_LEN) -1;
-       for (i = 0; i < 2; i++) {
-               snprintf(lineout, sizeof(lineout),
-                       "%s  %s  %s\n", out_prev.s[i], out_curm.s[i], out_next.s[i]);
-               my_putstring(lineout);
+                       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);
+               }
        }
-       for (i = 2; i < FMT_ST_LINES; i++) {
-               int w1, w2, w3;
-               w1 = w2 = w3 = width;
+}
 
-#if defined(HAVE_LIBNCURSES) || defined(HAVE_LIBNCURSESW) || defined(HAVE_LIBTERMCAP)
-               /* adjust width to allow for non printable characters */
-               w1 += (out_prev.s[i] == Hrow ? Slen : 0);
-               w2 += (out_curm.s[i] == Hrow ? Slen : 0);
-               w3 += (out_next.s[i] == Hrow ? Slen : 0);
-#endif
-               snprintf(lineout, sizeof(lineout), "%-*s %-*s %-*s\n",
-                      w1, out_prev.s[i],
-                      w2, out_curm.s[i],
-                      w3, out_next.s[i]);
+static void monthly(const struct cal_control *ctl)
+{
+       struct cal_month month;
 
-               my_putstring(lineout);
-       }
+       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);
 }
 
-void
-yearly(int day, int year, int julian) {
-       int col, *dp, i, month, row, which_cal;
-       int maxrow, sep_len, week_len;
-       int days[MONTHS_IN_YEAR][MAXDAYS];
-       char *p, lineout[100];
-
-       if (julian) {
-               maxrow = J_MONTH_COLS;
-               sep_len = J_HEAD_SEP;
-               week_len = J_WEEK_LEN;
+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 {
-               maxrow = MONTH_COLS;
-               sep_len = HEAD_SEP;
-               week_len = WEEK_LEN;
+               first_month = ctl->req.month - 1;
+               first_year = ctl->req.year;
        }
-       snprintf(lineout, sizeof(lineout), "%d", year);
-       /* 2013-04-28: The -1 near sep_len makes year header to be
-        * aligned exactly how it has been aligned for long time, but it
-        * is unexplainable.  */
-       center(lineout, (week_len + sep_len) * maxrow - sep_len - 1, 0);
-       my_putstring("\n\n");
 
-       for (i = 0; i < MONTHS_IN_YEAR; i++)
-               day_array(day, i + 1, year, days[i]);
-       for (month = 0; month < MONTHS_IN_YEAR; month += maxrow) {
-               center(full_month[month], week_len - 1, sep_len + 1);
-               if (julian) {
-                       center(full_month[month + 1], week_len - 1, 0);
-               } else {
-                       center(full_month[month + 1], week_len - 1, sep_len + 1);
-                       center(full_month[month + 2], week_len - 1, 0);
-               }
-               if (julian)
-                       snprintf(lineout, sizeof(lineout),
-                                "\n%s%*s %s\n", day_headings, sep_len, "", day_headings);
-               else
-                       snprintf(lineout, sizeof(lineout),
-                                "\n%s%*s %s%*s %s\n", day_headings, sep_len,
-                                "", day_headings, sep_len, "", day_headings);
-               my_putstring(lineout);
-               for (row = 0; row < DAYS_IN_WEEK - 1; row++) {
-                       p = lineout;
-                       for (which_cal = 0; which_cal < maxrow; which_cal++) {
-                               dp = &days[month + which_cal][row * DAYS_IN_WEEK];
-                               for (col = 0; col < DAYS_IN_WEEK; col++)
-                                       p = ascii_day(p, *dp++);
-                               p += sprintf(p, "  ");
-                       }
-                       *p = '\0';
-                       my_putstring(lineout);
-                       my_putstring("\n");
-               }
-       }
-       my_putstring("\n");
+       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);
 }
 
-/*
- * day_array --
- *     Fill in an array of 42 integers with a calendar.  Assume for a moment
- *     that you took the (maximum) 6 rows in a calendar and stretched them
- *     out end to end.  You would have 42 numbers or spaces.  This routine
- *     builds that array for any month from Jan. 1 through Dec. 9999.
- */
-void
-day_array(int day, int month, int year, int *days) {
-       int julday, daynum, dw, dm;
-       int *sep1752;
-
-       memcpy(days, empty, MAXDAYS * sizeof(int));
-       if (year == REFORMATION_YEAR && month == REFORMATION_MONTH) {
-               sep1752 = julian ? j_sep1752 : d_sep1752;
-               memcpy(days, sep1752 + weekstart,
-                      ((MAXDAYS / 2) - weekstart) * sizeof(int));
-               for (dm = 0; dm < MAXDAYS / 2; dm++)
-                       if (j_sep1752[dm] == day)
-                               days[dm] |= TODAY_FLAG;
-               return;
+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;
        }
-       dm = days_in_month[leap_year(year)][month];
-       dw = (day_in_week(1, month, year) - weekstart + DAYS_IN_WEEK) % DAYS_IN_WEEK;
-       julday = day_in_year(1, month, year);
-       daynum = julian ? julday : 1;
-       while (dm--) {
-               days[dw] = daynum++;
-               if (julday++ == day)
-                       days[dw] |= TODAY_FLAG;
-               dw++;
+
+       /* 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
  */
-int
-day_in_year(int day, int month, int year) {
+static int day_in_year(int day, int month, int32_t year)
+{
        int i, leap;
 
        leap = leap_year(year);
@@ -677,70 +788,107 @@ day_in_year(int day, int month, int year) {
  * 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.  Returns Thursday for all
- *     missing days.
+ *     3 Sep. 1752 through 13 Sep. 1752, and returns invalid weekday
+ *     during the period of 11 days.
  */
-int
-day_in_week(int day, int month, int year) {
-       long temp;
-
-       temp =
-           (long)(year - SMALLEST_YEAR) * DAYS_IN_YEAR +
-           leap_years_since_year_1(year - SMALLEST_YEAR)
-           + day_in_year(day, month, year);
-       if (temp < FIRST_MISSING_DAY)
-               return ((temp - 1 + FIRST_WEEKDAY) % DAYS_IN_WEEK);
-       if (temp >= (FIRST_MISSING_DAY + NUMBER_MISSING_DAYS))
-               return (((temp - 1 + FIRST_WEEKDAY) - NUMBER_MISSING_DAYS) % DAYS_IN_WEEK);
-       return(REFORMATION_WEEKDAY);
+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))
+               return (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;
 }
 
-char *
-ascii_day(char *p, int day) {
-       int display, val;
-       int highlight = 0;
-       static char *aday[] = {
-               "",
-               " 1", " 2", " 3", " 4", " 5", " 6", " 7",
-               " 8", " 9", "10", "11", "12", "13", "14",
-               "15", "16", "17", "18", "19", "20", "21",
-               "22", "23", "24", "25", "26", "27", "28",
-               "29", "30", "31",
-       };
+/*
+ * 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 (day == SPACE) {
-               int len = julian ? J_DAY_LEN : DAY_LEN;
-               memset(p, ' ', len);
-               return p+len;
-       }
-       if (day & TODAY_FLAG) {
-               day &= ~TODAY_FLAG;
-               p += sprintf(p, "%s", Senter);
-               highlight = 1;
-       }
-       if (julian) {
-               if ((val = day / 100)) {
-                       day %= 100;
-                       *p++ = val + '0';
-                       display = 1;
-               } else {
-                       *p++ = ' ';
-                       display = 0;
-               }
-               val = day / 10;
-               if (val || display)
-                       *p++ = val + '0';
-               else
-                       *p++ = ' ';
-               *p++ = day % 10 + '0';
-       } else {
-               *p++ = aday[day][0];
-               *p++ = aday[day][1];
+       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;
        }
-       if (highlight)
-               p += sprintf(p, "%s", Sexit);
-       *p++ = ' ';
-       return p;
+
+       /* 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;
 }
 
 /*
@@ -748,15 +896,14 @@ ascii_day(char *p, int day) {
  * 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.
  */
-int
-center_str(const char* src, char* dest, size_t dest_size, size_t width)
+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);
 }
 
-void
-center(const char *str, size_t len, int separate)
+static void center(const char *str, size_t len, int separate)
 {
        char lineout[FMT_ST_CHARS];
 
@@ -773,17 +920,25 @@ 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 current month (default)\n"), out);
-       fputs(_(" -3, --three           show previous, current and next month\n"), 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 whole current year\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);
 }