usr/src/usr.bin/cal/cal.c

/*
 * Copyright (c) 1989 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 are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
char copyright[] =
"@(#) Copyright (c) 1989 The Regents of the University of California.\n\
 All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)cal.c       4.5 (Berkeley) %G%";
#endif /* not lint */

#include <sys/types.h>
#include <sys/time.h>
#include <stdio.h>
#include <ctype.h>

#define THURSDAY                4               /* for reformation */
#define SATURDAY                6               /* 1 Jan 1 was a Saturday */
#define FIRST_MISSING_DAY       639787          /* 3 Sep 1752 */
#define NUMBER_MISSING_DAYS     11              /* 11 day correction */
#define SPACE                   99              /* used in day array */

static 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},
};

static int sep1752[42] = {
        SPACE, SPACE,     1,     2,    14,    15,    16,
           17,    18,    19,    20,    21,    22,    23,
           24,    25,    26,    27,    28,    29,    30,
        SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE,
        SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE,
        SPACE, SPACE, SPACE, SPACE, SPACE, SPACE, SPACE,
};

static char *month_names[12] = {
        "January", "February", "March", "April", "May", "June",
        "July", "August", "September", "October", "November", "December",
};

static char *day_headings = " S  M Tu  W Th  F  S";

/* leap year -- account for gregorian reformation in 1752 */
#define leap_year(yr) \
        ((yr) <= 1752 ? !((yr) % 4) : \
        !((yr) % 4) && ((yr) % 100) || !((yr) % 400))

/* number of centuries since 1700, not inclusive */
#define centuries_since_1700(yr) \
        ((yr) > 1700 ? (yr) / 100 - 17 : 0)

/* number of centuries since 1700 whose modulo of 400 is 0 */
#define quad_centuries_since_1700(yr) \
        ((yr) > 1600 ? ((yr) - 1600) / 400 : 0)

/* number of leap years between year 1 and this year, not inclusive */
#define leap_years_since_year_1(yr) \
        ((yr) / 4 - centuries_since_1700(yr) + quad_centuries_since_1700(yr))

main(argc, argv)
        int argc;
        char **argv;
{
        struct tm *local_time;
        time_t now, time();
        int month, year;

        ++argv;
        switch(argc) {
        case 3:
                if ((month = atoi(*argv++)) <= 0 || month > 12) {
                        (void)fprintf(stderr, "cal: illegal month value.\n");
                        exit(1);
                }
                /* FALLTHROUGH */
        case 2:
                if ((year = atoi(*argv)) <= 0 || year > 9999) {
                        (void)fprintf(stderr, "cal: illegal year value.\n");
                        exit(1);
                }
                break;
        case 1:
                (void)time(&now);
                local_time = localtime(&now);
                month = local_time->tm_mon + 1;
                year = local_time->tm_year + 1900;
                break;
        default:
                (void)fprintf(stderr, "usage: cal [[month] year]\n");
                exit(1);
        }
        if (month)
                print_monthly_calendar(month, year);
        else
                print_yearly_calendar(year);
        exit(0);
}

print_monthly_calendar(month, year)
        int month, year;
{
        register int col, row;
        register char *p;
        int days[42];
        char lineout[30];

        generate_day_array(month, year, days);
        (void)printf("   %s %d\n%s\n",
            month_names[month - 1], year, day_headings);
        for (row = 0; row < 6; row++) {
                for (col = 0, p = lineout; col < 7; col++, p += 3)
                        ascii_day(p, days[row * 7 + col]);
                trim_trailing_spaces(lineout);
                (void)printf("%s\n", lineout);
        }
}

print_yearly_calendar(year)
        int year;
{
        register int col, *dp, i, month, row, which_cal;
        register char *p;
        int days[12][42];
        char lineout[80];

        (void)printf("\n\n\n\t\t\t\t%d\n\n", year);
        for (i = 0; i < 12; i++)
                generate_day_array(i + 1, year, &days[i][0]);
        (void)memset(lineout, ' ', sizeof(lineout) - 1);
        lineout[sizeof(lineout) - 1] = '\0';
        for (month = 0; month < 12; month += 3) {
                (void)printf("\t %.3s\t\t\t%.3s\t\t       %.3s\n",
                    month_names[month], month_names[month + 1],
                    month_names[month + 2]);
                for (i = 0; i < 3; i++) {
                        (void)printf("%s", day_headings);
                        if (i < 2)
                                (void)printf("   ");
                }
                (void)printf("\n");
                for (row = 0; row < 6; row++) {
                        for (which_cal = 0; which_cal < 3; which_cal++) {
                                p = lineout + which_cal * 23;
                                dp = &days[month + which_cal][row * 7];
                                for (col = 0; col < 7; col++, p += 3)
                                        ascii_day(p, *dp++);
                        }
                        trim_trailing_spaces(lineout);
                        (void)printf("%s\n", lineout);
                }
        }
        (void)printf("\n\n\n");
}

/*
 * generate_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.
 */
generate_day_array(month, year, days)
        int month, year, *days;
{
        register int i, day, dw, dm;

        dm = days_in_month[leap_year(year)][month];
        dw = day_in_week(1, month, year);
        if (month == 9 && year == 1752)
                for (i = 0; i < 42; i++)
                        days[i] = sep1752[i];
        else {
                for (i = 0; i < 42; i++)
                        days[i] = SPACE;
                for (day = 1, i = dw; day <= dm; ++day, ++i)
                        days[i] = day;
        }
}

/*
 * day_in_year --
 *      return the 1 based day number within the year
 */
day_in_year(day, month, year)
        register int day, month;
        int year;
{
        register 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.  Returns Thursday for all
 *      missing days.
 */
day_in_week(day, month, year)
        int day, month, year;
{
        long temp;

        temp = (long)(year - 1) * 365 + leap_years_since_year_1(year - 1)
            + day_in_year(day, month, year);
        if (temp < FIRST_MISSING_DAY)
                return((temp - 1 + SATURDAY) % 7);
        if (temp >= (FIRST_MISSING_DAY + NUMBER_MISSING_DAYS))
                return(((temp - 1 + SATURDAY) - NUMBER_MISSING_DAYS) % 7);
        return(THURSDAY);
}

ascii_day(p, day)
        register char *p;
        register int day;
{
        register int ten;

        if (day == SPACE) {
                *p++ = ' ';
                *p++ = ' ';
        }
        else {
                ten = day / 10;
                *p++ = ten ? ten + '0' : ' ';
                *p++ = day % 10 + '0';
        }
        *p = ' ';
}

trim_trailing_spaces(s)
        register char *s;
{
        register char *p;

        for (p = s; *p; ++p);
        while (p > s && isspace(*--p));
        if (p > s)
                ++p;
        *p = '\0';
}