sbase/cal.c

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3.5 KiB
C
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/* See LICENSE file for copyright and license details. */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "util.h"
static int
isleap(int year)
{
if (year % 400 == 0)
return 1;
if (year % 100 == 0)
return 0;
return (year % 4 == 0);
}
static int
monthlength(int year, int month)
{
int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
return (month==1 && isleap(year)) ? 29 : mdays[month];
}
/* From http://www.tondering.dk/claus/cal/chrweek.php#calcdow */
static int
dayofweek(int year, int month, int dom)
{
int m, y, a;
month += 1; /* in this formula, 1 <= month <= 12 */
a = (14 - month) / 12;
y = year - a;
m = month + 12*a - 2;
return (dom + y + y/4 - y/100 + y/400 +((31*m)/12)) % 7;
}
static void
printgrid(int year, int month, int fday, int line)
{
int dom, offset, d=0;
offset = dayofweek(year, month, 1) - fday;
if (offset < 0)
offset += 7;
if (line==1) {
for ( ; d < offset; ++d)
printf(" ");
dom = 1;
} else {
dom = 8-offset + (line-2)*7;
}
for ( ; d < 7 && dom <= monthlength(year, month); ++d, ++dom)
printf("%2d ", dom);
for ( ; d < 7; ++d)
printf(" ");
}
static void
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drawcal(int year, int month, int ncols, int nmons, int fday)
{
char *smon[] = {" January", " February", " March", " April",
" May", " June", " July", " August",
"September", " October", " November", " December" };
char *days[] = { "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa", };
int m, n, col, cur_year, cur_month, line, dow;
for (m = 0; m < nmons; ) {
n = m;
for (col = 0; m < nmons && col < ncols; ++col, ++m) {
cur_year = year + m/12;
cur_month = month + m%12;
if (cur_month > 11) {
cur_month -= 12;
cur_year += 1;
}
printf(" %s %d ", smon[cur_month], cur_year);
printf(" ");
}
printf("\n");
for (col = 0, m = n; m < nmons && col < ncols; ++col, ++m) {
for (dow = fday; dow < (fday+7); ++dow)
printf("%s ", days[dow%7]);
printf(" ");
}
printf("\n");
for (line=1; line<=6; ++line) {
for (col=0, m=n; m<nmons && col<ncols; ++col, ++m) {
cur_year = year + m/12;
cur_month = month + m%12;
if (cur_month > 11) {
cur_month -= 12;
cur_year += 1;
}
printgrid(cur_year, cur_month, fday, line);
printf(" ");
}
printf("\n");
}
}
}
static void
usage(void)
{
eprintf("usage: %s [-1] [-3] [-m] [-s] [-y] [-c columns]"
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" [-f firstday] [-n nmonths] [ [month] year]\n",
argv0);
}
int
main(int argc, char *argv[])
{
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int year, month, ncols, nmons, fday;
struct tm *ltime;
time_t now;
now = time(NULL);
ltime = localtime(&now);
year = ltime->tm_year + 1900;
month = ltime->tm_mon + 1;
fday = 0;
ncols = 3;
nmons = 1;
ARGBEGIN {
case '1':
nmons = 1;
break;
case '3':
nmons = 3;
month -= 1;
if(month == 0) {
month = 12;
year--;
}
break;
case 'c':
ncols = estrtol(EARGF(usage()), 0);
break;
case 'f':
fday = estrtol(EARGF(usage()), 0);
break;
case 'm': /* Monday */
fday = 1;
break;
case 'n':
nmons = estrtol(EARGF(usage()), 0);
break;
case 's': /* Sunday */
fday = 0;
break;
case 'y':
month = 1;
nmons = 12;
break;
default:
usage();
} ARGEND;
switch (argc) {
case 2:
month = estrtol(argv[0], 0);
argv++;
case 1:
year = estrtol(argv[0], 0);
break;
case 0:
break;
default:
usage();
}
if (ncols < 0 || month < 1 || month > 12 || nmons < 1 || fday < 0 || fday > 6) {
usage();
}
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drawcal(year, month-1, ncols, nmons, fday);
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return 0;
}