/**
*
* strftime.c
*
* implements the ansi c function strftime()
*
* written 6 september 1989 by jim nutt
* released into the public domain by jim nutt
*
* modified 21-Oct-89 by Rob Duff
*
* modified 08-Dec-04 by Tobi Oetiker (added %V)
**/
#include <stddef.h> /* for size_t */
#include <stdarg.h> /* for va_arg */
#include <time.h> /* for struct tm */
#include "strftime.h"
static char *aday[] = {
"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
};
static char *day[] = {
"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"
};
static char *amonth[] = {
"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};
static char *month[] = {
"January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"
};
char *tzname_[2] = {"CST", "CDT"}; /* Add your own defaults here */
static char buf[26];
static void strfmt(char *str, const char *fmt, ...);
/**
*
* size_t strftime_(char *str,
* size_t maxs,
* const char *fmt,
* const struct tm *t)
*
* this functions acts much like a sprintf for time/date output.
* given a pointer to an output buffer, a format string and a
* time, it copies the time to the output buffer formatted in
* accordance with the format string. the parameters are used
* as follows:
*
* str is a pointer to the output buffer, there should
* be at least maxs characters available at the address
* pointed to by str.
*
* maxs is the maximum number of characters to be copied
* into the output buffer, included the '\0' terminator
*
* fmt is the format string. a percent sign (%) is used
* to indicate that the following character is a special
* format character. the following are valid format
* characters:
*
* %A full weekday name (Monday)
* %a abbreviated weekday name (Mon)
* %B full month name (January)
* %b abbreviated month name (Jan)
* %c standard date and time representation
* %d day-of-month (01-31)
* %H hour (24 hour clock) (00-23)
* %I hour (12 hour clock) (01-12)
* %j day-of-year (001-366)
* %M minute (00-59)
* %m month (01-12)
* %p local equivalent of AM or PM
* %S second (00-59)
* %U week-of-year, first day sunday (00-53)
* %W week-of-year, first day monday (00-53)
* %V ISO 8601 Week number
* %w weekday (0-6, sunday is 0)
* %X standard time representation
* %x standard date representation
* %Y year with century
* %y year without century (00-99)
* %Z timezone name
* %% percent sign
*
* the standard date string is equivalent to:
*
* %a %b %d %Y
*
* the standard time string is equivalent to:
*
* %H:%M:%S
*
* the standard date and time string is equivalent to:
*
* %a %b %d %H:%M:%S %Y
*
* strftime_() returns the number of characters placed in the
* buffer, not including the terminating \0, or zero if more
* than maxs characters were produced.
*
**/
size_t strftime_(char *s, size_t maxs, const char *f, const struct tm *t)
{
int w,d;
char *p, *q, *r;
p = s;
q = s + maxs - 1;
while ((*f != '\0'))
{
if (*f++ == '%')
{
r = buf;
switch (*f++)
{
case '%' :
r = "%";
break;
case 'a' :
r = aday[t->tm_wday];
break;
case 'A' :
r = day[t->tm_wday];
break;
case 'b' :
r = amonth[t->tm_mon];
break;
case 'B' :
r = month[t->tm_mon];
break;
case 'c' :
strfmt(r, "%0 %0 %2 %2:%2:%2 %4",
aday[t->tm_wday], amonth[t->tm_mon],
t->tm_mday,t->tm_hour, t->tm_min,
t->tm_sec, t->tm_year+1900);
break;
case 'd' :
strfmt(r,"%2",t->tm_mday);
break;
case 'H' :
strfmt(r,"%2",t->tm_hour);
break;
case 'I' :
strfmt(r,"%2",(t->tm_hour%12)?t->tm_hour%12:12);
break;
case 'j' :
strfmt(r,"%3",t->tm_yday+1);
break;
case 'm' :
strfmt(r,"%2",t->tm_mon+1);
break;
case 'M' :
strfmt(r,"%2",t->tm_min);
break;
case 'p' :
r = (t->tm_hour>11)?"PM":"AM";
break;
case 'S' :
strfmt(r,"%2",t->tm_sec);
break;
case 'U' :
w = t->tm_yday/7;
if (t->tm_yday%7 > t->tm_wday)
w++;
strfmt(r, "%2", w);
break;
case 'W' :
w = t->tm_yday/7;
if (t->tm_yday%7 > (t->tm_wday+6)%7)
w++;
strfmt(r, "%2", w);
break;
case 'V':
/* ISO 8601 Week Of Year:
If the week (Monday - Sunday) containing January 1 has four or more
days in the new year, then it is week 1; otherwise it is week 53 of
the previous year and the next week is week one. */
w = (t->tm_yday + 7 - (t->tm_wday ? t->tm_wday - 1 : 6)) / 7;
d = (t->tm_yday + 7 - (t->tm_wday ? t->tm_wday - 1 : 6)) % 7;
if (d >= 4) { w++; } else if (w == 0) { w = 53; }
strfmt(r, "%2", w);
break;
case 'w' :
strfmt(r,"%1",t->tm_wday);
break;
case 'x' :
strfmt(r, "%3s %3s %2 %4", aday[t->tm_wday],
amonth[t->tm_mon], t->tm_mday, t->tm_year+1900);
break;
case 'X' :
strfmt(r, "%2:%2:%2", t->tm_hour,
t->tm_min, t->tm_sec);
break;
case 'y' :
strfmt(r,"%2",t->tm_year%100);
break;
case 'Y' :
strfmt(r,"%4",t->tm_year+1900);
break;
case 'Z' :
r = (t->tm_isdst && tzname_[1][0]) ?
tzname_[1] : tzname_[0];
break;
default:
buf[0] = '%'; /* reconstruct the format */
buf[1] = f[-1];
buf[2] = '\0';
if (buf[1] == 0)
f--; /* back up if at end of string */
}
while (*r)
{
if (p == q)
{
*q = '\0';
return 0;
}
*p++ = *r++;
}
}
else
{
if (p == q)
{
*q = '\0';
return 0;
}
*p++ = f[-1];
}
}
*p = '\0';
return p - s;
}
/*
* stdarg.h
*
typedef void *va_list;
#define va_start(vp,v) (vp=((char*)&v)+sizeof(v))
#define va_arg(vp,t) (*((t*)(vp))++)
#define va_end(vp)
*
*/
static int pow[5] = { 1, 10, 100, 1000, 10000 };
/**
* static void strfmt(char *str, char *fmt);
*
* simple sprintf for strftime
*
* each format descriptor is of the form %n
* where n goes from zero to four
*
* 0 -- string %s
* 1..4 -- int %?.?d
*
**/
static void strfmt(char *str, const char *fmt, ...)
{
int ival, ilen;
char *sval;
va_list vp;
va_start(vp, fmt);
while (*fmt)
{
if (*fmt++ == '%')
{
ilen = *fmt++ - '0';
if (ilen == 0) /* zero means string arg */
{
sval = va_arg(vp, char*);
while (*sval)
*str++ = *sval++;
}
else /* always leading zeros */
{
ival = va_arg(vp, int);
while (ilen)
{
ival %= pow[ilen--];
*str++ = (char)('0' + ival / pow[ilen]);
}
}
}
else *str++ = fmt[-1];
}
*str = '\0';
va_end(vp);
}
#ifdef TEST
#include <stdio.h> /* for printf */
#include <time.h> /* for strftime */
char test[80];
int main(int argc, char *argv[])
{
int len;
char *fmt;
time_t now;
time(&now);
fmt = (argc == 1) ? "%I:%M %p\n%c\n" : argv[1];
len = strftime_(test,sizeof test, fmt, localtime(&now));
printf("%d: %s\n", len, test);
return !len;
}
#endif /* TEST */