source: buchla-68k/orig/DATE/GDATE.C@ b8080f6

/* gdate.c -- get date -- Version 1 -- 1986-01-09 */
/* requires the "notorious" timeb.h and ftime() */

/*

        Here's a string->tm converter that I wrote quite some time ago
        that takes several forms of date input and heuristically tries
        to figure out what it might be, more or less inspired by TOPS-20
        (handles more date formats I think.)

        This is what date(1) should have been built out of!

        It's just one file, the comments should be enough to figure out
        what is going on (very simple to interface, probably hairy to
        modify tho.) 

        Original code by:
        -Barry Shein, Boston University

        Various mods by:
        -D.N. Lynx Crowe

*/

#include "stdio.h"
#include "ctype.h"

#include "types.h"

#include "time.h"
#include "timeb.h"

#define MAXTOK 20

/*
 * routines to turn a date from various formats to other formats
 *
 *      Primary interesting routine is gdate() which eats a date
 *      string of several common formats (see comment) and
 *      fills in a standard UNIX tm structure.
 *
 *      if you compile it with DEBUG defined it will
 *      pull in a main() routine to run standalone for testing.
 */

#define AMBIG  -1       /* ambiguous month */
#define FALSE  -2       /* bad syntax      */

char *months[] = {

        "january", "february", "march", "april", "may", "june", "july",
        "august", "september", "october", "november", "december", 0
};

char *dow[] = {

        "sunday", "monday", "tuesday", "wednesday", "thursday",
        "friday", "saturday", 0
};

/*
 *      known time-zone name list
 */

char *tz[] = {

        "adt", "ast", "edt", "est", "cdt", "cst", "mst", "mdt",
        "pdt", "pst", "gmt",
        0
} ;

char mdays[] = {

        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
} ;

lcase(c)
register char c ;
{
        return(isupper(c) ? tolower(c) : c) ;
}

/*
 *  get a digit string from sp into bp (buffer) returning new sp
 */

char *
dstring(bp,sp)
register char *sp, *bp  ;
{
        register int i = 0 ;
        while(isdigit(*sp))
                if(i++ == MAXTOK) break ;
                else *bp++ = *sp++ ;
        *bp = '\0' ;
        return(sp) ;
}

/*
 *  skip white space returning updated ptr
 */

char *
skipw(sp)
register char *sp ;
{
        while(isspace(*sp) || *sp == '-') ++sp ;
        return(sp) ;
}

/*
 *  return how many chars of s1 prefix s2
 */

prefix(s1,s2)
register char *s1, *s2 ;
{
        register int i = 0  ;

        for(; *s1 == *s2 ; s1++,s2++,i++)
                if(*s2 == '\0') break ;
        return(*s1 == '\0' ? i : 0) ;
}

/*
 *  look up str in list for non-ambiguous (prefix) match
 */

find(sp,lp)
register char *sp, **lp ;
{
        int i,j,ambig = 0 ;
        register int k ;
        int ret  = FALSE ;

        for(i = 0,k = 0 ; *lp ; lp++,k++)
                if((j  = prefix(sp,*lp)) > i)
                {
                        ambig = 0 ;
                        i = j ;
                        ret = k + 1 ;
                }
                else if(j && (i == j)) ++ambig ;
        return(ambig ? AMBIG : ret) ;
}

/*
 * like find but demands exact match
 */

lookup(sp,lp)
register char *sp, **lp ;
{
        int i = 0 ;

        for(i=0 ; *lp ; lp++,i++)
                if(strcmp(sp,*lp) == 0) return(i+1) ;
        return(0) ;
}

/*
 * extract a token
 */

char *
extract(bp,sp)
register char *bp, *sp ;
{
        register int i = 0 ;

        sp = skipw(sp) ;
        for(; isalnum(*sp); sp++)
                if(i++ == MAXTOK) break ;
                else *bp++ = lcase(*sp) ;
        *bp = '\0' ;
        return(sp) ;
}

/*
 *  fill up an area with a value (eg. zeros)
 */

fill(cp,c,n)
register char *cp, c;
register int n ;
{
        while(n--) *cp++ = c ;
}

char *gdate(), *gtime() ;
long totime();

#if DEBUG
/*
 *  test driver
 *      translates first arg from command line (argv[1])
 *      and dumps out structure built.
 */

usage(sp) char *sp ;
{
        fprintf(stderr,"Usage: %s date\n",sp) ;
        exit(1) ;
}

main(argc,argv) int argc ; char **argv ;
{
        char *cp ;
        struct tm tm ;
        long t,t2 ;

        if(argc != 2) usage(*argv) ;
        if((cp = gdate(*++argv,&tm)) != NULL)
                printf("error: %s (%s)\n",*argv,cp) ;
        printf("year : %d month: %d day: %d\n",
                tm.tm_year,tm.tm_mon,tm.tm_mday);
        printf("day of month: %d hour: %d minute: %d second: %d\n",
                tm.tm_mday,tm.tm_hour,tm.tm_min,tm.tm_sec) ;
        printf("day of year: %d day of week: %d dst: %d\n",
                tm.tm_yday, tm.tm_wday, tm.tm_isdst) ;
        time(&t) ;
        t2 = totime(&tm) ;
        printf("%D %D %D\n",t,t2,t2-t) ;
        exit(0) ;
}
#endif  /* DEBUG */

/*
 *      gdate(date_str_ptr,time_buf_ptr)
 *      (see CTIME(3) in UPM for second arg format)
 *      takes many reasonable date strings and translates to
 *      the time-buf structure (integers)
 *
 *      formats (eg.):
 *              oct 19, 1983
 *              OcT 19, 1983 12:43
 *              oCt 19, 1983 12:43:33
 *              oct 19 1983 ...
 *              19 oct 83 ....
 *              10/19/83 12:43:33
 *              19-OCT-83 12:43:00 (DEC style)
 *              Wed Oct 19 12:43 EST 83 (UNIX style)
 *              oct. 19, 83 1:44 pm est
 *              831019124333    (see date(1))
 *      some variations on those themes also.
 *
 *      BUGS: probably a few (maybe some in the eye of the beholder)
 *              does not set dst flag (unless 'EDT' is in string)
 */

char *
gdate(sp,tp) register char *sp ; register struct tm *tp ;
{
        char buf[MAXTOK] ;

        fill(tp,'\0',sizeof *tp) ;
        sp = skipw(sp) ;
        if(isdigit(*sp))        /* either '7/12/83' or '12 jul 83' */
        {
                if(isdigit(sp[1]) && isdigit(sp[2])) /* UNIX yymmddhhmmss */
                {
                        buf[2] = '\0' ;
                        strncpy(buf,sp,2) ;
                        tp->tm_year = atoi(buf) ;
                        strncpy(buf,sp += 2,2) ;
                        tp->tm_mon = atoi(buf) ;
                        sp += 2 ;

                        if(!isdigit(*sp)) goto badday ;

                        strncpy(buf,sp,2) ;
                        tp->tm_mday = atoi(buf) ;
                        sp += 2 ;

                        if(!isdigit(*sp)) goto check ;

                        strncpy(buf,sp,2) ;
                        tp->tm_hour ;
                        sp += 2 ;

                        if(!isdigit(*sp)) goto check ;

                        strncpy(buf,sp,2) ;
                        tp->tm_min = atoi(buf) ;
                        sp += 2 ;

                        if(!isdigit(*sp)) goto check ;

                        strncpy(buf,sp,2) ;
                        tp->tm_min = atoi(buf) ;
                        goto check ;
                }

                sp = dstring(buf,sp) ;
                sp = skipw(sp) ;

                if(*sp == '/')  /* must be '7/12/83' */
                {
                        if((tp->tm_mon = atoi(buf)) < 1 || (tp->tm_mon > 12))
                        {
                                tp->tm_mon = FALSE ;
                                goto badmon ;
                        }

                        sp = skipw(++sp) ;

                        if(!isdigit(*sp)) goto badday ;

                        sp = dstring(buf,sp) ;
                        tp->tm_mday = atoi(buf) ;

                        sp = skipw(sp) ;

                        if(*sp != '/') goto badyr ;

                        sp = skipw(++sp) ;

                        if(!isdigit(*sp)) goto badyr ;

                        sp = dstring(buf,sp) ;
                        tp->tm_year = atoi(buf) ;

                        sp = gtime(sp,tp) ;

                        } else {

                        /*
                         * must be '12 jul 83'
                         */
                        tp->tm_mday = atoi(buf) ;

                        sp = extract(buf,sp) ;
                        if((tp->tm_mon = find(buf,months)) < 1) goto badmon ;

                        if(*sp == '.') ++sp ;

                        sp = skipw(sp) ;

                        if(!isdigit(*sp)) goto badyr ;

                        sp = dstring(buf,sp) ;
                        tp->tm_year = atoi(buf) ;

                        sp = gtime(sp,tp) ;
                }

        } else {

                int flag = 0 ;  /* used to indicate looking for UNIX style */

                /*
                 * either 'jul 12 83' or (UNIX) Wed jul 12 18:33 EST 1983
                 */

                sp = extract(buf,sp) ;

                if(find(buf,dow) > 0) {
                        sp = extract(buf,sp) ;
                        ++flag ;
                }

                if((tp->tm_mon = find(buf,months)) < 1) goto badmon ;

                if(*sp == '.') ++sp ;

                sp = skipw(sp) ;

                if(!isdigit(*sp)) goto badday ;

                sp = dstring(buf,sp) ;
                tp->tm_mday = atoi(buf) ;

                sp = skipw(sp) ;

                if(*sp == ',') sp++ ;

                sp = skipw(sp) ;

                if(flag) sp = skipw(gtime(sp,tp)) ;

                if(!isdigit(*sp)) goto badyr ;

                sp = dstring(buf,sp) ;
                tp->tm_year = atoi(buf) ;

                if(!flag) sp = gtime(sp,tp) ;
        }
check:
        /*
         * check for ridiculous numbers
         */

        if(tp->tm_mday < 1) goto badday ;

        if(tp->tm_mday > mdays[tp->tm_mon-1])
                if(!((tp->tm_mon == 2) &&       /* check for Feb 29 */
                        (tp->tm_mday == 29) && (days(tp->tm_year) == 365) ))
                                goto badday ;

        if(tp->tm_year >= 1900) tp->tm_year -= 1900 ;

        if(tp->tm_hour > 23) {
                tp->tm_hour = FALSE ;
                return(sp) ;
        }

        if(tp->tm_min > 59) {
                tp->tm_hour = FALSE ;
                return(sp) ;
        }

        if(tp->tm_sec > 59) {
                tp->tm_sec = FALSE ;
                return(sp) ;
        }

        /*
         *      fill in day of year, day of week (these calls must be
         *      in this order as dowk() needs doyr()
         */

        doyr(tp) ;
        dowk(tp) ;

        /*
         * all done !
         */

        return(NULL) ;

badday :
        tp->tm_mday = FALSE ;
        return(sp) ;

badmon :
        return(sp) ;

badyr :
        tp->tm_year = FALSE ;
        return(sp) ;
}

/*
 *  get  hh:mm:ss
 */

char *
gtime(sp,tp)
register char *sp;
register struct tm *tp ;
{
        char buf[MAXTOK],*cp ;

        sp = skipw(sp) ;

        if(isdigit(*sp)) {
                sp = dstring(buf,sp) ;
                tp->tm_hour = atoi(buf) ;
                sp = skipw(sp) ;

                if(*sp == ':')
                        sp = skipw(++sp) ;
                else 
                        goto out ;

                if(isdigit(*sp)) {
                        sp = dstring(buf,sp) ;
                        tp->tm_min = atoi(buf) ;
                        sp = skipw(sp) ;

                        if(*sp == ':')
                                sp = skipw(++sp) ;
                        else 
                                goto out ;

                        if(isdigit(*sp)) {
                                sp = dstring(buf,sp) ;
                                tp->tm_sec = atoi(buf) ;
                        }
                }
        }
out :
        sp = skipw(sp) ;

        if(isalpha(*sp)) {      /* PM:AM or time zone or both */

                cp = extract(buf,sp) ;

                if(strcmp(buf,"am") == 0 || strcmp(buf,"pm") == 0) {

                        if(buf[0] == 'p' && tp->tm_hour < 12)
                                tp->tm_hour += 12 ;

                        sp = cp = skipw(cp) ;
                        cp = extract(buf,cp) ;
                }

                if(lookup(buf,tz)) {
                        if(buf[1] == 'd') tp->tm_isdst++ ;
                        sp = skipw(cp) ;
                }
        }

        return(sp) ;
}

/*
 *      Ok, you were all wondering so here it is folks...
 *      THE LEAP YEAR CALCULATION
 *      note: does not take into account 1752.
 */

days(y)
register int y ;
{
        if(y < 1970)
                y += 1900 ;

        if(((y % 4) == 0) && ( (y % 100) || ((y % 400)==0) ))
                y = 366 ;
        else
                y = 365 ;

        return(y) ;
}

/*
 *      translate a time.h structure to seconds since 1/1/70
 *      (ie. UNIX internal time format...GMT)
 */

long
totime(tp) 
register struct tm *tp ;
{
        long ret = 0 ;
        int i,j ;

        struct timeb tb ;

        if(tp->tm_year < 70) return(0) ;

        for(i=1970,j=tp->tm_year+1900 ; i<j ; i++)
                ret += days(i) ;

        for(i=1 ; i < tp->tm_mon ; i++)
                ret += mdays[i-1] ;

        if((days(tp->tm_year) == 366) && (tp->tm_mon > 2))
                ++ret ;

        ret += (tp->tm_mday - 1) ;
        ret *= 24 ;
        ret += tp->tm_hour ;
        ret *= 60 ;

        ftime(&tb) ;

        ret += (tp->tm_min + tb.timezone) ;
        ret *= 60 ;
        ret += tp->tm_sec ;
        return(ret) ;
}

/*
 *      return day of the week
 *      of jan 1 of given year
 */

jan1(yr)
{
        register y, d;

/*
 *      normal gregorian calendar
 *      one extra day per four years
 */

        y = yr;
        d = 4+y+(y+3)/4;

/*
 *      julian calendar
 *      regular gregorian
 *      less three days per 400
 */

        if(y > 1800) {
                d -= (y-1701)/100;
                d += (y-1601)/400;
        }

/*
 *      take care of weirdness at 1752.
 */

        if(y > 1752)
                d += 3;

        return(d%7);
}

/*
 *      given day of year and year calculate and insert day-of-week (0..6)
 */

dowk(tp) register struct tm *tp ;
{
        tp->tm_wday = (jan1(tp->tm_year+1900) + tp->tm_yday) % 7 ;
}

/*
 *      calculate day of year from year
 */

doyr(tp) register struct tm *tp ;
{
        register int i,j ;

        j = ((tp->tm_mon > 2) && (days(tp->tm_year) == 366)) ? 1 : 0 ;

        for(i=1 ; i < tp->tm_mon ; i++)
                j += mdays[i-1] ;

        tp->tm_yday = j + tp->tm_mday - 1 ;
}