/*	rev_ctime.c (c)2002 Dave Von Pless (drdvp@freeshell.org)

	This file is placed in the public domain.  Use as you see fit.

	Libray routine to perform the reverse of ctime(), i.e. convert
	ctime() formatted timestamp to a time_t.

	Usage: int rev_ctime(const char *ctime, time_t *timeptr);

	Input:  26-char string in ctime() format (Trailing '\n' will
		be handled, if present), pointer to a time_t.

	Return: 1 for success, 0 on failure.
		The correct time_t will be stored in the time_t
		pointer supplied.


	Compile with -DDEBUG to dump errors to stderr.  These will be
	either a malloc() failure or bad token parsing.

	Compile with -DDEBUG=2 for parse info.

EXAMPLE:	

...
time_t some_time;
if((rev_ctime("Wed Dec 11 21:30:58 2002", &some_time)) {
	... 
}
...
	
*/
#ifdef DEBUG
#include <stdio.h>		/* for printf() */
#endif
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define NUM_FIELDS 7		/* wday mon day hh:mm:ss yyyy */

int  month2num(char *MonStr);   /* Month text to int lookup */

/*
	Make a copy of the input string, as we'll clobber it
	in the parsing.  Next, loop through the 7 fields, 
	populating a struct tm with parsed data.  Lastly,
	call mktime() to get the time_t
*/
int rev_ctime(const char *ctime, time_t *timeptr)
{
	char	*mystr, *p, *param;
	char	sep=' ';	/* ctime() string splits on space */
	int	field=0;
	struct	tm tm;

	mystr=malloc(strlen(ctime)+1);
	if(!mystr) {
#ifdef DEBUG
		fprintf(stderr,"rev_ctime(): malloc failure.\n");
#endif
		return 0;
	}
	strcpy(mystr,ctime);
	p=strchr(mystr,'\n');	/* Handle trailing newline,
					   if present */
	if(p) {
		*p='\0';
	}
	param=mystr;

	while(field < NUM_FIELDS) {
		p=strchr(param,sep);
		if(!p) {	/* We've failed */
#ifdef DEBUG
			fprintf(stderr,"rev_ctime(): Bad input @field %d\n\t"
			  "-- can't find  '%c' before %s in '%s'\n", field,
			  sep,param, ctime);
#endif
			free(mystr);
			return 0;
		}
		*p='\0';
		p++;
#if DEBUG==2
				/* Show what we're parsing */
		fprintf(stderr,"field=%d, param=%s, p=%s sep='%c'\n", field,
			param,p,sep);
#endif
		switch(field) {
			case 0: break;	/* We don't need tm_mday */
			case 1: tm.tm_mon=month2num(param);
				if(tm.tm_mon > 12) {
#ifdef DEBUG
					fprintf(stderr,"rev_ctime(): "
						"Bad month input -- "
			  			" %s\n", param);
#endif
					free(mystr);
					return 0;
				}
				break;
			case 2: tm.tm_mday=atoi(param);
				sep=':';	/* Time splits on ':' */
				break;
			case 3: tm.tm_hour=atoi(param);
				break;
			case 4: tm.tm_min=atoi(param);
				sep=' ';	/* Split on ' ' */
				break;
			case 5: tm.tm_sec=atoi(param);
				sep='\0';	/* Find string end */
				break;
			case 6: tm.tm_year=(atoi(param)-1900);
				break;
		}
		param=p;
		field++;
	}
	tm.tm_isdst=-1;			/* Have mktime() figure out DST */
	*timeptr=mktime(&tm);
	free(mystr);
	return 1;
}

/* Return month number 0-11.  Send 13 on error. */
int month2num(char *MonStr)
{
	char *mons[]={ "Jan","Feb","Mar","Apr","May", "Jun","Jul","Aug",
		"Sep","Oct","Nov","Dec" };
	int i;

	for(i=0;i<12;i++) {
		if(!strcmp(MonStr,mons[i])) {
			return i;
		}
	}
	return 13;			/* Failed, impossible month! */
}