undefined reference to strptime之自定义strptime函数

详见博客 : http://blog.csdn.net/freeape/article/details/47132843

简介

  strptime()函数能够按照特定时间格式将字符串转换为时间类型。简单点说可以将字符串时间转化为时间戳。这个函数包含在time.h头文件中，在Unix或者类Unix系统中，我们会经常接触到。但是到了跑Nuttx系统的Pixhawk，真是醉了，很多东西都没有，或者少了很多东西，比如time.h中就没有这个函数的实现，又如dirent.h中的一些文件类型的宏定义也没有了。但是我们很需要，比如在时间的比较上，我们不能去拿字符串去操作来比较，会搞死人的，直接得到时间戳，三下两除二就搞定了，那就要用到strptime这个函数了。

实现

mystrptime.c

/* * Note:因time.h中没有strptime函数(UNIX中是有的)，本文件是对strptime功能的自定义实现； * We do not implement alternate representations. However, we always * check whether a given modifier is allowed for a certain conversion. */
 * Note:因time.h中没有strptime函数(UNIX中是有的)，本文件是对strptime功能的自定义实现；
 * We do not implement alternate representations. However, we always
 * check whether a given modifier is allowed for a certain conversion.
 */
#include "mystrptime.h"


static const char *day[7] = {
	"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
	"Friday", "Saturday"
};
static const char *abday[7] = {
	"Sun","Mon","Tue","Wed","Thu","Fri","Sat"
};
static const char *mon[12] = {
	"January", "February", "March", "April", "May", "June", "July",
	"August", "September", "October", "November", "December"
};
static const char *abmon[12] = {
	"Jan", "Feb", "Mar", "Apr", "May", "Jun",
	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};
static const char *am_pm[2] = {
	"AM", "PM"
};


static int conv_num(const char **buf, int *dest, int llim, int ulim){

	int result = 0;

	/* The limit also determines the number of valid digits. */
	int rulim = ulim;

	if (**buf < '0' || **buf > '9')
		return (0);

	do {
		result *= 10;
		result += *(*buf)++ - '0';
		rulim /= 10;
	} while ((result * 10 <= ulim) && rulim && **buf >= '0' && **buf <= '9');

	if (result < llim || result > ulim)
		return (0);

	*dest = result;
	return (1);
}

char * mystrptime(const char *buf, const char *fmt, struct tm *tm){

	char c;
	const char *bp;
	size_t len = 0;
	int alt_format, i, split_year = 0;

	bp = buf;

	while ((c = *fmt) != '\0') {
		/* Clear `alternate' modifier prior to new conversion. */
		alt_format = 0;

		/* Eat up white-space. */
		if (isspace(c)) {
			while (isspace(*bp))
				bp++;

			fmt++;
			continue;
		}

		if ((c = *fmt++) != '%')
			goto literal;


again:		switch (c = *fmt++) {
		case '%':	/* "%%" is converted to "%". */
literal:
			if (c != *bp++)
				return (0);
			break;

		/*		 * "Alternative" modifiers. Just set the appropriate flag		 * and start over again.		 */
		 * "Alternative" modifiers. Just set the appropriate flag
		 * and start over again.
		 */
		case 'E':	/* "%E?" alternative conversion modifier. */
			LEGAL_ALT(0);
			alt_format |= ALT_E;
			goto again;

		case 'O':	/* "%O?" alternative conversion modifier. */
			LEGAL_ALT(0);
			alt_format |= ALT_O;
			goto again;

		/*		 * "Complex" conversion rules, implemented through recursion.		 */
		 * "Complex" conversion rules, implemented through recursion.
		 */
		case 'c':	/* Date and time, using the locale's format. */
			LEGAL_ALT(ALT_E);
			if (!(bp = mystrptime(bp, "%x %X", tm)))
				return (0);
			break;

		case 'D':	/* The date as "%m/%d/%y". */
			LEGAL_ALT(0);
			if (!(bp = mystrptime(bp, "%m/%d/%y", tm)))
				return (0);
			break;

		case 'R':	/* The time as "%H:%M". */
			LEGAL_ALT(0);
			if (!(bp = mystrptime(bp, "%H:%M", tm)))
				return (0);
			break;

		case 'r':	/* The time in 12-hour clock representation. */
			LEGAL_ALT(0);
			if (!(bp = mystrptime(bp, "%I:%M:%S %p", tm)))
				return (0);
			break;

		case 'T':	/* The time as "%H:%M:%S". */
			LEGAL_ALT(0);
			if (!(bp = mystrptime(bp, "%H:%M:%S", tm)))
				return (0);
			break;

		case 'X':	/* The time, using the locale's format. */
			LEGAL_ALT(ALT_E);
			if (!(bp = mystrptime(bp, "%H:%M:%S", tm)))
				return (0);
			break;

		case 'x':	/* The date, using the locale's format. */
			LEGAL_ALT(ALT_E);
			if (!(bp = mystrptime(bp, "%m/%d/%y", tm)))
				return (0);
			break;

		/*		 * "Elementary" conversion rules.		 */
		 * "Elementary" conversion rules.
		 */
		case 'A':	/* The day of week, using the locale's form. */
		case 'a':
			LEGAL_ALT(0);
			for (i = 0; i < 7; i++) {
				/* Full name. */
				len = strlen(day[i]);
				if (strncasecmp(day[i], bp, len) == 0)
					break;

				/* Abbreviated name. */
				len = strlen(abday[i]);
				if (strncasecmp(abday[i], bp, len) == 0)
					break;
			}

			/* Nothing matched. */
			if (i == 7)
				return (0);

			tm->tm_wday = i;
			bp += len;
			break;

		case 'B':	/* The month, using the locale's form. */
		case 'b':
		case 'h':
			LEGAL_ALT(0);
			for (i = 0; i < 12; i++) {
				/* Full name. */
				len = strlen(mon[i]);
				if (strncasecmp(mon[i], bp, len) == 0)
					break;

				/* Abbreviated name. */
				len = strlen(abmon[i]);
				if (strncasecmp(abmon[i], bp, len) == 0)
					break;
			}

			/* Nothing matched. */
			if (i == 12)
				return (0);

			tm->tm_mon = i;
			bp += len;
			break;

		case 'C':	/* The century number. */
			LEGAL_ALT(ALT_E);
			if (!(conv_num(&bp, &i, 0, 99)))
				return (0);

			if (split_year) {
				tm->tm_year = (tm->tm_year % 100) + (i * 100);
			} else {
				tm->tm_year = i * 100;
				split_year = 1;
			}
			break;

		case 'd':	/* The day of month. */
		case 'e':
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &tm->tm_mday, 1, 31)))
				return (0);
			break;

		case 'k':	/* The hour (24-hour clock representation). */
			LEGAL_ALT(0);
			/* FALLTHROUGH */
		case 'H':
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &tm->tm_hour, 0, 23)))
				return (0);
			break;

		case 'l':	/* The hour (12-hour clock representation). */
			LEGAL_ALT(0);
			/* FALLTHROUGH */
		case 'I':
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &tm->tm_hour, 1, 12)))
				return (0);
			if (tm->tm_hour == 12)
				tm->tm_hour = 0;
			break;

		case 'j':	/* The day of year. */
			LEGAL_ALT(0);
			if (!(conv_num(&bp, &i, 1, 366)))
				return (0);
			tm->tm_yday = i - 1;
			break;

		case 'M':	/* The minute. */
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &tm->tm_min, 0, 59)))
				return (0);
			break;

		case 'm':	/* The month. */
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &i, 1, 12)))
				return (0);
			tm->tm_mon = i - 1;
			break;

		case 'p':	/* The locale's equivalent of AM/PM. */
			LEGAL_ALT(0);
			/* AM? */
			if (strcasecmp(am_pm[0], bp) == 0) {
				if (tm->tm_hour > 11)
					return (0);

				bp += strlen(am_pm[0]);
				break;
			}
			/* PM? */
			else if (strcasecmp(am_pm[1], bp) == 0) {
				if (tm->tm_hour > 11)
					return (0);

				tm->tm_hour += 12;
				bp += strlen(am_pm[1]);
				break;
			}

			/* Nothing matched. */
			return (0);

		case 'S':	/* The seconds. */
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &tm->tm_sec, 0, 61)))
				return (0);
			break;

		case 'U':	/* The week of year, beginning on sunday. */
		case 'W':	/* The week of year, beginning on monday. */
			LEGAL_ALT(ALT_O);
			/*			 * XXX This is bogus, as we can not assume any valid			 * information present in the tm structure at this			 * point to calculate a real value, so just check the			 * range for now.			 */
			 * XXX This is bogus, as we can not assume any valid
			 * information present in the tm structure at this
			 * point to calculate a real value, so just check the
			 * range for now.
			 */
			 if (!(conv_num(&bp, &i, 0, 53)))
				return (0);
			 break;

		case 'w':	/* The day of week, beginning on sunday. */
			LEGAL_ALT(ALT_O);
			if (!(conv_num(&bp, &tm->tm_wday, 0, 6)))
				return (0);
			break;

		case 'Y':	/* The year. */
			LEGAL_ALT(ALT_E);
			if (!(conv_num(&bp, &i, 0, 9999)))
				return (0);

			tm->tm_year = i - TM_YEAR_BASE;
			break;

		case 'y':	/* The year within 100 years of the epoch. */
			LEGAL_ALT(ALT_E | ALT_O);
			if (!(conv_num(&bp, &i, 0, 99)))
				return (0);

			if (split_year) {
				tm->tm_year = ((tm->tm_year / 100) * 100) + i;
				break;
			}
			split_year = 1;
			if (i <= 68)
				tm->tm_year = i + 2000 - TM_YEAR_BASE;
			else
				tm->tm_year = i + 1900 - TM_YEAR_BASE;
			break;

		/*		 * Miscellaneous conversions.		 */
		 * Miscellaneous conversions.
		 */
		case 'n':	/* Any kind of white-space. */
		case 't':
			LEGAL_ALT(0);
			while (isspace(*bp))
				bp++;
			break;


		default:	/* Unknown/unsupported conversion. */
			return (0);
		}


	}

	/* LINTED functional specification */
	return ((char *)bp);
}


time_t to_seconds(const char *date,int mode)
{
    struct tm storage={0,0,0,0,0,0,0,0,0};
    char *p=NULL;
    time_t retval=0;

    if(1 == mode)p=(char *)mystrptime(date,"%Y-%m-%d",&storage);
    else if(0 == mode)p=(char *)mystrptime(date,"%Y_%m_%d",&storage);
    if(p==NULL)
    {
        retval=0;
    }
    else
    {
        retval=mktime(&storage);
    }
    return retval;
}

mystrptime.h

#ifndef MYSTRPTIME_H_
#define MYSTRPTIME_H_

#include <stdio.h>
#include <time.h>
#include <ctype.h>
#include <string.h>

#define ALT_E			0x01
#define ALT_O			0x02
#define	LEGAL_ALT(x)		{ if (alt_format & ~(x)) return (0); }
#define TM_YEAR_BASE 1900

char *mystrptime(const char *buf, const char *fmt, struct tm *tm);
time_t to_seconds(const char *date,int mode);

#endif

测试

/*Test*/
/*#intclude <stdio.h>#include "mystrptime.h"int main (){	time_t ts;	ts = to_seconds("2015-07-29",1);	//ts = to_seconds("2015_07_29",0);	printf("ts=%d\n",ts);    return(0);}*/
#intclude <stdio.h>
#include "mystrptime.h"

int main ()
{
	time_t ts;
	ts = to_seconds("2015-07-29",1);
	//ts = to_seconds("2015_07_29",0);
	printf("ts=%d\n",ts);
    return(0);
}
*/