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nuttx/libs/libc/time/lib_strptime.c
anjiahao e6f77aeb9a libc/lib_strptime:change code format & add notes 
Signed-off-by: anjiahao <anjiahao@xiaomi.com>
2022-04-13 10:16:42 +08:00

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/****************************************************************************
* libs/libc/time/lib_strptime.c
*
* $OpenBSD: strptime.c,v 1.11 2005/08/08 08:05:38 espie Exp $
* $NetBSD: strptime.c,v 1.12 1998/01/20 21:39:40 mycroft Exp $
*
* Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code was contributed to The NetBSD Foundation by Klaus Klein.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <ctype.h>
#include <locale.h>
#include <strings.h>
#include <time.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define TM_YEAR_BASE 1900
#define _ctloc(x) (g_defaulttimelocale.x)
/* We do not implement alternate representations. However, we always
* check whether a given modifier is allowed for a certain conversion.
*/
#define _ALT_E 0x01
#define _ALT_O 0x02
#define _LEGAL_ALT(x) { if (alt_format & ~(x)) return (0); }
/****************************************************************************
* Private Data
****************************************************************************/
static const struct
{
const char *abday[7];
const char *day[7];
const char *abmon[12];
const char *mon[12];
const char *am_pm[2];
const char *d_t_fmt;
const char *d_fmt;
const char *t_fmt;
const char *t_fmt_ampm;
} g_defaulttimelocale =
{
{
"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",
},
{
"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Saturday"
},
{
"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
},
{
"January", "February", "March", "April", "May", "June", "July",
"August", "September", "October", "November", "December"
},
{
"AM", "PM"
},
"%a %b %d %H:%M:%S %Y",
"%m/%d/%y",
"%H:%M:%S",
"%I:%M:%S %p"
};
struct century_relyear
{
int century;
int relyear;
};
/****************************************************************************
* Private Functions
****************************************************************************/
static int _conv_num(FAR const unsigned char **buf, FAR int *dest,
int llim, int ulim)
{
int result = 0;
int rulim = ulim;
while (isspace(**buf))
{
(*buf)++;
}
if (**buf < '0' || **buf > '9')
{
return 0;
}
/* we use rulim to break out of the loop when we run out of digits */
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;
}
static FAR const unsigned char *_strptime(FAR const unsigned char *buf,
FAR const char *fmt,
FAR struct tm *tm,
FAR struct century_relyear *cr)
{
unsigned char c;
FAR const unsigned char *bp;
size_t len = 0;
int alt_format;
int i;
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 NULL;
}
break;
/* "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. */
case 'c': /* Date and time, using the locale's format. */
_LEGAL_ALT(_ALT_E);
if (!(bp = _strptime(bp, _ctloc(d_t_fmt), tm, cr)))
{
return NULL;
}
break;
case 'D': /* The date as "%m/%d/%y". */
_LEGAL_ALT(0);
if (!(bp = _strptime(bp, "%m/%d/%y", tm, cr)))
{
return NULL;
}
break;
case 'R': /* The time as "%H:%M". */
_LEGAL_ALT(0);
if (!(bp = _strptime(bp, "%H:%M", tm, cr)))
{
return NULL;
}
break;
case 'r': /* The time as "%I:%M:%S %p". */
_LEGAL_ALT(0);
if (!(bp = _strptime(bp, "%I:%M:%S %p", tm, cr)))
{
return NULL;
}
break;
case 'T': /* The time as "%H:%M:%S". */
_LEGAL_ALT(0);
if (!(bp = _strptime(bp, "%H:%M:%S", tm, cr)))
{
return NULL;
}
break;
case 'X': /* The time, using the locale's format. */
_LEGAL_ALT(_ALT_E);
if (!(bp = _strptime(bp, _ctloc(t_fmt), tm, cr)))
{
return NULL;
}
break;
case 'x': /* The date, using the locale's format. */
_LEGAL_ALT(_ALT_E);
if (!(bp = _strptime(bp, _ctloc(d_fmt), tm, cr)))
{
return NULL;
}
break;
/* "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(_ctloc(day[i]));
if (strncasecmp(_ctloc(day[i]),
(const char *)bp, len) == 0)
break;
/* Abbreviated name. */
len = strlen(_ctloc(abday[i]));
if (strncasecmp(_ctloc(abday[i]),
(const char *)bp, len) == 0)
break;
}
/* Nothing matched. */
if (i == 7)
{
return NULL;
}
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(_ctloc(mon[i]));
if (strncasecmp(_ctloc(mon[i]),
(const char *)bp, len) == 0)
{
break;
}
/* Abbreviated name. */
len = strlen(_ctloc(abmon[i]));
if (strncasecmp(_ctloc(abmon[i]),
(const char *)bp, len) == 0)
{
break;
}
}
/* Nothing matched. */
if (i == 12)
{
return NULL;
}
tm->tm_mon = i;
bp += len;
break;
case 'C': /* The century number. */
_LEGAL_ALT(_ALT_E);
if (!(_conv_num(&bp, &i, 0, 99)))
{
return (NULL);
}
cr->century = i * 100;
break;
case 'd': /* The day of month. */
case 'e':
_LEGAL_ALT(_ALT_O);
if (!(_conv_num(&bp, &tm->tm_mday, 1, 31)))
{
return (NULL);
}
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 NULL;
}
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 (NULL);
}
break;
case 'j': /* The day of year. */
_LEGAL_ALT(0);
if (!(_conv_num(&bp, &tm->tm_yday, 1, 366)))
{
return NULL;
}
tm->tm_yday--;
break;
case 'M': /* The minute. */
_LEGAL_ALT(_ALT_O);
if (!(_conv_num(&bp, &tm->tm_min, 0, 59)))
{
return NULL;
}
break;
case 'm': /* The month. */
_LEGAL_ALT(_ALT_O);
if (!(_conv_num(&bp, &tm->tm_mon, 1, 12)))
{
return NULL;
}
tm->tm_mon--;
break;
case 'p': /* The locale's equivalent of AM/PM. */
_LEGAL_ALT(0);
/* AM? */
len = strlen(_ctloc(am_pm[0]));
if (strncasecmp(_ctloc(am_pm[0]), (const char *)bp, len) == 0)
{
if (tm->tm_hour > 12) /* i.e., 13:00 AM ?! */
{
return NULL;
}
else if (tm->tm_hour == 12)
{
tm->tm_hour = 0;
}
bp += len;
break;
}
/* PM? */
len = strlen(_ctloc(am_pm[1]));
if (strncasecmp(_ctloc(am_pm[1]), (const char *)bp, len) == 0)
{
if (tm->tm_hour > 12) /* i.e., 13:00 PM ?! */
{
return NULL;
}
else if (tm->tm_hour < 12)
{
tm->tm_hour += 12;
}
bp += len;
break;
}
/* Nothing matched. */
return NULL;
case 'S': /* The seconds. */
_LEGAL_ALT(_ALT_O);
if (!(_conv_num(&bp, &tm->tm_sec, 0, 61)))
{
return NULL;
}
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.
*/
if (!(_conv_num(&bp, &i, 0, 53)))
{
return NULL;
}
break;
case 'w': /* The day of week, beginning on sunday. */
_LEGAL_ALT(_ALT_O);
if (!(_conv_num(&bp, &tm->tm_wday, 0, 6)))
{
return NULL;
}
break;
case 'Y': /* The year. */
_LEGAL_ALT(_ALT_E);
if (!(_conv_num(&bp, &i, 0, 9999)))
{
return NULL;
}
cr->relyear = -1;
tm->tm_year = i - TM_YEAR_BASE;
break;
case 'y': /* The year within the century (2 digits). */
_LEGAL_ALT(_ALT_E | _ALT_O);
if (!(_conv_num(&bp, &cr->relyear, 0, 99)))
{
return NULL;
}
break;
/* Miscellaneous conversions. */
case 'n': /* Any kind of white-space. */
case 't':
_LEGAL_ALT(0);
while (isspace(*bp))
{
bp++;
}
break;
default: /* Unknown/unsupported conversion. */
return NULL;
}
}
/* We need to evaluate the two digit year spec (%y)
* last as we can get a century spec (%C) at any time.
*/
if (cr->relyear != -1)
{
if (cr->century == TM_YEAR_BASE)
{
if (cr->relyear <= 68)
{
tm->tm_year = cr->relyear + 2000 - TM_YEAR_BASE;
}
else
{
tm->tm_year = cr->relyear + 1900 - TM_YEAR_BASE;
}
}
else
{
tm->tm_year = cr->relyear + cr->century - TM_YEAR_BASE;
}
}
return bp;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: strptime
*
* Description:
* Convert a string to a time type according to a specific time format
* The strptime() function processes the input string from left to
* right. Each of the three possible input elements (whitespace,
* literal, or format) are handled one after the other. If the
* input cannot be matched to the format string, the function stops.
* The remainder of the format and input strings are not processed.
* The supported input field descriptors are listed below. In case
* a text string (such as the name of a day of the week or a month
* name) is to be matched, the comparison is case insensitive. In
* case a number is to be matched, leading zeros are permitted but
* not required.
* %a The abbreviated weekday name according to the current locale.
* %A The full weekday name according to the current locale.
* %b The abbreviated month name according to the current locale.
* %B The full month name according to the current locale.
* %C The century number (year/100) as a 2-digit integer. (SU)
* %d The day of the month as a decimal number (range 01 to 31).
* %e Like %d, the day of the month as a decimal number, but a leading
* zero is replaced by a space.
* %h Equivalent to %b. (SU)
* %H The hour as a decimal number using a 24-hour clock
* (range 00 to 23).
* %I The hour as a decimal number using a 12-hour clock
* (range 01 to 12).
* %j The day of the year as a decimal number (range 001 to 366).
* %k The hour (24-hour clock) as a decimal number (range 0 to 23);
* single digits are preceded by a blank. (See also %H.) (TZ)
* %l The hour (12-hour clock) as a decimal number (range 1 to 12);
* single digits are preceded by a blank. (See also %I.) (TZ)
* %m The month as a decimal number (range 01 to 12).
* %M The minute as a decimal number (range 00 to 59).
* %n A newline character. (SU)
* %p Either "AM" or "PM" according to the given time value, or the
* corresponding strings for the current locale. Noon is treated
* as "PM" and midnight as "AM".
* %P Like %p but in lowercase: "am" or "pm" or a corresponding string
* for the current locale. (GNU)
* %S The second as a decimal number (range 00 to 60). (The range is
* up to 60 to allow for occasional leap seconds.)
* %t A tab character. (SU)
* %y The year as a decimal number without a century (range 00 to 99).
* %Y The year as a decimal number including the century.
* %% A literal '%' character.
*
* Returned Value:
* The return value of the function is a pointer to the first
* character not processed in this function call. In case the input
* string contains more characters than required by the format
* string, the return value points right after the last consumed
* input character. In case the whole input string is consumed, the
* return value points to the null byte at the end of the string.
* If strptime() fails to match all of the format string and
* therefore an error occurred, the function returns NULL.
*
****************************************************************************/
FAR char *strptime(FAR const char *buf, FAR const char *fmt,
FAR struct tm *tm)
{
struct century_relyear cr;
cr.century = TM_YEAR_BASE;
cr.relyear = -1;
return (FAR char *)(_strptime((FAR const unsigned char *)buf,
fmt, tm, &cr));
}
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