timezone.c

给出了 zip 压缩算法的完整实现过程。

/*
  Copyright (c) 1990-2001 Info-ZIP.  All rights reserved.

  See the accompanying file LICENSE, version 2000-Apr-09 or later
  (the contents of which are also included in zip.h) for terms of use.
  If, for some reason, all these files are missing, the Info-ZIP license
  also may be found at:  ftp://ftp.info-zip.org/pub/infozip/license.html
*/
/* Replacement time library functions, based on platform independent public
 * domain timezone code from ftp://elsie.nci.nih.gov/pub, with mktime and
 * mkgmtime from our own mktime.c in Zip.
 *
 * Contains:  tzset()
 *            __tzset()
 *            gmtime()
 *            localtime()
 *            mktime()
 *            mkgmtime()
 *            GetPlatformLocalTimezone()  [different versions]
 */

/* HISTORY/CHANGES
 * 17 Jun 00, Paul Kienitz, added the PD-based tzset(), localtime(), and so on
 *            to amiga/filedate.c, replacing GNU-based functions which had
 *            replaced time_lib.c, both having been rejected for licensing
 *            reasons.  Support for timezone files and leap seconds was removed.
 *
 * 23 Aug 00, Paul Kienitz, split into separate timezone.c file, made platform
 *            independent, copied in mktime() and mkgmtime() from Zip, renamed
 *            locale_TZ as GetPlatformLocalTimezone(), for use as a generic
 *            hook by other platforms.
 */

#ifndef __timezone_c
#define __timezone_c


#include "zip.h"
#include "timezone.h"
#include <ctype.h>
#include <errno.h>

#ifdef IZTZ_DEFINESTDGLOBALS
long timezone = 0;
int daylight = 0;
char *tzname[2];
#endif

#ifndef IZTZ_GETLOCALETZINFO
#  define IZTZ_GETLOCALETZINFO(ptzstruct, pgenrulefunct) (FALSE)
#endif

int real_timezone_is_set = FALSE;       /* set by tzset() */


#define TZDEFRULESTRING ",M4.1.0,M10.5.0"
#define TZDEFAULT       "EST5EDT"

#define SECSPERMIN      60
#define MINSPERHOUR     60
#define HOURSPERDAY     24
#define DAYSPERWEEK     7
#define DAYSPERNYEAR    365
#define DAYSPERLYEAR    366
#define SECSPERHOUR     (SECSPERMIN * MINSPERHOUR)
#define SECSPERDAY      ((long) SECSPERHOUR * HOURSPERDAY)
#define MONSPERYEAR 12

#define EPOCH_WDAY      4     /* Jan 1, 1970 was thursday */
#define EPOCH_YEAR      1970
#define TM_YEAR_BASE    1900
#define FIRST_GOOD_YEAR ((time_t) -1 < (time_t) 1 ? EPOCH_YEAR-68 : EPOCH_YEAR)
#define LAST_GOOD_YEAR  (EPOCH_YEAR + ((time_t) -1 < (time_t) 1 ? 67 : 135))

#define YDAYS(month, year) yr_days[leap(year)][month]

/* Nonzero if `y' is a leap year, else zero. */
#define leap(y)  (((y) % 4 == 0 && (y) % 100 != 0) || (y) % 400 == 0)

/* Number of leap years from EPOCH_YEAR  to `y' (not including `y' itself). */
#define _P4      ((EPOCH_YEAR / 4) * 4 + 1)
#define _P100    ((EPOCH_YEAR / 100) * 100 + 1)
#define _P400    ((EPOCH_YEAR / 400) * 400 + 1)
#define nleap(y) (((y) - _P4) / 4 - ((y) - _P100) / 100 + ((y) - _P400) / 400)

/* Length of month `m' (0 .. 11) */
#define monthlen(m, y) (yr_days[0][(m)+1] - yr_days[0][m] + \
                        ((m) == 1 && leap(y)))

/* internal module-level constants */
#ifndef IZ_MKTIME_ONLY
static ZCONST char  gmt[] = "GMT";
static ZCONST int    mon_lengths[2][MONSPERYEAR] = {
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};
#endif /* !IZ_MKTIME_ONLY */
static ZCONST int    yr_days[2][MONSPERYEAR+1] = {
    { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },
    { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }
};
#ifndef IZ_MKTIME_ONLY
static ZCONST int   year_lengths[2] = {
    DAYSPERNYEAR, DAYSPERLYEAR
};

/* internal variables */
static struct state statism;


/* prototypes of static functions */
static time_t transtime OF((ZCONST time_t janfirst, ZCONST int year,
                            ZCONST struct rule * ZCONST rulep,
                            ZCONST long offset));
static void generate_transitions OF((register struct state * ZCONST sp,
                                     ZCONST struct rule * ZCONST start,
                                     ZCONST struct rule * ZCONST end));
static ZCONST char *getzname OF((ZCONST char *strp));
static ZCONST char *getnum OF((ZCONST char *strp, int * ZCONST nump,
                               ZCONST int min, ZCONST int max));
static ZCONST char *getsecs OF((ZCONST char *strp, long * ZCONST secsp));
static ZCONST char *getoffset OF((ZCONST char *strp, long * ZCONST offsetp));
static ZCONST char *getrule OF((ZCONST char *strp, struct rule * ZCONST rulep));
static int Parse_TZ OF((ZCONST char *name, register struct state * ZCONST sp));


static time_t transtime(janfirst, year, rulep, offset)
     ZCONST time_t janfirst;
     ZCONST int year;
     ZCONST struct rule * ZCONST rulep;
     ZCONST long offset;
{
    register int    leapyear;
    register time_t value;
    register int    i;
    int             d, m1, yy0, yy1, yy2, dow;

    value = 0;
    leapyear = leap(year);
    switch (rulep->r_type) {

    case JULIAN_DAY:
        /*
        ** Jn - Julian day, 1 == January 1, 60 == March 1 even in leap
        ** years.
        ** In non-leap years, or if the day number is 59 or less, just
        ** add SECSPERDAY times the day number-1 to the time of
        ** January 1, midnight, to get the day.
        */
        value = janfirst + (rulep->r_day - 1) * SECSPERDAY;
        if (leapyear && rulep->r_day >= 60)
            value += SECSPERDAY;
        break;

    case DAY_OF_YEAR:
        /*
        ** n - day of year.
        ** Just add SECSPERDAY times the day number to the time of
        ** January 1, midnight, to get the day.
        */
        value = janfirst + rulep->r_day * SECSPERDAY;
        break;

    case MONTH_NTH_DAY_OF_WEEK:
        /*
        ** Mm.n.d - nth "dth day" of month m.
        */
        value = janfirst;
/*
        for (i = 0; i < rulep->r_mon - 1; ++i)
            value += mon_lengths[leapyear][i] * SECSPERDAY;
*/
        value += yr_days[leapyear][rulep->r_mon - 1] * SECSPERDAY;

        /*
        ** Use Zeller's Congruence to get day-of-week of first day of
        ** month.
        */
        m1 = (rulep->r_mon + 9) % 12 + 1;
        yy0 = (rulep->r_mon <= 2) ? (year - 1) : year;
        yy1 = yy0 / 100;
        yy2 = yy0 % 100;
        dow = ((26 * m1 - 2) / 10 +
            1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
        if (dow < 0)
            dow += DAYSPERWEEK;

        /*
        ** "dow" is the day-of-week of the first day of the month.  Get
        ** the day-of-month (zero-origin) of the first "dow" day of the
        ** month.
        */
        d = rulep->r_day - dow;
        if (d < 0)
            d += DAYSPERWEEK;
        for (i = 1; i < rulep->r_week; ++i) {
            if (d + DAYSPERWEEK >= mon_lengths[leapyear][rulep->r_mon - 1])
                break;
            d += DAYSPERWEEK;
        }

        /*
        ** "d" is the day-of-month (zero-origin) of the day we want.
        */
        value += d * SECSPERDAY;
        break;
    }

    /*
    ** "value" is the Epoch-relative time of 00:00:00 UTC on the day in
    ** question.  To get the Epoch-relative time of the specified local
    ** time on that day, add the transition time and the current offset
    ** from UTC.
    */
    return value + rulep->r_time + offset;
}

static void generate_transitions(sp, start, end)
     register struct state * ZCONST sp;
     ZCONST struct rule * ZCONST start;
     ZCONST struct rule * ZCONST end;
{
    register int             year;
    register time_t          janfirst;
    time_t                   starttime;
    time_t                   endtime;
    long                     stdoffset = -sp->ttis[0].tt_gmtoff;
    long                     dstoffset = -sp->ttis[1].tt_gmtoff;
    register time_t *        atp;
    register unsigned char * typep;

    /*
    ** Two transitions per year, from EPOCH_YEAR to LAST_GOOD_YEAR.
    */
    sp->timecnt = 2 * (LAST_GOOD_YEAR - EPOCH_YEAR + 1);
    atp = sp->ats;
    typep = sp->types;
    janfirst = 0;
    for (year = EPOCH_YEAR; year <= LAST_GOOD_YEAR; ++year) {
        starttime = transtime(janfirst, year, start, stdoffset);
        endtime = transtime(janfirst, year, end, dstoffset);
        if (starttime > endtime) {
            *atp++ = endtime;
            *typep++ = 0;   /* DST ends */
            *atp++ = starttime;
            *typep++ = 1;   /* DST begins */
        } else {
            *atp++ = starttime;
            *typep++ = 1;   /* DST begins */
            *atp++ = endtime;
            *typep++ = 0;   /* DST ends */
        }
        janfirst += year_lengths[leap(year)] * SECSPERDAY;
    }
}

static ZCONST char *getzname(strp)
     ZCONST char *strp;
{
    register char   c;

    while ((c = *strp) != '\0' && !isdigit(c) && c != ',' && c != '-' &&
        c != '+')
            ++strp;
    return strp;
}

static ZCONST char *getnum(strp, nump, min, max)
     ZCONST char *strp;
     int * ZCONST nump;
     ZCONST int min;
     ZCONST int max;
{
    register char   c;
    register int    num;

    if (strp == NULL || !isdigit(c = *strp))
        return NULL;
    num = 0;
    do {
        num = num * 10 + (c - '0');
        if (num > max)
            return NULL;    /* illegal value */
        c = *++strp;
    } while (isdigit(c));
    if (num < min)
        return NULL;        /* illegal value */
    *nump = num;
    return strp;
}

static ZCONST char *getsecs(strp, secsp)
     ZCONST char *strp;
     long * ZCONST secsp;
{
    int num;

    /*
    ** `HOURSPERDAY * DAYSPERWEEK - 1' allows quasi-Posix rules like
    ** "M10.4.6/26", which does not conform to Posix,
    ** but which specifies the equivalent of
    ** ``02:00 on the first Sunday on or after 23 Oct''.
    */
    strp = getnum(strp, &num, 0, HOURSPERDAY * DAYSPERWEEK - 1);
    if (strp == NULL)
        return NULL;
    *secsp = num * (long) SECSPERHOUR;
    if (*strp == ':') {
        ++strp;
        strp = getnum(strp, &num, 0, MINSPERHOUR - 1);
        if (strp == NULL)
            return NULL;
        *secsp += num * SECSPERMIN;
        if (*strp == ':') {
            ++strp;
            /* `SECSPERMIN' allows for leap seconds.  */
            strp = getnum(strp, &num, 0, SECSPERMIN);
            if (strp == NULL)
                return NULL;
            *secsp += num;
        }
    }
    return strp;
}

static ZCONST char *getoffset(strp, offsetp)
     ZCONST char *strp;
     long * ZCONST offsetp;
{
    register int    neg = 0;

    if (*strp == '-') {
        neg = 1;
        ++strp;
    } else if (*strp == '+')
        ++strp;
    strp = getsecs(strp, offsetp);
    if (strp == NULL)
        return NULL;        /* illegal time */
    if (neg)
        *offsetp = -*offsetp;
    return strp;
}

static ZCONST char *getrule(strp, rulep)
     ZCONST char *strp;
     struct rule * ZCONST rulep;
{
    if (*strp == 'J') {
        /*
        ** Julian day.
        */
        rulep->r_type = JULIAN_DAY;
        ++strp;
        strp = getnum(strp, &rulep->r_day, 1, DAYSPERNYEAR);
    } else if (*strp == 'M') {
        /*
        ** Month, week, day.
        */
        rulep->r_type = MONTH_NTH_DAY_OF_WEEK;
        ++strp;
        strp = getnum(strp, &rulep->r_mon, 1, MONSPERYEAR);
        if (strp == NULL)
            return NULL;
        if (*strp++ != '.')
            return NULL;
        strp = getnum(strp, &rulep->r_week, 1, 5);
        if (strp == NULL)
            return NULL;
        if (*strp++ != '.')
            return NULL;
        strp = getnum(strp, &rulep->r_day, 0, DAYSPERWEEK - 1);
    } else if (isdigit(*strp)) {
        /*
        ** Day of year.
        */
        rulep->r_type = DAY_OF_YEAR;
        strp = getnum(strp, &rulep->r_day, 0, DAYSPERLYEAR - 1);
    } else  return NULL;        /* invalid format */
    if (strp == NULL)
        return NULL;
    if (*strp == '/') {
        /*
        ** Time specified.
        */
        ++strp;
        strp = getsecs(strp, &rulep->r_time);
    } else
        rulep->r_time = 2 * SECSPERHOUR;    /* default = 2:00:00 */
    return strp;
}

static int Parse_TZ(name, sp)
     ZCONST char *name;
     register struct state * ZCONST sp;
{
    ZCONST char *            stdname;
    ZCONST char *            dstname;
    size_t                   stdlen;
    size_t                   dstlen;
    long                     stdoffset;
    long                     dstoffset;
    register char *          cp;

    dstname = NULL;
    stdname = name;
    name = getzname(name);