Subversion Repositories planix.SVN

#include <stdlib.h>
#include <sys/types.h>
#include <fcntl.h>
#include <time.h>
#include <ctype.h>
#include <string.h>
#include <unistd.h>

#define TZFILE  "/etc/TZ"

static char TZ[128];
static char std[32] = "GMT0";
static char dst[32];
char *tzname[2] = {
        std, dst
};
time_t tzoffset, tzdstoffset;
int tzdst = 0;

static int
offset(char *env, time_t *off)
{
        int n, sign;
        size_t len, retlen;

        retlen = 0;
        sign = 1;
        /*
         * strictly, no sign is allowed in the 'time' part of the
         * dst start/stop rules, but who cares?
         */
        if (*env == '-' || *env == '+') {
                if (*env++ == '-')
                        sign = -1;
                retlen++;
        }
        if ((len = strspn(env, ":0123456789")) == 0)
                return 0;
        retlen += len;
        for (*off = 0; len && isdigit(*env); len--)             /* hours */
                *off = *off*10 + (*env++ - '0')*60*60;
        if (len) {
                if (*env++ != ':')
                        return 0;
                len--;
        }
        for (n = 0; len && isdigit(*env); len--)                /* minutes */
                n = n*10 + (*env++ - '0')*60;
        *off += n;
        if (len) {
                if (*env++ != ':')
                        return 0;
                len--;
        }
        for (n = 0; len && isdigit(*env); len--)                /* seconds */
                n = n*10 + (*env++ - '0');
        *off = (*off + n)*sign;
        return retlen;
}

/*
 * TZ=stdoffset[dst[offset][,start[/time],end[/time]]]
 */
void
tzset(void)
{
        char *env, *p, envbuf[128];
        int fd, i;
        size_t len, retlen;
        time_t off;

        /*
         * get the TZ environment variable and check for validity.
         * the implementation-defined manner for dealing with the
         * leading ':' format is to reject it.
         * if it's ok, stash a copy away for quick comparison next time.
         */
        if ((env = getenv("TZ")) == 0) {
                if ((fd = open(TZFILE, O_RDONLY)) == -1)
                        return;
                if (read(fd, envbuf, sizeof(envbuf)-1) == -1) {
                        close(fd);
                        return;
                }
                close(fd);
                for (i = 0; i < sizeof(envbuf); i++) {
                        if (envbuf[i] != '\n')
                                continue;
                        envbuf[i] = '\0';
                        break;
                }
                env = envbuf;
        }
        if (strcmp(env, TZ) == 0)
                return;
        if (*env == 0 || *env == ':')
                return;
        strncpy(TZ, env, sizeof(TZ)-1);
        TZ[sizeof(TZ)-1] = 0;
        /*
         * get the 'std' string.
         * before committing, check there is a valid offset.
         */
        if ((len = strcspn(env, ":0123456789,-+")) == 0)
                return;
        if ((retlen = offset(env+len, &off)) == 0)
                return;
        for (p = std, i = len+retlen; i; i--)
                *p++ = *env++;
        *p = 0;
        tzoffset = -off;
        /*
         * get the 'dst' string (if any).
         */
        if (*env == 0 || (len = strcspn(env, ":0123456789,-+")) == 0)
                return;
        for (p = dst; len; len--)
                *p++ = *env++;
        *p = 0;
        /*
         * optional dst offset.
         * default is one hour.
         */
        tzdst = 1;
        if (retlen = offset(env+len, &off)) {
                tzdstoffset = -off;
                env += retlen;
        }
        else
                tzdstoffset = tzoffset + 60*60;
        /*
         * optional rule(s) for start/end of dst.
         */
        if (*env == 0 || *env != ',' || *(env+1) == 0)
                return;
        env++;
        /*
         * we could go on...
         * but why bother?
         */
        USED(env);
}