tz2timezone.c File Reference

#include <vxWorks.h>
#include <envLib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <epicsTime.h>

Include dependency graph for tz2timezone.c:

Go to the source code of this file.

Functions
int	tz2timezone (void)

Function Documentation

int tz2timezone

(

void

)

Definition at line 158 of file tz2timezone.c.

{
    const char *tz = getenv("TZ");
    /* Spec. says that zone names must be at least 3 chars.
     * I've never seen a longer zone name, but I'll allocate
     * 40 chars. If you live in a zone with a longer name,
     * you may want to think about the benefits of relocation.
     */
    char zone[40];
    char start[10], stop[10]; /* only really need 7 bytes now */
    int hours = 0, minutes = 0, sign = 1;
    /* This is more than enough, even with a 40-char zone
     * name, and 4-char offset.
     */
    char timezone[100];
    int i = 0; /* You *always need an "i" :-) */
    epicsTimeStamp now;
    struct tm current;

    /* First let's get the current time. We need the year to
     * compute the start/stop dates for DST.
     */
    if (epicsTimeGetCurrent(&now) ||
        epicsTimeToTM(&current, NULL, &now))
        return ERROR;

    /* Make sure TZ exists.
     * Spec. says that ZONE must be at least 3 chars.
     */
    if ((!tz) || (strlen(tz) < 3))
        return ERROR;

    /* OK, now a bunch of brute-force parsing. My brain hurts if
     * I try to think of an elegant regular expression for the
     * string.
     */

    /* Start extracting zone name, must be alpha */
    while ((i < sizeof(zone) - 1) && isalpha((int) *tz)) {
        zone[i++] = *tz++;
    }
    if (i < 3)
        return ERROR; /* Too short, not a real zone name? */

    zone[i] = 0; /* Nil-terminate (for now) */

    /* Now extract offset time. The format is [+/-]hh[:mm[:ss]]
     * Recall that TIMEZONE doesn't support seconds....
     */
    if (*tz == '-') {
        sign = -1;
        tz++;
    }
    else if (*tz == '+') {
        tz++;
    }

    /* Need a digit now */
    if (!isdigit((int) *tz))
        return ERROR;

    /* First get the hours */
    tz = getTime(tz, &hours);
    if (hours > 24)
        return ERROR;

    if (*tz == ':') { /* There is a minutes part */
        /* Need another digit now */
        if (!isdigit((int) *++tz))
            return ERROR;

        /* Extract the minutes */
        tz = getTime(tz, &minutes);
        if (minutes > 60)
            return ERROR;

        /* Skip any seconds part */
        if (*tz == ':') {
            int seconds;
            tz = getTime(tz + 1, &seconds);
        }
    }

    /* Extract any DST zone name, must be alpha */
    if (isalpha((int) *tz)) {
        zone[i++] = '/'; /* Separate the names */

        while ((i < sizeof(zone) - 1) && isalpha((int) *tz)) {
            zone[i++] = *tz++;
        }
        zone[i] = 0; /* Nil-terminate */
    }

    minutes += hours * 60;
    minutes *= sign;

    /* Look for start/stop dates - require neither or both */
    tz = strchr(tz, ',');
    if (!tz) {  /* No daylight savings time here */
        /* Format the env. variable */
        sprintf(timezone, "TIMEZONE=%s::%d", zone, minutes);
    }
    else {
        if (extractDate(tz, &current, start) != OK)
            return ERROR;

        tz = strchr(tz + 1, ',');
        if (!tz)
            return ERROR;
        if (extractDate(tz, &current, stop) != OK)
            return ERROR;

        /* Format the env. variable */
        sprintf(timezone, "TIMEZONE=%s::%d:%s:%s", zone, minutes, start, stop);
    }

    /* Make it live! */
    putenv(timezone);

    return OK;
}