qtime.c

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 * Copyright (c) 2010-2026 Seungyoung Kim.
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/**
 * @file qtime.c Time handling APIs.
 */
 
#define __USE_XOPEN
#define _XOPEN_SOURCE
#define _BSD_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <sys/time.h>
#include "qinternal.h"
#include "utilities/qtime.h"
 
/**
 * Returns the current time in milliseconds.
 *
 * @return current time in milliseconds.
 */
long qtime_current_milli(void) {
    struct timeval tv;
    gettimeofday(&tv, NULL);
    long time = (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
    return time;
}
 
/**
 * Format a local time string with a custom format.
 *
 * @param buf       output buffer
 * @param size      buffer size
 * @param utctime   0 for the current time, or a specific UTC time
 * @param format    format string for `strftime()`
 *
 * @return pointer to `buf`
 *
 * @code
 *   char *timestr = qtime_localtime_strf(0, "%H:%M:%S"); // HH:MM:SS
 *   free(timestr);
 *   char *timestr = qtime_localtime_strf(0, "%Y%m%d%H%M%S"); // YYMMDDhhmmss
 *   free(timestr);
 * @endcode
 */
char *qtime_localtime_strf(char *buf, int size, time_t utctime,
                           const char *format) {
    if (utctime == 0)
        utctime = time(NULL);
    struct tm *localtm = localtime(&utctime);
 
    if (strftime(buf, size, format, localtm) == 0) {
        snprintf(buf, size, "(buffer small)");
    }
 
    return buf;
}
 
/**
 * Get local time string formatted like '02-Nov-2007 16:37:39 +0900'.
 *
 * @param utctime   0 for the current time, or a specific UTC time
 *
 * @return allocated time string.
 *
 * @code
 *   char *timestr;
 *   timestr = qtime_localtime_str(0);  // now
 *   free(timestr);
 *   timestr = qtime_localtime_str(time(NULL));  // same as above
 *   free(timestr);
 *   timestr = qtime_localtime_str(time(NULL) - 86400));  // 1 day before
 *   free(timestr);
 * @endcode
 */
char *qtime_localtime_str(time_t utctime) {
    int size = sizeof(char) * (CONST_STRLEN("00-Jan-0000 00:00:00 +0000") + 1);
    char *timestr = (char *) malloc(size);
    if (timestr == NULL)
        return NULL;
 
    qtime_localtime_strf(timestr, size, utctime, "%d-%b-%Y %H:%M:%S %z");
    return timestr;
}
 
/**
 * Get local time string formatted like '02-Nov-2007 16:37:39 +0900'.
 *
 * @param utctime   0 for the current time, or a specific UTC time
 *
 * @return internal static time string.
 *
 * @code
 *   printf("%s", qtime_localtime_staticstr(0));  // now
 *   printf("%s", qtime_localtime_staticstr(time(NULL) + 86400)); // 1 day later
 * @endcode
 */
const char *qtime_localtime_staticstr(time_t utctime) {
    static char timestr[sizeof(char)
            * (CONST_STRLEN("00-Jan-0000 00:00:00 +0000") + 1)];
    qtime_localtime_strf(timestr, sizeof(timestr), utctime,
                         "%d-%b-%Y %H:%M:%S %z");
    return timestr;
}
 
/**
 * Format a GMT time string with a custom format.
 *
 * @param buf       output buffer
 * @param size      buffer size
 * @param utctime   0 for the current time, or a specific UTC time
 * @param format    format string for `strftime()`
 *
 * @return pointer to `buf`
 *
 * @code
 *   char timestr[8+1];
 *   qtime_gmt_strf(buf, sizeof(buf), 0, "%H:%M:%S"); // HH:MM:SS
 * @endcode
 */
char *qtime_gmt_strf(char *buf, int size, time_t utctime, const char *format) {
    if (utctime == 0)
        utctime = time(NULL);
    struct tm *gmtm = gmtime(&utctime);
 
    strftime(buf, size, format, gmtm);
    return buf;
}
 
/**
 * Get GMT time string formatted like 'Wed, 11-Nov-2007 23:19:25 GMT'.
 *
 * @param utctime   0 for the current time, or a specific UTC time
 *
 * @return allocated GMT time string.
 *
 * @code
 *   char *timestr;
 *   timestr = qtime_gmt_str(0);           // now
 *   free(timestr);
 *   timestr = qtime_gmt_str(time(NULL));      // same as above
 *   free(timestr);
 *   timestr = qtime_gmt_str(time(NULL) - 86400)); // 1 day before
 *   free(timestr);
 * @endcode
 */
char *qtime_gmt_str(time_t utctime) {
    int size = sizeof(char)
            * (CONST_STRLEN("Mon, 00 Jan 0000 00:00:00 GMT") + 1);
    char *timestr = (char *) malloc(size);
    if (timestr == NULL)
        return NULL;
 
    qtime_gmt_strf(timestr, size, utctime, "%a, %d %b %Y %H:%M:%S GMT");
    return timestr;
}
 
/**
 * Get GMT time string formatted like 'Wed, 11-Nov-2007 23:19:25 GMT'.
 *
 * @param utctime   0 for the current time, or a specific UTC time
 *
 * @return internal static GMT time string.
 *
 * @code
 *   printf("%s", qtime_gmt_staticstr(0));         // now
 *   printf("%s", qtime_gmt_staticstr(time(NULL) + 86400));    // 1 day later
 * @endcode
 */
const char *qtime_gmt_staticstr(time_t utctime) {
    static char timestr[sizeof(char)
            * (CONST_STRLEN("Mon, 00-Jan-0000 00:00:00 GMT") + 1)];
    qtime_gmt_strf(timestr, sizeof(timestr), utctime,
                   "%a, %d %b %Y %H:%M:%S GMT");
    return timestr;
}
 
/**
 * Parse a GMT or timezone-formatted time string and return UTC time.
 *
 * Examples:
 * 'Sun, 04 May 2008 18:50:39 GMT'
 * 'Mon, 05 May 2008 03:50:39 +0900'
 *
 * @param gmtstr    GMT/timezone-formatted time string
 *
 * @return UTC time. Returns -1 on conversion error.
 *
 * @code
 *   time_t t = time(NULL);
 *   char *s =  qtime_parse_gmtstr(t);
 *   printf("%d\n", t);
 *   printf("%s\n", s);
 *   printf("%d\n", qtime_parse_gmtstr(s)); // this must be same as t
 *   free(s);
 * @endcode
 */
time_t qtime_parse_gmtstr(const char *gmtstr) {
    struct tm gmtm;
    if (strptime(gmtstr, "%a, %d %b %Y %H:%M:%S", &gmtm) == NULL)
        return 0;
    time_t utc = timegm(&gmtm);
    if (utc < 0)
        return -1;
 
// Parse timezone.
    char *p;
    if ((p = strstr(gmtstr, "+")) != NULL) {
        utc -= ((atoi(p + 1) / 100) * 60 * 60);
        if (utc < 0)
            return -1;
    } else if ((p = strstr(gmtstr, "-")) != NULL) {
        utc += ((atoi(p + 1) / 100) * 60 * 60);
    }
 
    return utc;
}