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faketime.c
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faketime.c
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/*
* Copyright 2013-2020 Fabian Groffen
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#ifndef HAVE_RTLD_NEXT
# error must have dlsym/RTLD_NEXT to fake time
#endif
#if 0
/* we cannot include time.h and sys/time.h due to gettimeofday
* definition being different on some platforms with
* complex/incompatible restrict definitions, but we do need struct
* timeval, so we're faking the necessary bits here */
#include <time.h>
#include <sys/time.h>
#else
#define _TIME_H
#define _SYS_TIME_H
/* internal definition, we only access tv_sec so don't care about the
* type/definition of tv_usec */
#if SIZEOF_TIME_T == 4
#define fttime_t int
#elif SIZEOF_TIME_T == 8
#define fttime_t long long int
#else
#define fttime_t ssize_t
#endif
struct fttimeval {
fttime_t tv_sec;
};
#define NULL (void *)0
#endif
#include <dlfcn.h>
/* for repeatability, always return time starting from 1981-02-01 from the
* first call to time(). This way we can control the aggregator time
* buckets */
#define MYEPOCH 349830000
fttime_t (*orig_time)(fttime_t *tloc) = NULL;
int (*orig_gettimeofday)(struct fttimeval *tp, void *tz) = NULL;
fttime_t fake_offset = 0;
__attribute__((constructor)) void init(void) {
orig_time = dlsym(RTLD_NEXT, "time");
orig_gettimeofday = dlsym(RTLD_NEXT, "gettimeofday");
}
fttime_t time(fttime_t *tloc) {
fttime_t now;
(void)orig_time(&now);
if (fake_offset == 0)
fake_offset = now - MYEPOCH;
now -= fake_offset;
if (tloc)
*tloc = now;
return now;
}
int gettimeofday(struct fttimeval *tp, void *tzp) {
/* some platforms, like Darwin and Solaris, have an implementation
* of gettimeofday that does not call time(), others, like glibc do
* which means we need to deal with that here */
fttime_t now;
int ret = orig_gettimeofday(tp, tzp);
if (ret != 0)
return ret;
/* setup clock offset */
now = time(NULL);
now += fake_offset;
if (now >= tp->tv_sec)
tp->tv_sec -= fake_offset;
return 0;
}