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-rw-r--r--src/util/rand_sleep.c89
1 files changed, 89 insertions, 0 deletions
diff --git a/src/util/rand_sleep.c b/src/util/rand_sleep.c
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+/*++
+/* NAME
+/* rand_sleep 3
+/* SUMMARY
+/* sleep for randomized interval
+/* SYNOPSIS
+/* #include <iostuff.h>
+/*
+/* void rand_sleep(delay, variation)
+/* unsigned delay;
+/* unsigned variation;
+/* DESCRIPTION
+/* rand_sleep() blocks the current process for an amount of time
+/* pseudo-randomly chosen from the interval (delay +- variation/2).
+/*
+/* Arguments:
+/* .IP delay
+/* Time to sleep in microseconds.
+/* .IP variation
+/* Variation in microseconds; must not be larger than delay.
+/* DIAGNOSTICS
+/* Panic: interface violation. All system call errors are fatal.
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <myrand.h>
+#include <iostuff.h>
+
+/* rand_sleep - block for random time */
+
+void rand_sleep(unsigned delay, unsigned variation)
+{
+ const char *myname = "rand_sleep";
+ unsigned usec;
+
+ /*
+ * Sanity checks.
+ */
+ if (delay == 0)
+ msg_panic("%s: bad delay %d", myname, delay);
+ if (variation > delay)
+ msg_panic("%s: bad variation %d", myname, variation);
+
+ /*
+ * Use the semi-crappy random number generator.
+ */
+ usec = (delay - variation / 2) + variation * (double) myrand() / RAND_MAX;
+ doze(usec);
+}
+
+#ifdef TEST
+
+#include <msg_vstream.h>
+
+int main(int argc, char **argv)
+{
+ int delay;
+ int variation;
+
+ msg_vstream_init(argv[0], VSTREAM_ERR);
+ if (argc != 3)
+ msg_fatal("usage: %s delay variation", argv[0]);
+ if ((delay = atoi(argv[1])) <= 0)
+ msg_fatal("bad delay: %s", argv[1]);
+ if ((variation = atoi(argv[2])) < 0)
+ msg_fatal("bad variation: %s", argv[2]);
+ rand_sleep(delay * 1000000, variation * 1000000);
+ exit(0);
+}
+
+#endif