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Diffstat (limited to 'contrib/ntp/libntp/adjtime.c')
| -rw-r--r-- | contrib/ntp/libntp/adjtime.c | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/contrib/ntp/libntp/adjtime.c b/contrib/ntp/libntp/adjtime.c new file mode 100644 index 0000000..72be860 --- /dev/null +++ b/contrib/ntp/libntp/adjtime.c @@ -0,0 +1,152 @@ +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif + +#ifdef NEED_HPUX_ADJTIME +/*************************************************************************/ +/* (c) Copyright Tai Jin, 1988. All Rights Reserved. */ +/* Hewlett-Packard Laboratories. */ +/* */ +/* Permission is hereby granted for unlimited modification, use, and */ +/* distribution. This software is made available with no warranty of */ +/* any kind, express or implied. This copyright notice must remain */ +/* intact in all versions of this software. */ +/* */ +/* The author would appreciate it if any bug fixes and enhancements were */ +/* to be sent back to him for incorporation into future versions of this */ +/* software. Please send changes to tai@iag.hp.com or ken@sdd.hp.com. */ +/*************************************************************************/ + +/* + * Revision history + * + * 9 Jul 94 David L. Mills, Unibergity of Delabunch + * Implemented variable threshold to limit age of + * corrections; reformatted code for readability. + */ + +#ifndef lint +static char RCSid[] = "adjtime.c,v 3.1 1993/07/06 01:04:42 jbj Exp"; +#endif + +#include <sys/types.h> +#include <sys/ipc.h> +#include <sys/msg.h> +#include <time.h> +#include <signal.h> +#include "adjtime.h" + +#define abs(x) ((x) < 0 ? -(x) : (x)) + +/* + * The following paramters are appropriate for an NTP adjustment + * interval of one second. + */ +#define ADJ_THRESH 200 /* initial threshold */ +#define ADJ_DELTA 4 /* threshold decrement */ + +static long adjthresh; /* adjustment threshold */ +static long saveup; /* corrections accumulator */ + +/* + * clear_adjtime - reset accumulator and threshold variables + */ +void +_clear_adjtime(void) +{ + saveup = 0; + adjthresh = ADJ_THRESH; +} + +/* + * adjtime - hp-ux copout of the standard Unix adjtime() system call + */ +int +adjtime( + register struct timeval *delta, + register struct timeval *olddelta + ) +{ + struct timeval newdelta; + + /* + * Corrections greater than one second are done immediately. + */ + if (delta->tv_sec) { + adjthresh = ADJ_THRESH; + saveup = 0; + return(_adjtime(delta, olddelta)); + } + + /* + * Corrections less than one second are accumulated until + * tripping a threshold, which is initially set at ADJ_THESH and + * reduced in ADJ_DELTA steps to zero. The idea here is to + * introduce large corrections quickly, while making sure that + * small corrections are introduced without excessive delay. The + * idea comes from the ARPAnet routing update algorithm. + */ + saveup += delta->tv_usec; + if (abs(saveup) >= adjthresh) { + adjthresh = ADJ_THRESH; + newdelta.tv_sec = 0; + newdelta.tv_usec = saveup; + saveup = 0; + return(_adjtime(&newdelta, olddelta)); + } else { + adjthresh -= ADJ_DELTA; + } + + /* + * While nobody uses it, return the residual before correction, + * as per Unix convention. + */ + if (olddelta) + olddelta->tv_sec = olddelta->tv_usec = 0; + return(0); +} + +/* + * _adjtime - does the actual work + */ +int +_adjtime( + register struct timeval *delta, + register struct timeval *olddelta + ) +{ + register int mqid; + MsgBuf msg; + register MsgBuf *msgp = &msg; + + /* + * Get the key to the adjtime message queue (note that we must + * get it every time because the queue might have been removed + * and recreated) + */ + if ((mqid = msgget(KEY, 0)) == -1) + return (-1); + msgp->msgb.mtype = CLIENT; + msgp->msgb.tv = *delta; + if (olddelta) + msgp->msgb.code = DELTA2; + else + msgp->msgb.code = DELTA1; + + /* + * Tickle adjtimed and snatch residual, if indicated. Lots of + * fanatic error checking here. + */ + if (msgsnd(mqid, &msgp->msgp, MSGSIZE, 0) == -1) + return (-1); + if (olddelta) { + if (msgrcv(mqid, &msgp->msgp, MSGSIZE, SERVER, 0) == -1) + return (-1); + *olddelta = msgp->msgb.tv; + } + return (0); +} + +#else /* not NEED_HPUX_ADJTIME */ +int adjtime_bs; +#endif /* not NEED_HPUX_ADJTIME */ |
