Created services for distributing delta times over the network which are
interpreted according to a globally established base time. git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@1404 542714f4-19e9-0310-aa3c-eee0fc999fb1
This commit is contained in:
Michael Bayne
@@ -0,0 +1,23 @@
|
||||
//
|
||||
// $Id: TimeBaseCodes.java,v 1.1 2002/05/28 23:14:06 mdb Exp $
|
||||
|
||||
package com.threerings.presents.data;
|
||||
|
||||
/**
|
||||
* Codes and constants relating to the Presents time base services.
|
||||
*/
|
||||
public interface TimeBaseCodes
|
||||
{
|
||||
/** The module name for the time services. */
|
||||
public static final String MODULE_NAME = "time";
|
||||
|
||||
/** The message identifier for a request to obtain a particular time
|
||||
* object. */
|
||||
public static final String GET_TIME_OID_REQUEST = "GetTimeOid";
|
||||
|
||||
/** A response generated for a successful getTimeOid request. */
|
||||
public static final String TIME_OID_RESPONSE = "TimeOid";
|
||||
|
||||
/** An error response generated for GetTimeOid requests. */
|
||||
public static final String NO_SUCH_TIME_BASE = "m.no_such_time_base";
|
||||
}
|
||||
@@ -0,0 +1,104 @@
|
||||
//
|
||||
// $Id: TimeBaseObject.dobj,v 1.1 2002/05/28 23:14:06 mdb Exp $
|
||||
|
||||
package com.threerings.presents.data;
|
||||
|
||||
import com.threerings.presents.dobj.DObject;
|
||||
|
||||
/**
|
||||
* Used to communicate time bases to clients so that more efficient delta
|
||||
* times can be transmitted over the network. Two time stamps are
|
||||
* maintained: even and odd. When the even time base is sufficiently old
|
||||
* that our delta time container (usually a short or an int) will exceed
|
||||
* its maximum value, we switch to the odd time base. The bouncing between
|
||||
* two separate values prevents problems from arising when the base time
|
||||
* is changed, yet values using the old base time might still be
|
||||
* propagating through the system.
|
||||
*
|
||||
* <p> Note that for sufficiently small delta time containers, stale
|
||||
* values could still linger longer than the time required for two swaps
|
||||
* (two byte delta stamps for example, must swap every 30 seconds).
|
||||
*/
|
||||
public class TimeBaseObject extends DObject
|
||||
{
|
||||
/** The even time base, used to decode even delta times. */
|
||||
public long evenBase;
|
||||
|
||||
/** The odd time base, used to decode odd delta times. */
|
||||
public long oddBase;
|
||||
|
||||
/**
|
||||
* Converts the supplied time stamp into a time delta (measured
|
||||
* relative to the appropriate time base, even or odd) with maximum
|
||||
* value of 2^15. (One bit must be used to indicate that it is an even
|
||||
* or odd time stamp).
|
||||
*/
|
||||
public short toShortDelta (long timeStamp)
|
||||
{
|
||||
return (short)getDelta(timeStamp, Short.MAX_VALUE);
|
||||
}
|
||||
|
||||
/**
|
||||
* Converts the supplied time stamp into a time delta (measured
|
||||
* relative to the appropriate time base, even or odd) with maximum
|
||||
* value of 2^31. (One bit must be used to indicate that it is an even
|
||||
* or odd time stamp).
|
||||
*/
|
||||
public int toIntDelta (long timeStamp)
|
||||
{
|
||||
return (int)getDelta(timeStamp, Integer.MAX_VALUE);
|
||||
}
|
||||
|
||||
/**
|
||||
* Converts the supplied delta time back to a wall time based on the
|
||||
* base time in this time base object. Either an int or short delta
|
||||
* can be passed to this method (the short will have been promoted to
|
||||
* an int in the process but that will not mess up its encoded value).
|
||||
*/
|
||||
public long fromDelta (int delta)
|
||||
{
|
||||
boolean even = (delta > 0);
|
||||
long time = even ? evenBase : oddBase;
|
||||
if (even) {
|
||||
time += delta;
|
||||
} else {
|
||||
time += (-1 - delta);
|
||||
}
|
||||
return time;
|
||||
}
|
||||
|
||||
/**
|
||||
* Obtains a delta with the specified maximum value, swapping from
|
||||
* even to odd, if necessary.
|
||||
*/
|
||||
protected long getDelta (long timeStamp, long maxValue)
|
||||
{
|
||||
boolean even = (evenBase > oddBase);
|
||||
long base = even ? evenBase : oddBase;
|
||||
long delta = timeStamp - base;
|
||||
|
||||
// make sure this timestamp is not sufficiently old that we can't
|
||||
// generate a delta time with it
|
||||
if (delta < 0) {
|
||||
String errmsg = "Time stamp too old for conversion to delta time";
|
||||
throw new IllegalArgumentException(errmsg);
|
||||
}
|
||||
|
||||
// see if it's time to swap
|
||||
if (delta > maxValue) {
|
||||
if (even) {
|
||||
setOddBase(timeStamp);
|
||||
} else {
|
||||
setEvenBase(timeStamp);
|
||||
}
|
||||
delta = 0;
|
||||
}
|
||||
|
||||
// if we're odd, we need to mark the value as such
|
||||
if (!even) {
|
||||
delta = (-1 - delta);
|
||||
}
|
||||
|
||||
return delta;
|
||||
}
|
||||
}
|
||||
@@ -0,0 +1,138 @@
|
||||
//
|
||||
// $Id: TimeBaseObject.java,v 1.1 2002/05/28 23:14:06 mdb Exp $
|
||||
|
||||
package com.threerings.presents.data;
|
||||
|
||||
import com.threerings.presents.dobj.DObject;
|
||||
|
||||
/**
|
||||
* Used to communicate time bases to clients so that more efficient delta
|
||||
* times can be transmitted over the network. Two time stamps are
|
||||
* maintained: even and odd. When the even time base is sufficiently old
|
||||
* that our delta time container (usually a short or an int) will exceed
|
||||
* its maximum value, we switch to the odd time base. The bouncing between
|
||||
* two separate values prevents problems from arising when the base time
|
||||
* is changed, yet values using the old base time might still be
|
||||
* propagating through the system.
|
||||
*
|
||||
* <p> Note that for sufficiently small delta time containers, stale
|
||||
* values could still linger longer than the time required for two swaps
|
||||
* (two byte delta stamps for example, must swap every 30 seconds).
|
||||
*/
|
||||
public class TimeBaseObject extends DObject
|
||||
{
|
||||
/** The field name of the <code>evenBase</code> field. */
|
||||
public static final String EVEN_BASE = "evenBase";
|
||||
|
||||
/** The field name of the <code>oddBase</code> field. */
|
||||
public static final String ODD_BASE = "oddBase";
|
||||
|
||||
/** The even time base, used to decode even delta times. */
|
||||
public long evenBase;
|
||||
|
||||
/** The odd time base, used to decode odd delta times. */
|
||||
public long oddBase;
|
||||
|
||||
/**
|
||||
* Converts the supplied time stamp into a time delta (measured
|
||||
* relative to the appropriate time base, even or odd) with maximum
|
||||
* value of 2^15. (One bit must be used to indicate that it is an even
|
||||
* or odd time stamp).
|
||||
*/
|
||||
public short toShortDelta (long timeStamp)
|
||||
{
|
||||
return (short)getDelta(timeStamp, Short.MAX_VALUE);
|
||||
}
|
||||
|
||||
/**
|
||||
* Converts the supplied time stamp into a time delta (measured
|
||||
* relative to the appropriate time base, even or odd) with maximum
|
||||
* value of 2^31. (One bit must be used to indicate that it is an even
|
||||
* or odd time stamp).
|
||||
*/
|
||||
public int toIntDelta (long timeStamp)
|
||||
{
|
||||
return (int)getDelta(timeStamp, Integer.MAX_VALUE);
|
||||
}
|
||||
|
||||
/**
|
||||
* Converts the supplied delta time back to a wall time based on the
|
||||
* base time in this time base object. Either an int or short delta
|
||||
* can be passed to this method (the short will have been promoted to
|
||||
* an int in the process but that will not mess up its encoded value).
|
||||
*/
|
||||
public long fromDelta (int delta)
|
||||
{
|
||||
boolean even = (delta > 0);
|
||||
long time = even ? evenBase : oddBase;
|
||||
if (even) {
|
||||
time += delta;
|
||||
} else {
|
||||
time += (-1 - delta);
|
||||
}
|
||||
return time;
|
||||
}
|
||||
|
||||
/**
|
||||
* Obtains a delta with the specified maximum value, swapping from
|
||||
* even to odd, if necessary.
|
||||
*/
|
||||
protected long getDelta (long timeStamp, long maxValue)
|
||||
{
|
||||
boolean even = (evenBase > oddBase);
|
||||
long base = even ? evenBase : oddBase;
|
||||
long delta = timeStamp - base;
|
||||
|
||||
// make sure this timestamp is not sufficiently old that we can't
|
||||
// generate a delta time with it
|
||||
if (delta < 0) {
|
||||
String errmsg = "Time stamp too old for conversion to delta time";
|
||||
throw new IllegalArgumentException(errmsg);
|
||||
}
|
||||
|
||||
// see if it's time to swap
|
||||
if (delta > maxValue) {
|
||||
if (even) {
|
||||
setOddBase(timeStamp);
|
||||
} else {
|
||||
setEvenBase(timeStamp);
|
||||
}
|
||||
delta = 0;
|
||||
}
|
||||
|
||||
// if we're odd, we need to mark the value as such
|
||||
if (!even) {
|
||||
delta = (-1 - delta);
|
||||
}
|
||||
|
||||
return delta;
|
||||
}
|
||||
|
||||
/**
|
||||
* Requests that the <code>evenBase</code> field be set to the specified
|
||||
* value. The local value will be updated immediately and an event
|
||||
* will be propagated through the system to notify all listeners that
|
||||
* the attribute did change. Proxied copies of this object (on
|
||||
* clients) will apply the value change when they received the
|
||||
* attribute changed notification.
|
||||
*/
|
||||
public void setEvenBase (long evenBase)
|
||||
{
|
||||
this.evenBase = evenBase;
|
||||
requestAttributeChange(EVEN_BASE, new Long(evenBase));
|
||||
}
|
||||
|
||||
/**
|
||||
* Requests that the <code>oddBase</code> field be set to the specified
|
||||
* value. The local value will be updated immediately and an event
|
||||
* will be propagated through the system to notify all listeners that
|
||||
* the attribute did change. Proxied copies of this object (on
|
||||
* clients) will apply the value change when they received the
|
||||
* attribute changed notification.
|
||||
*/
|
||||
public void setOddBase (long oddBase)
|
||||
{
|
||||
this.oddBase = oddBase;
|
||||
requestAttributeChange(ODD_BASE, new Long(oddBase));
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user