/*
* Aphelion
* Copyright (c) 2013 Joris van der Wel
*
* This file is part of Aphelion
*
* Aphelion is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, version 3 of the License.
*
* Aphelion is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with Aphelion. If not, see <http://www.gnu.org/licenses/>.
*
* In addition, the following supplemental terms apply, based on section 7 of
* the GNU Affero General Public License (version 3):
* a) Preservation of all legal notices and author attributions
* b) Prohibition of misrepresentation of the origin of this material, and
* modified versions are required to be marked in reasonable ways as
* different from the original version (for example by appending a copyright notice).
*
* Linking this library statically or dynamically with other modules is making a
* combined work based on this library. Thus, the terms and conditions of the
* GNU Affero General Public License cover the whole combination.
*
* As a special exception, the copyright holders of this library give you
* permission to link this library with independent modules to produce an
* executable, regardless of the license terms of these independent modules,
* and to copy and distribute the resulting executable under terms of your
* choice, provided that you also meet, for each linked independent module,
* the terms and conditions of the license of that module. An independent
* module is a module which is not derived from or based on this library.
*/
package aphelion.shared.swissarmyknife;
/**
* Rolling ticked history which permits null values.
* @param <T>
* @author Joris
*/
public class RollingHistory<T>
{
public final int HISTORY_LENGTH;
private int history_index = 0;
private long history_tick = 0;
private final T[] history;
public RollingHistory(long initial_tick, int history_length)
{
if (history_length < 1)
{
throw new IllegalArgumentException();
}
this.HISTORY_LENGTH = history_length;
this.history_tick = initial_tick;
history = (T[]) new Object[HISTORY_LENGTH];
}
protected void updated() {}
/** Set the history value for a particular tick.
* If this tick is greater than getMostRecentTick(),
* the oldest value might be removed if the history length has been reached.
* If this tick is too old, nothing is set and this method returns -1;
* @param tick
* @param value
* @return The index in the internal array that the value was set on. or -1 on failure
*/
public int setHistory(long tick, T value)
{
while (tick > history_tick)
{
++history_index;
++history_tick;
if (history_index == HISTORY_LENGTH)
{
history_index = 0;
}
history[history_index] = null;
}
long tick_diff = history_tick - tick;
if (tick_diff >= HISTORY_LENGTH)
{
// My history does not go back that far
return -1;
}
int index = history_index - (int) tick_diff;
if (index < 0)
{
index += HISTORY_LENGTH;
}
history[index] = value;
updated();
return index;
}
/** Get a value relative to getMostRecentTick().
* @param ticks_ago Relative tick value
* @return historic value previously set by setHistory()
* @throws IllegalArgumentException if ticks_ago < 0 || ticks_ago >= HISTORY_LENGTH
*/
public T getRelative(int ticks_ago) throws IllegalArgumentException
{
if (ticks_ago < 0 || ticks_ago >= HISTORY_LENGTH)
{
throw new IllegalArgumentException();
}
int index = history_index - ticks_ago;
if (index < 0) { index += HISTORY_LENGTH; }
return history[index];
}
/** Get a value.
* @param tick Absolute tick value
* @return historic value previously set by setHistory() or null if there is no value for this tick.
*/
public T get(long tick)
{
long ticks_ago = history_tick - tick;
if (ticks_ago < 0 || ticks_ago >= HISTORY_LENGTH)
{
return null;
}
int index = history_index - (int) ticks_ago;
if (index < 0) { index += HISTORY_LENGTH; }
return history[index];
}
/** The highest tick we have a value for.
* @return tick
*/
public long getMostRecentTick()
{
return history_tick;
}
/** The oldest tick we might a value for.
* This value might be null or have never been actually set.
* @return tick
*/
public long getOldestTick()
{
return history_tick - HISTORY_LENGTH + 1;
}
/** Set this instance to be identical to another instance.
* This method avoids triggering garbage collection (versus .clone()).
* @param other
*/
public void set(RollingHistory<T> other)
{
if (other.HISTORY_LENGTH > this.HISTORY_LENGTH)
{
throw new IllegalArgumentException();
}
this.history_tick = other.history_tick;
this.history_index = this.HISTORY_LENGTH - 1;
int myIndex = this.history_index;
int otherIndex = other.history_index;
boolean moreData = true;
while (myIndex >= 0)
{
if (moreData)
{
this.history[myIndex] = other.history[otherIndex];
--otherIndex;
if (otherIndex == -1)
{
otherIndex = other.HISTORY_LENGTH-1;
}
assert otherIndex >= 0;
if (otherIndex == other.history_index)
{
moreData = false;
}
}
else
{
this.history[myIndex] = null;
}
--myIndex;
}
updated();
}
@Override
public String toString()
{
StringBuilder ret = new StringBuilder();
ret.append(history_tick);
ret.append(": ");
for (int t = 0; t < HISTORY_LENGTH; ++t)
{
ret.append(getRelative(t));
ret.append(" ");
}
return ret.toString();
}
}