/*
* XNap - A P2P framework and client.
*
* See the file AUTHORS for copyright information.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation.
*
* This program 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 General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package mobac.utilities.stream;
import org.apache.log4j.Logger;
/**
* Provides a throttle implementation based on time ticks. Clients can allocate a limited amount of bytes for each tick.
* If all bandwidth has been allocated clients are stalled until the next tick.
*/
public class ThrottleSupport {
// --- Constant(s) ---
/**
* The default length of a tick.
*/
public static final long TICK_LENGTH = 512; // = 2^9
// --- Data field(s) ---
private static Logger logger = Logger.getLogger(ThrottleSupport.class);
/**
* bytes per tick
*/
protected long bandwidth = 0;
protected long allocated = 0;
protected long tick = 0;
protected Object lock = new Object();
// --- Constructor(s) ---
public ThrottleSupport() {
}
/**
* Sets the maximum bandwidth.
*
* @param bandwidth
* byte / s
*/
public void setBandwidth(long bandwidth) {
synchronized (lock) {
this.bandwidth = (bandwidth * TICK_LENGTH) / 1024;
}
}
/**
* Returns the number of bytes that the calling thread is allowed to send. Blocks until at least one byte could be
* allocated.
*
* @return -1, if interrupted;
*/
public int allocate(int bytes) {
if (bytes == 0)
return 0;
synchronized (lock) {
while (true) {
if (bandwidth == 0) {
// no limit
return bytes;
}
long currentTick = System.currentTimeMillis() >> 9;
if (currentTick > tick) {
logger.debug("* new tick: " + bandwidth + " to allocate *");
tick = currentTick;
allocated = 0;
lock.notifyAll();
}
if (bytes < bandwidth - allocated) {
// we still have some bandwidth left
allocated += bytes;
logger.debug("returning " + bytes + " allocated now " + allocated);
return bytes;
}
if (bandwidth - allocated > 0) {
// don't have enough, but return all we have left
bytes = (int) (bandwidth - allocated);
allocated = bandwidth;
logger.debug("returning " + bytes + " allocated now " + allocated);
return bytes;
}
// we could not allocate any bandwidth, wait until the next
// tick is started
// this is a bit too long
long t = TICK_LENGTH - (System.currentTimeMillis() % TICK_LENGTH);
if (t > 0) {
try {
logger.debug("waiting for " + t);
lock.wait(t);
} catch (InterruptedException e) {
return -1;
}
}
}
}
}
}