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Core Getdown functionality
//
// Getdown - application installer, patcher and launcher
// Copyright (C) 2004-2016 Getdown authors
// https://github.com/threerings/getdown/blob/master/LICENSE
package com.threerings.getdown.net;
import java.io.File;
import java.io.IOException;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import com.threerings.getdown.data.Resource;
import static com.threerings.getdown.Log.log;
/**
* Handles the download of a collection of files, first issuing HTTP head requests to obtain size
* information and then downloading the files individually, reporting progress back via a callback
* interface.
*/
public abstract class Downloader extends Thread
{
/**
* An interface used to communicate status back to an external entity. Note: these
* methods are all called on the download thread, so implementors must take care to only
* execute thread-safe code or simply pass a message to the AWT thread, for example.
*/
public interface Observer
{
/**
* Called before the downloader begins the series of HTTP head requests to determine the
* size of the files it needs to download.
*/
public void resolvingDownloads ();
/**
* Called to inform the observer of ongoing progress toward completion of the overall
* downloading task. The caller is guaranteed to get at least one call reporting 100%
* completion.
*
* @param percent the percent completion, in terms of total file size, of the downloads.
* @param remaining the estimated download time remaining in seconds, or -1 if
* the time can not yet be determined.
*
* @return true if the download should continue, false if it should be aborted.
*/
public boolean downloadProgress (int percent, long remaining);
/**
* Called if a failure occurs while checking for an update or downloading a file.
*
* @param rsrc the resource that was being downloaded when the error occurred, or
* null if the failure occurred while resolving downloads.
* @param e the exception detailing the failure.
*/
public void downloadFailed (Resource rsrc, Exception e);
}
/**
* Creates a downloader that will download the supplied list of resources and communicate with
* the specified observer. The {@link #download} method must be called on the downloader to
* initiate the download process.
*/
public Downloader (Collection resources, Observer obs)
{
super("Downloader");
_resources = resources;
_obs = obs;
}
/**
* This method is invoked as the downloader thread and performs the actual downloading.
*/
@Override
public void run ()
{
download();
}
/**
* Start downloading the resources in this downloader.
*
* @return true if the download completed or failed for unexpected reasons (in which case the
* observer will have been notified), false if it was aborted by the observer.
*/
public boolean download ()
{
Resource current = null;
try {
// let the observer know that we're computing download size
if (_obs != null) {
_obs.resolvingDownloads();
}
// first compute the total size of our download
for (Resource resource : _resources) {
discoverSize(resource);
}
long totalSize = sum(_sizes.values());
log.info("Downloading " + totalSize + " bytes...");
// make a note of the time at which we started the download
_start = System.currentTimeMillis();
// now actually download the files
for (Resource resource : _resources) {
download(resource);
}
// finally report our download completion if we did not already do so when downloading
// our final resource
if (_obs != null && !_complete && !_obs.downloadProgress(100, 0)) {
return false;
}
} catch (DownloadAbortedException e) {
return false;
} catch (Exception e) {
if (_obs != null) {
_obs.downloadFailed(current, e);
} else {
log.warning("Observer failed.", e);
}
}
return true;
}
/**
* Notes the amount of data needed to download the given resource..
*/
protected void discoverSize (Resource rsrc)
throws IOException
{
_sizes.put(rsrc, Math.max(checkSize(rsrc), 0L));
}
/**
* Performs the protocol-specific portion of checking download size.
*/
protected abstract long checkSize (Resource rsrc) throws IOException;
/**
* Downloads the specified resource from its remote location to its local location.
*/
protected void download (Resource rsrc)
throws IOException
{
// make sure the resource's target directory exists
File parent = new File(rsrc.getLocal().getParent());
if (!parent.exists() && !parent.mkdirs()) {
log.warning("Failed to create target directory for resource '" + rsrc + "'. " +
"Download will certainly fail.");
}
doDownload(rsrc);
}
/**
* Periodically called by the protocol-specific downloaders to update their progress. This
* should be called at least once for each resource to be downloaded, with the total downloaded
* size for that resource. It can also be called periodically along the way for each resource
* to communicate incremental progress.
*
* @param rsrc the resource currently being downloaded.
* @param currentSize the number of bytes currently downloaded for said resource.
* @param actualSize the size reported for this resource now that we're actually downloading
* it. Some web servers lie about Content-length when doing a HEAD request, so by reporting
* updated sizes here we can recover from receiving bogus information in the earlier {@link
* #checkSize} phase.
*/
protected void updateObserver (Resource rsrc, long currentSize, long actualSize)
throws IOException
{
// update the actual size for this resource (but don't let it shrink)
_sizes.put(rsrc, actualSize = Math.max(actualSize, _sizes.get(rsrc)));
// update the current downloaded size for said resource; don't allow the downloaded bytes
// to exceed the original claimed size of the resource, otherwise our progress will get
// booched and we'll end up back on the Daily WTF: http://tinyurl.com/29wt4oq
_downloaded.put(rsrc, Math.min(actualSize, currentSize));
// notify the observer if it's been sufficiently long since our last notification
long now = System.currentTimeMillis();
if ((now - _lastUpdate) >= UPDATE_DELAY) {
_lastUpdate = now;
// total up our current and total bytes
long downloaded = sum(_downloaded.values());
long totalSize = sum(_sizes.values());
// compute our bytes per second
long secs = (now - _start) / 1000L;
long bps = (secs == 0) ? 0 : (downloaded / secs);
// compute our percentage completion
int pctdone = (totalSize == 0) ? 0 : (int)((downloaded * 100f) / totalSize);
// estimate our time remaining
long remaining = (bps <= 0 || totalSize == 0) ? -1 : (totalSize - downloaded) / bps;
// make sure we only report 100% exactly once
if (pctdone < 100 || !_complete) {
_complete = (pctdone == 100);
if (!_obs.downloadProgress(pctdone, remaining)) {
throw new DownloadAbortedException();
}
}
}
}
/**
* Sums the supplied values.
*/
protected static long sum (Iterable values)
{
long acc = 0L;
for (Long value : values) {
acc += value;
}
return acc;
}
/**
* Accomplishes the copying of the resource from remote location to local location using
* protocol-specific code
*/
protected abstract void doDownload (Resource rsrc) throws IOException;
/** The resources to be downloaded. */
protected Collection _resources;
/** The reported sizes of our resources. */
protected Map _sizes = new HashMap<>();
/** The bytes downloaded for each resource. */
protected Map _downloaded = new HashMap<>();
/** The observer with whom we are communicating. */
protected Observer _obs;
/** Used while downloading. */
protected byte[] _buffer = new byte[4096];
/** The time at which the file transfer began. */
protected long _start;
/** The current transfer rate in bytes per second. */
protected long _bytesPerSecond;
/** The time at which the last progress update was posted to the progress observer. */
protected long _lastUpdate;
/** Whether the download has completed and the progress observer notified. */
protected boolean _complete;
/** The delay in milliseconds between notifying progress observers of file download
* progress. */
protected static final long UPDATE_DELAY = 500L;
}