/**
* Downloads the specified file from a peer that is hosting said file
*
* @param peer A Socket connected to the peer that is hosting the file
* @param start The starting byte of the piece that will be downloaded from this peer
* @param end The end of the piece that will be downloaded from this peer, not inclusive
* @throws java.io.IOException if an error occurs during the download
*/
private void downloadFromPeer(Socket peer, int start, int end) throws IOException {
if (start >= end) {
throw new IllegalStateException(
"Start byte (" + start + ") must be less than the end byte (" + end + ")");
}
DataInputStream in = new DataInputStream(peer.getInputStream());
PrintWriter out = new PrintWriter(peer.getOutputStream(), true);
// Tell peer what file to download and the desired chunk size
out.println("<GET download " + _file + " " + _chunkSize + " " + start + " " + end + ">");
// Make sure the chunk size is valid
String response = in.readUTF();
switch (response) {
case "<GET invalid>":
System.err.println("[DownloadFromPeerRunnable] Error: Invalid chunk size");
break;
case "<GET begin>":
saveFile(in, start, end);
_callback.onFinishChunk(_file, true);
break;
default:
throw new UnexpectedResponseException(response);
}
}
/**
* Reads a file from the given InputStream and saves it into the local download directory
*
* @param in The InputStream from which to read the file
* @param start The starting byte of the piece that will be downloaded from this peer
* @param end The end byte (exclusive) of the piece that will be downloaded from this peer
* @throws java.io.IOException if an error occurs while downloading the file
*/
private void saveFile(InputStream in, int start, int end) throws IOException {
if (start >= end) {
throw new IllegalStateException(
"Start byte (" + start + ") must be less than the end byte (" + end + ")");
}
RandomAccessFile fileOut = null;
try {
File downloadFile = new File(Client.downloadDir, _file);
// Open the file in read/write mode with synchronous content/metadata writing
fileOut = new RandomAccessFile(downloadFile, "rws");
fileOut.seek(start);
byte[] bytes = new byte[_chunkSize];
int bytesRead;
int pos = start;
while ((bytesRead = in.read(bytes, 0, _chunkSize)) >= 0 && pos < end) {
fileOut.write(bytes, 0, Math.min(bytesRead, end - pos));
pos += bytesRead;
}
} catch (SocketException e) {
System.err.println(
"[DownloadFromPeerRunnable] Disconnected from peer at " + _peer.getInetAddress());
_callback.onFinishChunk(_file, false);
} finally {
if (fileOut != null) {
try {
fileOut.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/** Run the thread */
@Override
public void run() {
try {
downloadFromPeer(_peer, _start, _end);
} catch (IOException e) {
e.printStackTrace();
_callback.onFinishChunk(_file, false);
}
}
