download code and tests

core/src/main/groovy/com/muwire/core/Constants.groovy

@@ -5,4 +5,7 @@ import net.i2p.crypto.SigType
 class Constants {
     public static final byte PERSONA_VERSION = (byte)1
     public static final SigType SIG_TYPE = SigType.ECDSA_SHA512_P521 // TODO: decide which
+    
+    public static final int MAX_HEADER_SIZE = 0x1 << 14
+    public static final int MAX_HEADERS = 16
 }

core/src/main/groovy/com/muwire/core/download/DownloadSession.groovy

@@ -0,0 +1,139 @@
+package com.muwire.core.download;
+
+import net.i2p.data.Base64
+
+import com.muwire.core.Constants
+import com.muwire.core.InfoHash
+import com.muwire.core.connection.Endpoint
+import static com.muwire.core.util.DataUtil.readTillRN
+
+import groovy.util.logging.Log
+
+import java.nio.ByteBuffer
+import java.nio.channels.FileChannel
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.StandardOpenOption
+import java.security.MessageDigest
+import java.security.NoSuchAlgorithmException
+
+@Log
+class DownloadSession {
+    
+    private final Pieces pieces
+    private final InfoHash infoHash
+    private final Endpoint endpoint
+    private final File file
+    private final int pieceSize
+    private final long fileLength
+    private final MessageDigest digest
+    
+    private ByteBuffer mapped
+    
+    DownloadSession(Pieces pieces, InfoHash infoHash, Endpoint endpoint, File file, 
+        int pieceSize, long fileLength) {
+        this.pieces = pieces
+        this.endpoint = endpoint
+        this.infoHash = infoHash
+        this.file = file
+        this.pieceSize = pieceSize
+        this.fileLength = fileLength
+        try {
+            digest = MessageDigest.getInstance("SHA-256")
+        } catch (NoSuchAlgorithmException impossible) {
+            digest = null
+            System.exit(1)
+        }
+    }
+    
+    public void request() throws IOException {
+        OutputStream os = endpoint.getOutputStream()
+        InputStream is = endpoint.getInputStream()
+        
+        int piece = pieces.getRandomPiece()
+        long start = piece * pieceSize
+        long end = Math.min(fileLength, start + pieceSize) - 1
+        long length = end - start + 1
+        
+        String root = Base64.encode(infoHash.getRoot())
+                
+        FileChannel channel
+        try {
+            os.write("GET $root\r\n".getBytes(StandardCharsets.US_ASCII))
+            os.write("Range: $start-$end\r\n\r\n".getBytes(StandardCharsets.US_ASCII))
+            os.flush()
+            String code = readTillRN(is)
+            if (code.startsWith("404 ")) {
+                log.warning("file not found")
+                endpoint.close()
+                return
+            }
+                
+            if (code.startsWith("416 ")) {
+                log.warning("range $start-$end cannot be satisfied")
+                return // leave endpoint open
+            }
+            
+            if (!code.startsWith("200 ")) {
+                log.warning("unknown code $code")
+                endpoint.close()
+                return
+            }
+
+            // parse all headers
+            Set<String> headers = new HashSet<>()
+            String header
+            while((header = readTillRN(is)) != "" && headers.size() < Constants.MAX_HEADERS) 
+                headers.add(header)
+
+            long receivedStart = -1
+            long receivedEnd = -1
+            for (String receivedHeader : headers) {
+                def group = (receivedHeader =~ /^Content-Range: (\d+)-(\d+)$/)
+                if (group.size() != 1) {
+                    log.info("ignoring header $receivedHeader")
+                    continue
+                } 
+
+                receivedStart = Long.parseLong(group[0][1])
+                receivedEnd = Long.parseLong(group[0][2])
+            }
+            
+            if (receivedStart != start || receivedEnd != end) {
+                log.warning("We don't support mismatching ranges yet")
+                endpoint.close()
+                return
+            }
+            
+            // start the download
+            channel = Files.newByteChannel(file.toPath(), EnumSet.of(StandardOpenOption.READ, StandardOpenOption.WRITE, 
+                StandardOpenOption.SPARSE, StandardOpenOption.CREATE)) // TODO: double-check, maybe CREATE_NEW
+            mapped = channel.map(FileChannel.MapMode.READ_WRITE, start, end - start + 1)
+            
+            byte[] tmp = new byte[0x1 << 13]
+            while(mapped.hasRemaining()) {
+                int read = is.read(tmp)
+                if (read == -1)
+                    throw new IOException()
+                synchronized(this) {
+                    mapped.put(tmp, 0, read)
+                }
+            }
+            
+            mapped.clear()
+            digest.update(mapped)
+            byte [] hash = digest.digest()
+            byte [] expected = new byte[32]
+            System.arraycopy(infoHash.getHashList(), piece * 32, expected, 0, 32)    
+            if (hash != expected) {
+                log.warning("hash mismatch")
+                endpoint.close()
+                return
+            }
+            
+            pieces.markDownloaded(piece)        
+        } finally {
+            try { channel?.close() } catch (IOException ignore) {}
+        }
+    }
+}

core/src/main/groovy/com/muwire/core/upload/Request.groovy

@@ -2,6 +2,7 @@ package com.muwire.core.upload
 
 import java.nio.charset.StandardCharsets
 
+import com.muwire.core.Constants
 import com.muwire.core.InfoHash
 
 import groovy.util.logging.Log
@@ -19,8 +20,8 @@ class Request {
     
     static Request parse(InfoHash infoHash, InputStream is) throws IOException {
         Map<String,String> headers = new HashMap<>()
-        byte [] tmp = new byte[0x1 << 14]
+        byte [] tmp = new byte[Constants.MAX_HEADER_SIZE]
-        while(true) {
+        while(headers.size() < Constants.MAX_HEADERS) {
             boolean r = false
             boolean n = false
             int idx = 0

core/src/main/groovy/com/muwire/core/util/DataUtil.groovy

@@ -2,6 +2,8 @@ package com.muwire.core.util
 
 import java.nio.charset.StandardCharsets
 
+import com.muwire.core.Constants
+
 class DataUtil {
 	
 	private final static int MAX_SHORT = (0x1 << 16) - 1
@@ -61,4 +63,20 @@ class DataUtil {
         daos.close()
         baos.toByteArray()
     }
+    
+    public static String readTillRN(InputStream is) {
+        def baos = new ByteArrayOutputStream()
+        while(baos.size() < (Constants.MAX_HEADER_SIZE)) {
+            byte read = is.read()
+            if (read == -1)
+                throw new IOException()
+            if (read == '\r') {
+                if (is.read() != '\n')
+                    throw new IOException("invalid header")
+                break
+            }
+            baos.write(read)
+        }
+        new String(baos.toByteArray(), StandardCharsets.US_ASCII)
+    }
 }

core/src/test/groovy/com/muwire/core/download/DownloadSessionTest.groovy

@@ -0,0 +1,89 @@
+package com.muwire.core.download
+
+import org.junit.After
+import org.junit.Test
+
+import com.muwire.core.InfoHash
+import com.muwire.core.connection.Endpoint
+import com.muwire.core.files.FileHasher
+import static com.muwire.core.util.DataUtil.readTillRN
+
+import net.i2p.data.Base64
+
+class DownloadSessionTest {
+    
+    private File source, target
+    private InfoHash infoHash
+    private Endpoint endpoint
+    private Pieces pieces
+    private String rootBase64
+    
+    private DownloadSession session
+    private Thread downloadThread
+    
+    private InputStream fromDownloader, fromUploader
+    private OutputStream toDownloader, toUploader
+    
+    private void initSession(int size) {
+        Random r = new Random()
+        byte [] content = new byte[size]
+        r.nextBytes(content)
+        
+        source = File.createTempFile("source", "tmp")
+        source.deleteOnExit()
+        def fos = new FileOutputStream(source)
+        fos.write(content)
+        fos.close()
+        
+        def hasher = new FileHasher()
+        infoHash = hasher.hashFile(source)
+        rootBase64 = Base64.encode(infoHash.getRoot())
+        
+        target = File.createTempFile("target", "tmp")
+        int pieceSize = 1 << FileHasher.getPieceSize(size)
+        
+        int nPieces
+        if (size % pieceSize == 0)
+            nPieces = size / pieceSize
+        else
+            nPieces = size / pieceSize + 1
+        pieces = new Pieces(nPieces)
+        
+        fromDownloader = new PipedInputStream()
+        fromUploader = new PipedInputStream()
+        toDownloader = new PipedOutputStream(fromUploader)
+        toUploader = new PipedOutputStream(fromDownloader)
+        endpoint = new Endpoint(null, fromUploader, toUploader, null)
+        
+        session = new DownloadSession(pieces, infoHash, endpoint, target, pieceSize, size)
+        downloadThread = new Thread( { session.request() } as Runnable)
+        downloadThread.setDaemon(true)
+        downloadThread.start()
+    }
+    
+    @After
+    public void teardown() {
+        source?.delete()
+        target?.delete()
+        downloadThread?.interrupt()
+        Thread.sleep(50)
+    }
+    
+    @Test
+    public void testSmallFile() {
+        initSession(20)
+        assert "GET $rootBase64" == readTillRN(fromDownloader)
+        assert "Range: 0-19" == readTillRN(fromDownloader)
+        assert "" == readTillRN(fromDownloader)
+        
+        toDownloader.write("200 OK\r\n".bytes)
+        toDownloader.write("Content-Range: 0-19\r\n\r\n".bytes)
+        toDownloader.write(source.bytes)
+        toDownloader.flush()
+        
+        Thread.sleep(150)
+        
+        assert pieces.isComplete()
+        assert target.bytes == source.bytes
+    }
+}