added OpenSubtitlesHasher

source/net/sourceforge/filebot/ui/panel/sfv/ChecksumComputationTask.java

@@ -12,7 +12,7 @@ import javax.swing.SwingWorker;
 
 public class ChecksumComputationTask extends SwingWorker<Long, Object> {
 	
-	private static final int MAX_READ_LENGTH = 200 * 1024; // 200 KB
+	private static final int CHUNK_SIZE = 20 * 1024;
 	
 	private File file;
 	
@@ -27,29 +27,25 @@ public class ChecksumComputationTask extends SwingWorker<Long, Object> {
 		CheckedInputStream cis = new CheckedInputStream(new FileInputStream(file), new CRC32());
 		
 		long length = file.length();
-		long done = 0;
 		
-		int bufferLength = (int) Math.min(length, MAX_READ_LENGTH);
-		
-		// don't allow bufferLength == 0
-		if (bufferLength < 1)
-			bufferLength = 1;
-		
-		byte[] buffer = new byte[bufferLength];
-		
-		int bytesRead = 0;
-		
-		while ((bytesRead = cis.read(buffer)) >= 0) {
-			if (isCancelled())
-				break;
+		if (length > 0) {
+			long done = 0;
 			
-			done += bytesRead;
+			int bufferLength = (int) Math.min(length, CHUNK_SIZE);
 			
-			if (length > 0) {
+			byte[] buffer = new byte[bufferLength];
+			
+			int bytesRead = 0;
+			
+			while ((bytesRead = cis.read(buffer)) >= 0) {
+				if (isCancelled())
+					break;
+				
+				done += bytesRead;
+				
 				int progress = (int) ((done * 100) / length);
 				setProgress(progress);
 			}
-			
 		}
 		
 		cis.close();

source/net/sourceforge/filebot/web/HtmlUtil.java

@@ -23,7 +23,7 @@ import org.xml.sax.InputSource;
 import org.xml.sax.SAXException;
 
 
-public class HtmlUtil {
+class HtmlUtil {
 	
 	private static Charset getCharset(String contentType) {
 		if (contentType != null) {

source/net/sourceforge/filebot/web/OpenSubtitlesHasher.java

@@ -0,0 +1,112 @@
+
+package net.sourceforge.filebot.web;
+
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+
+
+/**
+ * Hash code is based on Media Player Classic. In natural language it calculates: size + 64bit
+ * checksum of the first and last 64k (even if they overlap because the file is smaller than
+ * 128k).
+ */
+class OpenSubtitlesHasher {
+	
+	/**
+	 * Size of the chunks that will be hashed in bytes (64 KB)
+	 */
+	private static final int HASH_CHUNK_SIZE = 64 * 1024;
+	
+	/**
+	 * Size of the checksum in bytes (64 Bit)
+	 */
+	private static final int HASH_SIZE = 8;
+	
+	
+	public static String computeHash(File file) throws IOException {
+		long size = file.length();
+		long chunkSizeForFile = Math.min(HASH_CHUNK_SIZE, size);
+		
+		FileChannel fileChannel = new FileInputStream(file).getChannel();
+		
+		BigInteger head = computeHashForChunk(fileChannel, 0, chunkSizeForFile);
+		BigInteger tail = computeHashForChunk(fileChannel, Math.max(size - HASH_CHUNK_SIZE, 0), chunkSizeForFile);
+		
+		fileChannel.close();
+		
+		// size + head + tail
+		BigInteger bigHash = BigInteger.valueOf(size).add(head.add(tail));
+		
+		byte[] hash = getTrailingBytes(bigHash.toByteArray(), HASH_SIZE);
+		return format(new BigInteger(1, hash));
+	}
+	
+
+	private static BigInteger computeHashForChunk(FileChannel fileChannel, long start, long size) throws IOException {
+		MappedByteBuffer buffer = fileChannel.map(MapMode.READ_ONLY, start, size);
+		
+		BigInteger bigHash = BigInteger.ZERO;
+		byte[] bytes = new byte[HASH_SIZE];
+		
+		while (buffer.hasRemaining()) {
+			buffer.get(bytes, 0, Math.min(HASH_SIZE, buffer.remaining()));
+			
+			// BigInteger expects a big-endian byte-order, so we reverse the byte array
+			bigHash = bigHash.add(new BigInteger(1, reverse(bytes)));
+		}
+		
+		return bigHash;
+	}
+	
+
+	private static String format(BigInteger hash) {
+		// 1 byte -> 2 hex digits
+		int minLength = HASH_SIZE * 2;
+		
+		StringBuffer sb = new StringBuffer(minLength);
+		
+		sb.append(hash.toString(16));
+		
+		while (sb.length() < minLength) {
+			sb.insert(0, "0");
+		}
+		
+		return sb.toString();
+	}
+	
+
+	/**
+	 * copy the last n bytes to a new array
+	 * 
+	 * @param bytes original array
+	 * @param n number of trailing bytes
+	 * @return new array
+	 */
+	private static byte[] getTrailingBytes(byte[] src, int n) {
+		int length = Math.min(src.length, n);
+		
+		byte[] dest = new byte[length];
+		
+		int offsetSrc = Math.max(src.length - n, 0);
+		System.arraycopy(src, offsetSrc, dest, 0, length);
+		
+		return dest;
+	}
+	
+
+	private static byte[] reverse(byte[] bytes) {
+		byte[] reverseBytes = new byte[bytes.length];
+		
+		for (int forward = 0, backward = bytes.length; forward < bytes.length; ++forward)
+			reverseBytes[forward] = bytes[--backward];
+		
+		return reverseBytes;
+	}
+	
+}