* ability to calculate osdb hash from any InputStream, not just files

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

@@ -2,9 +2,11 @@
 package net.sourceforge.filebot.web;
 
 
+import java.io.DataInputStream;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
+import java.io.InputStream;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.LongBuffer;
@@ -42,6 +44,34 @@ public class OpenSubtitlesHasher {
 	}
 	
 
+	public static String computeHash(InputStream stream, long length) throws IOException {
+		
+		int chunkSizeForFile = (int) Math.min(HASH_CHUNK_SIZE, length);
+		
+		// buffer that will contain the head and the tail chunk, chunks will overlap if length is smaller than two chunks
+		byte[] chunkBytes = new byte[(int) Math.min(2 * HASH_CHUNK_SIZE, length)];
+		
+		DataInputStream in = new DataInputStream(stream);
+		
+		// first chunk
+		in.readFully(chunkBytes, 0, chunkSizeForFile);
+		
+		long position = chunkSizeForFile;
+		long tailChunkPosition = length - chunkSizeForFile;
+		
+		// seek to position of the tail chunk, or not at all if length is smaller than two chunks
+		while (position < tailChunkPosition && (position += in.skip(tailChunkPosition - position)) >= 0);
+		
+		// second chunk, or the rest of the data if length is smaller than two chunks
+		in.readFully(chunkBytes, chunkSizeForFile, chunkBytes.length - chunkSizeForFile);
+		
+		long head = computeHashForChunk(ByteBuffer.wrap(chunkBytes, 0, chunkSizeForFile));
+		long tail = computeHashForChunk(ByteBuffer.wrap(chunkBytes, chunkBytes.length - chunkSizeForFile, chunkSizeForFile));
+		
+		return String.format("%016x", length + head + tail);
+	}
+	
+
 	private static long computeHashForChunk(ByteBuffer buffer) {
 		
 		LongBuffer longBuffer = buffer.order(ByteOrder.LITTLE_ENDIAN).asLongBuffer();