Changes between Version 8 and Version 9 of HashSourceCodes

Timestamp:

Dec 21, 2008, 2:04:05 PM (16 years ago)

Author:

guest

Comment:

--

HashSourceCodes

@@ -143 +143 @@
                         fileChannel.close();
                 }
+        }
+        
+
+        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);
         }