Synnefo » Pithos MS Client

        public static byte[] CalculateTopHash(IList<byte[]> hashMap, string algorithm)

            Contract.EndContractBlock();            

            var hashCount = hashMap.Count;

            //The tophash of an empty hashmap is an empty array

                return new byte[0];

            //The tophash of a one-item hashmap is the hash itself

                return hashMap[0];

            //Calculate the required number of leaf nodes

            //The size of all nodes is the same and equal to the size of the input hashes

            var hashSize = hashMap[0].Length;

            //If the hashmap containes fewer nodes than the required leaf count, we need to fill

            //the rest with empty blocks

            byte[] empty=null;            

            if (hashCount < leafs)

                empty = new byte[hashSize];

            //New hashes will be stored in a dictionary keyed by their step to preserve order

            var newHashes=new ConcurrentDictionary<int, byte[]>();            

            Parallel.For(0, leafs/2,

                (step, state) =>

                    using (var hasher = HashAlgorithm.Create(algorithm))

                    {

                        var i = step*2;

                        var block1 = i <= hashCount - 1 ? hashMap[i] : empty;

                        var block2 = i <= hashCount - 2 ? hashMap[i + 1] : empty;

                        hasher.TransformBlock(block1, 0, block1.Length, null, 0);

                        hasher.TransformFinalBlock(block2, 0, block2.Length);

                        var finalHash = hasher.Hash;

                        //Store the final value in its proper place

                        newHashes[step] = finalHash;

                    }

                });

/*

            Parallel.For(0, leafs/2,

                () => HashAlgorithm.Create(algorithm),

                (step, state, hasher) =>

                {

                    var i = step*2;

                    var block1 = i <= hashCount - 1 ? hashMap[i]: empty;

                    var block2 = i <= hashCount - 2 ? hashMap[i + 1] : empty;

                    hasher.TransformFinalBlock(block2, 0, block2.Length);

                    //Store the final value in its proper place

                    newHashes[step] = finalHash;

                    return hasher;

                },

                hasher => hasher.Dispose());

*/

            //Extract the hashes to a list ordered by their step 

            var hashes = newHashes.OrderBy(pair => pair.Key).Select(pair => pair.Value).ToList();

            return CalculateTopHash(hashes, algorithm);                   

      /*  public static string CalculateTopHash(string hashString, string algorithm)

        }*/