Blake2Sharp.Blake2BCore.BytesToUInt64 C# (CSharp) Method

        internal static ulong BytesToUInt64(byte[] buf, int offset)
        {
            return
                ((ulong)buf[offset + 7] << 7 * 8 |
                ((ulong)buf[offset + 6] << 6 * 8) |
                ((ulong)buf[offset + 5] << 5 * 8) |
                ((ulong)buf[offset + 4] << 4 * 8) |
                ((ulong)buf[offset + 3] << 3 * 8) |
                ((ulong)buf[offset + 2] << 2 * 8) |
                ((ulong)buf[offset + 1] << 1 * 8) |
                ((ulong)buf[offset]));
        }

        public static ulong[] ConfigB(Blake2BConfig config, Blake2BTreeConfig treeConfig)
        {
            bool isSequential = treeConfig == null;

            if (isSequential)
            {
                treeConfig = SequentialTreeConfig;
            }
            var rawConfig = new ulong[8];
            var result    = new ulong[8];

            //digest length
            if (config.OutputSizeInBytes <= 0 | config.OutputSizeInBytes > 64)
            {
                throw new ArgumentOutOfRangeException("config.OutputSize");
            }
            rawConfig[0] |= (ulong)(uint)config.OutputSizeInBytes;

            //Key length
            if (config.Key != null)
            {
                if (config.Key.Length > 64)
                {
                    throw new ArgumentException("config.Key", "Key too long");
                }
                rawConfig[0] |= (ulong)((uint)config.Key.Length << 8);
            }
            // FanOut
            rawConfig[0] |= (uint)treeConfig.FanOut << 16;
            // Depth
            rawConfig[0] |= (uint)treeConfig.MaxHeight << 24;
            // Leaf length
            rawConfig[0] |= ((ulong)(uint)treeConfig.LeafSize) << 32;
            // Inner length
            if (!isSequential && (treeConfig.IntermediateHashSize <= 0 || treeConfig.IntermediateHashSize > 64))
            {
                throw new ArgumentOutOfRangeException("treeConfig.TreeIntermediateHashSize");
            }
            rawConfig[2] |= (uint)treeConfig.IntermediateHashSize << 8;
            // Salt
            if (config.Salt != null)
            {
                if (config.Salt.Length != 16)
                {
                    throw new ArgumentException("config.Salt has invalid length");
                }
                rawConfig[4] = Blake2BCore.BytesToUInt64(config.Salt, 0);
                rawConfig[5] = Blake2BCore.BytesToUInt64(config.Salt, 8);
            }
            // Personalization
            if (config.Personalization != null)
            {
                if (config.Personalization.Length != 16)
                {
                    throw new ArgumentException("config.Personalization has invalid length");
                }
                rawConfig[6] = Blake2BCore.BytesToUInt64(config.Personalization, 0);
                rawConfig[7] = Blake2BCore.BytesToUInt64(config.Personalization, 8);
            }

            return(rawConfig);
        }