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#region

/* -----------------------------------------------------------------------

 * <copyright file="BlockExtensions.cs" company="GRNet">

 * 

 * Copyright 2011-2012 GRNET S.A. All rights reserved.

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 * Redistribution and use in source and binary forms, with or

 * without modification, are permitted provided that the following

 * conditions are met:

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 *   1. Redistributions of source code must retain the above

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 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

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 * -----------------------------------------------------------------------

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#endregion

using System;

using System.Collections.Generic;

using System.Diagnostics.Contracts;

using System.Linq;

using System.Text;

using System.IO;

using System.Text.RegularExpressions;

using System.Threading.Tasks;

using Pithos.Network;

namespace Pithos.Core.Agents

{

    static class BlockExtensions

    {

        public static int Read(this FileInfo fileInfo,byte[] buffer,int offset,int count)

        {            

            //Open the stream only long enough to read a block

            using (var stream = fileInfo.OpenRead())

            {

                stream.Seek(offset, SeekOrigin.Begin);

                return  stream.Read(buffer, 0, count);                

            }

        }

       public static string CalculateHash(this FileSystemInfo info,int blockSize,string algorithm)

        {

            if (info==null)

                throw new ArgumentNullException("info");

            if (String.IsNullOrWhiteSpace(info.FullName))

                throw new ArgumentException("info");

            if (blockSize<=0)

                throw new ArgumentOutOfRangeException("blockSize",blockSize,"blockSize must be greater than 0");

            if (String.IsNullOrWhiteSpace(algorithm))

                throw new ArgumentNullException("algorithm");

            Contract.EndContractBlock();

           //The hash for directories is an empty string

           if (info is DirectoryInfo)

                return String.Empty;

           //The hash for non-existent files is an empty string

           if (!info.Exists)

               return String.Empty;

           var fileInfo = (FileInfo)info;

           if (fileInfo.Length <= blockSize)

                return Signature.CalculateMD5(info.FullName);

            else

                return Signature.CalculateTreeHash(info.FullName, blockSize, algorithm).TopHash.ToHashString();

        }

    }

}