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#region

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

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

 * 

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

 *

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

 * without modification, are permitted provided that the following

 * conditions are met:

 *

 *   1. Redistributions of source code must retain the above

 *      copyright notice, this list of conditions and the following

 *      disclaimer.

 *

 *   2. Redistributions in binary form must reproduce the above

 *      copyright notice, this list of conditions and the following

 *      disclaimer in the documentation and/or other materials

 *      provided with the distribution.

 *

 *

 * 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,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED

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 * The views and conclusions contained in the software and

 * documentation are those of the authors and should not be

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 * </copyright>

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

 */

#endregion

using System;

using System.Collections.Generic;

using System.Diagnostics.Contracts;

using System.Linq;

using System.Reflection;

using System.Security.Cryptography;

using System.Text;

using System.IO;

using System.Text.RegularExpressions;

using System.Threading.Tasks;

using Pithos.Network;

using log4net;

namespace Pithos.Core.Agents

{

    static class BlockExtensions

    {

        private static readonly ILog Log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);

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

        {

            if (offset < 0)

                throw new ArgumentOutOfRangeException("offset", offset, "The file offset can't be negative");

            Contract.EndContractBlock();

            //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();

           info.Refresh();

           //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;

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

        }

       /// <summary>

       ///Calculates a simple hash for an entire file

       /// </summary>

       /// <param name="info">The file to hash</param>

       /// <param name="hasher">The hash algorithm to use</param>

       /// <returns>A hash value for the entire file. An empty string if the file does not exist.</returns>

       public static string ComputeShortHash(this FileInfo info, HashAlgorithm hasher)

       {

           if(info == null)

               throw new ArgumentNullException("info");

           if(hasher== null)

               throw new ArgumentNullException("hasher");

           Contract.EndContractBlock();

           info.Refresh();

           if (!info.Exists)

               return String.Empty;

           if (Log.IsDebugEnabled)

                Log.DebugFormat("Short Hashing [{0}] ",info.FullName);

           using (var stream = info.Open(FileMode.Open, FileAccess.Read, FileShare.Read))

           {

               var hash = hasher.ComputeHash(stream);

                var hashString = hash.ToHashString();

               return hashString;

           }

       }

        public static string ComputeShortHash(this FileInfo info)

       {

           if(info == null)

               throw new ArgumentNullException("info");

            Contract.EndContractBlock();

           using (var hasher=HashAlgorithm.Create("sha1"))

           {               

               return ComputeShortHash(info,hasher);

           }

       }

    }

}