code.grnet.gr Git - pithos-ms-client/blob - trunk/Pithos.Core/NetworkGate.cs

   1 using System;
   2 using System.Collections.Concurrent;
   3 using System.Collections.Generic;
   4 using System.Diagnostics.Contracts;
   5 using System.IO;
   6
   7 namespace Pithos.Core
   8 {
   9     public enum NetworkOperation
  10     {
  11         None,
  12         Uploading,
  13         Downloading
  14     }
  15
  16     //The NetworkGate prevents starting download/uploads for files that are already in the process of downloading,
  17     //uploading.
  18     public class NetworkGate:IDisposable
  19     {
  20         //The state of each file is stored in a thread-safe dictionary
  21         static readonly ConcurrentDictionary<string, NetworkOperation> NetworkState = new ConcurrentDictionary<string, NetworkOperation>();
  22
  23         public static NetworkOperation GetNetworkState(string path)
  24         {
  25             if (String.IsNullOrWhiteSpace(path))
  26                 throw new ArgumentNullException("path");
  27             if (!Path.IsPathRooted(path))
  28                 throw new ArgumentException("path must be a rooted path", "path");
  29             Contract.EndContractBlock();
  30
  31             NetworkOperation operation;
  32             if (NetworkState.TryGetValue(path.ToLower(), out operation))
  33                 return operation;
  34             return NetworkOperation.None;
  35         }
  36
  37         //Store a network operation for the specified path
  38         public static void SetNetworkState(string path, NetworkOperation operation)
  39         {
  40             if (String.IsNullOrWhiteSpace(path))
  41                 throw new ArgumentNullException("path");
  42             if (!Path.IsPathRooted(path))
  43                 throw new ArgumentException("path must be a rooted path", "path");
  44             Contract.EndContractBlock();
  45
  46             var lower = path.ToLower();
  47             NetworkState[lower] = operation;
  48             //By default, None values don't need to be stored. They are stored anyway
  49             //because TryRemove may fail.
  50             if (operation == NetworkOperation.None)
  51             {
  52                 NetworkOperation oldOperation;
  53                 NetworkState.TryRemove(lower, out oldOperation);
  54             }
  55         }
  56
  57         //Clients should acquire a NetworkGate before starting any network operation.
  58         //If Acquire fails, another network operation is already in progress
  59         public static NetworkGate Acquire(string path, NetworkOperation operation)
  60         {
  61             if (String.IsNullOrWhiteSpace(path))
  62                 throw new ArgumentNullException("path");
  63             if (!Path.IsPathRooted(path))
  64                 throw new ArgumentException("path must be a rooted path", "path");
  65             Contract.EndContractBlock();
  66
  67             var state = GetNetworkState(path);
  68             //If no operation is in progress, return a NetworkGate
  69             return (state == NetworkOperation.None)
  70                        ? new NetworkGate(path, operation)
  71                    //otherwise return a gate with Fail flagged
  72                        : new NetworkGate(path, NetworkOperation.None);
  73         }
  74
  75
  76
  77         public string FilePath { get; private set; }
  78         public NetworkOperation Operation { get; private set; }
  79
  80         private NetworkGate(string path,NetworkOperation operation)
  81         {
  82             if (String.IsNullOrWhiteSpace(path))
  83                 throw new ArgumentNullException("path");
  84             Contract.EndContractBlock();
  85
  86             Operation = operation;
  87             FilePath = path.ToLower();
  88
  89             //Skip dummy operations (those with Operation == None)
  90             if (Operation != NetworkOperation.None)
  91                 //and store the file's operation
  92                 SetNetworkState(FilePath, operation);
  93         }
  94
  95         //A NetworkGate has Failed if its operation is None
  96         public bool Failed { get { return Operation == NetworkOperation.None; } }
  97
  98         //Release a gate by setting the NetworkOperation to None
  99         public void Release()
 100         {
 101             //Skip Failed flags
 102             if (!Failed)
 103                 //And reset the operation state for the file
 104                 SetNetworkState(FilePath,NetworkOperation.None);
 105         }
 106
 107
 108         public void Dispose()
 109         {
 110             Dispose(true);
 111             GC.SuppressFinalize(this);
 112         }
 113
 114         protected void Dispose(bool disposing)
 115         {
 116             if (disposing)
 117             {
 118                 Release();
 119             }
 120         }
 121
 122     }
 123 }