src/Tizen.Multimedia/MediaTool/MediaPacket.Lock.cs

   1 /*
   2  * Copyright (c) 2016 Samsung Electronics Co., Ltd All Rights Reserved
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the License);
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an AS IS BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 using System;
  18 using System.Diagnostics;
  19 using System.Runtime.InteropServices;
  20 using System.Threading;
  21 using Tizen.Internals.Errors;
  22
  23 namespace Tizen.Multimedia
  24 {
  25     /// <summary>
  26     /// Represents a packet for multimedia.
  27     /// </summary>
  28     /// <since_tizen> 3 </since_tizen>
  29     public abstract partial class MediaPacket : IDisposable
  30     {
  31         private readonly LockState _lock = new LockState();
  32
  33         /// <summary>
  34         /// Validates the current object is not locked.
  35         /// </summary>
  36         /// <exception cref="ObjectDisposedException">The MediaPacket has already been disposed of.</exception>
  37         /// <exception cref="InvalidOperationException">The MediaPacket is in use by another module.</exception>
  38         private void ValidateNotLocked()
  39         {
  40             ValidateNotDisposed();
  41
  42             if (_lock.IsLocked)
  43             {
  44                 throw new InvalidOperationException("Can't perform any writing operation." +
  45                     "The packet is in use, internally.");
  46             }
  47         }
  48
  49         /// <summary>
  50         /// Provides a thread-safe lock state controller.
  51         /// </summary>
  52         private sealed class LockState
  53         {
  54             const int LOCKED = 1;
  55             const int UNLOCKED = 0;
  56
  57             private int _locked = UNLOCKED;
  58
  59             internal void SetLock()
  60             {
  61                 if (Interlocked.CompareExchange(ref _locked, LOCKED, UNLOCKED) == LOCKED)
  62                 {
  63                     throw new InvalidOperationException("The packet is already locked.");
  64                 }
  65             }
  66
  67             internal void SetUnlock()
  68             {
  69                 if (Interlocked.CompareExchange(ref _locked, UNLOCKED, LOCKED) == UNLOCKED)
  70                 {
  71                     Debug.Fail("The packet to unlock is not locked. " +
  72                         "There must be an error somewhere that a lock isn't disposed correctly.");
  73                 }
  74             }
  75
  76             internal bool IsLocked => Interlocked.CompareExchange(ref _locked, 0, 0) == LOCKED;
  77         }
  78
  79         /// <summary>
  80         /// Provides a thread-safe lock controller.
  81         /// </summary>
  82         /// <example>
  83         /// using (var lock = BaseMediaPacket.Lock(mediaPacket))
  84         /// {
  85         ///     ....
  86         /// }
  87         /// </example>
  88         internal sealed class Lock : IDisposable
  89         {
  90             private readonly MediaPacket _packet;
  91             private readonly GCHandle _gcHandle;
  92             private int _lockCount;
  93
  94             internal static Lock Get(MediaPacket packet)
  95             {
  96                 Debug.Assert(packet != null);
  97
  98                 lock (packet._lock)
  99                 {
 100                     Lock lck = FromHandle(packet._handle) ?? new Lock(packet);
 101
 102                     lck._lockCount++;
 103
 104                     return lck;
 105                 }
 106             }
 107
 108             private Lock(MediaPacket packet)
 109             {
 110                 Debug.Assert(packet != null, "The packet is null!");
 111
 112                 packet.ValidateNotDisposed();
 113
 114                 _packet = packet;
 115
 116                 _packet._lock.SetLock();
 117
 118                 _gcHandle = GCHandle.Alloc(this);
 119
 120                 SetExtra(GCHandle.ToIntPtr(_gcHandle));
 121             }
 122
 123             internal static Lock FromHandle(IntPtr handle)
 124             {
 125                 Debug.Assert(handle != IntPtr.Zero);
 126
 127                 IntPtr extra = GetExtra(handle);
 128
 129                 if (extra == IntPtr.Zero)
 130                 {
 131                     return null;
 132                 }
 133
 134                 return (Lock)GCHandle.FromIntPtr(extra).Target;
 135             }
 136
 137             private void SetExtra(IntPtr ptr)
 138             {
 139                 int ret = Interop.MediaPacket.SetExtra(_packet._handle, ptr);
 140
 141                 MultimediaDebug.AssertNoError(ret);
 142             }
 143
 144             private static IntPtr GetExtra(IntPtr handle)
 145             {
 146                 int ret = Interop.MediaPacket.GetExtra(handle, out var value);
 147
 148                 MultimediaDebug.AssertNoError(ret);
 149
 150                 return value;
 151             }
 152
 153             internal IntPtr GetHandle() => _packet.GetHandle();
 154
 155             internal MediaPacket MediaPacket => _packet;
 156
 157             private bool _isDisposed = false;
 158
 159             public void Dispose()
 160             {
 161                 if (!_isDisposed)
 162                 {
 163                     lock (_packet._lock)
 164                     {
 165                         _lockCount--;
 166
 167                         if (_lockCount == 0)
 168                         {
 169                             SetExtra(IntPtr.Zero);
 170
 171                             if (_gcHandle.IsAllocated)
 172                             {
 173                                 _gcHandle.Free();
 174                             }
 175
 176                             // We can assure that at this point '_packet' is always locked by this lock.
 177                             _packet._lock.SetUnlock();
 178                         }
 179                     }
 180
 181                     _isDisposed = true;
 182                 }
 183             }
 184         }
 185     }
 186 }