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 using Native = Tizen.Multimedia.Interop.MediaPacket;
  23
  24 namespace Tizen.Multimedia
  25 {
  26     /// <summary>
  27     /// Represents a packet for multimedia.
  28     /// </summary>
  29     /// <since_tizen> 3 </since_tizen>
  30     public abstract partial class MediaPacket : IDisposable
  31     {
  32         private readonly LockState _lock = new LockState();
  33
  34         /// <summary>
  35         /// Validates the current object is not locked.
  36         /// </summary>
  37         /// <exception cref="ObjectDisposedException">The MediaPacket has already been disposed of.</exception>
  38         /// <exception cref="InvalidOperationException">The MediaPacket is in use by another module.</exception>
  39         private void ValidateNotLocked()
  40         {
  41             ValidateNotDisposed();
  42
  43             if (_lock.IsLocked)
  44             {
  45                 throw new InvalidOperationException("Can't perform any writing operation." +
  46                     "The packet is in use, internally.");
  47             }
  48         }
  49
  50         /// <summary>
  51         /// Provides a thread-safe lock state controller.
  52         /// </summary>
  53         private sealed class LockState
  54         {
  55             const int LOCKED = 1;
  56             const int UNLOCKED = 0;
  57
  58             private int _locked = UNLOCKED;
  59
  60             internal void SetLock()
  61             {
  62                 if (Interlocked.CompareExchange(ref _locked, LOCKED, UNLOCKED) == LOCKED)
  63                 {
  64                     throw new InvalidOperationException("The packet is already locked.");
  65                 }
  66             }
  67
  68             internal void SetUnlock()
  69             {
  70                 if (Interlocked.CompareExchange(ref _locked, UNLOCKED, LOCKED) == UNLOCKED)
  71                 {
  72                     Debug.Fail("The packet to unlock is not locked. " +
  73                         "There must be an error somewhere that a lock isn't disposed correctly.");
  74                 }
  75             }
  76
  77             internal bool IsLocked => Interlocked.CompareExchange(ref _locked, 0, 0) == LOCKED;
  78         }
  79
  80         /// <summary>
  81         /// Provides a thread-safe lock controller.
  82         /// </summary>
  83         /// <example>
  84         /// using (var lock = BaseMediaPacket.Lock(mediaPacket))
  85         /// {
  86         ///     ....
  87         /// }
  88         /// </example>
  89         internal sealed class Lock : IDisposable
  90         {
  91             private readonly MediaPacket _packet;
  92             private readonly GCHandle _gcHandle;
  93             private int _lockCount;
  94
  95             internal static Lock Get(MediaPacket packet)
  96             {
  97                 Debug.Assert(packet != null);
  98
  99                 lock (packet._lock)
 100                 {
 101                     Lock lck = FromHandle(packet._handle) ?? new Lock(packet);
 102
 103                     lck._lockCount++;
 104
 105                     return lck;
 106                 }
 107             }
 108
 109             private Lock(MediaPacket packet)
 110             {
 111                 Debug.Assert(packet != null, "The packet is null!");
 112
 113                 packet.ValidateNotDisposed();
 114
 115                 _packet = packet;
 116
 117                 _packet._lock.SetLock();
 118
 119                 _gcHandle = GCHandle.Alloc(this);
 120
 121                 SetExtra(GCHandle.ToIntPtr(_gcHandle));
 122             }
 123
 124             internal static Lock FromHandle(IntPtr handle)
 125             {
 126                 Debug.Assert(handle != IntPtr.Zero);
 127
 128                 IntPtr extra = GetExtra(handle);
 129
 130                 if (extra == IntPtr.Zero)
 131                 {
 132                     return null;
 133                 }
 134
 135                 return (Lock)GCHandle.FromIntPtr(extra).Target;
 136             }
 137
 138             private void SetExtra(IntPtr ptr)
 139             {
 140                 int ret = Native.SetExtra(_packet._handle, ptr);
 141
 142                 MultimediaDebug.AssertNoError(ret);
 143             }
 144
 145             private static IntPtr GetExtra(IntPtr handle)
 146             {
 147                 int ret = Native.GetExtra(handle, out var value);
 148
 149                 MultimediaDebug.AssertNoError(ret);
 150
 151                 return value;
 152             }
 153
 154             internal IntPtr GetHandle() => _packet.GetHandle();
 155
 156             internal MediaPacket MediaPacket => _packet;
 157
 158             private bool _isDisposed = false;
 159
 160             public void Dispose()
 161             {
 162                 if (!_isDisposed)
 163                 {
 164                     lock (_packet._lock)
 165                     {
 166                         _lockCount--;
 167
 168                         if (_lockCount == 0)
 169                         {
 170                             SetExtra(IntPtr.Zero);
 171
 172                             if (_gcHandle.IsAllocated)
 173                             {
 174                                 _gcHandle.Free();
 175                             }
 176
 177                             // We can assure that at this point '_packet' is always locked by this lock.
 178                             _packet._lock.SetUnlock();
 179                         }
 180                     }
 181
 182                     _isDisposed = true;
 183                 }
 184             }
 185         }
 186     }
 187 }