Add lazy initialization to AdcController

source/Windows.Devices.Adc/AdcChannel.cs

@@ -13,12 +13,19 @@ namespace Windows.Devices.Adc
     /// </summary>
     public sealed class AdcChannel : IAdcChannel, IDisposable
     {
+        // this is used as the lock object 
+        // a lock is required because multiple threads can access the channel
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
+        private readonly object _syncLock = new object();
+
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
         private readonly int  _channelNumber;
+
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
         private AdcController _adcController;
 
-        // this is used as the lock object 
-        // a lock is required because multiple threads can access the AdcChannel
-        private object _syncLock = new object();
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
+        private bool _disposed;
 
         internal AdcChannel(AdcController controller, int channelNumber)
         {
@@ -63,7 +70,7 @@ public int ReadValue()
             lock (_syncLock)
             {
                 // check if pin has been disposed
-                if (_disposedValue) { throw new ObjectDisposedException(); }
+                if (_disposed) { throw new ObjectDisposedException(); }
 
                 return NativeReadValue();
             }
@@ -72,16 +79,14 @@ public int ReadValue()
         private void ThowIfDisposed()
         {
             // check if pin has been disposed
-            if (_disposedValue)
+            if (_disposed)
             {
                 throw new ObjectDisposedException();
             }
         }
 
         #region IDisposable Support
 
-        private bool _disposedValue;
-
         private void Dispose(bool disposing)
         {
             if (_adcController != null)
@@ -93,7 +98,7 @@ private void Dispose(bool disposing)
 
                 }
 
-                _disposedValue = true;
+                _disposed = true;
             }
         }
 
@@ -104,7 +109,7 @@ public void Dispose()
         {
             lock (_syncLock)
             {
-                if (!_disposedValue)
+                if (!_disposed)
                 {
                     Dispose(true);
                     GC.SuppressFinalize(this);

source/Windows.Devices.Adc/AdcController.cs

@@ -14,27 +14,66 @@ namespace Windows.Devices.Adc
     /// </summary>
     public sealed class AdcController : IAdcController
     {
-        private readonly int _deviceId;
+        // this is used as the lock object 
+        // a lock is required because multiple threads can access the AdcController
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
+        private readonly object _syncLock = new object();
+
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
+        private readonly int _controllerId;
+
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
         private AdcChannelMode _channelMode;
 
-        // need to store the ADC controllers that are open
-        internal static Hashtable s_deviceCollection = new Hashtable();
+        // backing field for DeviceCollection
+        [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)]
+        private Hashtable s_deviceCollection;
+
+        /// <summary>
+        /// Device collection associated with this <see cref="AdcController"/>.
+        /// </summary>
+        /// <remarks>
+        /// This collection is for internal use only.
+        /// </remarks>
+        internal Hashtable DeviceCollection
+        {
+            get
+            {
+                if (s_deviceCollection == null)
+                {
+                    lock (_syncLock)
+                    {
+                        if (s_deviceCollection == null)
+                        {
+                            s_deviceCollection = new Hashtable();
+                        }
+                    }
+                }
+
+                return s_deviceCollection;
+            }
+
+            set
+            {
+                s_deviceCollection = value;
+            }
+        }
 
         internal AdcController(string adcController)
         {
             // check if this device is already opened
-            if (!s_deviceCollection.Contains(adcController))
+            if (!AdcControllerManager.ControllersCollection.Contains(adcController))
             {
                 // the ADC id is an ASCII string with the format 'ADCn'
                 // need to grab 'n' from the string and convert that to the integer value from the ASCII code (do this by subtracting 48 from the char value)
-                _deviceId = adcController[3] - 48;
+                _controllerId = adcController[3] - '0';
 
                 // call native init to allow HAL/PAL inits related with ADC hardware
                 // this is also used to check if the requested ADC actually exists
                 NativeInit();
 
                 // add ADC controller to collection
-                s_deviceCollection.Add(adcController, this);
+                AdcControllerManager.ControllersCollection.Add(adcController, this);
             }
             else
             {
@@ -121,18 +160,26 @@ public int ResolutionInBits {
         /// </returns>
         public static AdcController GetDefault()
         {
-            string controllers = GetDeviceSelector();
-            string[] devices = controllers.Split(',');
+            string controllersAqs = GetDeviceSelector();
+            string[] controllers = controllersAqs.Split(',');
 
-            if(devices.Length > 0)
+            if(controllers.Length > 0)
             {
-                if (s_deviceCollection.Contains(devices[0]))
+                //////////////////////////////////////////////////////////////////
+                // note that, by design, the default controller is              //
+                // the first one in the collection returned from the native end //
+                //////////////////////////////////////////////////////////////////
+
+                if (AdcControllerManager.ControllersCollection.Contains(controllers[0]))
                 {
-                    // this is already open
-                    return (AdcController)s_deviceCollection[devices[0]];
+                    // controller is already open
+                    return (AdcController)AdcControllerManager.ControllersCollection[controllers[0]];
+                }
+                else
+                {
+                    // there is no controller yet, create one
+                    return new AdcController(controllers[0]);
                 }
-
-                return new AdcController(devices[0]);
             }
 
             // the system has no ADC controller 

source/Windows.Devices.Adc/AdcControllerManager.cs

@@ -0,0 +1,48 @@
+//
+// Copyright (c) 2018 The nanoFramework project contributors
+// See LICENSE file in the project root for full license information.
+//
+
+using System.Collections;
+
+namespace Windows.Devices.Adc
+{
+    internal sealed class AdcControllerManager
+    {
+        private static readonly object _syncLock = new object();
+
+        // backing field for ControllersCollection
+        // to store the controllers that are open
+        private static Hashtable s_controllersCollection;
+
+        /// <summary>
+        /// <see cref="AdcController"/> collection.
+        /// </summary>
+        /// <remarks>
+        /// This collection is for internal use only.
+        /// </remarks>
+        internal static Hashtable ControllersCollection
+        {
+            get
+            {
+                if (s_controllersCollection == null)
+                {
+                    lock (_syncLock)
+                    {
+                        if (s_controllersCollection == null)
+                        {
+                            s_controllersCollection = new Hashtable();
+                        }
+                    }
+                }
+
+                return s_controllersCollection;
+            }
+
+            set
+            {
+                s_controllersCollection = value;
+            }
+        }
+    }
+}

source/Windows.Devices.Adc/Windows.Devices.Adc.nfproj

@@ -54,6 +54,7 @@
     <Compile Include="AdcChannel.cs" />
     <Compile Include="AdcChannelMode.cs" />
     <Compile Include="AdcController.cs" />
+    <Compile Include="AdcControllerManager.cs" />
     <Compile Include="IAdcChannel.cs" />
     <Compile Include="IAdcController.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
@@ -81,4 +82,4 @@
     </PropertyGroup>
     <Error Condition="!Exists('..\packages\Nerdbank.GitVersioning.2.2.33\build\Nerdbank.GitVersioning.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Nerdbank.GitVersioning.2.2.33\build\Nerdbank.GitVersioning.targets'))" />
   </Target>
-</Project>
+</Project>