Adding Linux native dll loading

Former-commit-id: 5993e028f751f80aaa9fe82a33831a7fef57e02b

src/ImageProcessor/Configuration/NativeBinaryFactory.cs

@@ -94,7 +94,7 @@ namespace ImageProcessor.Configuration
                     Assembly assembly = Assembly.GetExecutingAssembly();
                     string targetBasePath = new Uri(assembly.Location).LocalPath;
                     string targetPath = Path.GetFullPath(Path.Combine(targetBasePath, "..\\" + folder + "\\" + name));
-                    
+
                     // Copy the file across if necessary.
                     FileInfo fileInfo = new FileInfo(targetPath);
                     bool rewrite = true;
@@ -122,8 +122,13 @@ namespace ImageProcessor.Configuration
 
                     try
                     {
+#if !__MonoCS__
                         // Load the binary into memory.
                         pointer = NativeMethods.LoadLibrary(targetPath);
+#else
+                        // Load the binary into memory. The second parameter forces it to load immediately.
+                        pointer = NativeMethods.dlopen(targetPath, 2);
+#endif
                     }
                     catch (Exception ex)
                     {
@@ -187,9 +192,13 @@ namespace ImageProcessor.Configuration
             {
                 IntPtr pointer = nativeBinary.Value;
 
+#if !__MonoCS__
                 // According to http://stackoverflow.com/a/2445558/427899 you need to call this twice.
                 NativeMethods.FreeLibrary(pointer);
                 NativeMethods.FreeLibrary(pointer);
+#else
+                NativeMethods.dlclose(pointer);
+#endif
             }
         }
     }

src/ImageProcessor/Configuration/NativeMethods.cs

@@ -40,5 +40,33 @@ namespace ImageProcessor.Configuration
         /// <returns>If the function succeeds, the return value is nonzero; otherwise zero.</returns>
         [DllImport("kernel32", CharSet = CharSet.Auto)]
         public static extern bool FreeLibrary(IntPtr hModule);
+
+        /// <summary>
+        /// Loads the specified module into the address space of the calling process. 
+        /// The specified module may cause other modules to be loaded.
+        /// </summary>
+        /// <param name="libname">
+        /// The name of the module. This can be either a library module or 
+        /// an executable module. 
+        /// </param>
+        /// <param name="flags">
+        /// The flag indicating whether to load the library immediately or lazily.
+        /// </param>
+        /// <returns>
+        /// If the function succeeds, the return value is a handle to the module; otherwise null.
+        /// </returns>
+        [System.Runtime.InteropServices.DllImport("libdl")]
+        public static extern IntPtr dlopen(string libname, int flags);
+
+        /// <summary>
+        /// Frees the loaded dynamic-link library (DLL) module and, if necessary, decrements its reference count. 
+        /// When the reference count reaches zero, the module is unloaded from the address space of the calling 
+        /// process and the handle is no longer valid.
+        /// </summary>
+        /// <param name="hModule">A handle to the loaded library module. 
+        /// The LoadLibrary, LoadLibraryEx, GetModuleHandle, or GetModuleHandleEx function returns this handle.</param>
+        /// <returns>If the function succeeds, the return value is nonzero; otherwise zero.</returns>
+        [System.Runtime.InteropServices.DllImport("libdl")]
+        public static extern int dlclose(IntPtr hModule);
     }
 }