Initial checkin of gRPC to third_party/

third_party/grpc/src/csharp/Grpc.Core/Internal/UnmanagedLibrary.cs

+#region Copyright notice and license
+
+// Copyright 2015-2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Collections.Concurrent;
+using System.Diagnostics;
+using System.IO;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+using Grpc.Core.Logging;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core.Internal
+{
+    /// <summary>
+    /// Represents a dynamically loaded unmanaged library in a (partially) platform independent manner.
+    /// An important difference in library loading semantics is that on Windows, once we load a dynamic library using LoadLibrary,
+    /// that library becomes instantly available for <c>DllImport</c> P/Invoke calls referring to the same library name.
+    /// On Unix systems, dlopen has somewhat different semantics, so we need to use dlsym and <c>Marshal.GetDelegateForFunctionPointer</c>
+    /// to obtain delegates to native methods.
+    /// See http://stackoverflow.com/questions/13461989/p-invoke-to-dynamically-loaded-library-on-mono.
+    /// </summary>
+    internal class UnmanagedLibrary
+    {
+        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<UnmanagedLibrary>();
+
+        // flags for dlopen
+        const int RTLD_LAZY = 1;
+        const int RTLD_GLOBAL = 8;
+
+        readonly string libraryPath;
+        readonly IntPtr handle;
+
+        public UnmanagedLibrary(string libraryPath)
+        {
+            this.libraryPath = GrpcPreconditions.CheckNotNull(libraryPath);
+
+            if (!File.Exists(this.libraryPath))
+            {
+                throw new FileNotFoundException("Error loading native library. File does not exist.", this.libraryPath);
+            }
+
+            Logger.Debug("Attempting to load native library \"{0}\"", this.libraryPath);
+
+            this.handle = PlatformSpecificLoadLibrary(this.libraryPath);
+
+            if (this.handle == IntPtr.Zero)
+            {
+                throw new IOException(string.Format("Error loading native library \"{0}\"", this.libraryPath));
+            }
+        }
+
+        /// <summary>
+        /// Loads symbol in a platform specific way.
+        /// </summary>
+        /// <param name="symbolName"></param>
+        /// <returns></returns>
+        public IntPtr LoadSymbol(string symbolName)
+        {
+            if (PlatformApis.IsLinux)
+            {
+                if (PlatformApis.IsMono)
+                {
+                    return Mono.dlsym(this.handle, symbolName);
+                }
+                return Linux.dlsym(this.handle, symbolName);
+            }
+            if (PlatformApis.IsMacOSX)
+            {
+                return MacOSX.dlsym(this.handle, symbolName);
+            }
+            throw new InvalidOperationException("Unsupported platform.");
+        }
+
+        public T GetNativeMethodDelegate<T>(string methodName)
+            where T : class
+        {
+            var ptr = LoadSymbol(methodName);
+            if (ptr == IntPtr.Zero)
+            {
+                throw new MissingMethodException(string.Format("The native method \"{0}\" does not exist", methodName));
+            }
+            return Marshal.GetDelegateForFunctionPointer(ptr, typeof(T)) as T;
+        }
+
+        /// <summary>
+        /// Loads library in a platform specific way.
+        /// </summary>
+        private static IntPtr PlatformSpecificLoadLibrary(string libraryPath)
+        {
+            if (PlatformApis.IsWindows)
+            {
+                return Windows.LoadLibrary(libraryPath);
+            }
+            if (PlatformApis.IsLinux)
+            {
+                if (PlatformApis.IsMono)
+                {
+                    return Mono.dlopen(libraryPath, RTLD_GLOBAL + RTLD_LAZY);
+                }
+                return Linux.dlopen(libraryPath, RTLD_GLOBAL + RTLD_LAZY);
+            }
+            if (PlatformApis.IsMacOSX)
+            {
+                return MacOSX.dlopen(libraryPath, RTLD_GLOBAL + RTLD_LAZY);
+            }
+            throw new InvalidOperationException("Unsupported platform.");
+        }
+
+        private static class Windows
+        {
+            [DllImport("kernel32.dll")]
+            internal static extern IntPtr LoadLibrary(string filename);
+        }
+
+        private static class Linux
+        {
+            [DllImport("libdl.so")]
+            internal static extern IntPtr dlopen(string filename, int flags);
+
+            [DllImport("libdl.so")]
+            internal static extern IntPtr dlsym(IntPtr handle, string symbol);
+        }
+
+        private static class MacOSX
+        {
+            [DllImport("libSystem.dylib")]
+            internal static extern IntPtr dlopen(string filename, int flags);
+
+            [DllImport("libSystem.dylib")]
+            internal static extern IntPtr dlsym(IntPtr handle, string symbol);
+        }
+
+        /// <summary>
+        /// On Linux systems, using using dlopen and dlsym results in
+        /// DllNotFoundException("libdl.so not found") if libc6-dev
+        /// is not installed. As a workaround, we load symbols for
+        /// dlopen and dlsym from the current process as on Linux
+        /// Mono sure is linked against these symbols.
+        /// </summary>
+        private static class Mono
+        {
+            [DllImport("__Internal")]
+            internal static extern IntPtr dlopen(string filename, int flags);
+
+            [DllImport("__Internal")]
+            internal static extern IntPtr dlsym(IntPtr handle, string symbol);
+        }
+    }
+}