Merge branch '90-gc-cleanup'

Fix #90.

Reduce memory allocations and GC pressure for send, receive, and
forward operations.

src/ZeroMQ/Interop/DisposableIntPtr.cs

@@ -3,32 +3,21 @@
     using System;
     using System.Runtime.InteropServices;
 
-    internal class DisposableIntPtr : IDisposable
+    internal struct DisposableIntPtr : IDisposable
     {
+        public IntPtr Ptr;
+
         public DisposableIntPtr(int size)
         {
             Ptr = Marshal.AllocHGlobal(size);
         }
 
-        ~DisposableIntPtr()
-        {
-            Dispose(false);
-        }
-
-        public IntPtr Ptr { get; private set; }
-
         public static implicit operator IntPtr(DisposableIntPtr disposablePtr)
         {
             return disposablePtr.Ptr;
         }
 
         public void Dispose()
-        {
-            Dispose(true);
-            GC.SuppressFinalize(this);
-        }
-
-        protected virtual void Dispose(bool disposing)
         {
             if (Ptr != IntPtr.Zero)
             {

src/ZeroMQ/Interop/Retry.cs

@@ -0,0 +1,33 @@
+namespace ZeroMQ.Interop
+{
+    using System;
+
+    internal static class Retry
+    {
+        public static int IfInterrupted<T1, T2, T3>(Func<T1, T2, T3, int> operation, T1 arg1, T2 arg2, T3 arg3)
+        {
+            int rc;
+
+            do
+            {
+                rc = operation(arg1, arg2, arg3);
+            }
+            while (rc == -1 && LibZmq.zmq_errno() == ErrorCode.EINTR);
+
+            return rc;
+        }
+
+        public static int IfInterrupted<T1, T2, T3, T4>(Func<T1, T2, T3, T4, int> operation, T1 arg1, T2 arg2, T3 arg3, T4 arg4)
+        {
+            int rc;
+
+            do
+            {
+                rc = operation(arg1, arg2, arg3, arg4);
+            }
+            while (rc == -1 && LibZmq.zmq_errno() == ErrorCode.EINTR);
+
+            return rc;
+        }
+    }
+}