OpenSSL: Replace calls which are defines and not functions

Some functions are defines for calls of other functions with specific
parameters in the openssl header files. Add similar methods, and remove
unused methods where this would also be neccessary.

Author: thomas-v2

src/S7CommPlusDriver/OpenSSL/Native.cs

@@ -50,10 +50,6 @@ public class Native
         [DllImport(SSLDLLNAME, CallingConvention = CallingConvention.Cdecl)]
         public static extern int OPENSSL_init_ssl(UInt64 opts, IntPtr settings);
 
-        //void OPENSSL_free(void* addr);
-        [DllImport(SSLDLLNAME, CallingConvention = CallingConvention.Cdecl)]
-        public static extern void OPENSSL_free(IntPtr addr);
-
         #endregion
 
         #region SSL
@@ -223,10 +219,6 @@ public class Native
         [DllImport(SSLDLLNAME, CallingConvention = CallingConvention.Cdecl)]
         public static extern int SSL_want(IntPtr ssl);
 
-        // int SSL_want_write(const SSL* ssl);
-        [DllImport(SSLDLLNAME, CallingConvention = CallingConvention.Cdecl)]
-        public static extern int SSL_want_write(IntPtr ssl);
-
         // int SSL_write(SSL *ssl, const void *buf, int num);
         [DllImport(SSLDLLNAME, CallingConvention = CallingConvention.Cdecl)]
         public static extern int SSL_write(IntPtr ssl, byte[] buf, int len);
@@ -291,9 +283,16 @@ public class Native
         [DllImport(DLLNAME, CallingConvention = CallingConvention.Cdecl)]
         public static extern IntPtr BIO_s_mem();
 
-        // int BIO_should_retry(BIO *b);
+        // int BIO_test_flags(const BIO *b, int flags);
         [DllImport(DLLNAME, CallingConvention = CallingConvention.Cdecl)]
-        public static extern int BIO_should_retry(IntPtr b);
+        public static extern int BIO_test_flags(IntPtr b, int flags);
+
+        // int BIO_should_retry(BIO *b) -> define in bio.h: BIO_test_flags(a, BIO_FLAGS_SHOULD_RETRY)
+        const int BIO_FLAGS_SHOULD_RETRY = 0x08;
+        public static int BIO_should_retry(IntPtr b)
+        {
+            return Native.BIO_test_flags(b, BIO_FLAGS_SHOULD_RETRY);
+        }
 
         // int BIO_write(BIO *b, const void *data, int dlen);
         [DllImport(DLLNAME, CallingConvention = CallingConvention.Cdecl)]
@@ -330,47 +329,15 @@ public static long BIO_set_mem_eof_return(IntPtr b, int v)
         #endregion
 
         #region Utilities
-        public static string StaticString(IntPtr ptr)
-        {
-            return Marshal.PtrToStringAnsi(ptr);
-        }
-
-        public static string PtrToStringAnsi(IntPtr ptr, bool hasOwnership)
-        {
-            var len = 0;
-            for (var i = 0; i < 1024; i++, len++)
-            {
-                var octet = Marshal.ReadByte(ptr, i);
-                if (octet == 0)
-                    break;
-            }
-
-            if (len == 1024)
-                return "Invalid string";
-
-            var buf = new byte[len];
-            Marshal.Copy(ptr, buf, 0, len);
-            if (hasOwnership)
-                Native.OPENSSL_free(ptr);
-
-            return Encoding.ASCII.GetString(buf, 0, len);
-        }
 
-        public static IntPtr ExpectNonNull(IntPtr ptr)
+         public static IntPtr ExpectNonNull(IntPtr ptr)
         {
             if (ptr == IntPtr.Zero)
                 throw new Exception();
 
             return ptr;
         }
 
-        public static int ExpectSuccess(int ret)
-        {
-            if (ret <= 0)
-                throw new Exception();
-
-            return ret;
-        }
         #endregion
     }
 }