Backward compatibility for code using OpenSSL < 1.1.0.

Some application code using asio::ssl::stream<> explicitly tests for the
SSL_R_SHORT_READ error. For compatibility, when using older versions of
OpenSSL we will define the ssl::error::stream_truncated to use this
value.

include/boost/asio/ssl/error.hpp

@@ -41,8 +41,14 @@ namespace error {
 
 enum stream_errors
 {
+#if defined(GENERATING_DOCUMENTATION)
   /// The underlying stream closed before the ssl stream gracefully shut down.
+  stream_truncated
+#elif (OPENSSL_VERSION_NUMBER < 0x10100000L) && !defined(OPENSSL_IS_BORINGSSL)
+  stream_truncated = ERR_PACK(ERR_LIB_SSL, 0, SSL_R_SHORT_READ)
+#else
   stream_truncated = 1
+#endif
 };
 
 extern BOOST_ASIO_DECL

include/boost/asio/ssl/impl/error.ipp

@@ -52,6 +52,16 @@ const boost::system::error_category& get_ssl_category()
 } // namespace error
 namespace ssl {
 namespace error {
+
+#if (OPENSSL_VERSION_NUMBER < 0x10100000L) && !defined(OPENSSL_IS_BORINGSSL)
+
+const boost::system::error_category& get_stream_category()
+{
+  return boost::asio::error::get_ssl_category();
+}
+
+#else
+
 namespace detail {
 
 class stream_category : public boost::system::error_category
@@ -80,6 +90,8 @@ const boost::system::error_category& get_stream_category()
   return instance;
 }
 
+#endif
+
 } // namespace error
 } // namespace ssl
 } // namespace asio