When using an external handle, create a new service context handle so…

… that

there are no discrepancies in character sets between the service context and
the newly created environment handle
(oracle/python-cx_Oracle#273).

src/dpiConn.c

@@ -18,6 +18,8 @@
 #include <time.h>
 
 // forward declarations of internal functions only used in this file
+static int dpiConn__attachExternal(dpiConn *conn, void *externalHandle,
+        dpiError *error);
 static int dpiConn__createStandalone(dpiConn *conn, const char *userName,
         uint32_t userNameLength, const char *password, uint32_t passwordLength,
         const char *connectString, uint32_t connectStringLength,
@@ -45,6 +47,45 @@ static int dpiConn__setShardingKeyValue(dpiConn *conn, void *shardingKey,
         dpiShardingKeyColumn *column, dpiError *error);
 
 
+//-----------------------------------------------------------------------------
+// dpiConn__attachExternal() [INTERNAL]
+//   Attach to the server and session of an existing service context handle.
+//-----------------------------------------------------------------------------
+static int dpiConn__attachExternal(dpiConn *conn, void *externalHandle,
+        dpiError *error)
+{
+    // mark connection as using an external handle so that no attempts are
+    // made to close it
+    conn->externalHandle = 1;
+
+    // acquire handles from existing service context handle
+    conn->handle = externalHandle;
+    if (dpiConn__getHandles(conn, error) < 0) {
+        conn->handle = NULL;
+        return DPI_FAILURE;
+    }
+
+    // allocate a new service context handle which will use the new environment
+    // handle independent of the original service context handle
+    conn->handle = NULL;
+    if (dpiOci__handleAlloc(conn->env->handle, &conn->handle,
+            DPI_OCI_HTYPE_SVCCTX, "allocate service context handle",
+            error) < 0)
+        return DPI_FAILURE;
+
+    // set these handles on the newly created service context
+    if (dpiOci__attrSet(conn->handle, DPI_OCI_HTYPE_SVCCTX, conn->serverHandle,
+            0, DPI_OCI_ATTR_SERVER, "set server handle", error) < 0)
+        return DPI_FAILURE;
+    if (dpiOci__attrSet(conn->handle, DPI_OCI_HTYPE_SVCCTX,
+            conn->sessionHandle, 0, DPI_OCI_ATTR_SESSION, "set session handle",
+            error) < 0)
+        return DPI_FAILURE;
+
+    return DPI_SUCCESS;
+}
+
+
 //-----------------------------------------------------------------------------
 // dpiConn__check() [INTERNAL]
 //   Validate the connection handle and that it is still connected to the
@@ -183,6 +224,8 @@ static int dpiConn__close(dpiConn *conn, uint32_t mode, const char *tag,
 
     // handle connections created with an external handle
     if (conn->externalHandle) {
+        if (conn->handle)
+            dpiOci__handleFree(conn->handle, DPI_OCI_HTYPE_SVCCTX);
         conn->sessionHandle = NULL;
 
     // handle standalone connections
@@ -303,11 +346,9 @@ int dpiConn__create(dpiConn *conn, const dpiContext *context,
         return DPI_FAILURE;
 
     // if a handle is specified, use it
-    if (createParams->externalHandle) {
-        conn->handle = createParams->externalHandle;
-        conn->externalHandle = 1;
-        return dpiConn__getHandles(conn, error);
-    }
+    if (createParams->externalHandle)
+        return dpiConn__attachExternal(conn, createParams->externalHandle,
+                error);
 
     // connection class, sharding and the use of session pools require the use
     // of the OCISessionGet() method; all other cases use the OCISessionBegin()