Speed: Avoid some repeated string constant initialization

This patch introduces a basic concept to avoid the repetition of
string constant creation in Python by using helper functions
returning static instances.

There is currently no real shiboken finalization, so we postpone
finalization until shiboken has one:

- call the finalize_strings() function
- build finalization for other stuff (all signatures etc)

Initial-patch-by: Christian Tismer <tismer@stackless.com>
Task-number: PYSIDE-1087
Change-Id: If3483ba91f719ee0472eb53583460ba35163bc9d
Reviewed-by: Christian Tismer <tismer@stackless.com>

1 files changed, 62 insertions, 2 deletions

diff --git a/sources/shiboken2/libshiboken/sbkstring.cpp b/sources/shiboken2/libshiboken/sbkstring.cpp
index 9ba5be281..2e638a413 100644
--- a/sources/shiboken2/libshiboken/sbkstring.cpp
+++ b/sources/shiboken2/libshiboken/sbkstring.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2018 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of Qt for Python.
@@ -40,6 +40,8 @@
 #include "sbkstring.h"
 #include "autodecref.h"
 
+#include <vector>
+
 namespace Shiboken
 {
 
@@ -200,6 +202,64 @@ Py_ssize_t len(PyObject *str)
     return 0;
 }
 
-} // namespace String
+///////////////////////////////////////////////////////////////////////
+//
+// Implementation of efficient Python strings
+// ------------------------------------------
+//
+// Instead of repetitively executing
+//
+//     PyObject *attr = PyObject_GetAttrString(obj, "__name__");
+//
+// a helper of the form
+//
+// PyObject *name()
+// {
+//    static PyObject *const s = Shiboken::String::createStaticString("__name__");
+//    return result;
+// }
+//
+// can now be implemented, which registers the string into a static set avoiding
+// repetitive string creation. The resulting code looks like:
+//
+//     PyObject *attr = PyObject_GetAttr(obj, name());
+//
+// Missing:
+// There is no finalization for the string structures, yet.
+// But this is a global fault in shiboken. We are missing a true
+// finalization like in all other modules.
+
+using StaticStrings = std::vector<PyObject *>;
+
+static StaticStrings &staticStrings()
+{
+    static StaticStrings result;
+    return result;
+}
+
+PyObject *createStaticString(const char *str)
+{
+#if PY_VERSION_HEX >= 0x03000000
+    PyObject *result = PyUnicode_InternFromString(str);
+#else
+    PyObject *result = PyString_InternFromString(str);
+#endif
+    if (result == nullptr) {
+        // This error is never checked, but also very unlikely. Report and exit.
+        PyErr_Print();
+        Py_FatalError("unexpected error in createStaticString()");
+    }
+    staticStrings().push_back(result);
+    return result;
+}
 
+void finalizeStaticStrings() // Currently unused
+{
+    auto &list = staticStrings();
+    for (auto s : list)
+        Py_DECREF(s);
+    list.clear();
+}
+
+} // namespace String
 } // namespace Shiboken