Improve const-correctness policy

Change convention to passing QPDFObjectHandle by value, removing
some cases where we use const_cast to add const and some
cases where a reference was used for a efficiency alone. It seems
more clear to pass by value as a
way of expressing that the passed object is not modified.

At the same time, enforce const more strongly for code that deals
with pybind11 which is const-correct.

Exempt from this change is our custom type converter.

1 files changed, 10 insertions, 11 deletions

diff --git a/src/qpdf/pikepdf.h b/src/qpdf/pikepdf.h
index 212268d..120bbbe 100644
--- a/src/qpdf/pikepdf.h
+++ b/src/qpdf/pikepdf.h
@@ -61,7 +61,7 @@ namespace pybind11 { namespace detail {
 #if CUSTOM_TYPE_CONVERSION
 
 // From object_convert.cpp
-pybind11::object decimal_from_pdfobject(QPDFObjectHandle& h);
+pybind11::object decimal_from_pdfobject(QPDFObjectHandle h);
 
 namespace pybind11 { namespace detail {
     template <> struct type_caster<QPDFObjectHandle> : public type_caster_base<QPDFObjectHandle> {
@@ -187,21 +187,20 @@ PYBIND11_MAKE_OPAQUE(ObjectMap);
 
 
 // From object.cpp
-size_t list_range_check(QPDFObjectHandle& h, int index);
+size_t list_range_check(QPDFObjectHandle h, int index);
 void init_object(py::module& m);
 
 // From object_repr.cpp
-std::string objecthandle_scalar_value(QPDFObjectHandle& h, bool escaped=true);
-std::string objecthandle_pythonic_typename(QPDFObjectHandle& h, std::string prefix = "pikepdf.");
-std::string objecthandle_repr_typename_and_value(QPDFObjectHandle& h);
-std::string objecthandle_repr(QPDFObjectHandle& h);
+std::string objecthandle_scalar_value(QPDFObjectHandle h, bool escaped=true);
+std::string objecthandle_pythonic_typename(QPDFObjectHandle h, std::string prefix = "pikepdf.");
+std::string objecthandle_repr_typename_and_value(QPDFObjectHandle h);
+std::string objecthandle_repr(QPDFObjectHandle h);
 
 // From object_convert.cpp
-py::object decimal_from_pdfobject(QPDFObjectHandle& h);
-py::object objecthandle_decode(QPDFObjectHandle& h);
-QPDFObjectHandle objecthandle_encode(py::handle handle);
-std::vector<QPDFObjectHandle> array_builder(py::iterable iter);
-std::map<std::string, QPDFObjectHandle> dict_builder(py::dict dict);
+py::object decimal_from_pdfobject(QPDFObjectHandle h);
+QPDFObjectHandle objecthandle_encode(const py::handle handle);
+std::vector<QPDFObjectHandle> array_builder(const py::iterable iter);
+std::map<std::string, QPDFObjectHandle> dict_builder(const py::dict dict);
 
 // Support for recursion checks
 class StackGuard