Add options "stored_size" and "growth_factor" options to string. Make string's default growth factor the same as vector's (60%)

test/string_options_test.cpp

@@ -0,0 +1,142 @@
+//////////////////////////////////////////////////////////////////////////////
+//
+// (C) Copyright Ion Gaztanaga 2004-2013. Distributed under the Boost
+// Software License, Version 1.0. (See accompanying file
+// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/container for documentation.
+//
+//////////////////////////////////////////////////////////////////////////////
+#include <boost/container/string.hpp>
+#include <boost/container/allocator.hpp>
+#include <boost/container/detail/next_capacity.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <climits>
+
+using namespace boost::container;
+
+template<class Unsigned, class StringType>
+void test_stored_size_type_impl()
+{
+   #ifndef BOOST_NO_EXCEPTIONS
+   StringType s;
+   typedef typename StringType::size_type    size_type;
+   typedef typename StringType::value_type   value_type;
+   //We need a bit to store short/long info, minus the null terminator
+   size_type const max = Unsigned(-1)/2u - 1u;
+   s.resize(5);
+   s.resize(max);
+   BOOST_TEST_THROWS(s.resize(max+1),                    std::exception);
+   BOOST_TEST_THROWS(s.push_back(value_type(1)),         std::exception);
+   BOOST_TEST_THROWS(s.insert(s.begin(), value_type(1)), std::exception);
+   BOOST_TEST_THROWS(s.reserve(max+1),                   std::exception);
+   #endif
+}
+
+template<class Unsigned>
+void test_stored_size_type()
+{
+   #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
+   using options_t = string_options_t< stored_size<Unsigned> >;
+   #else
+   typedef typename string_options
+      < stored_size<Unsigned> >::type options_t;
+   #endif
+
+   basic_string<char, std::char_traits<char>, void> default_string_t;
+   //Test first with a typical allocator
+   {
+      typedef basic_string<char, std::char_traits<char>, void, options_t> string_t;
+      BOOST_CONTAINER_STATIC_ASSERT(sizeof(string_t) < sizeof(default_string_t));
+      test_stored_size_type_impl<Unsigned, string_t>();
+   }
+   //Test with a V2 allocator
+   {
+      basic_string<char, std::char_traits<char>, allocator<char>, options_t> string_t;
+      BOOST_CONTAINER_STATIC_ASSERT(sizeof(string_t) < sizeof(default_string_t));
+      //test_stored_size_type_impl<Unsigned, string_t>();
+   }
+   {
+      //Test initial capacity
+      typedef basic_string<char, std::char_traits<char>, void, options_t> string_t;
+      const std::size_t theoretical_long_repr_t = ((2 * sizeof(Unsigned) - 1u) / sizeof(void*) + 1u) * sizeof(void*) + sizeof(void*);
+      BOOST_CONTAINER_STATIC_ASSERT(sizeof(string_t)  == theoretical_long_repr_t);
+      const std::size_t theoretical_sso_cap = theoretical_long_repr_t - 2u;   //-2 --> 1 for short header, 1 for null terminator
+      string_t s;
+      BOOST_ASSERT(s.capacity() == theoretical_sso_cap);
+   }
+}
+
+void test_growth_factor_50()
+{
+   #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
+   using options_t = string_options_t< growth_factor<growth_factor_50> >;
+   #else
+   typedef string_options
+      < growth_factor<growth_factor_50> >::type options_t;
+   #endif
+
+   basic_string<char, std::char_traits<char>, void, options_t> s;
+
+   s.resize(5);
+   s.resize(s.capacity());
+   std::size_t old_capacity = s.capacity();
+   s.push_back(0);
+   std::size_t new_capacity = s.capacity();
+   std::size_t old_storage = old_capacity+1u;
+   std::size_t new_storage = new_capacity + 1u;
+   BOOST_TEST(new_storage == (old_storage + old_storage/2));
+}
+
+void test_growth_factor_60()
+{
+   #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
+   using options_t = string_options_t< growth_factor<growth_factor_60> >;
+   #else
+   typedef string_options
+      < growth_factor<growth_factor_60> >::type options_t;
+   #endif
+
+   basic_string<char, std::char_traits<char>, void, options_t> s;
+
+   s.resize(5);
+   s.resize(s.capacity());
+   std::size_t old_capacity = s.capacity();
+   s.push_back(0);
+   std::size_t new_capacity = s.capacity();
+   std::size_t old_storage = old_capacity+1u;
+   std::size_t new_storage = new_capacity + 1u;
+   BOOST_TEST(new_storage == (old_storage + 3*old_storage/5));
+}
+
+void test_growth_factor_100()
+{
+   #if !defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
+   using options_t = string_options_t< growth_factor<growth_factor_100> >;
+   #else
+   typedef string_options
+      < growth_factor<growth_factor_100> >::type options_t;
+   #endif
+
+   basic_string<char, std::char_traits<char>, void, options_t> s;
+
+   s.resize(5);
+   s.resize(s.capacity());
+   std::size_t old_capacity = s.capacity();
+   s.push_back(0);
+   std::size_t new_capacity = s.capacity();
+   std::size_t old_storage = old_capacity+1u;
+   std::size_t new_storage = new_capacity + 1u;
+   BOOST_TEST(new_storage == 2u*old_storage);
+}
+
+int main()
+{
+   test_growth_factor_50();
+   test_growth_factor_60();
+   test_growth_factor_100();
+   test_stored_size_type<unsigned char>();
+   test_stored_size_type<unsigned short>();
+
+   return ::boost::report_errors();
+}