Partial fix for #5660. Better performance and less memory usage for conversions to float type (and to double type, if sizeof(double) < sizeof(long double)). New test suits. Documentation update.

[SVN r72925]

test/lexical_cast_wchars_test.cpp

@@ -0,0 +1,56 @@
+//  Unit test for boost::lexical_cast.
+//
+//  See http://www.boost.org for most recent version, including documentation.
+//
+//  Copyright Antony Polukhin, 2011.
+//
+//  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).
+
+#include <boost/config.hpp>
+
+#if defined(__INTEL_COMPILER)
+#pragma warning(disable: 193 383 488 981 1418 1419)
+#elif defined(BOOST_MSVC)
+#pragma warning(disable: 4097 4100 4121 4127 4146 4244 4245 4511 4512 4701 4800)
+#endif
+
+#include <boost/lexical_cast.hpp>
+
+#include <boost/cstdint.hpp>
+#include <boost/test/unit_test.hpp>
+#include <boost/test/floating_point_comparison.hpp>
+
+using namespace boost;
+
+void test_char_types_conversions()
+{
+#ifndef BOOST_LCAST_NO_WCHAR_T
+    const char c_arr[]            = "Test array of chars";
+    const unsigned char uc_arr[]  = "Test array of chars";
+    const signed char sc_arr[]    = "Test array of chars";
+    const wchar_t wc_arr[]        =L"Test array of chars";
+
+    // Following tests depend on realization of std::locale
+    // and pass for popular compilers and STL realizations
+    BOOST_CHECK(boost::lexical_cast<wchar_t>(c_arr[0]) == wc_arr[0]);
+    BOOST_CHECK(boost::lexical_cast<std::wstring>(c_arr) == std::wstring(wc_arr));
+
+    BOOST_CHECK(boost::lexical_cast<std::wstring>(sc_arr) != std::wstring(wc_arr) );
+    BOOST_CHECK(boost::lexical_cast<std::wstring>(uc_arr) != std::wstring(wc_arr) );
+
+    BOOST_CHECK_THROW(boost::lexical_cast<wchar_t>(uc_arr[0]), boost::bad_lexical_cast);
+    BOOST_CHECK_THROW(boost::lexical_cast<wchar_t>(sc_arr[0]), boost::bad_lexical_cast);
+#endif
+    BOOST_CHECK(1);
+}
+
+unit_test::test_suite *init_unit_test_suite(int, char *[])
+{
+    unit_test_framework::test_suite *suite =
+        BOOST_TEST_SUITE("lexical_cast char<->wchar_t unit test");
+    suite->add(BOOST_TEST_CASE(&test_char_types_conversions));
+
+    return suite;
+}