From 07c77b45ba9f74cfe1bed547bea1eeb705f0582b Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sat, 13 Feb 2021 12:47:39 +0100
Subject: Support G++, support string type as template argument for convert()

---
 Makefile             | 14 +++++---------
 include/unicode.h    | 21 +++++++++++++++++++--
 src/test-unicode.cpp |  5 ++++-
 3 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index 7ea075e..39dcafb 100644
--- a/Makefile
+++ b/Makefile
@@ -5,16 +5,15 @@ DISTROS=base debian10 ubuntu2004 ubuntu2010
 
 ifeq ($(wildcard $(shell which clang++-11)),)
 ifeq ($(wildcard $(shell which clang++)),)
-$(error No clang++-11 nor clang++ available!)
+CXX=g++-10
 else
 CXX=clang++
 endif
 else
 CXX=clang++-11
-# GCC is buggy: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85282
-#CXX=g++-10
 endif
 
+# boost is buggy for C++20: error: static_assert failed due to requirement 'detail::is_endian_reversible_inplace<char8_t>
 STANDARD=c++17
 #STANDARD=c++20
 
@@ -35,11 +34,6 @@ COMPILER_SUITE=clang
 LIBS+=-fuse-ld=lld
 endif
 
-ifeq ($(COMPILER_SUITE),clang)
-# libc++ is buggy for C++20: std::hash<char8_t> not implemented. Fixed in LLVM-12
-CXXFLAGS+=-stdlib=libc++
-endif
-
 LDLIBS+=\
 -lboost_context \
 -lboost_filesystem \
@@ -47,6 +41,8 @@ LDLIBS+=\
 -lboost_system \
 
 ifeq ($(COMPILER_SUITE),clang)
+# libc++ is buggy for C++20: std::hash<char8_t> not implemented. Fixed in LLVM-12
+CXXFLAGS+=-stdlib=libc++
 LIBS+= \
 -lc++ \
 -lc++abi
@@ -55,7 +51,7 @@ LIBS+= \
 #-lstdc++fs
 else
 LIBS+= \
--lstdc++
+-lstdc++ \
 -lstdc++fs
 endif
 
diff --git a/include/unicode.h b/include/unicode.h
index d6f8e51..171496e 100644
--- a/include/unicode.h
+++ b/include/unicode.h
@@ -12,6 +12,7 @@
 #include <memory>
 #include <stdexcept>
 #include <string>
+#include <type_traits>
 #include <unordered_map>
 
 #ifdef __cpp_char8_t
@@ -526,7 +527,7 @@ namespace unicode {
  typedef UTF<utf_iterator<char32_t>, utf_back_insert_iterator<char32_t>> UTF_32;
 
  // From and To are facets
- template<typename From, typename To>
+ template<typename From, typename To, std::enable_if_t<std::is_empty<From>::value && std::is_empty<To>::value, bool> = true>
  std::basic_string<typename To::value_type> convert(const std::basic_string<typename From::value_type>& s)
  {
   std::basic_string<typename To::value_type> result;
@@ -561,7 +562,9 @@ namespace unicode {
  };
 
  // From and To are from: utf8_t, char16_t and char32_t
- template<typename From, typename To>
+ template<typename From, typename To,
+  std::enable_if_t<std::is_trivial<From>::value && std::is_trivial<To>::value, bool> = true
+ >
  std::basic_string<To> convert(const std::basic_string<From>& s)
  {
   typedef UTF<utf_iterator<From>, utf_back_insert_iterator<To>> UTF_Trait;
@@ -573,6 +576,20 @@ namespace unicode {
   return result;
  }
 
+ template<typename FromContainer, typename ToContainer,
+  std::enable_if_t<!std::is_empty<FromContainer>::value && !std::is_empty<ToContainer>::value, bool> = true
+ >
+ ToContainer convert(const FromContainer& s)
+ {
+  typedef UTF<utf_iterator<typename FromContainer::value_type>, utf_back_insert_iterator<typename ToContainer::value_type>> UTF_Trait;
+  
+  ToContainer result;
+
+  std::copy(UTF_Trait::begin(s), UTF_Trait::end(s), UTF_Trait::back_inserter(result));
+
+  return result;
+ }
+
  // basic type version
  template<typename T>
  bool is_valid_utf(const std::basic_string<T>& s)
diff --git a/src/test-unicode.cpp b/src/test-unicode.cpp
index 99a8f99..5f5ebbf 100644
--- a/src/test-unicode.cpp
+++ b/src/test-unicode.cpp
@@ -351,6 +351,10 @@ BOOST_AUTO_TEST_CASE(convert)
  BOOST_CHECK((unicode::convert<char, wchar_t>(u8"\U0001F63A")) == std::wstring{L"\U0001F63A"});
  BOOST_CHECK((unicode::convert<wchar_t, char32_t>(L"\U0001F63A")) == std::u32string{U"\U0001F63A"});
  BOOST_CHECK((unicode::convert<wchar_t, char>(L"\U0001F63A")) == std::string{u8"\U0001F63A"});
+ 
+ BOOST_CHECK((unicode::convert<std::string, std::wstring>(std::string{"äöü"})) == std::wstring{L"äöü"});
+ 
+ //BOOST_CHECK((unicode::convert<std::vector<char>, std::vector<wchar_t>>(std::vector<char>{})) == std::vector<wchar_t>{});
 }
 
 BOOST_AUTO_TEST_CASE(is_valid_utf)
@@ -375,6 +379,5 @@ BOOST_AUTO_TEST_CASE(string_u8string)
 
 // TODO:
 //
-// char8_t, char16_t, char32_t, char, wchar_t (UTF-16 on Windows, UTF-32 on Linux)
 // string, vector?
 // uint8_t, uint16_t, uint32_t?
-- 
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