Core/Utils: Fix Unicode handling

src/common/Utilities/Containers.h

@@ -21,6 +21,8 @@
 #include "Define.h"
 #include "Random.h"
 #include <algorithm>
+#include <exception>
+#include <iterator>
 #include <utility>
 #include <vector>
 
@@ -38,6 +40,34 @@ namespace Trinity
         return std::addressof(not_ptr);
     }
 
+    template <class T>
+    class BufferWriteGuard
+    {
+        public:
+            using iterator_category = std::output_iterator_tag;
+            using value_type = void;
+            using pointer = T*;
+            using reference = T&;
+            using difference_type = std::ptrdiff_t;
+
+            BufferWriteGuard(T* buf, size_t n) : _buf(buf), _n(n) {}
+
+            T& operator*() const { check(); return *_buf; }
+            BufferWriteGuard& operator++() { check(); ++_buf; --_n; return *this; }
+            T* operator++(int) { check(); T* b = _buf; ++_buf; --_n; return b; }
+
+            size_t size() const { return _n; }
+
+        private:
+            T* _buf;
+            size_t _n;
+            void check()
+            {
+                if (!_n)
+                    throw std::out_of_range("index");
+            }
+    };
+
     namespace Containers
     {
         // replace with std::size in C++17

src/common/Utilities/Util.cpp

@@ -18,6 +18,7 @@
 
 #include "Util.h"
 #include "Common.h"
+#include "Containers.h"
 #include "IpAddress.h"
 #include <utf8.h>
 #include <algorithm>
@@ -252,18 +253,10 @@ bool Utf8toWStr(char const* utf8str, size_t csize, wchar_t* wstr, size_t& wsize)
 {
     try
     {
-        size_t len = utf8::distance(utf8str, utf8str+csize);
-        if (len > wsize)
-        {
-            if (wsize > 0)
-                wstr[0] = L'\0';
-            wsize = 0;
-            return false;
-        }
-
-        wsize = len;
-        utf8::utf8to16(utf8str, utf8str+csize, wstr);
-        wstr[len] = L'\0';
+        Trinity::BufferWriteGuard<wchar_t> guard(wstr, wsize);
+        guard = utf8::utf8to16(utf8str, utf8str+csize, guard);
+        wsize -= guard.size(); // remaining unused space
+        wstr[wsize] = L'\0';
     }
     catch(std::exception)
     {
@@ -278,13 +271,10 @@ bool Utf8toWStr(char const* utf8str, size_t csize, wchar_t* wstr, size_t& wsize)
 
 bool Utf8toWStr(const std::string& utf8str, std::wstring& wstr)
 {
+    wstr.clear();
     try
     {
-        if (size_t len = utf8::distance(utf8str.c_str(), utf8str.c_str()+utf8str.size()))
-        {
-            wstr.resize(len);
-            utf8::utf8to16(utf8str.c_str(), utf8str.c_str()+utf8str.size(), &wstr[0]);
-        }
+        utf8::utf8to16(utf8str.c_str(), utf8str.c_str()+utf8str.size(), std::back_inserter(wstr));
     }
     catch(std::exception)
     {