Use again back fast_oss.h after code cleanup

include/c11log/details/fast_oss.h

@@ -0,0 +1,105 @@
+#pragma once
+
+// Faster than ostringstream--returns its string by ref
+#include <ostream>
+#include "stack_buf.h"
+
+namespace c11log
+{
+namespace details
+{
+
+
+class stack_devicebuf :public std::streambuf
+{
+public:
+    using Base = std::streambuf;
+    stack_devicebuf() = default;
+    ~stack_devicebuf() = default;
+    stack_devicebuf& operator=(const stack_devicebuf&) = delete;
+
+    stack_devicebuf(const stack_devicebuf& other) :std::basic_streambuf<char>(), _stackbuf(other._stackbuf)
+    {}
+
+    stack_devicebuf(stack_devicebuf&& other) :std::basic_streambuf<char>(), _stackbuf(std::move(other._stackbuf))
+    {
+        other.clear();
+    }
+
+    bufpair_t buf() const
+    {
+        return _stackbuf.get();
+    }
+
+    std::size_t size() const
+    {
+        return _stackbuf.size();
+    }
+
+    void clear()
+    {
+        _stackbuf.clear();
+    }
+
+protected:
+    // copy the give buffer into the accumulated fast buffer
+    std::streamsize xsputn(const char_type* s, std::streamsize count) override
+    {
+        _stackbuf.append(s, static_cast<unsigned int>(count));
+        return count;
+    }
+
+    int_type overflow(int_type ch) override
+    {
+        if (traits_type::not_eof(ch))
+        {
+            char c = traits_type::to_char_type(ch);
+            xsputn(&c, 1);
+        }
+        return ch;
+    }
+private:
+    stack_buf<256> _stackbuf;
+};
+
+class fast_oss :public std::ostream
+{
+public:
+    fast_oss() :std::ostream(&_dev) {}
+    ~fast_oss() = default;
+
+    fast_oss& operator=(const fast_oss& other) = delete;
+    fast_oss& operator=(const fast_oss&& other) = delete;
+
+    fast_oss(const fast_oss& other) :std::basic_ios<char>(), std::ostream(&_dev), _dev(other._dev)
+    {}
+
+    fast_oss(fast_oss&& other) :std::basic_ios<char>(), std::ostream(&_dev), _dev(std::move(other._dev))
+    {
+        other.clear();
+    }
+
+
+    std::string str()
+    {
+        auto buf = _dev.buf();
+        return std::string(buf.first, buf.second);
+    }
+
+
+
+    std::size_t size() const
+    {
+        return _dev.size();
+    }
+
+    void clear()
+    {
+        _dev.clear();
+    }
+
+private:
+    stack_devicebuf _dev;
+};
+}
+}