Use again back fast_oss.h after code cleanup

include/c11log/details/stack_buf.h

@@ -0,0 +1,111 @@
+#pragma once
+
+#include <array>
+#include <vector>
+#include <algorithm>
+#include <cstring>
+
+// Fast memory storage
+// stores its contents on the stack when possible, in vector<char> otherwise
+// NOTE: User should be remember that returned buffer might be on the stack!!
+namespace c11log
+{
+namespace details
+{
+
+using bufpair_t = std::pair<const char*, std::size_t>;
+
+template<std::size_t STACK_SIZE = 128>
+class stack_buf
+{
+public:
+    stack_buf() :_v(), _stack_array(), _stack_size(0) {}
+    ~stack_buf() {};
+
+    stack_buf& operator=(const stack_buf& other) = delete;
+
+    stack_buf(const bufpair_t& buf_to_copy) :stack_buf()
+    {
+        append(buf_to_copy);
+    }
+
+    stack_buf(const stack_buf& other)
+    {
+        _stack_size = other._stack_size;
+        if (!other._v.empty())
+            _v = other._v;
+        else if (_stack_size)
+            std::copy(other._stack_array.begin(), other._stack_array.begin() + _stack_size, _stack_array.begin());
+    }
+
+    stack_buf(stack_buf&& other)
+    {
+        _stack_size = other._stack_size;
+        if (!other._v.empty())
+            _v = std::move(other._v);
+        else if (_stack_size)
+            std::copy(other._stack_array.begin(), other._stack_array.begin() + _stack_size, _stack_array.begin());
+        other.clear();
+    }
+
+    void append(const char* buf, std::size_t buf_size)
+    {
+        //If we are aleady using _v, forget about the stack
+        if (!_v.empty())
+        {
+            _v.insert(_v.end(), buf, buf + buf_size);
+        }
+        //Try use the stack
+        else
+        {
+            if (_stack_size + buf_size <= STACK_SIZE)
+            {
+                std::memcpy(&_stack_array[_stack_size], buf, buf_size);
+                _stack_size += buf_size;
+            }
+            //Not enough stack space. Copy all to _v
+            else
+            {
+                _v.reserve(_stack_size + buf_size);
+                if (_stack_size)
+                    _v.insert(_v.end(), _stack_array.begin(), _stack_array.begin() + _stack_size);
+                _v.insert(_v.end(), buf, buf + buf_size);
+            }
+        }
+    }
+
+    void append(const bufpair_t &buf)
+    {
+        append(buf.first, buf.second);
+    }
+
+    void clear()
+    {
+        _stack_size = 0;
+        _v.clear();
+    }
+
+    bufpair_t get() const
+    {
+        if (!_v.empty())
+            return bufpair_t(_v.data(), _v.size());
+        else
+            return bufpair_t(_stack_array.data(), _stack_size);
+    }
+
+    std::size_t size() const
+    {
+        if (!_v.empty())
+            return _v.size();
+        else
+            return _stack_size;
+    }
+
+private:
+    std::vector<char> _v;
+    std::array<char, STACK_SIZE> _stack_array;
+    std::size_t _stack_size;
+};
+
+}
+} //namespace c11log { namespace details {