fast_buf

include/c11log/details/fast_buf.h

@@ -0,0 +1,103 @@
+#pragma once
+
+#include <cstddef>
+#include <utility>
+#include <cstring>
+#include <vector>
+
+// Fast buffer
+// 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
+{
+
+template<std::size_t STACK_SIZE=128>
+class fast_buf
+{
+public:
+    fast_buf():_stack_size(0) {}
+    ~fast_buf() {};
+
+	fast_buf(const bufpair_t& buf_to_copy):fast_buf()
+	{
+		append(buf_to_copy);
+	}
+
+    fast_buf(const fast_buf& other)
+    {
+        _stack_size = other._stack_size;
+        if(!other._v.empty())
+            _v = other._v;
+        else if(_stack_size)
+            std::copy(other._stack_buf.begin(), other._stack_buf.begin()+_stack_size, _stack_buf.begin());
+    }
+
+    fast_buf(fast_buf&& other)
+    {
+        _stack_size = other._stack_size;
+        if(!other._v.empty())
+            _v = other._v;
+        else if(_stack_size)
+            std::copy(other._stack_buf.begin(), other._stack_buf.begin()+_stack_size, _stack_buf.begin());
+        other.clear();
+    }
+
+    fast_buf& operator=(const fast_buf& other) = delete;
+	fast_buf& operator=(fast_buf&& other) = delete;
+
+    void append(const char* buf, std::size_t size)
+    {
+        //If we are aleady using _v, forget about the stack
+        if(!_v.empty())
+        {
+            _v.insert(_v.end(), buf, buf+ size);
+        }
+        //Try use the stack
+        else
+        {
+            if(_stack_size+size <= STACK_SIZE)
+            {
+                std::memcpy(&_stack_buf[_stack_size], buf, size);
+                _stack_size+=size;
+            }
+            //Not enough stack space. Copy all to _v
+            else
+            {
+				_v.reserve(_stack_size+size);
+                if(_stack_size)
+                    _v.insert(_v.end(), _stack_buf.begin(), _stack_buf.begin() +_stack_size);
+                _v.insert(_v.end(), buf, buf+size);
+            }
+        }
+    }
+
+	void append(const bufpair_t &buf)
+	{
+		append(buf.first, buf.second);
+	}
+
+    void clear()
+    {
+        _stack_size = 0;
+        _v.clear();
+    }
+
+    bufpair_t get()
+    {
+        if(!_v.empty())
+            return bufpair_t(_v.data(), _v.size());
+        else
+            return bufpair_t(_stack_buf.data(), _stack_size);
+    }
+
+private:
+    std::vector<char> _v;
+    std::array<char, STACK_SIZE> _stack_buf;
+    std::size_t _stack_size;	
+};
+
+}
+} //namespace c11log { namespace details {