diff --git a/include/logger.h b/include/logger.h
new file mode 100644
index 0000000..3a926ae
--- /dev/null
+++ b/include/logger.h
@@ -0,0 +1,42 @@
+#ifndef _LOGGER_H_
+#define _LOGGER_H_
+
+#include <sstream>
+#include <stdexcept>
+#include <iostream>
+#include <atomic>
+
+class logger
+{
+private:
+    std::atomic<bool> _isLogging;
+    std::stringstream _logLine;
+
+public:
+    logger();
+    void log(const char* s);
+
+    template<typename T, typename... Args> void log(const char* s, const T& value, const Args&... args)
+    {
+        if(!_isLogging)
+        {
+            _isLogging.store(true);
+            _logLine.str("");
+        }
+
+        while (*s)
+        {
+            if (*s == '%' && *++s != '%')
+            {
+                _logLine << value;
+                return log(s, args...);
+            }
+            _logLine << *s++;
+        }
+        throw std::runtime_error("extra arguments provided");
+    }
+};
+
+extern logger ulog;
+
+#endif // _LOGGER_H_
diff --git a/src/asm/linux/x86_64/ustring_asm.s b/src/asm/linux/x86_64/ustring_asm.s
index d03bc5f..db97f71 100644
--- a/src/asm/linux/x86_64/ustring_asm.s
+++ b/src/asm/linux/x86_64/ustring_asm.s
@@ -30,38 +30,44 @@ npos = -1
 
 _asm_ucs4_strstr:
 
-	xor		r8, r8
+	push	r12
 	mov		r9d, dword [rdx]
+	mov		rax, rdx
+	lea		r8, [rdi + rsi*4]
+	lea		r10, [rdx + rcx*4]
 
 	strstr_try_next_symbol:
 
-		cmp		r9d, dword [rdi + r8*4]
+		cmp		r9d, dword [rdi]
 		je 		strstr_init_counter
-		inc		r8
-		cmp		rsi, r8
+		add		rdi, 4
+		cmp		rdi, r8
 		jne		strstr_try_next_symbol
+		pop		r12
 		mov		rax, 0
 		ret
 
 	strstr_init_counter:
 
-		xor		r10, r10
+		mov		rdx, rax
+		mov		r12, rdi
 
 	strstr_symbol_found:
 
-		inc		r10
-		cmp		r10, rcx
+		add		rdx, 4
+		cmp		rdx, r10
 		je 		strstr_the_end
-		lea		rax, [r8 + r10]
-		mov		r11d, dword [rdi + rax*4]
-		cmp		r11d, dword [rdx + r10*4]
+		add		r12, 4
+		mov		r11d, dword [r12]
+		cmp		r11d, dword [rdx]
 		je		strstr_symbol_found
-		inc 	r8
+		add		rdi, 4
 		jmp		strstr_try_next_symbol
 
 	strstr_the_end:
 
-		lea		rax, [rdi + r8*4]
+		pop		r12
+		mov		rax, rdi
 
 	ret
 
diff --git a/src/logger.cpp b/src/logger.cpp
new file mode 100644
index 0000000..bfd1b4a
--- /dev/null
+++ b/src/logger.cpp
@@ -0,0 +1,30 @@
+#include "logger.h"
+#include <iostream>
+#include <stdexcept>
+
+logger ulog;
+
+logger::logger(): _isLogging(ATOMIC_FLAG_INIT)
+{
+}
+
+void logger::log(const char *s)
+{
+    if(!_isLogging)
+    {
+        _isLogging.store(true);
+        _logLine.str("");
+    }
+
+    while (*s)
+    {
+        if (*s == '%' && *++s != '%')
+            throw std::runtime_error("invalid format string: missing arguments");
+        _logLine << *s++;
+    }
+
+    std::cout << _logLine.str() << std::endl;
+
+    _isLogging.store(false);
+}
+
diff --git a/test/main.cpp b/test/main.cpp
index 011da48..4488b54 100755
--- a/test/main.cpp
+++ b/test/main.cpp
@@ -1,5 +1,6 @@
 #include "ustring.h"
 #include "utf.h"
+#include "logger.h"
 #include <iostream>
 #include <string>
 #include <fstream>
@@ -562,6 +563,6 @@ TEST(Ustring, replace_string)
 
 int main(int argc, char **argv)
 {
-	::testing::InitGoogleTest(&argc, argv);
-	return RUN_ALL_TESTS();
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
 }