diff --git a/src/main.cc b/src/main.cc
index 3e1e48f..eb72a9d 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -378,7 +378,9 @@ int main() {
 
 //    std::cout << CommonCode(RawCode(RawCode::extract(0x4FEA13400))) << std::endl;
 
-    std::cout << CommonCode(0x4FEA13400).to_raw_code().to_common_code() << std::endl;
+//    std::cout << CommonCode(0x4FEA13400).to_raw_code().to_common_code() << std::endl;
+
+    std::cout << RawCode::check(CommonCode(0x4FEA13400).to_raw_code().unwrap()) << std::endl;
 
 //    std::cerr << (clock() - start_time) * 1000 / CLOCKS_PER_SEC << "ms" << std::endl;
     std::cerr << (clock() - start_time) * 1000000 / CLOCKS_PER_SEC << "us" << std::endl;
diff --git a/src/raw_code/convert.cc b/src/raw_code/convert.cc
index f826361..eebb6eb 100644
--- a/src/raw_code/convert.cc
+++ b/src/raw_code/convert.cc
@@ -6,14 +6,15 @@ RawCode::RawCode(const CommonCode &common_code) {
     code = RawCode::extract(common_code.unwrap()); // load from common code
 }
 
-CommonCode RawCode::to_common_code() const {
-
-    // TODO: check before release common code
-    // TODO: raw code pass RawCode::check -> using CommonCode::unsafe_create directly
+RawCode RawCode::from_common_code(const CommonCode &common_code) {
+    return RawCode(common_code); // load from common code
+}
 
+CommonCode RawCode::to_common_code() const {
     if (!RawCode::check(code)) {
         throw std::runtime_error("invalid raw code");
     }
+    /// pass check -> common code must valid
     return CommonCode::unsafe_create(RawCode::compact(code)); // release common code
 }
 
diff --git a/src/raw_code/raw_code.cc b/src/raw_code/raw_code.cc
index 5c13d74..4a62031 100644
--- a/src/raw_code/raw_code.cc
+++ b/src/raw_code/raw_code.cc
@@ -6,6 +6,73 @@ uint64_t RawCode::unwrap() const { // get raw uint64_t code
     return code;
 }
 
+#include <iostream>
+
+/// we can check any raw_code in this function
+bool RawCode::check(uint64_t raw_code) {
+
+    if (raw_code >> 60) {
+        return false; // high 4-bits must be zero
+    }
+
+    int head_num = 0;
+    int space_num = 0;
+
+    for (int addr = 0; addr < 20; ++addr, raw_code >>= 3) {
+
+//        std::cout << "addr = " << addr << " | block = " << (raw_code & 0b111) << std::endl;
+
+        switch (raw_code & 0b111) {
+            case B_space:
+                ++space_num;
+                break;
+            case B_1x1:
+                /// do nothing
+                break;
+            case B_1x2:
+
+                if ((addr & 0b11) == 0b11 || (raw_code & F_1x2) != C_1x2) {
+                    return false;
+                }
+
+                break;
+            case B_2x1:
+
+                if (addr > 15 || (raw_code & F_2x1) != C_2x1) {
+                    return false;
+                }
+
+                break;
+            case B_2x2:
+                ++head_num;
+
+                if (addr > 14 || (addr & 0b11) == 0b11 || (raw_code & F_2x2) != C_2x2) {
+                    return false;
+                }
+
+                break;
+
+            case B_fill:
+                /// do nothing
+                break;
+
+            default:
+                return false; // unknown flag
+        }
+
+    }
+
+    // TODO: one 2x2 / >=2 space
+
+    // TODO: check head_num and space_num
+
+    if (head_num != 1 || space_num < 2) {
+        return false;
+    }
+
+    return true;
+}
+
 std::string RawCode::dump_case() const {
     std::string result;
     result.reserve(40); // 5 lines * ("x x x x\n")
@@ -25,20 +92,3 @@ std::string RawCode::dump_case() const {
     }
     return result;
 }
-
-bool RawCode::check(uint64_t raw_code) {
-
-    // TODO: check function for RawCode
-
-    /// we can check any raw_code in this function
-
-    // TODO: for check function -> one 2x2 / >=2 space
-
-    // TODO: check the high 4-bits equal to zero
-
-    return true;
-}
-
-
-
-
diff --git a/src/raw_code/raw_code.h b/src/raw_code/raw_code.h
index 40ee27c..e7a2084 100644
--- a/src/raw_code/raw_code.h
+++ b/src/raw_code/raw_code.h
@@ -25,7 +25,7 @@ public:
 
 
 //    static RawCode create(uint64_t raw_code);
-//    static RawCode from_common_code(const CommonCode &common_code);
+    static RawCode from_common_code(const CommonCode &common_code);
 
     // TODO: unsafe_create static function