diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ad9082d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/.idea/
+/cmake-build*/
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..335eee4
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "third_party/googletest"]
+	path = third_party/googletest
+	url = https://github.com/google/googletest.git
+[submodule "third_party/benchmark"]
+	path = third_party/benchmark
+	url = https://github.com/google/benchmark.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..6af91ad
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,26 @@
+cmake_minimum_required(VERSION 3.5)
+project(md5sum LANGUAGES CXX)
+
+option(MD5_ENABLE_TESTING "Enable testing of the md5sum library." ON)
+option(MD5_ENABLE_BENCHMARK "Enable benchmark of the md5sum library." ON)
+
+set(CMAKE_CXX_STANDARD 20)
+
+add_compile_options(-fno-rtti -fno-exceptions -Wall -Wextra)
+
+add_library(md5sum STATIC src/md5_core.cc)
+target_include_directories(md5sum INTERFACE src/)
+
+include(third_party/ThirdParty.cmake)
+add_library(md5sum::md5sum ALIAS md5sum)
+
+if (MD5_ENABLE_TESTING)
+    enable_testing()
+    add_executable(md5_test test/md5_update.cc)
+    target_link_libraries(md5_test PRIVATE md5sum::md5sum GTest::gtest_main)
+endif()
+
+if (MD5_ENABLE_BENCHMARK)
+    add_executable(md5_benchmark benchmark.cc)
+    target_link_libraries(md5_benchmark PRIVATE md5sum::md5sum benchmark::benchmark_main)
+endif()
diff --git a/benchmark.cc b/benchmark.cc
new file mode 100644
index 0000000..cecebf6
--- /dev/null
+++ b/benchmark.cc
@@ -0,0 +1,26 @@
+#include <benchmark/benchmark.h>
+
+#include "md5.h"
+
+std::string test_data() {
+    char data[64];
+    for (char i = 0; i < 64; ++i) {
+        data[i] = i;
+    }
+    return {data, data + 64};
+}
+
+static void BM_MD5_NEXT(benchmark::State &state) {
+    const auto data = test_data();
+
+    md5::MD5::md5_ctx c;
+    md5::MD5::md5_reset(&c);
+
+    for (auto _ : state) {
+        md5::MD5::md5_update(&c, data.c_str(), 64);
+    }
+}
+
+BENCHMARK(BM_MD5_NEXT);
+
+BENCHMARK_MAIN();
diff --git a/md5_core.h b/md5_core.h
deleted file mode 100644
index 165e497..0000000
--- a/md5_core.h
+++ /dev/null
@@ -1,29 +0,0 @@
-#pragma once
-
-#include <cstdint>
-
-namespace md5 {
-
-constexpr uint32_t MD5_A = 0x67452301;
-constexpr uint32_t MD5_B = 0xefcdab89;
-constexpr uint32_t MD5_C = 0x98badcfe;
-constexpr uint32_t MD5_D = 0x10325476;
-
-struct md5_ctx {
-    uint32_t A = MD5_A;
-    uint32_t B = MD5_B;
-    uint32_t C = MD5_C;
-    uint32_t D = MD5_D;
-    uint64_t size = 0;
-};
-
-/// Reset md5 ctx with algorithm constants.
-void md5_reset(md5_ctx *ctx);
-
-/// Update md5 ctx with specified data, note that `len` is a multiple of 64.
-void md5_update(md5_ctx *ctx, const void *buffer, uint64_t len);
-
-/// Update and end the md5 hash with the specified data, the value of `len` has no limit.
-void md5_final(md5_ctx *ctx, const void *buffer, uint64_t len);
-
-} // namespace md5
diff --git a/src/md5.h b/src/md5.h
new file mode 100644
index 0000000..62e786f
--- /dev/null
+++ b/src/md5.h
@@ -0,0 +1,40 @@
+#pragma once
+
+#include <cstdint>
+
+namespace md5 {
+
+class MD5 {
+public:
+    MD5() = default;
+
+public:
+    static constexpr uint32_t MD5_A = 0x67452301;
+    static constexpr uint32_t MD5_B = 0xefcdab89;
+    static constexpr uint32_t MD5_C = 0x98badcfe;
+    static constexpr uint32_t MD5_D = 0x10325476;
+
+    struct md5_ctx {
+        uint32_t A = MD5_A;
+        uint32_t B = MD5_B;
+        uint32_t C = MD5_C;
+        uint32_t D = MD5_D;
+        uint64_t size = 0;
+    };
+
+    /// Reset md5 ctx with algorithm constants.
+    static void md5_reset(md5_ctx *ctx);
+
+    /// Update md5 ctx with specified data, note that `len` is a multiple of 64.
+    static void md5_update(md5_ctx *ctx, const void *buffer, uint64_t len);
+
+    /// Update and end the md5 hash with the specified data, the value of `len` has no limit.
+    static void md5_final(md5_ctx *ctx, const void *buffer, uint64_t len);
+
+private:
+    md5_ctx ctx_;
+    char buffer_[64] = {};
+    char buffer_size_ = 0;
+};
+
+} // namespace md5
diff --git a/md5_core.cc b/src/md5_core.cc
similarity index 94%
rename from md5_core.cc
rename to src/md5_core.cc
index 35cb60c..05f8e61 100644
--- a/md5_core.cc
+++ b/src/md5_core.cc
@@ -1,5 +1,6 @@
 #include <cstring>
-#include "md5_core.h"
+
+#include "md5.h"
 #include "md5_math.h"
 
 #define RA A, B, C, D
@@ -58,7 +59,7 @@ consteval uint32_t T(int index) { // index -> [0, 64)
     return static_cast<uint32_t>(std::abs(val) * 0x100000000);
 }
 
-void md5_reset(md5_ctx *ctx) {
+void MD5::md5_reset(md5_ctx *ctx) {
     ctx->A = MD5_A;
     ctx->B = MD5_B;
     ctx->C = MD5_C;
@@ -66,7 +67,7 @@ void md5_reset(md5_ctx *ctx) {
     ctx->size = 0;
 }
 
-void md5_update(md5_ctx *ctx, const void *data, uint64_t len) {
+void MD5::md5_update(md5_ctx *ctx, const void *data, uint64_t len) {
     auto *block = reinterpret_cast<const uint32_t *>(data);
     auto *limit = block + (len >> 2);
     auto A = ctx->A;
@@ -97,7 +98,7 @@ void md5_update(md5_ctx *ctx, const void *data, uint64_t len) {
     ctx->size += len; // processed size in byte
 }
 
-void md5_final(md5_ctx *ctx, const void *data, uint64_t len) {
+void MD5::md5_final(md5_ctx *ctx, const void *data, uint64_t len) {
     if (len >= 120) { // len -> [64 + 56, INF)
         auto size = len & ~(uint64_t)0b111111;
         md5_update(ctx, data, size);
diff --git a/md5_math.h b/src/md5_math.h
similarity index 100%
rename from md5_math.h
rename to src/md5_math.h
diff --git a/main.cc b/test/md5_update.cc
similarity index 75%
rename from main.cc
rename to test/md5_update.cc
index 3a010d1..f99b626 100644
--- a/main.cc
+++ b/test/md5_update.cc
@@ -1,6 +1,6 @@
-#include <iostream>
+#include <gtest/gtest.h>
 
-#include "md5_core.h"
+#include "md5.h"
 
 std::string test_data() {
     char data[64];
@@ -10,7 +10,7 @@ std::string test_data() {
     return {data, data + 64};
 }
 
-void dump_ctx(const md5::md5_ctx *c) {
+void dump_ctx(const md5::MD5::md5_ctx *c) {
     std::cout << std::hex << c->A << std::endl;
     std::cout << std::hex << c->B << std::endl;
     std::cout << std::hex << c->C << std::endl;
@@ -18,10 +18,10 @@ void dump_ctx(const md5::md5_ctx *c) {
     std::cout << std::dec << c->size << std::endl;
 }
 
-int main() {
+TEST(md5sum, main) {
     auto data = test_data() + test_data() + test_data() + test_data();
 
-    md5::md5_ctx c;
+    md5::MD5::md5_ctx c;
     dump_ctx(&c);
 
     // md5::md5_update(&c, data.c_str(), data.size());
@@ -33,10 +33,11 @@ int main() {
     // md5::md5_update(&c, data.c_str(), data.size());
     // dump_ctx(&c);
 
-    md5::md5_final(&c, data.c_str(), 0);
+    md5::MD5::md5_final(&c, data.c_str(), 0);
     dump_ctx(&c);
 
-    md5::md5_reset(&c);
-    md5::md5_final(&c, data.c_str(), data.size());
+    md5::MD5::md5_reset(&c);
+    md5::MD5::md5_final(&c, data.c_str(), data.size());
     dump_ctx(&c);
+
 }
diff --git a/third_party/ThirdParty.cmake b/third_party/ThirdParty.cmake
new file mode 100644
index 0000000..8356d91
--- /dev/null
+++ b/third_party/ThirdParty.cmake
@@ -0,0 +1,10 @@
+if (MD5_ENABLE_TESTING)
+    add_subdirectory(third_party/googletest/ EXCLUDE_FROM_ALL)
+endif()
+
+if (MD5_ENABLE_BENCHMARK)
+    set(BENCHMARK_ENABLE_LTO ON)
+    set(BENCHMARK_ENABLE_TESTING OFF)
+    set(BENCHMARK_ENABLE_EXCEPTIONS OFF)
+    add_subdirectory(third_party/benchmark/ EXCLUDE_FROM_ALL)
+endif()
diff --git a/third_party/benchmark b/third_party/benchmark
new file mode 160000
index 0000000..3441176
--- /dev/null
+++ b/third_party/benchmark
@@ -0,0 +1 @@
+Subproject commit 344117638c8ff7e239044fd0fa7085839fc03021
diff --git a/third_party/googletest b/third_party/googletest
new file mode 160000
index 0000000..f8d7d77
--- /dev/null
+++ b/third_party/googletest
@@ -0,0 +1 @@
+Subproject commit f8d7d77c06936315286eb55f8de22cd23c188571