diff --git a/.gitignore b/.gitignore
index c6127b3..4d3ceeb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,3 +50,5 @@ modules.order
 Module.symvers
 Mkfile.old
 dkms.conf
+
+build
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..f744169
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,13 @@
+cmake_minimum_required(VERSION 3.0.0)
+project(simple-protobuf)
+
+include(TestBigEndian)
+test_big_endian(isBigEndian)
+if (${isBigEndian})
+    add_library(spb SHARED protobuf_be.c)
+else()
+    add_library(spb SHARED protobuf_le.c)
+endif()
+
+add_executable(test test.c)
+target_link_libraries(test spb)
\ No newline at end of file
diff --git a/README.md b/README.md
index 3411da6..88e5221 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,41 @@
 # simple-protobuf
-A subset of Google's ProtoBuf.
+
+English | [简体中文](README_ZH.md)
+
+A simplified variant of Google's ProtoBuf.
+
+# format
+A simple-protobuf file can be filled into a C struct directly, but no pointer is supported.
+
+The sp file format is shown below.
+
+```bash
+[struct_len] + n*[[type][data_len][data]]
+```
+
+1. `type` is an one-byte number indicating the type length(2^type^bytes) of this struct item.
+2. `*_len` is a length-variable LE number(less than 2^57^) indicating the length of `*`.
+3. `data` contains `data_len` bytes of the data.
+
+# usage
+You can read `test.c` to find out the detailed usage.
+
+## Save a struct
+### 1. Create items type info array
+
+This array has type `uint8_t`, which indicates the length of each struct item. Note that the length of each item must be 2^n^.
+
+### 2. Align items type info array
+
+You can use function `align_struct` to align each item to the proper size.
+
+If you are sure that your struct has been aligned, you won't need to run `align_struct`.
+
+### 3. Call set_pb to save
+
+
+## Read into a struct
+
+### 1. Open file
+
+### 2. Call get_pb to read
\ No newline at end of file
diff --git a/README_ZH.md b/README_ZH.md
new file mode 100644
index 0000000..f99fc15
--- /dev/null
+++ b/README_ZH.md
@@ -0,0 +1,37 @@
+# simple-protobuf
+
+[English](README.md) | 简体中文
+
+Google ProtoBuf的简化变体。
+
+# 数据格式
+本程序生成的文件与C结构体一一映射，但该结构体不可包含指针，具体如下所示。
+
+```bash
+[struct_len] + n*[[type][data_len][data]]
+```
+
+1. `type` 指明该项的类型，亦即其在结构体中实际占用的空间的对数。
+2. `*_len` 是一个小于 2^57^ 的变长数字。
+3. `data` 是 `data_len` 长度的数据。
+
+# 用法
+比较简单，详见`test.c`。
+
+## 保存结构体
+### 1. 创建 items_type 数组
+
+是结构体所有项的`type`组成的数组。
+
+### 2. 类型对齐
+
+接下来需要用`align_struct`进行对齐。如果您已经将数组对齐或结构体本身是对齐的，则无需此步骤。
+
+### 3. 调用 set_pb 保存
+
+
+## 读入结构体
+
+### 1. 打开文件
+
+### 2. 调用 get_pb 读取
diff --git a/protobuf_le.c b/protobuf_le.c
new file mode 100644
index 0000000..c8e0b83
--- /dev/null
+++ b/protobuf_le.c
@@ -0,0 +1,75 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "simple_protobuf.h"
+
+//#define DEBUG
+
+static uint64_t read_num(FILE* fp) {
+    uint8_t c;
+    uint64_t n = 0;
+    uint8_t i = 0;
+    do {
+        c = fgetc(fp);
+        n |= (c & 0x7f) << (7 * i++);
+    } while(c & 0x80);
+    return n;
+}
+
+static int write_num(FILE* fp, uint64_t n) {
+    char* c = (char*)(&n);
+    int i = 0;
+    while(*c) {
+        int ch = *c & 0x7f;
+        if(c[1]) ch |= 0x80;
+        fputc(ch, fp);
+        n >>= 7;
+        i++;
+    }
+    return i;
+}
+
+SIMPLE_PB* get_pb(FILE* fp) {
+    uint64_t struct_len = read_num(fp);
+    if(struct_len > 1) {
+        SIMPLE_PB* spb = malloc(struct_len + sizeof(uint64_t));
+        #ifdef DEBUG
+            printf("Malloc %llu + %lu bytes.\n", struct_len, sizeof(uint64_t));
+        #endif
+        if(spb) {
+            spb->len = struct_len;
+            char* p = spb->target;
+            char* end = p + struct_len;
+            memset(p, 0, struct_len);
+            while(p < end) {
+                uint64_t offset = 1u << fgetc(fp);
+                uint64_t data_len = read_num(fp);
+                #ifdef DEBUG
+                    printf("Offset: %llu, data_len: %llu.\n", offset, data_len);
+                #endif
+                fread(p, data_len, 1, fp);
+                p += offset;
+            }
+            return spb;
+        }
+    }
+    return NULL;
+}
+
+int set_pb(FILE* fp, uint8_t* items_type, uint64_t struct_len, void* target) {
+    uint64_t offset = 0;
+    uint32_t i = 0;
+    char* p = (char*)target;
+    write_num(fp, struct_len);
+    while(offset < struct_len) {
+        uint8_t type = items_type[i++];
+        uint64_t data_len = 1u << type;
+        fputc(type, fp);
+        char* this = p + offset;
+        offset += data_len;
+        if(data_len > 1) while(!this[data_len - 1]) data_len--;
+        write_num(fp, data_len);
+        fwrite(this, data_len, 1, fp);
+    }
+    return i;
+}
\ No newline at end of file
diff --git a/simple_protobuf.h b/simple_protobuf.h
new file mode 100644
index 0000000..851eff9
--- /dev/null
+++ b/simple_protobuf.h
@@ -0,0 +1,43 @@
+#ifndef _SIMPLE_PROTOBUF_H_
+#define _SIMPLE_PROTOBUF_H_
+
+#include <stdint.h>
+
+struct SIMPLE_PB {
+    uint64_t len;
+    char target[];
+};
+typedef struct SIMPLE_PB SIMPLE_PB;
+
+SIMPLE_PB* get_pb(FILE* fp);
+int set_pb(FILE* fp, uint8_t* items_type, uint64_t struct_len, void* target);
+
+uint8_t first_set(uint64_t n) {
+    uint8_t i = 0;
+    while(!(n & 1)) {
+        n >>= 1;
+        i++;
+    }
+    return i;
+}
+
+void align_struct(uint8_t* items_type, uint64_t items_cnt, uint64_t struct_size) {
+    uint64_t sum = 0;
+    uint64_t min_cnt = 0;
+    uint8_t min = 255;
+    for(uint64_t i = 0; i < items_cnt; i++) {
+        sum += 1u << items_type[i];
+        if(min > items_type[i]) min = items_type[i];
+    }
+    while(sum < struct_size) {
+        uint8_t new_min = 255;
+        sum = 0;
+        for(uint64_t i = 0; i < items_cnt; i++) {
+            if(items_type[i] == min) items_type[i]++;
+            if(new_min > items_type[i]) new_min = items_type[i];
+            sum += 1u << items_type[i];
+        }
+    }
+}
+
+#endif
\ No newline at end of file
diff --git a/test.c b/test.c
new file mode 100644
index 0000000..1d65574
--- /dev/null
+++ b/test.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <string.h>
+#include "simple_protobuf.h"
+
+struct TEST {
+    uint8_t a;
+    uint16_t b;
+    uint32_t c;
+    uint64_t d;
+    char e[256];
+};
+
+struct TEST t;
+uint64_t items_len[5] = {sizeof(t.a), sizeof(t.b), sizeof(t.c), sizeof(t.d), sizeof(t.e)};
+uint8_t types_len[5];
+
+int main() {
+    t.a = 0xAB;
+    t.b = 63345;
+    t.c = 1234567890;
+    t.d = 1234567898765435432ULL;
+    strcpy(t.e, "Hello world! This is a message from simple protobuf.");
+    for(int i = 0; i < 5; i++) {
+        types_len[i] = first_set(items_len[i]);
+        printf("Item %d has type %d with size %llu\n", i, types_len[i], items_len[i]);
+    }
+    align_struct(types_len, 5, sizeof(struct TEST));
+    for(int i = 0; i < 5; i++) {
+        printf("Item %d's type after align: %u\n", i, types_len[i]);
+    }
+    FILE* fp = fopen("test.sp", "wb");
+    if(fp) {
+        set_pb(fp, types_len, sizeof(struct TEST), &t);
+        memset(&t, 0, sizeof(struct TEST));
+        fclose(fp);
+        puts("Write file succeed.");
+        fp = NULL;
+        fp = fopen("test.sp", "rb");
+        if(fp) {
+            SIMPLE_PB* spb = get_pb(fp);
+            memcpy(&t, spb->target, sizeof(struct TEST));
+            printf("a:%u\nb:%u\nc:%u\nd:%llu\ne:%s\n", t.a, t.b, t.c, t.d, t.e);
+        } else perror("[SPB]");
+    } else perror("[SPB]");
+}
\ No newline at end of file