实现

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