Update README.md

Author: phyunsj

README.md

@@ -1 +1,54 @@
-# oncrpc-api-design
+# ONC/RPC API Design
+
+
+- Example 1 [rls](https://github.com/phyunsj/oncrpc-api-design/tree/master/rls) (remote `ls` - original version)
+
+- Example 2 [rls_v2](https://github.com/phyunsj/oncrpc-api-design/tree/master/rls_v2) (revised)
+
+- Example 3 [calc](https://github.com/phyunsj/oncrpc-api-design/tree/master/calc)
+
+## Example 3 calc
+
+**ONCRPC** restricted us to remote procedures that accept a single parameter and return a single parameter. (Might not be true now but stick to this restriction)
+
+Instead of starting with **IDL** (like Example 1 & 2), start wtih **API.h** and generate ONCRPC middle-layer automatically. Keep (or share) the same local implementation between RPC server and RPC client.
+
+
+Similar to non-RPC application, the below files are manaully created. Create RPC middle-layer to integrate the local APIs defined in `cl_calc.h`.
+
+`cl_common.c/h` : RPC Client handler
+`cl_calc.c/h` : functions declaration, definition.
+`cl_client.c` : client main program
+
+**CL** is an imaginary product name for example 3. 
+
+
+1. **cpp** cl_calc.h -o cl_calc.i
+2. **pycparser** to generate AST
+3. AST visitor extracts ***typdef*** & *** fucntion declaration *** out of AST
+4. generate IDL & RPC middle-layer Interface
+
+The following files are generated from `cl_calc.h`
+
+- CL.x (ONCRPC IDL)
+- CL_proc.c (Client Middlelayer)
+- CL_svc_proc.c (Server Middlelayer)
+- CL_proc.h
+
+`CL.x` generates :
+
+- CL.h
+- CL_svc.c
+- CL_clnt.c
+- CL_xdr.c
+
+
+## FYI
+
+### pycparser
+
+Complete C99 parser in pure Python
+
+**pycparser** installation. ( powered by [PLY](https://github.com/dabeaz/ply) )
+
+> pip install --index-url=https://pypi.python.org/simple/ pycparser