add dev docs

llvmpy/README

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-# README
-
-This is a reimplementation of the LLVM binding, aiming to provide a more familiar interface to the C++ API whenever possible.
-
-The implementation uses a custom DSL in python to describe the interface (under binding directory). The DSL serves as input to *gen.py* for generation of the .cpp and .py files for the actual binding.

llvmpy/README.md

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+# README
+
+This is a reimplementation of the LLVM binding, aiming to provide a more 
+familiar interface to the C++ API whenever possible.
+
+The implementation uses a custom DSL in python to describe the interface. 
+The DSL serves as input to *gen/gen.py* for generation of the .cpp and .py files 
+for the actual binding.
+
+# How to Add New Class
+
+Let's use the `llvm::Module` as an example because it should be one of the most
+familiar class in LLVM.
+
+Reference code in https://github.com/llvmpy/llvmpy/blob/master/llvmpy/src/Module.py
+and see LLVM documentation at http://llvm.org/docs/doxygen/html/classllvm_1_1Module.html
+
+1) Import binding helpers
+
+```python
+from binding import *
+# Yes, it is bad practice to import star.
+# I will fix it one day.
+```
+
+2) Import LLVM namespace
+
+```python
+from .namespace import llvm
+```
+
+3) Declare the class
+
+```python
+Module = llvm.Class()
+```
+
+4) Import all the dependencies for the definition
+
+5) Define the class
+
+```python
+@Module
+class Module:
+    ...
+```
+
+## Inside the definition...
+
+5.1) Use the ``_include_`` attribute to add include files.
+
+5.2) Use ``Enum`` to create an enumerator type.
+
+5.3) Make constructor 
+
+Not every class needs to have a binding for the constructor.
+Only add things that will be used.
+
+```python
+new = Constructor(cast(str, StringRef), ref(LLVMContext))
+```
+
+The constructor must be named as "new".
+
+The args to ``Constructor`` are parameters of the signature.
+The first parameter means cast Python string to a StringRef.
+The second parameter means pass LLVMContext object as a value reference.
+
+5.4) Make destructor
+
+Not every class needs to have a binding for the destructor.
+Only add things that will be used.
+If it is always owned by another object, it usually does not need to have one.
+
+```python
+delete = Destructor()
+```
+
+The destructor must be named as "delete".
+
+5.5) Add Simple Methods
+
+```python
+getFunction = Method(ptr(Function), cast(str, StringRef))
+```
+
+The first arg is the return type: a ponter to Function.
+The rest of the args are for the parameters.
+
+Note: ``cast(fromtype, totype)`` can be used as return-type as well.
+In that case, the ``fromtype`` will usually refer to a LLVM object
+and the ``totype`` will refer to the Python object.
+
+5.6) Add custom methods defined in C++
+
+The ``list_functions`` is created as a ``CustomMethod``.
+
+```python
+list_functions = CustomMethod('Module_list_functions', PyObjectPtr)
+```
+
+The first arg is the name that appears in C++.
+The second argument is the return-type.
+The rest of the arguments are parameters.
+
+The definition of ``Module_list_functions`` is located in 
+"include/llvm_binding/extra.h".
+
+5.7) Add custom python method
+
+One can also add custom methods in Python, e.g. ``__str__``.
+
+```python
+@CustomPythonMethod
+def __str__(self):
+    from llvmpy import extra
+    os = extra.make_raw_ostream_for_printing()
+    self.print_(os, None)
+    return os.str()
+```
+
+The body of ``__str__`` is directly copied to the Python output file.
+Thus, it can't reference to anything in current file scope.
+
+# Static Methods
+
+``StaticMethod`` https://github.com/llvmpy/llvmpy/blob/master/llvmpy/src/PassRegistry.py
+
+``CustomStaticMethod`` https://github.com/llvmpy/llvmpy/blob/master/llvmpy/src/Support/TargetRegistry.py
+
+
+# Namespace
+
+``Namespace`` https://github.com/llvmpy/llvmpy/blob/master/llvmpy/src/Support/CodeGen.py
+
+# Functions
+
+``Function`` https://github.com/llvmpy/llvmpy/blob/master/llvmpy/src/Assembly/Parser.py
+
+``CustomFunction`` https://github.com/llvmpy/llvmpy/blob/master/llvmpy/src/Bitcode/ReaderWriter.py
+
+
+
+
+
+# Other Things from the binding.py
+
+https://github.com/llvmpy/llvmpy/blob/master/llvmpy/gen/binding.py
+
+The list of C++ types: https://github.com/llvmpy/llvmpy/blob/master/llvmpy/gen/binding.py#L218
+