A light weight component library
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README

Author: Gaetan Guidet - gatgui@gmail.com

What's lwc?
-----------

lwc stands for "Light Weight Component"


Why lwc?
--------



What's implemented so far?
--------------------------

The base library implements the base introspection and call system and the registry
from which you can create new objects.
Python, Ruby and LUA bridges.
A bridge is the set of the base library wrapper and a component loader for that language
The component loader is in charge of creating component written in that language so they
can be used in any other supported language.

  
How to use lwc?
---------------
  
  * Initialization:
  
    C++:
      lwc::Registry *reg = lwc::Registry::Initialize();
    
    Python:
      import lwcpy
      reg = lwcpy.Initialize()
    
    Ruby:
      require "RLWC"
      reg = RLWC.Initialize()
    
    LUA:
      require "llwc"
      reg = llwc.Initialize()
  
  * Add directories to look component loaders for (language support):
  
    C++:
      reg->addLoaderPath("./components/loaders")
    
    Python/Ruby:
      reg.addLoaderPath("./components/loaders")
    
    LUA:
      reg:addLoaderPath("./components/loaders")
  
  * Add directories to look modules for (modules are a set of objects that can be instanciated via the registry)
  
    C++:
      reg->addModulePath("./components/modules")
    
    Python/Ruby:
      reg.addModulePath("./components/modules")
    
    LUA:
      reg:addModulePath("./components/modules")
  
  * Check available types:
  
    C++:  
      size_t n = reg->numTypes();
      const char *tn = reg->getTypeName(0);
      reg->hasType("myType");
  
    Python/Ruby:
      n = reg.numTypes()
      tn = reg.getTypeName(0)
      reg.hasType("myType")
    
    LUA:
      n = reg:numTypes()
      tn = reg:getTypeName(0)
      reg:hasType("myType")
      
  * Creating and destroying objects:
  
    C++:
      lwc::Object *obj = reg->create("myType");
      reg->destroy(obj);
    
    Python/Ruby:
      obj = reg.create("myType")
      reg.destroy(obj)
    
    LUA:
      obj = reg:create("myType")
      reg:destroy(obj)
  
  * Calling objects method:
  
    Limitation:
      Objects method can have no more that 16 arguments
      This is an implementation issue. At the time being, i use template class and methods
        to do the type checking.
    
    C++:
      obj->call("methodName", arg0, arg1, ...);
    
    Python/Ruby:
      obj.methodName(arg0, arg1, ...)
    
    LUA:
      obj:methodName(arg0, arg1, ...)
  
  * Cleanup:
  
    C++:
      lwc::Registry::DeInitialize();
    
    Python:
      lwcpy.DeInitialize()
    
    Ruby:
      RLWC.DeInitialize()
    
    LUA:
      llwc.DeInitialize()
  
  How to create Modules:
    
    But first, some details on methods' description...
    
    in C++:
      This is by far the most annoying language to write components in.
      
      You need first to create subclass of lwc::Object for each of your types
      
      Then you'all have to create factory objects (either one for each of your types,
      or a single one, whichever you prefer)
      
      Define the module functions required by the C loader
      
      > simple.cpp
      
      
    in Ruby:
      Create a file name <modulename>.rb
      
      The file must contain a real Ruby module named after the file (with first letter
        uppercased [this is a ruby requirement for module names])
      
      For each of the components you want to put in that module, define a new sub-class
        of RWLC::Object, and add a class constant named "Methods" to contain the description
        of all the methods you want to expose.
      
      Define the module functions required by the ruby loader 
        LWC_ModuleGetTypeCount()
        LWC_ModuleGetTypeName(idx)
        LWC_ModuleGetTypeClass(idx)
        
      > simple.rb
      
      require "RLWC"
      
      module Simple
        
        class Test < RWLC::Object
          
          Methods = {
            :doSomething0 => [[RWLC::AD_IN, RWLC::AT_STRING], [RWLC::AD_RETURN, RWLC::AT_INT]],
            :doSomething1 => [[RWLC::AD_RETURN, RWLC::AT_INT]]
          }
          
          def initialize()
            super()
            @longDict = {}
          end
          
          def doSomething0(key)
            if not @longDict.has_key?(key) then
              raise "Invalid key"
            end
            return @longDict[key]
          end
          
          def doSomething1()
            return @longDict.size
          end
          
        end
        
        
        def self.LWC_ModuleGetTypeCount()
          return 1
        end
        
        def self.LWC_ModuleGetTypeName(idx)
          return (idx == 0 ? "simple.Test" : nil)
        end
        
        def self.LWC_ModuleGetTypeClass(idx)
          return (idx == 0 ? Simple : nil)
        end
      end
    
    in Python:
      Create a file name <modulename>.py
      
      For each of the components you want to put in that module, define a new sub-class
        of lwcpy.Object, and add a class constant named "Methods" to contain the description
        of all the methods you want to expose.
      
      Define the module functions required by the python loader 
        LWC_ModuleGetTypeCount()
        LWC_ModuleGetTypeName(idx)
        LWC_ModuleGetTypeClass(idx)
      
      > simple.py
      
      import lwcpy
      
      class Test(lwcpy.Object):
          
        Methods = {
          "doSomething0": [(lwcpy.AD_IN, lwcpy.AT_STRING), (lwcpy.AD_RETURN, lwcpy.AT_INT)],
          "doSomething1": [(lwcpy.AD_RETURN, lwcpy.AT_INT)]
        }
        
        def __init__(self):
          lwcpy.Object.__init__(self)
          self.longDict = {}
        
        def doSomething0(self, key):
          if not key in self.longDict:
            raise Exception("Invalid key")
          return self.longDict[key]
        
        def doSomething1(self):
          return len(self.longDict)
        
      
      def LWC_ModuleGetTypeCount():
        return 1
      
      def LWC_ModuleGetTypeName(idx):
        return "simple.Test" if idx == 0 else None
      
      def LWC_ModuleGetTypeClass(idx):
        return Simple if idx == else None
      
    
    in LUA:  
      
      Create a file name <modulename>.lua
      
      Create a new module
      
      For each of the components you want to put in that module, define a new table
        (which will be used as a metatable) and add a member named "Methods" to contain
        the description of all the methods you want to expose.
      
      If your object is to be a direct sub-class of llwc.Object (remember, LUA does not
      have classes, it uses metatables) you'll have to define the __index member in your
      type metatable so that it forwards any non-defined member request to its "lwcobj"
      member obj (this member is set by the loader automatically, the reason why the __index
      event cannot be automatically generated is that it's not necessarily required for every new type)
      
      You also have to define a "new" function to your type tables that returns a new table with its metatable
      set properly
      
      NOTE:
        there is room for improvement in the way the loader handles components
      
      Define the module functions required by the lua loader 
        LWC_ModuleGetTypeCount()
        LWC_ModuleGetTypeName(idx)
        LWC_ModuleGetTypeClass(idx)
      
      > simple.lua
      
      require "llwc"
      
      module(..., package.seeall)
      
      local Test = {}
      
      Test.Methods = {}
      Test.Methods.doSomething0 = {{llwc.AD_IN, llwc.AT_STRING}, {llwc.AD_RETURN, llwc.AT_INT}}
      Test.Methods.doSomething1 = {{llwc.AD_RETURN, llwc.AT_INT}}
      
      Test.__index = function (self, member)
        val = Test[member]
        if val == nil then
          val = self.lwcobj[member]
        end
        return val
      end
      
      Test.new = function ()
        self = {}
        self.lwcobj = nil -- no required, it will be set by the loader if you forget
        self.longDict = {}
        setmetatable(self, Test)
        return self
      end
      
      Test.doSomething0 = function (self, key)
        return self.longDict[key]
      end
      
      Test.doSomething1 = function (self)
        n = 0
        for k,v in pairs(self.longDict) do
          n = n + 1
        end
        return n
      end
      
      
      function LWC_ModuleGetTypeCount()
        return 1
      end
      
      function LWC_ModuleGetTypeName(idx)
        if idx == 1 then
          return "simple.Test"
        else
          return nil
        end
      end
      
      function LWC_ModuleGetTypeClass(idx)
        if idx == 1 then
          return Test
        else
          return nil
        end
      end


ToDo list
---------

* Test suite
* Add support for module constants
* Add support for module functions
x Remove the "const" specifier from the argument declaration
x Embedded the "array" specifier in the type
x Restrict list of types to: boolean, integer, real, string, object
  (in most scripting language, there's no distinction between long, int, short or char.
   Pretty much the same way, no distinction between signed and un-signed. This makes
   things too cryptic anyway, just use long)