Embedding Lua in C Programs

1 The Programming Language Lua
The Lua Interpreter
Syntax and such
Modules
2 Embedding Lua in C Programs
State Manipulation
Calling C from Lua
Calling Lua from C
3 Lua in the NetBSD Kernel
Use Cases
Implementation Overview
Implementation Details

The Programming Language Lua

The Lua Interpreter
Running from C
 int luaL dole(lua State *L, const char *lename)
 int luaL dostring(lua State *L, const char *str)
Syntax and such
Values, Variables, and, Data Types
 Variables have no type
 Values do have a type
 Functions are rst-class values
Tables
 Tables are THE data structure in Lua
 Nice constructor syntax
 Tables make Lua a good DDL
 Metatables can be associated with every object
Lua Table Constructor
Create and initialize a table, access a eld:
mytable = {
name = ‘Marc’,
surname = ‘Balmer’,
email = ‘m@x.org’
}
print(mytable.email)
Modules
Extending Lua Programs
Acess GPIO pins from Lua:
require ‘gpio’
g = gpio.open(‘/dev/gpio0’)
g:write(4, gpio.PIN_HIGH)
g:close()

Embedding Lua in C Programs

State Manipulation
Calling a C Function
 Function has been registered in luaopen module()
 int function(lua State *L)
 Parameters popped from the stack
 Return values pushed on the stack
 Return Nr. of return values
Calling a Lua Function
 Find the function and make sure is *is* a function
 Push parameters on the stack
 Use lua call(lua State *L, int index)
 or lua pcall(lua State *L, int index)
 Pop return values from the stack

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Lua in the NetBSD Kernel (1,37 MO) (Cours PDF)