book

Creating Solid APIs with Lua

by Tyler Neylon

February 2017

Intermediate to advanced

133 pages

2h 43m

English

O'Reilly Media, Inc.

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Acknowledgments
An Overview of the C/Lua InterfaceAn Example: EatyGuyGetting the Lua SourceIf You’re Using macOS or Linux…If You’re Using Windows…This Book’s GitHub RepoRunning a Lua Script from CLua Modules and Loading Them from CDrawing MazesOne Way to Call a Lua Function from CStack IndexesGiving Lua the Power of C
EatyGuy Version 1: A Lua-Callable C FunctionThe tput Shell CommandThe Core Mechanics of Lua-Callable C FunctionsEatyGuy Version 2: Adding an Animated PlayerStrings and Multiple Arguments with set_color() and set_pos()Sending a Return Value from C to Lua by Using timestamp()Fancier Maze DrawingStarting, Stopping, and Sharing Functions with LuaGame State and Lua’s Event LoopUpdating Player StateDrawing the Player StateCalling Lua Functions from C More Effectively
EatyGuy Version 3: Passing Data to a Lua FunctionReceiving Arrow Key PressesEatyGuy Version 4: Implementing API Functions Within LuaFixing the tput BottleneckEatyGuy Version 5: Working with Lua Tables from CWhere Tables LiveThe Primary Table FunctionsUsing a Table to Send Game State to LuaAdding Some Class to Your API
EatyGuy Version 6: Writing a Class in LuaA Common Code Pattern for Lua ClassesThe Character Class ExampleEatyGuy Version 7: Class InheritanceSubclasses in LuaThe Baddy ClassEatyGuy Version 8: Introducing the userdata TypeWriting a Lua-Loadable Module in CImplementing a Class-Like userdata TypeIntegrating a C Module into Your APIMaking Your Code Debug-Friendly
Throwing and Catching Errors in LuaWhen Should You Throw an Exception?Don’t Panic!Lua Errors in CHow lua_pcall() Handles ErrorsTurtles All the Way DownGetting Strict About Globals and TyposThe Environment of Freshly Loaded ChunksA Version of strict.luaEatyGuy Version 9: Death, StrictlyA Brief but Quickly Dismissed Question of Morality
EatyGuy Version 10: The Baddy Construction KitThe Code of Scum and VillainyScripts Gone WildControlling Library AccessManaging Memory UseManaging CPU UseEnd == Nigh

Content preview from Creating Solid APIs with Lua

Chapter 1. Running a Lua Script from C

In the first part of this book, the focus is on understanding the data and control flows between Lua and C. After those ideas have been established, we’ll be ready to tackle security in the second part, which begins with Chapter 5.

An Overview of the C/Lua Interface

Many programming languages are distributed in the form of a language-specific compiler or interpreter. Lua, on the other hand, is essentially distributed as a C API. Many users interact with Lua by using the official interpreter, but even this interpreter is built on top of the C API, without any special access to the language’s implementation. In other words, Lua is not only written in C; it is also written to be used from C.

Lua’s C API can create or destroy entire runtime environments, which are referred to as Lua states. A Lua state is a C pointer to an opaque data structure. This structure knows everything about a running Lua environment, including all global values, closures, coroutines, and loaded modules. Virtually every function in Lua’s C API accepts a Lua state as its first parameter.

Because Lua states are opaque structures, we need to use API functions to access the Lua values stored within a state. To this end, every Lua state has a Lua stack, which is a container for Lua values such as Lua strings or tables. You can think of the Lua stack as a window into the set of Lua values currently relevant to your C code. We’ll dive into all the relevant details of this stack ...