In LuaJIT's FFI, ctype objects carry C data structures and functions. Unfortunately, while there are several functions to handle and compose ctype objects, there's very little introspection capabilities. This library inspects the information provided by ffi.typeinfo() to recreate useful descriptions of ctype objects, as Lua tables, C declarations and GraphViz diagrams.

It's a single Lua file, just put it anywhere in your $LUA_PATH.

MIT licensed, like the Lua and LuaJIT languages/implementations

Returns a table tree describing the given type. Some of the fields appear only on appropriate types. Most interesting fields include:

• type a label ('num', 'union', 'struct', 'ptr', 'complex', 'array', 'void', 'enum', 'function', 'typedef', 'field', 'bitfield', 'const', 'keyword'), hopefully useful to traverse the tree.
• name if available.
• c a reconstructed C definition.
• size data size in bytes.
• fields (in union, struct, enum and functions) array of descriptions of elements or arguments.
• subtype a "content" type description. For arrays, pointers and typedefs it's the description of the inner type; for functions it's the description of the return type.

Creates a diagram of the whole type structure in the 'dot' language, to be processed by GraphViz utilities. The optional horizgroups flag makes the elements joined by 'sib' links to align horizonally. I find it much easier to understand, but works only for relatively simple structures, complex graphs get hopelessly mangled. For the general case, leave the flag out; the resultant graph is much more vertical but should be far cleaner.