API_LOADINFO.md

LoadInfo : Loading Classes, Categories, Strings

Classes, categories, static strings are all added with the same function mulle_objc_loadinfo_enqueue_nofail. Usually the compiler produces these calls automatically for you.

Functions

mulle_objc_loadinfo_enqueue_nofail

void   mulle_objc_loadinfo_enqueue_nofail( struct _mulle_objc_loadinfo *info)

Take info and queue the contained classes, categories, strings up for inclusion into the runtime. If the base class of a class or category is already present, it will be added immediately to the runtime. Otherwise the inclusion will be delayed until the base class appears.

The unfailing in mulle_objc_loadinfo_enqueue_nofail indicates, that the function will throw an exception or abort, if the runtime is not properly setup or if it detects errors in info.

This information is usually created by the compiler, but if you want to add a class at runtime, you would also do it via mulle_objc_loadinfo_enqueue_nofail.

Checkout demo1.c for a fairly well documented example, how to do this.

mulle_objc_loadinfo_enqueue_nofail will treat the contents of _mulle_objc_loadinfo as if they are in read only memory, with all its implications, with respect to lifetime and mutability.

Calculating the various ids

The various needed ids are simply calculated by using the mulle_objc_uniqueid_from_string on the name of the desired entity. Usually the compiler will do all this for you.

Example:

	mulle_objc_uniqueid_t   hash;

	hash = mulle_objc_uniqueid_from_string( "Foo");
	printf( "%s : "%08lx\n", "Foo", hash);

There is also a standalone tool called mulle-objc-uniqueid that can do this for you:

$ mulle-objc-uniqueid Foo
40413ff3

Calculating the class ivarhash

Probably only interesting to compiler writers.

The ivarhash is the concatenation of the name and the signature, separated by ':' of each instance variable in order of offsetof of a class hierarchy. Each item is separated by ','.

Example:

@interface Foo
{
	id     a;
	double b;
}
@end

The string to hash is "a" ":" @encode(id) "," "b" ":" @encode(double). That boils down to "a:@,b:d". The FNV1-32 hash is then 0x941dbdbc. Now lets add a subclass:

@interface Bar : Foo
{
	id   c;
}

The inherited string to hash from Foo is "a:@,b:d". Bar adds "c" ":" @encode(id), which makes the complete string a:@,b:d,c:@. The ivarhash for Bar is then 0x2fb45c51.