You can see Haxe custom annotations here.
Haxe target has some support native classes here: https://github.com/jtransc/jtransc/tree/master/jtransc-rt/resources
short… so they extend
java.lang.Objectand provide useful methods for reading, writting or constructing/deconstructing from/to Haxe primitive types.
HaxeDynamicLoadclass provides some methods for dynamic library loading
HaxeFfiLibraryinterface works as internal interface for FFI loading
HaxeFormatprovides a portable C/Java like String.format.
HaxeIOprovides portable IO utilities for all haxe targets.
N class, provides some utility methods used by the runtime and that can be used by libraries. You can find which methods contains just examining those files.
R class provides an internal class for doing reflection stuff. Since there are potentially tons of calls to this class methods, it has a short name.