API Types

Architecture Independent API Types

API Type	.NET Type	Where defined?	Comment
haddr_t	System.UInt64	H5public.h
hbool_t	System.UInt32	H5public.h
herr_t	System.Int32	H5public.h
hid_t	System.Int[32,64]	H5Ipublic.h	32-bit in HDF5 1.8, 64-bit in HDF5 1.10
hsize_t	System.UInt64	H5public.h
hssize_t	System.Int64	H5public.h
htri_t	System.Int32	H5public.h

Architecture Dependent API Types

API Type	.NET Type	Where defined?
size_t	System.IntPtr	C-header files, e.g., stddef.h, stdlib.h, etc.
ssize_t	System.IntPtr	H5public.h

Strictly speaking, ssize_t is the signed version of size_t, and would be System.Int32 or System.Int64 on 32-bit or 64-bit architectures, respectively. In order to support AnyCPU builds, representing both as System.IntPtr seems to be worth the inconvenience of having to convert pointers to integers. (And the number of API calls with ssize_t arguments or returns is rather small.)