Sizeof tip for Go types

Just a small tip to check yourself when organizing structs.

import . "unsafe"

Fixed sizes

Type	Sizeof() bytes
struct{}	0
[0]Type	0
bool	1
int8, uint8, byte	1
int16, uint16	2
int32, uint32, rune	4
float32	4
int, uint	4 or 8
int64, uint64	8
float64	8
complex64	8
uintptr	8
*struct{}, *Type	8
map[Type1]Type2	8
chan Type	8
func()	8
string	16
complex128	16
[]Type	24

Array

Formula: Sizeof([N]Type) = N * Sizeof(Type)

Examples:

Type	Sizeof() bytes
[5]bool	5
[2][]bool{}	48

Struct

Struct size depends on how struct is packed.

Formula:
Sizeof(struct{T1; ... TN}) = StructPackSize * PacksNum,
where StructPackSize = min(max(Sizeof(T1), ... Sizeof(TN)), Sizeof(uintptr))
and PacksNum depends on how struct fields are packed due to their order.

Examples:

Type	StructPackSize	PacksNum	Sizeof() bytes
struct{a struct{}}	0	1	0
struct{a struct{}; b bool}	1	1	1
struct{b bool; u int32}	4	2	8
struct{a bool; b bool; u int32}	4	2	8
struct{u int32; a bool; b bool}	4	2	8
struct{a bool; u int32; b bool}	4	3	12
struct{a bool; s string; b bool}	8	4	32