go-sizeof-tip
go-sizeof-tip copied to clipboard
Published
20 hours ago •
tyranron
tyranron
Sizeof tip for Go types.
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 |
tyranron