forked from ardanlabs/gotraining
-
Notifications
You must be signed in to change notification settings - Fork 0
/
example1.go
48 lines (36 loc) · 1.06 KB
/
example1.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
// All material is licensed under the Apache License Version 2.0, January 2004
// http://www.apache.org/licenses/LICENSE-2.0
// http://play.golang.org/p/IIubKW34GA
// Sample program to show how the backing array for a referene type can
// be placed contiguous in memory with the header value. Must be run locally
// and not in the playground.
package main
import (
"fmt"
"unsafe"
)
func main() {
bs := []byte("HELLO")
s := string(bs)
// Capture the address to the slice structure
address := unsafe.Pointer(&s)
// Capture the address where the length
lenAddr := uintptr(address) + uintptr(8)
// Create pointers to the length
lenPtr := (*int)(unsafe.Pointer(lenAddr))
// Create a pointer to the underlying array
arrPtr := (*[5]byte)(unsafe.Pointer(*(*uintptr)(address)))
fmt.Printf("String Addr[%p] Len Addr[0x%x] Arr Addr[%p]\n",
address,
lenAddr,
arrPtr)
fmt.Printf("String Length[%d]\n",
*lenPtr)
for index := 0; index < *lenPtr; index++ {
fmt.Printf("[%d] %p %c\n",
index,
&(*arrPtr)[index],
(*arrPtr)[index])
}
fmt.Printf("\n\n")
}