golang Golang Snippet - 使用不安全指针进行切片变异

Posted 2021-05-24

package main

import (
	"fmt"
	"unsafe"
)

type X struct {
	i int
}

var slice = []X{
	X{i: 1},X{i: 2},X{i: 3},
}

const (
	limit = 10
)

func main() {
	start := unsafe.Pointer(&slice[0])
	size := unsafe.Sizeof(slice[0])
	for i := 0 ; i<len(slice) ; i++  {	
	p := (*X)(unsafe.Pointer(uintptr(start) + size*uintptr(i)))
	(*X)(p).i += 10
	fmt.Printf("Slice item ptr=%p | value=%d\n", p, *p)
	}
	fmt.Printf("Result: %v\n", slice)
}

golang 来自https://www.oschina.net/code/snippet_197499_22376

package main
 
import (
    "fmt"
    "io/ioutil"
    "os/exec"
    "time"
)
 
func run() {
    cmd := exec.Command("/bin/sh", "-c", "ping 127.0.0.1")
    _, err := cmd.Output()
    if err != nil {
        panic(err.Error())
    }
 
    if err := cmd.Start(); err != nil {
        panic(err.Error())
    }
 
    if err := cmd.Wait(); err != nil {
        panic(err.Error())
    }
}
 
func main() {
    go run()
    time.Sleep(1e9)
 
    cmd := exec.Command("/bin/sh", "-c", `ps -ef | grep -v "grep" | grep "ping"`)
    stdout, err := cmd.StdoutPipe()
    if err != nil {
        fmt.Println("StdoutPipe: " + err.Error())
        return
    }
 
    stderr, err := cmd.StderrPipe()
    if err != nil {
        fmt.Println("StderrPipe: ", err.Error())
        return
    }
 
    if err := cmd.Start(); err != nil {
        fmt.Println("Start: ", err.Error())
        return
    }
 
    bytesErr, err := ioutil.ReadAll(stderr)
    if err != nil {
        fmt.Println("ReadAll stderr: ", err.Error())
        return
    }
 
    if len(bytesErr) != 0 {
        fmt.Printf("stderr is not nil: %s", bytesErr)
        return
    }
 
    bytes, err := ioutil.ReadAll(stdout)
    if err != nil {
        fmt.Println("ReadAll stdout: ", err.Error())
        return
    }
 
    if err := cmd.Wait(); err != nil {
        fmt.Println("Wait: ", err.Error())
        return
    }
 
    fmt.Printf("stdout: %s", bytes)
}
 
// 运行命令: go run main.go