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@leepro
Forked from jedy/reader.go
Created February 28, 2018 18:27
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processes communicate with shared memory in golang
package main
// #include <stdlib.h>
// #include "wrapper.c"
import "C"
import "unsafe"
import "fmt"
func read(filename string) string {
f := C.CString(filename)
defer C.free(unsafe.Pointer(f))
s := C.my_shm_read(f)
defer C.free(unsafe.Pointer(s))
return C.GoString(s)
}
func main() {
fmt.Println(read("/tmp"))
}
#include <stdlib.h>
#include <string.h>
#include <sys/shm.h>
#include <sys/types.h>
int my_shm_open(char* filename, int open_flag){
int shm_id;
key_t key;
key = ftok(filename, 0x03);
if(key == -1){
return -1;
}
if(open_flag)
shm_id = shmget(key, 4096, IPC_CREAT|IPC_EXCL|0600);
else
shm_id = shmget(key, 0, 0);
if(shm_id == -1){
return -1;
}
return shm_id;
}
int my_shm_update(int shm_id, char* content){
char* addr;
addr = (char*)shmat(shm_id, NULL, 0);
if(addr == (char*)-1){
return -1;
}
if(strlen(content) > 4095)
return -1;
strcpy(addr, content);
shmdt(addr);
return 0;
}
int my_shm_close(int shm_id){
shmctl(shm_id, IPC_RMID, NULL);
return 0;
}
char* my_shm_read(char* filename){
int shm_id;
char* addr;
char* s;
shm_id = my_shm_open(filename, 0);
if(shm_id == -1)
return NULL;
addr = (char*)shmat(shm_id, NULL, 0);
if(addr == (char*)-1){
return NULL;
}
s = (char*)malloc(strlen(addr) + 1);
strcpy(s, addr);
shmdt(addr);
return s;
}
package main
// #include <stdlib.h>
// #include "wrapper.c"
import "C"
import "unsafe"
import (
"log"
"time"
)
type errorString struct {
s string
}
func (e *errorString) Error() string {
return e.s
}
func open(file string) (int, error) {
f := C.CString(file)
defer C.free(unsafe.Pointer(f))
r := int(C.my_shm_open(f, C.int(1)))
if r == -1 {
return 0, &errorString{"error"}
}
return r, nil
}
func update(shm_id int, content string) error {
c := C.CString(content)
defer C.free(unsafe.Pointer(c))
r := int(C.my_shm_update(C.int(shm_id), c))
if r == -1 {
return &errorString{"update error"}
}
return nil
}
func close(shm_id int) error {
C.my_shm_close(C.int(shm_id))
return nil
}
func main() {
id, err := open("/tmp")
if err != nil {
log.Fatal(err)
}
defer close(id)
err = update(id, "hello world")
if err != nil {
log.Fatal(err)
}
time.Sleep(1e9 * 100)
}
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