英文:
Mapping an array to a file via Mmap in Go
问题
我正在尝试通过Mmap将一个数组映射到一个文件中，这个数组可以是任何类型，比如float64。在C语言中，我找到了这个链接。在阅读了一些文本之后，我写了这个示例。我不知道它是否正确，并且它没有将值写入文件。如果我将数组的大小从1000增加到10000，程序会崩溃。如果有人知道正确的方法，请告诉我。
谢谢！
英文:
I'm trying to map an array to a file via Mmap, the array could be any type, like float64. In C, I find this one. After reading some texts, I wrote this sample. I don't know if it is correct, and it is not writing the values to the file. If I increase the size of array a lot, e.g from 1000 to 10000, it crashes. If someone know how to do that in the correctly way, please, tell me.
Thanks!
答案1
得分: 31
例如，修改您的示例程序，
package main
import (
"fmt"
"os"
"syscall"
"unsafe"
)
func main() {
const n = 1e3
t := int(unsafe.Sizeof(0)) * n
map_file, err := os.Create("/tmp/test.dat")
if err != nil {
fmt.Println(err)
os.Exit(1)
}
_, err = map_file.Seek(int64(t-1), 0)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
_, err = map_file.Write([]byte(" "))
if err != nil {
fmt.Println(err)
os.Exit(1)
}
mmap, err := syscall.Mmap(int(map_file.Fd()), 0, int(t), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
map_array := (*[n]int)(unsafe.Pointer(&mmap[0]))
for i := 0; i < n; i++ {
map_array[i] = i * i
}
fmt.Println(*map_array)
err = syscall.Munmap(mmap)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
err = map_file.Close()
if err != nil {
fmt.Println(err)
os.Exit(1)
}
}
英文:
For example, revising your sample program,
package main
import (
"fmt"
"os"
"syscall"
"unsafe"
)
func main() {
const n = 1e3
t := int(unsafe.Sizeof(0)) * n
map_file, err := os.Create("/tmp/test.dat")
if err != nil {
fmt.Println(err)
os.Exit(1)
}
_, err = map_file.Seek(int64(t-1), 0)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
_, err = map_file.Write([]byte(" "))
if err != nil {
fmt.Println(err)
os.Exit(1)
}
mmap, err := syscall.Mmap(int(map_file.Fd()), 0, int(t), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
map_array := (*[n]int)(unsafe.Pointer(&mmap[0]))
for i := 0; i < n; i++ {
map_array[i] = i * i
}
fmt.Println(*map_array)
err = syscall.Munmap(mmap)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
err = map_file.Close()
if err != nil {
fmt.Println(err)
os.Exit(1)
}
}
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