golang 大文件分割

package main
import (
    "fmt"
    "io/ioutil"
    "math"
    "os"
    "strconv"
)
const chunkSize int64 = 4 << 20
func main() {
    fileInfo, err := os.Stat("test.zip")
    if err != nil {
        fmt.Println(err)
    }

num := int(math.Ceil(float64(fileInfo.Size()) / float64(chunkSize)))

fi, err := os.OpenFile("test.zip", os.O_RDONLY, os.ModePerm)
if err != nil {
    fmt.Println(err)
    return
}
b := make([]byte, chunkSize)
var i int64 = 1
for ; i <= int64(num); i++ {

    fi.Seek((i-1)*(chunkSize), 0)

    if len(b) > int((fileInfo.Size() - (i-1)*chunkSize)) {
        b = make([]byte, fileInfo.Size()-(i-1)*chunkSize)
    }

    fi.Read(b)

    f, err := os.OpenFile("./"+strconv.Itoa(int(i))+".db", os.O_CREATE|os.O_WRONLY, os.ModePerm)
    if err != nil {
        fmt.Println(err)
        return
    }
    f.Write(b)
    f.Close()
}
fi.Close()
fii, err := os.OpenFile("test.zip", os.O_CREATE|os.O_WRONLY|os.O_APPEND, os.ModePerm)
if err != nil {
    fmt.Println(err)
    return
}
for i := 1; i <= num; i++ {
    f, err := os.OpenFile("./"+strconv.Itoa(int(i))+".db", os.O_RDONLY, os.ModePerm)
    if err != nil {
        fmt.Println(err)
        return
    }
    b, err := ioutil.ReadAll(f)
    if err != nil {
        fmt.Println(err)
        return
    }
    fii.Write(b)
    f.Close()
}
 
}</pre>