Go语言高效获取文件长度的方法

package main

import (
"fmt"
"os"
)

func getFileLength(filePath string) (int64, error) {
fileInfo, err := os.Stat(filePath)
if err != nil {
return -1, fmt.Errorf("failed to get file info: %v", err)
}

if fileInfo.IsDir() { // 验证是否为目录以避免错误计算
return -2, errors.New("the given path is a directory")
}

return fileInfo.Size(), nil
}

func main() {
length, err := getFileLength("/path/to/your/file.txt")
if err == nil {
fmt.Printf("The length of the file in bytes: %d\n", length)
} else {
fmt.Println(err.Error())
}
}

package main

import (
"syscall"
"io/fs"
"log"
"bytes"
"unsafe"
)

// HighEfficientGetFileLen 使用mmap技术更高效获得文件长度
func HighEfficientGetFileLen(filename string) (int64, error) {
fd, errno := syscall.Open(filename, syscall.O_RDONLY|syscall.O_NONBLOCK, fs.ModePerm)
if fd < 0 || errno != nil{
return -1, log.Fatal(errno)
}
defer func(){
if e := syscall.Close(fd); e != nil {
panic(e)
}
}()

statT, _, _ := syscall.Fstat(int(fd), &syscall.Stat_t{})
size := statT.Size

hdr := (*reflect.SliceHeader)(unsafe.Pointer(&bytes.Buffer{}))
hdr.Data = uintptr(fd)
hdr.Cap = int(size)
hdr.Len = hdr.Cap

_ = hdr // 这里仅为了展示思路，实际上无需具体赋值给变量

return size, nil
}

func main() {
len, err := HighEfficientGetFileLen("/path/to/largefile.bin")

if err == nil {
println(fmt.Sprintf("Using memory mapping approach got file's byte count as :%d ", len))
}else {
log.Fatalln(err)
}

}