zero_copy.go

package main

import (
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
	"syscall"
)

func main() {
	fmt.Println("Hello, World")
}

func SendFile(file os.File, conn net.Conn) error {
	fileInfo, err := file.Stat()
	if err != nil {
		return err
	}
	sizeBuf := make([]byte, 8)
	binary.LittleEndian.PutUint64(sizeBuf, uint64(fileInfo.Size()))
	_, err = conn.Write(sizeBuf)
	if err != nil {
		return err
	}
	buf := make([]byte, 1024)
	for {
		n, err := file.Read(buf)
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		_, err = conn.Write(buf[:n])
		if err != nil {
			return err
		}
	}
	return nil
}

func SendFileTwo(file os.File, conn net.Conn) error {
	fileInfo, err := file.Stat()
	if err != nil {
		return err
	}
	sizeBuf := make([]byte, 8)
	binary.LittleEndian.PutUint64(sizeBuf, uint64(fileInfo.Size()))
	_, err = conn.Write(sizeBuf)
	if err != nil {
		return err
	}
	tcpConn, ok := conn.(*net.TCPConn)
	if !ok {
		return errors.New("Casting error")
	}
	tcpFile, err := tcpConn.File()
	if err != nil {
		return err
	}
	_, err = syscall.Sendfile(int(tcpFile.Fd()), int(file.Fd()), nil, int(fileInfo.Size()))
	if err != nil {
		return err
	}
	return nil
}