Fileを読み込むやつ

gistfile1.txt

$ ./file_read                                                                                                                                    [~/d/src/go]
ReadFile:148545 elapsed:167.706µs
ReadLine:144946 elapsed:209.144µs
Scanner:144946 elapsed:553.246µs

readfile.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"time"
)

func Scanner(filepath string) {
	startAt := time.Now()
	fd, err := os.Open(filepath)
	if err != nil {
		panic(err)
	}
	defer fd.Close()

	scanner := bufio.NewScanner(fd)
	var txtLen int

	for scanner.Scan() {
		line := scanner.Text()
		txtLen += len(line)
	}
	fmt.Printf("Scanner:%d elapsed:%v\n", txtLen, time.Now().Sub(startAt))
}

func ReadEachLine(filepath string) {
	startAt := time.Now()
	fd, err := os.Open(filepath)
	if err != nil {
		panic(err)
	}
	defer fd.Close()

	r := bufio.NewReader(fd)
	var txtLen int

	for {
		line, _, err := r.ReadLine()
		txtLen += len(line)
		if err != nil {
			if err == io.EOF {
				break
			}
			panic(err)
		}
	}
	fmt.Printf("ReadLine:%d elapsed:%v\n", txtLen, time.Now().Sub(startAt))
}

func ReadFile(filepath string) {
	startAt := time.Now()
	txt, err := ioutil.ReadFile(filepath)
	if err != nil {
		panic(err)
	}
	fmt.Printf("ReadFile:%d elapsed:%v\n", len(txt), time.Now().Sub(startAt))
}

func main() {
	ReadFile("./alice30.txt")
	ReadEachLine("./alice30.txt")
	Scanner("./alice30.txt")
}