几种读取文件方法速度比较

package main

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

func read0(path string) string {
    f, err := ioutil.ReadFile(path)
    if err != nil {
        fmt.Printf("%s\n", err)
        panic(err)
    }
    return string(f)
}

func read1(path string) string {
    fi, err := os.Open(path)
    if err != nil {
        panic(err)
    }
    defer fi.Close()

    chunks := make([]byte, 1024, 1024)
    buf := make([]byte, 1024)
    for {
        n, err := fi.Read(buf)
        if err != nil && err != io.EOF {
            panic(err)
        }
        if 0 == n {
            break
        }
        chunks = append(chunks, buf[:n]...)
    }
    return string(chunks)
}

func read2(path string) string {
    fi, err := os.Open(path)
    if err != nil {
        panic(err)
    }
    defer fi.Close()
    r := bufio.NewReader(fi)

    chunks := make([]byte, 1024, 1024)

    buf := make([]byte, 1024)
    for {
        n, err := r.Read(buf)
        if err != nil && err != io.EOF {
            panic(err)
        }
        if 0 == n {
            break
        }
        chunks = append(chunks, buf[:n]...)
    }
    return string(chunks)
}

func read3(path string) string {
    fi, err := os.Open(path)
    if err != nil {
        panic(err)
    }
    defer fi.Close()
    fd, err := ioutil.ReadAll(fi)
    return string(fd)
}

func main() {

    file := "test.log"

    start := time.Now()

    read0(file)
    t0 := time.Now()
    fmt.Printf("Cost time %v\n", t0.Sub(start))

    read1(file)
    t1 := time.Now()
    fmt.Printf("Cost time %v\n", t1.Sub(t0))

    read2(file)
    t2 := time.Now()
    fmt.Printf("Cost time %v\n", t2.Sub(t1))

    read3(file)
    t3 := time.Now()
    fmt.Printf("Cost time %v\n", t3.Sub(t2))

}

运行结果：
Cost time 4.0105ms
Cost time 11.5043ms
Cost time 7.0042ms
Cost time 2.4983ms

Cost time 4.4925ms
Cost time 11.0053ms
Cost time 5.0082ms
Cost time 2.9992ms

Cost time 3.9866ms
Cost time 15.0085ms
Cost time 7.5054ms
Cost time 2.5035ms

Cost time 4.9989ms
Cost time 14.0112ms
Cost time 7.5045ms
Cost time 3.508ms

Cost time 3.0043ms
Cost time 15.0265ms
Cost time 8.9884ms
Cost time 2.0036ms

文章转载自:几种读取文件方法速度比较