我的第一个Go程序

读取一个TCPDump文件的包头并打印出来。用到了os.Open()、os.CLose()打开关闭文件。用到bufio.reader.read()读取数据到byte数组。

Go语言貌似不会自动转型，所以byte移位前要强制转型。

package main

import (
    "fmt"
    "os"
    "bufio"
 )

func parseTCPDumpHeader(h[] byte){
    var magic uint32 = uint32(h[3])<<24 | uint32(h[2])<<16 | uint32(h[1])<<8 | uint32(h[0]);
    var major uint16 = uint16(h[5])<<8 | uint16(h[4]);
    var minor uint16 = uint16(h[7])<<24 | uint16(h[6]);
    fmt.Printf("magic: 0x%x, major: %x, minor: %x\r\n", magic, major, minor);
}

func main() {
    fmt.Printf("Hello, %s!\r\n", "World")
    var f, err = os.Open("./1.cap")
    defer f.Close();
    if (err!=nil) {
        fmt.Printf("Open file failed.\r\n");
    }
    //var tcpDumpHeader = [4]byte;
    var reader = bufio.NewReader(f)

    var tcpDumpHeader = make([]byte, 24);
    fmt.Printf("len: %d\r\n", len(tcpDumpHeader));
    var n, err2 = reader.Read(tcpDumpHeader)
    if (err2!=nil){
        fmt.Printf("Read file error.\r\n");
    }
    if(n== len(tcpDumpHeader)) {
        parseTCPDumpHeader(tcpDumpHeader)
    }
}