字节片操作

Question

I'm writing a program that should parse and reply to network packets but I'm a bit annoyed because I can't do simple C style return (int)buffer[at]; with an array of bytes. Is there any better way to retrieve 4 bytes from byte[] as int32 than the following?

func (packet *Packet) GetInt32(at int) int32 {
    return int32(packet.buffer[at]) << 24 +
        int32(packet.buffer[at+1]) << 16 +
        int32(packet.buffer[at+2]) << 8 +
        int32(packet.buffer[at+3])
}

It works correctly but I was thinking if there was a better way to do this.

Answer 1

package main

import (
    "encoding/binary"
    "fmt"
    "math"
)

type Packet struct {
    buffer []byte
}

func (p *Packet) Int32(i int) int32 {
    return int32(binary.BigEndian.Uint32(p.buffer[i : i+4]))
}

func (p *Packet) Float32(i int) float32 {
    return math.Float32frombits(binary.BigEndian.Uint32(p.buffer[i : i+4]))
}

func main() {
    p := &Packet{buffer: []byte{0x01, 0x02, 0x00, 0x00, 0xFF, 0xFF, 0x07}}
    fmt.Println(p.Int32(2), p.Float32(2))
}


Output:  65535  9.1834e-41