用偏移量在Golang中写入固定大小的缓冲区 [英] Writing into fixed size Buffers in Golang with offsets

问题描述

我是Golang的新手，我正在尝试写入一个Buffer，在开始写入之前，它应该以0填充到特定大小.

I'm new to Golang and I'm trying to write into a Buffer that should be 0 filled to a specific size before starting writing into it.

我的尝试:

buf := bytes.NewBuffer(make([]byte, 52))

var pktInfo uint16 = 243
var pktSize uint16 = 52
var pktLine uint16 = binary.LittleEndian.Uint16(data)
var pktId uint16 = binary.LittleEndian.Uint16(data[6:])

// header
binary.Write(buf, binary.LittleEndian, pktInfo)
binary.Write(buf, binary.LittleEndian, pktSize)
binary.Write(buf, binary.LittleEndian, pktLine)

// body
binary.Write(buf, binary.LittleEndian, pktId)
(...a lot more)

fmt.Printf("%x\n", data)
fmt.Printf("%x\n", buf.Bytes())

问题是它在字节之后写入而不是从头开始写入.我该怎么办?

Problem is it writes after the bytes instead of writing from the start. How do I do that?

推荐答案

您不需要为 bytes.Buffer 重新分配切片，或者如果这样做，则需要设置上限镜头:

You don't need to reallocate the slice for bytes.Buffer, or if you do, you need to set the cap not the len:

buf := bytes.NewBuffer(make([]byte, 0, 52)) // or simply
buf := bytes.NewBuffer(nil)

还有 buf.Reset()，但这对于该特定示例来说是一个过大的杀伤力.

There's also buf.Reset() but that's an overkill for that specific example.

制作(切片，大小，上限):

切片:大小指定长度.切片的容量为等于它的长度.可以提供第二个整数参数指定不同的容量；它必须不小于长度，因此make([] int，0，10)分配长度为0的切片，容量10.

Slice: The size specifies the length. The capacity of the slice is equal to its length. A second integer argument may be provided to specify a different capacity; it must be no smaller than the length, so make([]int, 0, 10) allocates a slice of length 0 and capacity 10.

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