英文:
correct idiomatic byte buffer reading and writing
问题
你需要读取一个结构化协议的数据，其中包含消息长度、类型和值。你想知道在Go语言中如何实现这个功能，但是在io、bufio和encoding等包中找不到合适的方法和示例。你还需要组装一个回复，类似于WriteInt32、WriteString和WriteByte。你想将Python代码转换为Go代码，Python代码中使用了struct.unpack和pack函数。
英文:
I have a net/socket open. I need to read a structured protocol off the wire. Ie I have
messagelength|type|value|type|value ...
where messagelength is 4 bytes, type one byte, value depends on type,...
I am trying to work out the no-brainer way of doing this in go. I am swamped by io,bufio,encoding... I cant find the right place to start and cant find samples. Looking for ReadInt32, ReadByte,....
Next thing - i need to assemble a reply -> WriteInt32, WriteString, WriteByte,....
Trying to convert python to go, python code uses struct.unpack / pack
答案1
得分: 3
你可以使用包encoding/binary。你只需要用到Read()和Write()这两个函数。下面是如何使用它们：
Read()函数的签名如下：
func Read(r io.Reader, order ByteOrder, data interface{}) error
这个函数从r按照ByteOrder的顺序读取数据到data中。data必须是一个指向固定大小值的指针（例如int32、字节或只包含固定大小成员的结构体）或者是这些值的切片。如果你传递一个指向结构体的指针，结构体字段将被无填充地读取，对于空白字段（即那些命名为_的字段）的数据将被读取并丢弃（适用于填充）。
针对你的具体问题，声明一个与数据流头部匹配的结构体。
type Header struct {
Length uint32
Type uint8
}
读取一个数据包的头部（假设是大端序）：
var hdr Header
if err = Read(connection, binary.BigEndian, &hdr); err != nil {
// 处理读取错误
}
根据类型字节进行分支处理：
switch hdr.Type {
// 对于每种类型，读取到相应的特定类型的结构体中
// ...
}
Write()函数类似，但是用于写入数据而不是读取。
英文:
You can use the package encoding/binary. The only functions you will need are Read() and Write(). Here is how you use them:
The Read() function has the following signature:
func Read(r io.Reader, order ByteOrder, data interface{}) error
This function reads from r in order ByteOrder into data. data must be a pointer to a fixed-size value (e.g. an int32, a byte or a struct with only fixed size members) or a slice of such values. If you pass a pointer to a struct, struct fields are read in without padding, data corresponding for blank fields (i.e. those named _) is read and discarded (ideal for padding).
For your specific problem, declare a struct that matches the header of your data stream.
type Header struct {
Length uint32
Type uint8
}
Consume the header of a packet (assume big endian):
var hdr Header
if err = Read(connection, binary.BigEndian, &hdr); err != nil {
// deal with read error
}
Switch over the type byte:
switch hdr.Type {
// for each type, read into a type-specific struct
// ...
}
Write() is similar but writes instead of reading.
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