How to Serialize Structs with Unexported Fields into a Byte Array without Reflection?

Dumping Struct into Byte Array without Reflection

When working with structs that have unexported fields, encoding them into binary data can be a challenge. While the encoding/binary package offers a solution, its reliance on reflection can lead to issues with unexported fields.

Alternative Solution

To overcome this limitation, consider using the gob package. The gob package provides a simple and efficient way to serialize and deserialize data structures, even those with private fields. Here's how you can implement it:

1. Implement GobEncode and GobDecode Functions:
   Define these functions for structs with unexported fields. These functions will guide the gob package in serializing and deserializing the data.
2. Use gob.Encoder and gob.Decoder:
   Create instances of gob.Encoder and gob.Decoder to write or read the struct data to or from a byte buffer.

Example

Consider the following example code:

package main

import (
    "bytes"
    "encoding/gob"
    "fmt"
)

type Data struct {
    id    int32
    name   [16]byte
}

func (d *Data) GobEncode() ([]byte, error) {
    w := new(bytes.Buffer)
    enc := gob.NewEncoder(w)
    err := enc.Encode(d.id)
    if err != nil {
        return nil, err
    }
    err = enc.Encode(d.name)
    if err != nil {
        return nil, err
    }
    return w.Bytes(), nil
}

func (d *Data) GobDecode(buf []byte) error {
    r := bytes.NewBuffer(buf)
    dec := gob.NewDecoder(r)
    err := dec.Decode(&d.id)
    if err != nil {
        return err
    }
    return dec.Decode(&d.name)
}

func main() {
    d := Data{id: 7}
    copy(d.name[:], []byte("tree"))
    buffer := new(bytes.Buffer)

    // Write
    enc := gob.NewEncoder(buffer)
    err := enc.Encode(d)
    if err != nil {
        fmt.Println("Encode error:", err)
        return
    }

    // Read
    buffer = bytes.NewBuffer(buffer.Bytes())
    e := new(Data)
    dec := gob.NewDecoder(buffer)
    err = dec.Decode(e)
    if err != nil {
        fmt.Println("Decode error:", err)
        return
    }
    fmt.Println(e)
}

By following this approach, you can effectively dump and retrieve struct data with unexported fields into a byte array without relying on reflection.

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