将字节数组更改为Golang中的结构

Question

I am having some data in redis. The value is stored in form of bytes. I want to fetch the bytes and map that to a struct but I am not able to decode bytes data. This is the code I am using to persist data to redis:

    import (
    bytes "bytes"
    "encoding/gob"
    "fmt"
    "github.com/go-redis/redis"
    "time"
)

var convertor bytes.Buffer
var encoder = gob.NewEncoder(&convertor)
var decoder = gob.NewDecoder(&convertor)

func Set(field string,  value interface{}) (error){
    id := "sample-key";
    err := encoder.Encode(value)
    if err!=nil {
        fmt.Printf("error occured while marshaling data")
        return err;
    }

    valueBytes := convertor.Bytes()

    err = redisdb.HSet(id, field, valueBytes).Err();
    if err!=nil{
        fmt.Printf("error occured while setting data")
        return err;
    }
    return nil;
}

This is how I get data from redis:

result, err := redisdb.HGet(key, field).Result()
if err != nil{
    fmt.Println("error occured");
}

but I am not able to store it into struct. How can decode the bytes data to a struct?

Answer 1

Reusing the bytes.Buffer between encode operations will produce unexpected results. Every call to Encode appends data to the buffer. Calling Set multiple times will write the following data to the database: (value1), (value1, value2), (value1, value2, value3) and so on. Calling the function concurrently will create a data race.

Fix the Set function by creating a buffer and encoder for each call to the function:

func Set(field string, value interface{}) error {
    var buf bytes.Buffer
    var encoder = gob.NewEncoder(&buf)

    id := "sample-key"
    err := encoder.Encode(value)
    if err != nil {
        return err
    }
    return redisdb.HSet(id, field, buf.Bytes()).Err()
}

The Get function is the inverse of the set function:

func Get(field string, value interface{}) error {
    id := "sample-key"
    buf, err := redisdb.HGet(id, field).Bytes()
    if err != nil {
        return err
    }
    return gob.NewDecoder(bytes.NewReader(buf)).Decode(value)
}

Call the get function with a pointer to the value:

var d Data
err := Get(field, &d)