在磁盘上存储结构树

Question

I have the following struct:

type Post struct {
  Id    int
  Name  string
  Text  string
  Posts []Post
}

To add some data, I do the following:

var posts []Post

posts = append(posts, Post{Id: 0, Name: "a", Text: "b"})
posts[0].Posts = append(posts[0].Posts, Post{Id: 1, Name: "c", Text: "d"})

posts = append(posts, Post{Id: 2, Name: "e", Text: "f"})
posts[0].Posts = append(posts[0].Posts, Post{Id: 3, Name: "h", Text: "d"})

How can I efficiently store this struct tree on disk? I'm looking for something which can be used without a server (like SQLite). I would like to be able to search for Id 2 or 3, returning the entire struct with the Id 2 or 3, respectively. Also, I would like to be able to update a single struct, f.e. the one with Id 2.

Also, would it be better to use a map, using Id as the map's key?

Answer 1

Use the encoding/gob put the binary data in a file or get it out again

import (
    "bufio"
    "encoding/gob"
    "fmt"
    "os"
)

type Post struct {
    Id    int
    Name  string
    Text  string
    Posts []Post
}

func main() {

    var posts []Post

    posts = append(posts, Post{Id: 0, Name: "a", Text: "b"})
    posts[0].Posts = append(posts[0].Posts, Post{Id: 1, Name: "c", Text: "d"})

    posts = append(posts, Post{Id: 2, Name: "e", Text: "f"})
    posts[0].Posts = append(posts[0].Posts, Post{Id: 3, Name: "h", Text: "d"})
    fmt.Printf("%v
", posts)

    path := "post.gob"

    // write
    out, err1 := os.Create(path)
    if err1 != nil {
        fmt.Printf("File write error: %v
", err1)
        os.Exit(1)
    }
    w := bufio.NewWriter(out)
    enc := gob.NewEncoder(w)
    enc.Encode(posts)
    w.Flush()
    out.Close()

    // read
    b := make([]Post, 10)
    in, err2 := os.Open(path)
    if err2 != nil {
        fmt.Printf("File read error: %v
", err2)
        os.Exit(1)
    }
    r := bufio.NewReader(in)
    dec := gob.NewDecoder(r)
    dec.Decode(&b)

    fmt.Printf("%v
", b)

}