0284-KVS-分离读取文件逻辑

环境

• Time 2022-12-11
• WSL-Ubuntu 22.04
• Rust 1.65.0

前言

说明

参考：https://github.com/pingcap/talent-plan

目标

在上一节的基础上，将文件的读取逻辑存放到新的文件中。

Cargo.toml

[package]
edition = "2021"
name = "kvs"
version = "1.0.0"

[dependencies]
clap = {version = "4", features = ["derive"]}
serde = {version = "1", features = ["derive"]}
serde_json = "1"

log.rs

use std::collections::HashMap;
use std::fs::{File, OpenOptions};
use std::io::{BufWriter, Write};

use anyhow::{Ok, Result};

use crate::cmd::Command;

mod reader;

pub(crate) struct CommandLog {
    writer: BufWriter<File>,
    map: HashMap<String, String>,
}

pub type KvResult = Result<Option<String>>;

impl CommandLog {
    pub(crate) fn new() -> Result<Self> {
        let path = "/root/log/1.log";
        let writer = new_writer(path)?;
        let mut map = HashMap::default();
        reader::load(path, &mut map)?;
        Ok(Self { writer, map })
    }

    pub(crate) fn get(&mut self, key: &str) -> KvResult {
        Ok(self.map.get(key).map(String::from))
    }

    pub fn set(&mut self, key: String, value: String) -> KvResult {
        let command = Command::Set {
            key: key.to_string(),
            value: value.to_string(),
        };
        let json = serde_json::to_string(&command)?;
        self.writer.write_all(json.as_bytes())?;
        Ok(self.map.insert(key, value))
    }

    pub(crate) fn remove(&mut self, key: String) -> KvResult {
        let command = Command::Remove { key: &key };
        let json = serde_json::to_string(&command)?;
        self.writer.write_all(json.as_bytes())?;
        Ok(self.map.remove(&key))
    }
}

fn new_writer(path: &str) -> Result<BufWriter<File>> {
    let file = OpenOptions::new().append(true).create(true).open(path)?;
    Ok(BufWriter::new(file))
}

reader.rs

use std::collections::HashMap;
use std::fs::{File, OpenOptions};
use std::io::BufReader;

use anyhow::Result;
use serde_json::Deserializer;

use crate::cmd::Command;

pub fn load(path: &str, map: &mut HashMap<String, String>) -> Result<()> {
    let stream = Deserializer::from_reader(new_reader(path)?).into_iter();
    for cmd in stream {
        match cmd? {
            Command::Set { key, value } => map.insert(key, value),
            Command::Remove { key } => map.remove(key),
        };
    }
    Ok(())
}

fn new_reader(path: &str) -> Result<BufReader<File>> {
    let file = OpenOptions::new().read(true).open(path)?;
    Ok(BufReader::new(file))
}

运行

使用 cargo build --release 构建后运行。

root@jiangbo12490:~/git/game/target/release# ./kvs set name JiangBo
SET KEY: name, VALUE: None
root@jiangbo12490:~/git/game/target/release# ./kvs set name ZhangSan
SET KEY: name, VALUE: JiangBo
root@jiangbo12490:~/git/game/target/release# ./kvs get name
GET KEY: name, VALUE: ZhangSan
root@jiangbo12490:~/git/game/target/release# ./kvs rm name
REM KEY: name, VALUE: ZhangSan

查看文件

root@jiangbo12490:~/log# cat 1.log
{"Set":{"key":"name","value":"JiangBo"}}{"Set":{"key":"name","value":"ZhangSan"}}{"Remove":{"key":"name"}}

总结

将读取文件的逻辑分离到了单独的文件中。

附录