淺析webpack源碼之CachedInputFileSystem模塊(六(1))

本來寫的誤操做被吞了，下面是代碼記錄
這個模塊主要作了緩存文件操做

module.exports = class CachedInputFileSystem {
    constructor(fileSystem, duration) {
        this.fileSystem = fileSystem;
        //生成緩存容器,目前他們是同樣樣的都是new Storage(duration)，區別在於調用方法傳遞參數不同，分別儲存不一個類型的緩存
        this._statStorage = new Storage(duration);
        this._readdirStorage = new Storage(duration);
        this._readFileStorage = new Storage(duration);
        this._readJsonStorage = new Storage(duration);
        this._readlinkStorage = new Storage(duration);
        // 把文件信息賦值給對應屬性
        this._stat = this.fileSystem.stat ? this.fileSystem.stat.bind(this.fileSystem) : null;
        if(!this._stat) this.stat = null;

        //...

        if(this.fileSystem.readJson) {
            this._readJson = this.fileSystem.readJson.bind(this.fileSystem);
        } else if(this.readFile) {
             // 自定義JSON讀取
            this._readJson = (path, callback) => {
                // fs.readFile讀取文件
                this.readFile(path, (err, buffer) => {
                    if(err) return callback(err);
                    let data;
                    try {
                        data = JSON.parse(buffer.toString("utf-8"));
                    } catch(e) {
                        return callback(e);
                    }
                    callback(null, data);
                });
            };
        } else {
            this.readJson = null;
        }
            //...

    
    }
    //調用Storage對象方法
    stat(path, callback) {
        this._statStorage.provide(path, this._stat, callback);
    }

    //...

    readlinkSync(path) {
        return this._readlinkStorage.provideSync(path, this._readlinkSync);
    }
    //分別清除對應的Storage，what是傳入什麼，清除什麼，purge的中文的意思又整肅的意思，和clear有點區別，有完整清除不能被回退的感受
    purge(what) {
        this._statStorage.purge(what);
        this._readdirStorage.purge(what);
        this._readFileStorage.purge(what);
        this._readlinkStorage.purge(what);
        this._readJsonStorage.purge(what);
    }
};