浅析webpack源码之CachedInputFileSystem模块(六(1))

原本写的误操作被吞了，下面是代码记录
这个模块主要做了缓存文件操作

module.exports = class CachedInputFileSystem {
    constructor(fileSystem, duration) {
        this.fileSystem = fileSystem;
        //生成缓存容器,目前他们是一样样的都是new Storage(duration)，区别在于调用方法传递参数不一样，分别储存不一个类型的缓存
        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);
        // 把文件信息赋值给对应属性
        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) {
             // 自定义JSON读取
            this._readJson = (path, callback) => {
                // fs.readFile读取文件
                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;
        }
            //...

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

    //...

    readlinkSync(path) {
        return this._readlinkStorage.provideSync(path, this._readlinkSync);
    }
    //分别清除对应的Storage，what是传入什么，清除什么，purge的中文的意思又整肃的意思，和clear有点区别，有完整清除不能被回退的感觉
    purge(what) {
        this._statStorage.purge(what);
        this._readdirStorage.purge(what);
        this._readFileStorage.purge(what);
        this._readlinkStorage.purge(what);
        this._readJsonStorage.purge(what);
    }
};