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import {RWLock} from '@rocicorp/lock';import type {Read, Store, Value, Write} from './store';import {deleteSentinel, WriteImplBase} from './write-impl-base';
export class MemStore implements Store {  // protected to allow test sub class to use it.  protected readonly _map: Map<string, Value> = new Map();  private readonly _rwLock = new RWLock();  private _closed = false;
  async read(): Promise<Read> {    const release = await this._rwLock.read();    return new ReadImpl(this._map, release);  }
  async withRead<R>(fn: (read: Read) => R | Promise<R>): Promise<R> {    const read = await this.read();    try {      return await fn(read);    } finally {      read.release();    }  }
  async write(): Promise<Write> {    const release = await this._rwLock.write();    return new WriteImpl(this._map, release);  }
  async withWrite<R>(fn: (write: Write) => R | Promise<R>): Promise<R> {    const write = await this.write();    try {      return await fn(write);    } finally {      write.release();    }  }
  async close(): Promise<void> {    this._closed = true;  }
  get closed(): boolean {    return this._closed;  }}
class ReadImpl implements Read {  private readonly _map: Map<string, Value>;  private readonly _release: () => void;  private _closed = false;
  constructor(map: Map<string, Value>, relase: () => void) {    this._map = map;    this._release = relase;  }
  release() {    this._release();    this._closed = true;  }
  get closed(): boolean {    return this._closed;  }
  async has(key: string): Promise<boolean> {    return this._map.has(key);  }
  async get(key: string): Promise<Value | undefined> {    return this._map.get(key);  }}
class WriteImpl extends WriteImplBase implements Write {  private readonly _map: Map<string, Value>;
  constructor(map: Map<string, Value>, release: () => void) {    super(new ReadImpl(map, release));    this._map = map;  }
  async commit(): Promise<void> {    // HOT. Do not allocate entry tuple and destructure.    this._pending.forEach((value, key) => {      if (value === deleteSentinel) {        this._map.delete(key);      } else {        this._map.set(key, value);      }    });    this._pending.clear();    this.release();  }}