feat: 🎸 add readSync() method

demo/fsa/main.ts

@@ -85,6 +85,13 @@ const demo = async (dir: fsa.IFileSystemDirectoryHandle) => {
   const listInDir2 = fs.readdirSync('/dir', {withFileTypes: true}) as any;
   deepEqual(listInDir2[0].name, 'very-cool.txt');
   deepEqual(listInDir2[0].isFile(), true);
+
+  console.log('readSync() - can read a file into a buffer');
+  const buf = Buffer.alloc(3);
+  const readHandle = await fs.promises.open('/cool.txt', 'r');
+  const bytesRead = fs.readSync(readHandle.fd, buf, 0, 3, 0);
+  strictEqual(bytesRead, 3);
+  strictEqual(buf.toString('utf8'), 'wor');
 };
 
 const main = async () => {

src/fsa-to-node/FsaNodeFs.ts

@@ -958,8 +958,23 @@ export class FsaNodeFs extends FsaNodeCore implements FsCallbackApi, FsSynchrono
     return strToEncoding(filename, encoding);
   }
 
+  public readonly readSync: FsSynchronousApi['readSync'] = (
+    fd: number,
+    buffer: Buffer | ArrayBufferView | DataView,
+    offset: number,
+    length: number,
+    position: number,
+  ): number => {
+    validateFd(fd);
+    const filename = this.getFileName(fd);
+    const adapter = this.getSyncAdapter();
+    const uint8 = adapter.call('read', [filename, position, length]);
+    const dest = new Uint8Array(buffer.buffer, buffer.byteOffset, buffer.byteLength);
+    dest.set(uint8, offset);
+    return uint8.length;
+  };
+
   public readonly openSync: FsSynchronousApi['openSync'] = notSupported;
-  public readonly readSync: FsSynchronousApi['readSync'] = notSupported;
   public readonly writeSync: FsSynchronousApi['writeSync'] = notSupported;
 
   public readonly chmodSync: FsSynchronousApi['chmodSync'] = noop;

src/fsa-to-node/types.ts

@@ -21,6 +21,11 @@ export interface FsaNodeSyncAdapterApi {
   trunc(req: [filename: string, len: number]): void;
   unlink(req: [filename: string]): void;
   readdir(req: [filename: string]): FsaNodeSyncAdapterEntry[];
+  read(req: [
+    filename: string,
+    position: number,
+    length: number,
+  ]): Uint8Array;
 }
 
 export interface FsaNodeSyncAdapter {

src/fsa-to-node/worker/FsaNodeSyncWorker.ts

@@ -11,10 +11,10 @@ import type {
   FsaNodeWorkerMsgRootSet,
 } from './types';
 import type { FsLocation, FsaNodeSyncAdapterApi, FsaNodeSyncAdapterStats, FsaNodeSyncAdapterEntry } from '../types';
-import { IDirent } from '../../node/types/misc';
+import type { IDirent } from '../../node/types/misc';
 
 export class FsaNodeSyncWorker {
-  protected readonly sab: SharedArrayBuffer = new SharedArrayBuffer(1024 * 32);
+  protected readonly sab: SharedArrayBuffer = new SharedArrayBuffer(1024 * 1024);
   protected readonly messenger = new SyncMessenger(this.sab);
   protected root!: fsa.IFileSystemDirectoryHandle;
   protected fs!: FsaNodeFs;
@@ -171,5 +171,17 @@ export class FsaNodeSyncWorker {
       );
       return res;
     },
+    read: async ([filename, position, length]): Promise<Uint8Array> => {
+      let uint8 = new Uint8Array(length);
+      const handle = await this.fs.promises.open(filename, 'r');
+      const bytesRead = await new Promise<number>((resolve, reject) => {
+        this.fs.read(handle.fd, uint8, 0, length, position, (err, bytesRead) => {
+          if (err) return reject(err);
+          resolve(bytesRead || length);
+        });
+      });
+      if (bytesRead < length) uint8 = uint8.slice(0, bytesRead);
+      return uint8;
+    },
   };
 }