feat: 🎸 implement writeSync() method

demo/fsa/main.ts

@@ -92,6 +92,13 @@ const demo = async (dir: fsa.IFileSystemDirectoryHandle) => {
   const bytesRead = fs.readSync(readHandle.fd, buf, 0, 3, 0);
   strictEqual(bytesRead, 3);
   strictEqual(buf.toString('utf8'), 'wor');
+
+  console.log('writeSync() - can write into an open file');
+  const writeHandle = await fs.promises.open('/cool.txt', 'a');
+  const bytesWritten = fs.writeSync(writeHandle.fd, Buffer.from('W'), 0, 1, 0);
+  await writeHandle.close();
+  strictEqual(bytesWritten, 1);
+  strictEqual(fs.readFileSync('/cool.txt', 'utf8'), 'Worlds!');
 };
 
 const main = async () => {

src/fsa-to-node/FsaNodeFs.ts

@@ -34,6 +34,7 @@ import {
   validateCallback,
   validateFd,
   isFd,
+  getWriteSyncArgs,
 } from '../node/util';
 import { pathToLocation, testDirectoryIsWritable } from './util';
 import { ERRSTR, MODE } from '../node/constants';
@@ -974,8 +975,20 @@ export class FsaNodeFs extends FsaNodeCore implements FsCallbackApi, FsSynchrono
     return uint8.length;
   };
 
+  public readonly writeSync: FsSynchronousApi['writeSync'] = (
+    fd: number,
+    a: string | Buffer | ArrayBufferView | DataView,
+    b?: number,
+    c?: number | BufferEncoding,
+    d?: number,
+  ): number => {
+    const [, buf, offset, length, position] = getWriteSyncArgs(fd, a, b, c, d)
+    const filename = this.getFileName(fd);
+    const data = new Uint8Array(buf.buffer, buf.byteOffset + offset, length);
+    return this.getSyncAdapter().call('write', [filename, data, position || null]);
+  };
+
   public readonly openSync: FsSynchronousApi['openSync'] = notSupported;
-  public readonly writeSync: FsSynchronousApi['writeSync'] = notSupported;
 
   public readonly chmodSync: FsSynchronousApi['chmodSync'] = noop;
   public readonly chownSync: FsSynchronousApi['chownSync'] = noop;

src/fsa-to-node/types.ts

@@ -26,6 +26,11 @@ export interface FsaNodeSyncAdapterApi {
     position: number,
     length: number,
   ]): Uint8Array;
+  write(req: [
+    filename: string,
+    data: Uint8Array,
+    position: number | null,
+  ]): number;
 }
 
 export interface FsaNodeSyncAdapter {

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

@@ -183,5 +183,10 @@ export class FsaNodeSyncWorker {
       if (bytesRead < length) uint8 = uint8.slice(0, bytesRead);
       return uint8;
     },
+    write: async ([filename, data, position]): Promise<number> => {
+      const handle = await this.fs.promises.open(filename, 'a');
+      const {bytesWritten} = await handle.write(data, 0, data.length, position || undefined);
+      return bytesWritten;
+    },
   };
 }

src/node/constants.ts

@@ -34,10 +34,6 @@ const {
   O_TRUNC,
   O_APPEND,
   O_SYNC,
-  O_DIRECTORY,
-  F_OK,
-  COPYFILE_EXCL,
-  COPYFILE_FICLONE_FORCE,
 } = constants;
 
 // List of file `flags` as defined by Node.

src/node/util.ts

@@ -244,6 +244,39 @@ export const getWriteArgs = (
   return [fd, tipa === 'string', buf, offset, length!, position, cb];
 };
 
+export const getWriteSyncArgs = (
+  fd: number,
+  a: string | Buffer | ArrayBufferView | DataView,
+  b?: number,
+  c?: number | BufferEncoding,
+  d?: number,
+): [fd: number, buf: Buffer, offset: number, length?: number, position?: number] => {
+  validateFd(fd);
+  let encoding: BufferEncoding | undefined;
+  let offset: number | undefined;
+  let length: number | undefined;
+  let position: number | undefined;
+  const isBuffer = typeof a !== 'string';
+  if (isBuffer) {
+    offset = (b || 0) | 0;
+    length = c as number;
+    position = d;
+  } else {
+    position = b;
+    encoding = c as BufferEncoding;
+  }
+  const buf: Buffer = dataToBuffer(a, encoding);
+  if (isBuffer) {
+    if (typeof length === 'undefined') {
+      length = buf.length;
+    }
+  } else {
+    offset = 0;
+    length = buf.length;
+  }
+  return [fd, buf, offset || 0, length, position];
+};
+
 export function bufferToEncoding(buffer: Buffer, encoding?: TEncodingExtended): misc.TDataOut {
   if (!encoding || encoding === 'buffer') return buffer;
   else return buffer.toString(encoding);

src/volume.ts

@@ -48,6 +48,7 @@ import {
   dataToBuffer,
   getWriteArgs,
   bufferToEncoding,
+  getWriteSyncArgs,
 } from './node/util';
 import type { PathLike, symlink } from 'fs';
 import { WritevCallback } from './node/types/callback';
@@ -907,34 +908,7 @@ export class Volume {
     c?: number | BufferEncoding,
     d?: number,
   ): number {
-    validateFd(fd);
-
-    let encoding: BufferEncoding | undefined;
-    let offset: number | undefined;
-    let length: number | undefined;
-    let position: number | undefined;
-
-    const isBuffer = typeof a !== 'string';
-    if (isBuffer) {
-      offset = (b || 0) | 0;
-      length = c as number;
-      position = d;
-    } else {
-      position = b;
-      encoding = c as BufferEncoding;
-    }
-
-    const buf: Buffer = dataToBuffer(a, encoding);
-
-    if (isBuffer) {
-      if (typeof length === 'undefined') {
-        length = buf.length;
-      }
-    } else {
-      offset = 0;
-      length = buf.length;
-    }
-
+    const [, buf, offset, length, position] =  getWriteSyncArgs(fd, a, b, c, d)
     return this.writeBase(fd, buf, offset, length, position);
   }