Implemented seek and seekSync

Author: AlexanderOMara

packages/shim-deno/src/deno/stable/classes/FsFile.ts

@@ -12,6 +12,8 @@ import { read } from "../functions/read.js";
 import { readSync } from "../functions/readSync.js";
 import { write } from "../functions/write.js";
 import { writeSync } from "../functions/writeSync.js";
+import { seek } from "../functions/seek.js";
+import { seekSync } from "../functions/seekSync.js";
 
 (Symbol as any).dispose ??= Symbol("Symbol.dispose");
 (Symbol as any).asyncDispose ??= Symbol("Symbol.asyncDispose");
@@ -51,12 +53,12 @@ export class FsFile implements Deno.FsFile {
     return readSync(this.rid, p);
   }
 
-  seek(_offset: number, _whence: Deno.SeekMode): Promise<number> {
-    throw new Error("Method not implemented.");
+  async seek(offset: number, whence: Deno.SeekMode): Promise<number> {
+    return await seek(this.rid, offset, whence);
   }
 
-  seekSync(_offset: number, _whence: Deno.SeekMode): number {
-    throw new Error("Method not implemented.");
+  seekSync(offset: number, whence: Deno.SeekMode): number {
+    return seekSync(this.rid, offset, whence);
   }
 
   async stat(): Promise<Deno.FileInfo> {

packages/shim-deno/src/deno/stable/functions/close.ts

@@ -2,4 +2,9 @@
 
 import * as fs from "fs";
 
-export const close: typeof Deno.close = fs.closeSync;
+import { positions } from "./seekSync.ts";
+
+export const close: typeof Deno.close = function close(fd) {
+  fs.closeSync(fd);
+  positions.delete(fd);
+};

packages/shim-deno/src/deno/stable/functions/open.ts

@@ -4,6 +4,7 @@ import { open as _open } from "fs";
 import { promisify } from "util";
 
 import { File } from "../classes/FsFile.js";
+import { positions } from "../functions/seekSync.js";
 import { getFsFlag } from "../../internal/fs_flags.js";
 import mapError from "../../internal/errorMap.js";
 
@@ -25,6 +26,7 @@ export const open: typeof Deno.open = async function open(
   });
   try {
     const fd = await nodeOpen(path, flagMode, mode);
+    positions.set(fd, 0);
     return new File(fd);
   } catch (err) {
     throw mapError(err);

packages/shim-deno/src/deno/stable/functions/openSync.ts

@@ -3,6 +3,7 @@
 import { openSync as nodeOpenSync } from "fs";
 
 import { File } from "../classes/FsFile.js";
+import { positions } from "../functions/seekSync.js";
 import { getFsFlag } from "../../internal/fs_flags.js";
 import mapError from "../../internal/errorMap.js";
 
@@ -22,6 +23,7 @@ export const openSync: typeof Deno.openSync = function openSync(
   });
   try {
     const fd = nodeOpenSync(path, flagMode, mode);
+    positions.set(fd, 0);
     return new File(fd);
   } catch (err) {
     throw mapError(err);

packages/shim-deno/src/deno/stable/functions/read.ts

@@ -3,6 +3,8 @@
 import { promisify } from "util";
 import { read as nodeRead } from "fs";
 
+import { positions } from "./seekSync.js";
+
 const _read = promisify(nodeRead);
 
 export const read: typeof Deno.read = async function read(rid, buffer) {
@@ -13,7 +15,11 @@ export const read: typeof Deno.read = async function read(rid, buffer) {
     return 0;
   }
 
-  const { bytesRead } = await _read(rid, buffer, 0, buffer.length, null);
+  const position = positions.get(rid) ?? null;
+  const { bytesRead } = await _read(rid, buffer, 0, buffer.length, position);
+  if (position !== null) {
+    positions.set(rid, position + bytesRead);
+  }
   // node returns 0 on EOF, Deno expects null
   return bytesRead === 0 ? null : bytesRead;
 };

packages/shim-deno/src/deno/stable/functions/readSync.ts

@@ -2,8 +2,14 @@
 
 import * as fs from "fs";
 
+import { positions } from "./seekSync.js";
+
 export const readSync: typeof Deno.readSync = (fd, buffer) => {
-  const bytesRead = fs.readSync(fd, buffer);
+  const position = positions.get(fd) ?? null;
+  const bytesRead = fs.readSync(fd, buffer, { position });
+  if (position !== null) {
+    positions.set(fd, position + bytesRead);
+  }
   // node returns 0 on EOF, Deno expects null
   return bytesRead === 0 ? null : bytesRead;
 };

packages/shim-deno/src/deno/stable/functions/seek.ts

@@ -0,0 +1,30 @@
+///<reference path="../lib.deno.d.ts" />
+
+import { fstat } from "fs";
+import { promisify } from "util";
+
+import { positions } from "./seekSync.js";
+
+const nodeFstat = promisify(fstat);
+
+export const seek: typeof Deno.seek = async function (fd, offset, whence) {
+  let p = positions.get(fd);
+  if (p == null) {
+    throw new Error("Bad file descriptor");
+  }
+  switch (whence) {
+    case Deno.SeekMode.Start:
+      p = Number(offset);
+      break;
+    case Deno.SeekMode.Current:
+      p += Number(offset);
+      break;
+    case Deno.SeekMode.End:
+      p = (await nodeFstat(fd)).size + Number(offset);
+      break;
+    default:
+      throw new TypeError(`Invalid seek mode: ${whence}`);
+  }
+  positions.set(fd, p!);
+  return p!;
+};

packages/shim-deno/src/deno/stable/functions/seekSync.ts

@@ -0,0 +1,27 @@
+///<reference path="../lib.deno.d.ts" />
+
+import { fstatSync } from "fs";
+
+export const positions = new Map<number, number>();
+
+export const seekSync: typeof Deno.seekSync = function (fd, offset, whence) {
+  let p = positions.get(fd);
+  if (p == null) {
+    throw new Error("Bad file descriptor");
+  }
+  switch (whence) {
+    case Deno.SeekMode.Start:
+      p = Number(offset);
+      break;
+    case Deno.SeekMode.Current:
+      p += Number(offset);
+      break;
+    case Deno.SeekMode.End:
+      p = fstatSync(fd).size + Number(offset);
+      break;
+    default:
+      throw new TypeError(`Invalid seek mode: ${whence}`);
+  }
+  positions.set(fd, p!);
+  return p!;
+};

packages/shim-deno/tools/run_tests.mjs

@@ -51,14 +51,6 @@ const testsToSkip = new Set([
   "openNotFound", // includes full path in node.js
   "openModeWriteRead", // not implemented
   "readFileIsDirectoryErrorCode", // todo(https://github.com/denoland/deno/issues/18629): re-enable
-  "seekStart", // not implemented
-  "seekSyncStart", // not implemented
-  "seekCurrent", // not implemented
-  "seekStartBigInt", // not implemented
-  "seekSyncCurrent", // not implemented
-  "seekEnd", // not implemented
-  "seekSyncEnd", // not implemented
-  "seekMode", // not implemented
 
   // mkdir_test
   "mkdirMode", // depends on Deno.umask