fix(node/fs): position option of fs.read and fs.readSync works the same as Node

[PolarETech]

The behavior of position option in fs.read and fs.readSync is different between Deno and Node.
This PR fixes the behavior of Deno to be the same as Node's.

Actual Behavior

Node v18.9.0

If position is an integer,

• Specifies the number of bytes to start reading counting from the beginning of the file
• The file position will be unchanged

Ref: https://nodejs.org/api/fs.html#fsreadfd-buffer-offset-length-position-callback

Deno 1.25.3 with [email protected]

If position is an integer,

• Specifies the number of bytes to start reading counting from the current position of the file
• The file position will be updated

Sample code

// import for Node
import fs from 'fs';
import { Buffer } from 'node:buffer';
// or
// import for Deno
import fs from "https://deno.land/[email protected]/node/fs.ts";
import { Buffer } from "https://deno.land/[email protected]/node/buffer.ts";


const file = "./test.txt";
const text = "hello, world!";
const bufSize = 3;
const positions = [2, null, 2];
const data = [];

fs.writeFileSync(file, text);
const fd = fs.openSync(file);

for (const pos of positions) {
  const buf = Buffer.alloc(bufSize);
  fs.readSync(fd, buf, 0, buf.byteLength, pos);
  data.push(buf.toString("utf8"));
}

fs.closeSync(fd);
console.log(data);

Execution result in Node

[ 'llo', 'hel', 'llo' ] // [ 2-4 byte, 0-2 byte, 2-4 byte ]

Execution result in Deno

[ "llo", ", w", "ld!" ] // [ 2-4 byte, 5-7 byte, 10-12 byte ]

Tests

No applicable test for this issue has been found in the Node test suite. Unit tests have been updated.

Remarks

This issue has been found while implementing compatibility improvements to fs.ReadStream. #2653

[PolarETech]

There are two ci / node failures, but they appear to be issues outside the scope of this PR.

[PolarETech]

There was a lack of consideration regarding error handling.
A fix commit has been added.

[kt3k]

LGTM. Good catch!

[kt3k]

The CI failures should be fixed by denoland/deno#15954