buffer: buf.write(string, offset) with negative offset

All other Node.js Buffer methods either support negative offsets or throw errors for all negative integers stating that offset must be >= 0.

However, buf.write(string, offset) does not check if an offset is negative, but just converts it to uint32:

node/lib/buffer.js

Line 896 in 6eae414

offset = offset >>> 0;

This may cause some slightly confusing effects:

If -offset is > -buffer.constants.MAX_LENGTH, this produces not so clear error:

'use strict';

const buf = Buffer.alloc(10);

try {
  const len = buf.write('a', -1);
  console.log(buf.indexOf('a'));
} catch (err) {
  console.error(err.toString());
}

// Prints: RangeError [ERR_BUFFER_OUT_OF_BOUNDS]: Attempt to write outside buffer bounds

If -offset is < -buffer.constants.MAX_LENGTH, string can be written in an unexpected place:

'use strict';

const buf = Buffer.alloc(10);

try {
  const len = buf.write('a', -4294967296);
  console.log(buf.indexOf('a'));
} catch (err) {
  console.error(err);
}

// Prints: 0

So should the method check the sign before the converting?

@vsemozhetbyt

@vsemozhetbyt instead of checking for the sign, we could just use stricter input validation.

buffer: use stricter range checks

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buffer: buf.write(string, offset) with negative offset #27043

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buffer: buf.write(string, offset) with negative offset #27043

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BridgeAR commented on Apr 1, 2019

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