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buffer: coerce slice parameters consistenly #9101

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buffer: coerce slice parameters consistenly #9101

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7 changes: 3 additions & 4 deletions lib/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -807,11 +807,10 @@ Buffer.prototype.toJSON = function() {


function adjustOffset(offset, length) {
offset = +offset;
if (offset === 0 || Number.isNaN(offset)) {
offset |= 0;
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If you want the floor then please use Math.floor(). Using | allows wrap around. One reason why + was used before.

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@thefourtheye

String's slice also works like this only

This fails edge cases. For example:

'abcdefg'.slice(-(-1 >>> 0) - 1) === 'abcdefg';

But as this currently stands offset will be coerced to 2 with the above example.

if (offset === 0) {
return 0;
}
if (offset < 0) {
} else if (offset < 0) {
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Here's where the problem lies. There's no range check before the int32 coercion. A large number could fail this.

offset += length;
return offset > 0 ? offset : 0;
} else {
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10 changes: 10 additions & 0 deletions test/parallel/test-buffer-slice.js
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Expand Up @@ -62,3 +62,13 @@ assert.strictEqual(Buffer.alloc(0).slice(0, 1).length, 0);

// slice(0,0).length === 0
assert.strictEqual(0, Buffer.from('hello').slice(0, 0).length);

{
// Regression tests for https://github.com/nodejs/node/issues/9096
const buf = Buffer.from('abcd');
assert.strictEqual(buf.slice(buf.length / 3).toString(), 'bcd');
assert.strictEqual(
buf.slice(buf.length / 3, buf.length).toString(),
'bcd'
);
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If we're making the change to operate like String#slice() then edge case tests should be included. e.g.:

const b = Buffer.from('abcdefg');
assert.strictEqual(b.slice(-(-1 >>> 0) + 1).toString(), b.toString());

}