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buffer: don't set zero fill for zero-length buffer #2931

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buffer: don't set zero fill for zero-length buffer #2931

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19 changes: 14 additions & 5 deletions lib/buffer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,8 @@ const kNoZeroFill = 0;

function createPool() {
poolSize = Buffer.poolSize;
flags[kNoZeroFill] = 1;
if (poolSize > 0)
flags[kNoZeroFill] = 1;
allocPool = new Uint8Array(poolSize);
Object.setPrototypeOf(allocPool, Buffer.prototype);
poolOffset = 0;
Expand Down Expand Up @@ -64,7 +65,8 @@ Buffer.__proto__ = Uint8Array;
function SlowBuffer(length) {
if (+length != length)
length = 0;
flags[kNoZeroFill] = 1;
if (length > 0)
flags[kNoZeroFill] = 1;
const ui8 = new Uint8Array(+length);
Object.setPrototypeOf(ui8, Buffer.prototype);
return ui8;
Expand All @@ -75,8 +77,11 @@ SlowBuffer.__proto__ = Buffer;


function allocate(size) {
if (size === 0)
return SlowBuffer(0);
if (size === 0) {
const ui8 = new Uint8Array(size);
Object.setPrototypeOf(ui8, Buffer.prototype);
return ui8;
}
if (size < (Buffer.poolSize >>> 1)) {
if (size > (poolSize - poolOffset))
createPool();
Expand All @@ -85,7 +90,11 @@ function allocate(size) {
alignPool();
return b;
} else {
flags[kNoZeroFill] = 1;
// Even though this is checked above, the conditional is a safety net and
// sanity check to prevent the arraybuffer from being allocated with
// garbage.
if (size > 0)
flags[kNoZeroFill] = 1;
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Perhaps we should just reset the flag ourselves?

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Already considered that. If for some reason buffer instantiation throws, and is caught, it won't have a chance to reset the value. The likelihood of that happening is slim to none. Just being super paranoid. I can swap the impl if you think it's unnecessary.

const ui8 = new Uint8Array(size);
Object.setPrototypeOf(ui8, Buffer.prototype);
return ui8;
Expand Down
19 changes: 19 additions & 0 deletions test/parallel/test-buffer-zero-fill-reset.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
'use strict';

require('../common');
const assert = require('assert');


function testUint8Array(ui) {
const length = ui.length;
for (let i = 0; i < length; i++)
if (ui[i] !== 0) return false;
return true;
}


for (let i = 0; i < 100; i++) {
new Buffer(0);
let ui = new Uint8Array(65);
assert.ok(testUint8Array(ui), 'Uint8Array is not zero-filled');
}