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Improve performance of fallback mask and unmask functions #856

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merged 3 commits into from
Oct 12, 2016
Merged

Improve performance of fallback mask and unmask functions #856

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e2ac999
Improve performance of fallback mask and unmask functions
Oct 10, 2016
d502f59
Add comment regarding buffer.length regression
Oct 12, 2016
748e402
Fix lint
Oct 12, 2016
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30 changes: 4 additions & 26 deletions lib/BufferUtil.fallback.js
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Original file line number Diff line number Diff line change
Expand Up @@ -16,36 +16,14 @@ exports.BufferUtil = {
}
},
mask: function(source, mask, output, offset, length) {
var maskNum = mask.readUInt32LE(0, true);
var i = 0;
for (; i < length - 3; i += 4) {
var num = maskNum ^ source.readUInt32LE(i, true);
if (num < 0) num = 4294967296 + num;
output.writeUInt32LE(num, offset + i, true);
for (var i = 0; i < length; i++) {
output[offset + i] = source[i] ^ mask[i & 3];
}
/* eslint-disable no-fallthrough */
switch (length % 4) {
case 3: output[offset + i + 2] = source[i + 2] ^ mask[2];
case 2: output[offset + i + 1] = source[i + 1] ^ mask[1];
case 1: output[offset + i] = source[i] ^ mask[0];
}
/* eslint-enable no-fallthrough */
},
unmask: function(data, mask) {
var maskNum = mask.readUInt32LE(0, true);
var length = data.length;
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@Nibbler999 can you use data.length directly in the for loop? This variable is not very useful.

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It's there because of a regression in node I encountered when working on this - nodejs/node#9006

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Oh, ok.

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Maybe add a "remove when fixed" comment?

var i = 0;
for (; i < length - 3; i += 4) {
var num = maskNum ^ data.readUInt32LE(i, true);
if (num < 0) num = 4294967296 + num;
data.writeUInt32LE(num, i, true);
}
/* eslint-disable no-fallthrough */
switch (length % 4) {
case 3: data[i + 2] = data[i + 2] ^ mask[2];
case 2: data[i + 1] = data[i + 1] ^ mask[1];
case 1: data[i] = data[i] ^ mask[0];
for (var i = 0; i < length; i++) {
data[i] ^= mask[i & 3];
}
/* eslint-enable no-fallthrough */
}
}