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stream: code cleanup and micro-optimization #2479

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Merged
bnoordhuis merged 3 commits into from
Aug 24, 2015
Merged

stream: code cleanup and micro-optimization #2479

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1a3f4a8
stream: fix off-by-factor-16 error in comment
bnoordhuis Aug 20, 2015
3af8e45
stream: micro-optimize high water mark calculation
bnoordhuis Aug 20, 2015
caa0d0c
stream: rename poorly named function
bnoordhuis Aug 20, 2015
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12 changes: 8 additions & 4 deletions lib/_stream_readable.js
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Original file line number Diff line number Diff line change
Expand Up @@ -190,15 +190,19 @@ Readable.prototype.setEncoding = function(enc) {
return this;
};

// Don't raise the hwm > 128MB
// Don't raise the hwm > 8MB
const MAX_HWM = 0x800000;
function roundUpToNextPowerOf2(n) {
function computeNewHighWaterMark(n) {
if (n >= MAX_HWM) {
n = MAX_HWM;
} else {
// Get the next highest power of 2
n--;
for (var p = 1; p < 32; p <<= 1) n |= n >> p;
n |= n >>> 1;
n |= n >>> 2;
n |= n >>> 4;
n |= n >>> 8;
n |= n >>> 16;
n++;
}
return n;
Expand Down Expand Up @@ -227,7 +231,7 @@ function howMuchToRead(n, state) {
// power of 2, to prevent increasing it excessively in tiny
// amounts.
if (n > state.highWaterMark)
state.highWaterMark = roundUpToNextPowerOf2(n);
state.highWaterMark = computeNewHighWaterMark(n);

// don't have that much. return null, unless we've ended.
if (n > state.length) {
Expand Down