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string_decoder: make write after end to reset #16594

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b555911
string_decoder: make write after end to reset
thefourtheye Oct 29, 2017
dbf8fd2
sort the doc section
thefourtheye Oct 30, 2017
f34b251
make write hot path efficient
thefourtheye Nov 6, 2017
7c2286f
incorporate review comments
thefourtheye Dec 5, 2017
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make write hot path efficient
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@thefourtheye
thefourtheye committed Nov 6, 2017
commit f34b251aab6067f3310bee4f43ab3c1b25b238e0
29 changes: 18 additions & 11 deletions lib/string_decoder.js
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Original file line number Diff line number Diff line change
Expand Up @@ -45,15 +45,13 @@ function StringDecoder(encoding) {
this.lastNeed = 0;
this.lastTotal = 0;
this.lastChar = Buffer.allocUnsafe(this._nb || 0);
this._closed = false;
return;
}

this.encoding = normalizeEncoding(encoding);
switch (this.encoding) {
case 'utf16le':
this.text = utf16Text;
this.end = utf16End;
this._nb = 4;
break;
case 'utf8':
Expand All @@ -62,28 +60,21 @@ function StringDecoder(encoding) {
break;
case 'base64':
this.text = base64Text;
this.end = base64End;
this._nb = 3;
break;
default:
this.write = simpleWrite;
this.end = simpleEnd;
this._nb = 0;
this._closed = false;
return;
}
this.lastNeed = 0;
this.lastTotal = 0;
this.lastChar = Buffer.allocUnsafe(this._nb);
this._closed = false;
}

StringDecoder.prototype.reset = StringDecoder;

StringDecoder.prototype.write = function(buf) {
if (this._closed === true)
this.reset();

if (buf.length === 0)
return '';

Expand All @@ -103,7 +94,7 @@ StringDecoder.prototype.write = function(buf) {
return r || '';
};

StringDecoder.prototype.end = utf8End;
StringDecoder.prototype.end = end;

// Returns only complete characters in a Buffer
StringDecoder.prototype.text = utf8Text;
Expand Down Expand Up @@ -226,7 +217,6 @@ function utf8Text(buf, i) {
// character.
function utf8End(buf) {
const r = (buf && buf.length ? this.write(buf) : '');
this._closed = true;
if (this.lastNeed)
return r + '\ufffd';
return r;
Expand Down Expand Up @@ -299,3 +289,20 @@ function simpleWrite(buf) {
function simpleEnd(buf) {
return (buf && buf.length ? this.write(buf) : '');
}

function end(buf) {
let result = '';

if (this.encoding === 'utf16le')
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@mscdex mscdex Dec 1, 2017

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Might consider using a switch here.

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@thefourtheye thefourtheye Dec 5, 2017

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Ack.

result = utf16End.call(this, buf);
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@mscdex mscdex Dec 1, 2017

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If we're the only ones calling these methods directly, then we should be able to avoid the overhead of .call() and just pass an instance as another argument.

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@thefourtheye thefourtheye Dec 5, 2017

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Ack.

else if (this.encoding === 'utf8')
result = utf8End.call(this, buf);
else if (this.encoding === 'base64')
result = base64End.call(this, buf);
else
result = simpleEnd.call(this, buf);

this.reset();
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@mscdex mscdex Dec 1, 2017

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Would it be better to use this.reset(this.encoding) to avoid the switch in the constructor?

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@thefourtheye thefourtheye Dec 5, 2017

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We still cannot get rid of the switch in the constructor, right?

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@mscdex mscdex Dec 5, 2017 •
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Correct, but this.reset(this.encoding) would only hit that first if in the constructor, which might be better.


return result;
}
20 changes: 0 additions & 20 deletions test/parallel/test-string-decoder-end.js
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Expand Up @@ -76,23 +76,3 @@ function testBuf(encoding, buf) {
const result = decoder.write(euroPart2);
assert.notStrictEqual(result, '€');
}

{
// test to check if write after end reopens the decoder
const decoder = new SD();
assert.strictEqual(decoder._closed, false);
decoder.end();
assert.strictEqual(decoder._closed, true);
decoder.write(Buffer.from([0xE2]));
assert.strictEqual(decoder._closed, false);
}

{
// test to check if reset after end reopens the decoder
const decoder = new SD();
assert.strictEqual(decoder._closed, false);
decoder.end();
assert.strictEqual(decoder._closed, true);
decoder.reset();
assert.strictEqual(decoder._closed, false);
}