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perf: don't depend on limit to know when we hit the end of buffer
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@lddubeau
lddubeau committed Sep 12, 2019
1 parent be6bead commit ad4ab53
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Showing 2 changed files with 55 additions and 61 deletions.
2 changes: 2 additions & 0 deletions lib/.eslintrc.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,5 +2,7 @@ module.exports = {
extends: "../.eslintrc.js",
rules: {
"no-continue": "off",
// We use constant conditions quite often, for optimization reasons.
"no-constant-condition": "off",
},
}
114 changes: 53 additions & 61 deletions lib/saxes.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -571,8 +571,6 @@ class SaxesParser {
limit--;
this.trailingCR = true;
}
this.limit = limit;

this.chunk = chunk;
this.i = 0;
while (this.i < limit) {
Expand Down Expand Up @@ -630,6 +628,11 @@ class SaxesParser {
this.column = 0;
break;
default:
// eslint-disable-next-line no-restricted-globals
if (isNaN(code)) {
return undefined;
}

this.column++;
if (code >= 0xD800 && code <= 0xDBFF) {
code = 0x10000 + ((code - 0xD800) * 0x400) +
Expand Down Expand Up @@ -689,6 +692,11 @@ class SaxesParser {
break;

default:
// eslint-disable-next-line no-restricted-globals
if (isNaN(code)) {
return undefined;
}

this.column++;
if (code >= 0xD800 && code <= 0xDBFF) {
code = 0x10000 + ((code - 0xD800) * 0x400) +
Expand Down Expand Up @@ -735,20 +743,19 @@ class SaxesParser {
* ``undefined`` if we hit the end of the chunk.
*/
captureTo(chars, buffer) {
const { chunk, limit, i: start } = this;
while (this.i < limit) {
const { chunk, i: start } = this;
while (true) {
const c = this.getCode();
if (chars.includes(c)) {
// This is faster than adding codepoints one by one.
this[buffer] += chunk.substring(start,
this.i - (c <= 0xFFFF ? 1 : 2));
this[buffer] += chunk.substring(start, this.i - (c <= 0xFFFF ? 1 : 2));
return c;
}
}

// This is faster than adding codepoints one by one.
this[buffer] += chunk.substring(start);
return undefined;
if (c === undefined) {
this[buffer] += chunk.substring(start);
return undefined;
}
}
}

/**
Expand All @@ -764,20 +771,19 @@ class SaxesParser {
* into the end of the current chunk.
*/
captureToChar(char, buffer) {
const { chunk, limit, i: start } = this;
while (this.i < limit) {
const { chunk, i: start } = this;
while (true) {
const c = this.getCode();
if (c === char) {
// This is faster than adding codepoints one by one.
this[buffer] += chunk.substring(start,
this.i - (c <= 0xFFFF ? 1 : 2));
this[buffer] += chunk.substring(start, this.i - (c <= 0xFFFF ? 1 : 2));
return true;
}
}

// This is faster than adding codepoints one by one.
this[buffer] += chunk.substring(start);
return false;
if (c === undefined) {
this[buffer] += chunk.substring(start);
return false;
}
}
}

/**
Expand All @@ -790,20 +796,19 @@ class SaxesParser {
* ``undefined`` if we hit the end of the chunk.
*/
captureNameChars() {
const { chunk, limit, i: start } = this;
while (this.i < limit) {
const { chunk, i: start } = this;
while (true) {
const c = this.getCode();
if (c === undefined) {
this.name += chunk.substring(start);
return undefined;
}

if (!isNameChar(c)) {
// This is faster than adding codepoints one by one.
this.name += chunk.substring(start,
this.i - (c <= 0xFFFF ? 1 : 2));
this.name += chunk.substring(start, this.i - (c <= 0xFFFF ? 1 : 2));
return c;
}
}

// This is faster than adding codepoints one by one.
this.name += chunk.substring(start);
return undefined;
}

/**
Expand All @@ -818,20 +823,19 @@ class SaxesParser {
* ``undefined`` if we hit the end of the chunk.
*/
captureWhileNameCheck(buffer) {
const { chunk, limit, i: start } = this;
while (this.i < limit) {
const { chunk, i: start } = this;
while (true) {
const c = this.getCode();
if (c === undefined) {
this[buffer] += chunk.substring(start);
return undefined;
}

if (!this.nameCheck(c)) {
// This is faster than adding codepoints one by one.
this[buffer] += chunk.substring(start,
this.i - (c <= 0xFFFF ? 1 : 2));
this[buffer] += chunk.substring(start, this.i - (c <= 0xFFFF ? 1 : 2));
return c;
}
}

// This is faster than adding codepoints one by one.
this[buffer] += chunk.substring(start);
return undefined;
}

/**
Expand All @@ -843,15 +847,12 @@ class SaxesParser {
* ``undefined`` if we hit the end of the chunk.
*/
skipSpaces() {
const { limit } = this;
while (this.i < limit) {
while (true) {
const c = this.getCode();
if (!isS(c)) {
if (c === undefined || !isS(c)) {
return c;
}
}

return undefined;
}

/** @private */
Expand Down Expand Up @@ -946,29 +947,26 @@ class SaxesParser {
// Since we are using a specialized loop, we also keep track of the presence
// of ]]> in text data. The sequence ]]> is forbidden to appear as-is.
//
const { chunk, limit, i: start } = this;
const { chunk, i: start } = this;
let { forbiddenState } = this;
// eslint-disable-next-line no-labels, no-restricted-syntax
scanLoop:
// eslint-disable-next-line no-constant-condition
while (true) {
if (this.i >= limit) {
const code = this.getCode();
if (code === undefined) {
this.text += chunk.substring(start);
break;
}
const code = this.getCode();
switch (code) {
case LESS:
this.state = S_OPEN_WAKA;
// This is faster than adding codepoints one by one.
this.text += chunk.substring(start, this.i - 1);
forbiddenState = FORBIDDEN_START;
// eslint-disable-next-line no-labels
break scanLoop;
case AMP:
this.state = S_ENTITY;
this.entityReturnState = S_TEXT;
// This is faster than adding codepoints one by one.
this.text += chunk.substring(start, this.i - 1);
forbiddenState = FORBIDDEN_START;
// eslint-disable-next-line no-labels
Expand Down Expand Up @@ -1006,28 +1004,25 @@ class SaxesParser {
// for a specialized task. We keep track of the presence of non-space
// characters in the text since these are errors when appearing outside the
// document root element.
const { chunk, limit, i: start } = this;
const { chunk, i: start } = this;
let nonSpace = false;
// eslint-disable-next-line no-labels, no-restricted-syntax
outRootLoop:
// eslint-disable-next-line no-constant-condition
while (true) {
if (this.i >= limit) {
const code = this.getCode();
if (code === undefined) {
this.text += chunk.substring(start);
break;
}
const code = this.getCode();
switch (code) {
case LESS:
this.state = S_OPEN_WAKA;
// This is faster than adding codepoints one by one.
this.text += chunk.substring(start, this.i - 1);
// eslint-disable-next-line no-labels
break outRootLoop;
case AMP:
this.state = S_ENTITY;
this.entityReturnState = S_TEXT;
// This is faster than adding codepoints one by one.
this.text += chunk.substring(start, this.i - 1);
nonSpace = true;
// eslint-disable-next-line no-labels
Expand Down Expand Up @@ -1772,17 +1767,14 @@ class SaxesParser {
// We deliberately do not use captureTo here. The specialized code we use
// here is faster than using captureTo.
const { q } = this;
const { chunk, limit, i: start } = this;
// eslint-disable-next-line no-constant-condition
const { chunk, i: start } = this;
while (true) {
if (this.i >= limit) {
// This is faster than adding codepoints one by one.
const code = this.getCode();
if (code === undefined) {
this.text += chunk.substring(start);
return;
}
const code = this.getCode();
if (code === q || code === AMP || code === LESS) {
// This is faster than adding codepoints one by one.
const slice = chunk.substring(start, this.i - 1);
switch (code) {
case q:
Expand Down

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