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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/197255">197255</a></dd>
<dt>Author</dt> <dd>cdumez@apple.com</dd>
<dt>Date</dt> <dd>2016-02-27 10:30:58 -0800 (Sat, 27 Feb 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Optimize parseHTMLInteger()
https://bugs.webkit.org/show_bug.cgi?id=154772
Reviewed by Ryosuke Niwa.
Optimize parseHTMLInteger() a bit now that it is used a lot more and
that it has decent API test coverage. In particular, we now:
- Avoid using a StringBuilder for the digits.
- Get rid of a is8Bit() branch.
- Only traverse the input string once.
* html/parser/HTMLParserIdioms.cpp:
(WebCore::parseHTMLIntegerInternal):
(WebCore::parseHTMLInteger):
(WebCore::parseHTMLNonNegativeInteger): Deleted.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorehtmlparserHTMLParserIdiomscpp">trunk/Source/WebCore/html/parser/HTMLParserIdioms.cpp</a></li>
</ul>
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<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (197254 => 197255)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog 2016-02-27 17:49:29 UTC (rev 197254)
+++ trunk/Source/WebCore/ChangeLog 2016-02-27 18:30:58 UTC (rev 197255)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2016-02-27 Chris Dumez <cdumez@apple.com>
+
+ Optimize parseHTMLInteger()
+ https://bugs.webkit.org/show_bug.cgi?id=154772
+
+ Reviewed by Ryosuke Niwa.
+
+ Optimize parseHTMLInteger() a bit now that it is used a lot more and
+ that it has decent API test coverage. In particular, we now:
+ - Avoid using a StringBuilder for the digits.
+ - Get rid of a is8Bit() branch.
+ - Only traverse the input string once.
+
+ * html/parser/HTMLParserIdioms.cpp:
+ (WebCore::parseHTMLIntegerInternal):
+ (WebCore::parseHTMLInteger):
+ (WebCore::parseHTMLNonNegativeInteger): Deleted.
+
</ins><span class="cx"> 2016-02-27 Andreas Kling <akling@apple.com>
</span><span class="cx">
</span><span class="cx"> [iOS] Discard decoded image data on top-level navigation.
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlparserHTMLParserIdiomscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/parser/HTMLParserIdioms.cpp (197254 => 197255)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/parser/HTMLParserIdioms.cpp 2016-02-27 17:49:29 UTC (rev 197254)
+++ trunk/Source/WebCore/html/parser/HTMLParserIdioms.cpp 2016-02-27 18:30:58 UTC (rev 197255)
</span><span class="lines">@@ -155,66 +155,54 @@
</span><span class="cx"> template <typename CharacterType>
</span><span class="cx"> static bool parseHTMLIntegerInternal(const CharacterType* position, const CharacterType* end, int& value)
</span><span class="cx"> {
</span><del>- // Step 3
- bool isPositive = true;
-
- // Step 4
- while (position < end) {
- if (!isHTMLSpace(*position))
- break;
</del><ins>+ while (position < end && isHTMLSpace(*position))
</ins><span class="cx"> ++position;
</span><del>- }
</del><span class="cx">
</span><del>- // Step 5
</del><span class="cx"> if (position == end)
</span><span class="cx"> return false;
</span><del>- ASSERT_WITH_SECURITY_IMPLICATION(position < end);
</del><span class="cx">
</span><del>- // Step 6
</del><ins>+ bool isNegative = false;
</ins><span class="cx"> if (*position == '-') {
</span><del>- isPositive = false;
</del><ins>+ isNegative = true;
</ins><span class="cx"> ++position;
</span><span class="cx"> } else if (*position == '+')
</span><span class="cx"> ++position;
</span><del>- if (position == end)
- return false;
- ASSERT_WITH_SECURITY_IMPLICATION(position < end);
</del><span class="cx">
</span><del>- // Step 7
- if (!isASCIIDigit(*position))
</del><ins>+ if (position == end || !isASCIIDigit(*position))
</ins><span class="cx"> return false;
</span><span class="cx">
</span><del>- // Step 8
- StringBuilder cleanCharacters;
- if (!isPositive)
- cleanCharacters.append('-');
- while (position < end) {
- if (!isASCIIDigit(*position))
- break;
- cleanCharacters.append(*position++);
- }
</del><ins>+ constexpr int intMax = std::numeric_limits<int>::max();
+ constexpr int base = 10;
+ constexpr int maxMultiplier = intMax / base;
</ins><span class="cx">
</span><del>- // Step 9
- bool ok;
- if (cleanCharacters.is8Bit())
- value = charactersToIntStrict(cleanCharacters.characters8(), cleanCharacters.length(), &ok);
- else
- value = charactersToIntStrict(cleanCharacters.characters16(), cleanCharacters.length(), &ok);
- return ok;
</del><ins>+ unsigned result = 0;
+ do {
+ int digitValue = *position - '0';
+
+ if (result > maxMultiplier || (result == maxMultiplier && digitValue > (intMax % base) + isNegative))
+ return false;
+
+ result = base * result + digitValue;
+ ++position;
+ } while (position < end && isASCIIDigit(*position));
+
+ value = isNegative ? -result : result;
+ return true;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> // https://html.spec.whatwg.org/multipage/infrastructure.html#rules-for-parsing-integers
</span><span class="cx"> bool parseHTMLInteger(const String& input, int& value)
</span><span class="cx"> {
</span><del>- // Step 1
- // Step 2
</del><span class="cx"> unsigned length = input.length();
</span><del>- if (!length || input.is8Bit()) {
- const LChar* start = input.characters8();
</del><ins>+ if (!length)
+ return false;
+
+ if (LIKELY(input.is8Bit())) {
+ auto* start = input.characters8();
</ins><span class="cx"> return parseHTMLIntegerInternal(start, start + length, value);
</span><span class="cx"> }
</span><span class="cx">
</span><del>- const UChar* start = input.characters16();
</del><ins>+ auto* start = input.characters16();
</ins><span class="cx"> return parseHTMLIntegerInternal(start, start + length, value);
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre>
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