CSS Tokenizer: Fix edge cases in number parsing

Source/core/css/parser/CSSTokenizer.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/css/parser/CSSTokenizer.h"
 
 namespace blink {
 #include "core/CSSTokenizerCodepoints.cpp"
 }
@@ skipping 257 matching lines @@
 }
 
 static unsigned long long getInteger(CSSTokenizerInputStream& input, unsigned& offset)
 {
     unsigned intStartPos = offset;
     offset = input.skipWhilePredicate<isASCIIDigit>(offset);
     unsigned intEndPos = offset;
     return input.getUInt(intStartPos, intEndPos);
 }
 
-static double getFraction(CSSTokenizerInputStream& input, unsigned& offset, unsigned& digitsNumber)
+static double getFraction(CSSTokenizerInputStream& input, unsigned& offset)
 {
-    unsigned fractionStartPos = 0;
-    unsigned fractionEndPos = 0;
-    if (input.peek(offset) == '.' && isASCIIDigit(input.peek(++offset))) {
-        fractionStartPos = offset - 1;
-        offset = input.skipWhilePredicate<isASCIIDigit>(offset);
-        fractionEndPos = offset;
-    }
-    digitsNumber = fractionEndPos- fractionStartPos;
-    return input.getDouble(fractionStartPos, fractionEndPos);
+    if (input.peek(offset) != '.' || !isASCIIDigit(input.peek(offset + 1)))
+        return 0;
+    unsigned startOffset = offset;
+    offset = input.skipWhilePredicate<isASCIIDigit>(offset + 1);
+    return input.getDouble(startOffset, offset);
 }

[Yoav Weiss, 2014/10/20 07:06:45]

So beyond the refactoring (which I like), and the elimination of digitsNumber,
there is no functionality change here, right?

[Timothy Loh, 2014/10/20 07:18:24]

There's a change here which is to only consume the '.' when the following
character is a digit.

[Yoav Weiss, 2014/10/20 07:26:14]

Oh, right. So the move from 'isASCIIDigit(input.peek(++offset))' to
'isASCIIDigit(input.peek(offset + 1))' is the functional change here.

 
 static unsigned long long getExponent(CSSTokenizerInputStream& input, unsigned& offset, int& sign)
 {
     unsigned exponentStartPos = 0;
     unsigned exponentEndPos = 0;
     if ((input.peek(offset) == 'E' || input.peek(offset) == 'e')) {
         int offsetBeforeExponent = offset;
         ++offset;
         if (input.peek(offset) == '+') {
             ++offset;
@@ skipping 13 matching lines @@
 // This method merges the following spec sections for efficiency
 // http://www.w3.org/TR/css3-syntax/#consume-a-number
 // http://www.w3.org/TR/css3-syntax/#convert-a-string-to-a-number
 CSSParserToken CSSTokenizer::consumeNumber()
 {
     ASSERT(nextCharsAreNumber());
     NumericValueType type = IntegerValueType;
     double value = 0;
     unsigned offset = 0;
     int exponentSign = 1;
-    unsigned fractionDigits;
     int sign = getSign(m_input, offset);
     unsigned long long integerPart = getInteger(m_input, offset);
-    double fractionPart = getFraction(m_input, offset, fractionDigits);
+    unsigned integerPartEndOffset = offset;
+
+    double fractionPart = getFraction(m_input, offset);
     unsigned long long exponentPart = getExponent(m_input, offset, exponentSign);
     double exponent = pow(10, (float)exponentSign * (double)exponentPart);
     value = (double)sign * ((double)integerPart + fractionPart) * exponent;
 
     m_input.advance(offset);
-    if (fractionDigits > 0)
+    if (offset != integerPartEndOffset)

[Yoav Weiss, 2014/10/20 07:06:45]

This is where the magic happens, and exponents are turned into a number, right?

[Timothy Loh, 2014/10/20 07:18:24]

Yep

         type = NumberValueType;
 
     return CSSParserToken(NumberToken, value, type);
 }
 
 // http://www.w3.org/TR/css3-syntax/#consume-a-numeric-token
 CSSParserToken CSSTokenizer::consumeNumericToken()
 {
     CSSParserToken token = consumeNumber();
     if (nextCharsAreIdentifier())
@@ skipping 175 matching lines @@
 
 bool CSSTokenizer::nextCharsAreIdentifier()
 {
     UChar first = consume();
     bool areIdentifier = nextCharsAreIdentifier(first);
     reconsume(first);
     return areIdentifier;
 }
 
 } // namespace blink