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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include "config.h" |
| 6 #include "core/css/parser/SizesCalcParser.h" |
| 7 |
| 8 #include "core/css/MediaValues.h" |
| 9 #include "core/css/parser/MediaQueryToken.h" |
| 10 |
| 11 namespace WebCore { |
| 12 |
| 13 bool SizesCalcParser::parse(MediaQueryTokenIterator start, |
| 14 MediaQueryTokenIterator end, |
| 15 PassRefPtr<MediaValues> mediaValues, |
| 16 unsigned& result) |
| 17 { |
| 18 SizesCalcParser parser(mediaValues); |
| 19 if (!parser.calcToReversePolishNotation(start, end)) |
| 20 return false; |
| 21 return parser.calculate(result); |
| 22 } |
| 23 |
| 24 static bool operatorPriority(UChar cc, bool& highPriority) |
| 25 { |
| 26 if (cc == '+' || cc == '-') |
| 27 highPriority = false; |
| 28 else if (cc == '*' || cc == '/') |
| 29 highPriority = true; |
| 30 else |
| 31 return false; |
| 32 return true; |
| 33 } |
| 34 |
| 35 bool SizesCalcParser::handleOperator(Vector<MediaQueryToken>& stack, const Media
QueryToken& token) |
| 36 { |
| 37 // If the token is an operator, o1, then: |
| 38 // while there is an operator token, o2, at the top of the stack, and |
| 39 // either o1 is left-associative and its precedence is equal to that of o2, |
| 40 // or o1 has precedence less than that of o2, |
| 41 // pop o2 off the stack, onto the output queue; |
| 42 // push o1 onto the stack. |
| 43 bool stackOperatorPriority; |
| 44 bool incomingOperatorPriority; |
| 45 |
| 46 if (!operatorPriority(token.delimiter(), incomingOperatorPriority)) |
| 47 return false; |
| 48 if (!stack.isEmpty() && stack.last().type() == DelimiterToken) { |
| 49 if (!operatorPriority(stack.last().delimiter(), stackOperatorPriority)) |
| 50 return false; |
| 51 if (!incomingOperatorPriority || stackOperatorPriority) { |
| 52 appendOperator(stack.last()); |
| 53 stack.removeLast(); |
| 54 } |
| 55 } |
| 56 stack.append(token); |
| 57 return true; |
| 58 } |
| 59 |
| 60 void SizesCalcParser::appendNumber(const MediaQueryToken& token) |
| 61 { |
| 62 SizesCalcValue value; |
| 63 value.value = token.numericValue(); |
| 64 m_valueList.append(value); |
| 65 } |
| 66 |
| 67 bool SizesCalcParser::appendLength(const MediaQueryToken& token) |
| 68 { |
| 69 SizesCalcValue value; |
| 70 int result = 0; |
| 71 if (!m_mediaValues->computeLength(token.numericValue(), token.unitType(), re
sult)) |
| 72 return false; |
| 73 value.value = result; |
| 74 value.isLength = true; |
| 75 m_valueList.append(value); |
| 76 return true; |
| 77 } |
| 78 |
| 79 void SizesCalcParser::appendOperator(const MediaQueryToken& token) |
| 80 { |
| 81 SizesCalcValue value; |
| 82 value.operation = token.delimiter(); |
| 83 m_valueList.append(value); |
| 84 } |
| 85 |
| 86 bool SizesCalcParser::calcToReversePolishNotation(MediaQueryTokenIterator start,
MediaQueryTokenIterator end) |
| 87 { |
| 88 // This method implements the shunting yard algorithm, to turn the calc synt
ax into a reverse polish notation. |
| 89 // http://en.wikipedia.org/wiki/Shunting-yard_algorithm |
| 90 |
| 91 Vector<MediaQueryToken> stack; |
| 92 for (MediaQueryTokenIterator it = start; it != end; ++it) { |
| 93 MediaQueryTokenType type = it->type(); |
| 94 switch (type) { |
| 95 case NumberToken: |
| 96 appendNumber(*it); |
| 97 break; |
| 98 case DimensionToken: |
| 99 if (!CSSPrimitiveValue::isLength(it->unitType()) || !appendLength(*i
t)) |
| 100 return false; |
| 101 break; |
| 102 case DelimiterToken: |
| 103 if (!handleOperator(stack, *it)) |
| 104 return false; |
| 105 break; |
| 106 case FunctionToken: |
| 107 if (it->value() != "calc") |
| 108 return false; |
| 109 // "calc(" is the same as "(" |
| 110 case LeftParenthesisToken: |
| 111 // If the token is a left parenthesis, then push it onto the stack. |
| 112 stack.append(*it); |
| 113 break; |
| 114 case RightParenthesisToken: |
| 115 // If the token is a right parenthesis: |
| 116 // Until the token at the top of the stack is a left parenthesis, po
p operators off the stack onto the output queue. |
| 117 while (!stack.isEmpty() && stack.last().type() != LeftParenthesisTok
en && stack.last().type() != FunctionToken) { |
| 118 appendOperator(stack.last()); |
| 119 stack.removeLast(); |
| 120 } |
| 121 // If the stack runs out without finding a left parenthesis, then th
ere are mismatched parentheses. |
| 122 if (stack.isEmpty()) |
| 123 return false; |
| 124 // Pop the left parenthesis from the stack, but not onto the output
queue. |
| 125 stack.removeLast(); |
| 126 break; |
| 127 case CommentToken: |
| 128 case WhitespaceToken: |
| 129 case EOFToken: |
| 130 break; |
| 131 case PercentageToken: |
| 132 case IdentToken: |
| 133 case CommaToken: |
| 134 case ColonToken: |
| 135 case SemicolonToken: |
| 136 case LeftBraceToken: |
| 137 case LeftBracketToken: |
| 138 case RightBraceToken: |
| 139 case RightBracketToken: |
| 140 case StringToken: |
| 141 case BadStringToken: |
| 142 return false; |
| 143 } |
| 144 } |
| 145 |
| 146 // When there are no more tokens to read: |
| 147 // While there are still operator tokens in the stack: |
| 148 while (!stack.isEmpty()) { |
| 149 // If the operator token on the top of the stack is a parenthesis, then
there are mismatched parentheses. |
| 150 MediaQueryTokenType type = stack.last().type(); |
| 151 if (type == LeftParenthesisToken || type == FunctionToken) |
| 152 return false; |
| 153 // Pop the operator onto the output queue. |
| 154 appendOperator(stack.last()); |
| 155 stack.removeLast(); |
| 156 } |
| 157 return true; |
| 158 } |
| 159 |
| 160 static bool operateOnStack(Vector<SizesCalcValue>& stack, UChar operation) |
| 161 { |
| 162 if (stack.size() < 2) |
| 163 return false; |
| 164 SizesCalcValue rightOperand = stack.last(); |
| 165 stack.removeLast(); |
| 166 SizesCalcValue leftOperand = stack.last(); |
| 167 stack.removeLast(); |
| 168 switch (operation) { |
| 169 case '+': |
| 170 if (!rightOperand.isLength || !leftOperand.isLength) |
| 171 return false; |
| 172 stack.append(SizesCalcValue(leftOperand.value + rightOperand.value)); |
| 173 break; |
| 174 case '-': |
| 175 if (!rightOperand.isLength || !leftOperand.isLength) |
| 176 return false; |
| 177 stack.append(SizesCalcValue(leftOperand.value - rightOperand.value)); |
| 178 break; |
| 179 case '*': |
| 180 if (rightOperand.isLength && leftOperand.isLength) |
| 181 return false; |
| 182 stack.append(SizesCalcValue(leftOperand.value * rightOperand.value)); |
| 183 break; |
| 184 case '/': |
| 185 if (!leftOperand.isLength || rightOperand.isLength || rightOperand.value
== 0) |
| 186 return false; |
| 187 stack.append(SizesCalcValue(leftOperand.value / rightOperand.value)); |
| 188 break; |
| 189 default: |
| 190 return false; |
| 191 } |
| 192 return true; |
| 193 } |
| 194 |
| 195 bool SizesCalcParser::calculate(unsigned& result) |
| 196 { |
| 197 Vector<SizesCalcValue> stack; |
| 198 for (Vector<SizesCalcValue>::iterator it = m_valueList.begin(); it != m_valu
eList.end(); ++it) { |
| 199 if (it->operation == 0) { |
| 200 stack.append(*it); |
| 201 } else { |
| 202 if (!operateOnStack(stack, it->operation)) |
| 203 return false; |
| 204 } |
| 205 } |
| 206 if (stack.size() == 1) { |
| 207 result = clampTo<unsigned>(stack.last().value); |
| 208 return true; |
| 209 } |
| 210 return false; |
| 211 } |
| 212 |
| 213 } // namespace WebCore |
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