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// 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/SizesCalcParser.h"
#include "core/css/MediaValues.h"
#include "core/css/parser/MediaQueryToken.h"
namespace WebCore {
bool SizesCalcParser::parse(MediaQueryTokenIterator start, MediaQueryTokenIterator end, PassRefPtr<MediaValues> mediaValues, unsigned& result)
{
SizesCalcParser parser(mediaValues);
if (!parser.calcToReversePolishNotation(start, end))
return false;
return parser.calculate(result);
}
static bool operatorPriority(UChar cc, bool& highPriority)
{
if (cc == '+' || cc == '-')
highPriority = false;
else if (cc == '*' || cc == '/')
highPriority = true;
else
return false;
return true;
}
bool SizesCalcParser::handleOperator(Vector<MediaQueryToken>& stack, const MediaQueryToken& token)
{
// If the token is an operator, o1, then:
// while there is an operator token, o2, at the top of the stack, and
// either o1 is left-associative and its precedence is equal to that of o2,
// or o1 has precedence less than that of o2,
// pop o2 off the stack, onto the output queue;
// push o1 onto the stack.
bool stackOperatorPriority;
bool incomingOperatorPriority;
if (!operatorPriority(token.delimiter(), incomingOperatorPriority))
return false;
if (!stack.isEmpty() && stack.last().type() == DelimiterToken) {
if (!operatorPriority(stack.last().delimiter(), stackOperatorPriority))
return false;
if (!incomingOperatorPriority || stackOperatorPriority) {
appendOperator(stack.last());
stack.removeLast();
}
}
stack.append(token);
return true;
}
void SizesCalcParser::appendNumber(const MediaQueryToken& token)
{
SizesCalcValue value;
value.value = token.numericValue();
m_valueList.append(value);
}
bool SizesCalcParser::appendLength(const MediaQueryToken& token)
{
SizesCalcValue value;
double result = 0;
if (!m_mediaValues->computeLength(token.numericValue(), token.unitType(), result))
return false;
value.value = result;
value.isLength = true;
m_valueList.append(value);
return true;
}
void SizesCalcParser::appendOperator(const MediaQueryToken& token)
{
SizesCalcValue value;
value.operation = token.delimiter();
m_valueList.append(value);
}
bool SizesCalcParser::calcToReversePolishNotation(MediaQueryTokenIterator start, MediaQueryTokenIterator end)
{
// This method implements the shunting yard algorithm, to turn the calc syntax into a reverse polish notation.
// http://en.wikipedia.org/wiki/Shunting-yard_algorithm
Vector<MediaQueryToken> stack;
for (MediaQueryTokenIterator it = start; it != end; ++it) {
MediaQueryTokenType type = it->type();
switch (type) {
case NumberToken:
appendNumber(*it);
break;
case DimensionToken:
if (!CSSPrimitiveValue::isLength(it->unitType()) || !appendLength(*it))
return false;
break;
case DelimiterToken:
if (!handleOperator(stack, *it))
return false;
break;
case FunctionToken:
if (it->value() != "calc")
return false;
// "calc(" is the same as "("
case LeftParenthesisToken:
// If the token is a left parenthesis, then push it onto the stack.
stack.append(*it);
break;
case RightParenthesisToken:
// If the token is a right parenthesis:
// Until the token at the top of the stack is a left parenthesis, pop operators off the stack onto the output queue.
while (!stack.isEmpty() && stack.last().type() != LeftParenthesisToken && stack.last().type() != FunctionToken) {
appendOperator(stack.last());
stack.removeLast();
}
// If the stack runs out without finding a left parenthesis, then there are mismatched parentheses.
if (stack.isEmpty())
return false;
// Pop the left parenthesis from the stack, but not onto the output queue.
stack.removeLast();
break;
case CommentToken:
case WhitespaceToken:
case EOFToken:
break;
case PercentageToken:
case IdentToken:
case CommaToken:
case ColonToken:
case SemicolonToken:
case LeftBraceToken:
case LeftBracketToken:
case RightBraceToken:
case RightBracketToken:
case StringToken:
case BadStringToken:
return false;
}
}
// When there are no more tokens to read:
// While there are still operator tokens in the stack:
while (!stack.isEmpty()) {
// If the operator token on the top of the stack is a parenthesis, then there are mismatched parentheses.
MediaQueryTokenType type = stack.last().type();
if (type == LeftParenthesisToken || type == FunctionToken)
return false;
// Pop the operator onto the output queue.
appendOperator(stack.last());
stack.removeLast();
}
return true;
}
static bool operateOnStack(Vector<SizesCalcValue>& stack, UChar operation)
{
if (stack.size() < 2)
return false;
SizesCalcValue rightOperand = stack.last();
stack.removeLast();
SizesCalcValue leftOperand = stack.last();
stack.removeLast();
bool isLength;
switch (operation) {
case '+':
if (rightOperand.isLength != leftOperand.isLength)
return false;
isLength = (rightOperand.isLength && leftOperand.isLength);
stack.append(SizesCalcValue(leftOperand.value + rightOperand.value, isLength));
break;
case '-':
if (rightOperand.isLength != leftOperand.isLength)
return false;
isLength = (rightOperand.isLength && leftOperand.isLength);
stack.append(SizesCalcValue(leftOperand.value - rightOperand.value, isLength));
break;
case '*':
if (rightOperand.isLength && leftOperand.isLength)
return false;
isLength = (rightOperand.isLength || leftOperand.isLength);
stack.append(SizesCalcValue(leftOperand.value * rightOperand.value, isLength));
break;
case '/':
if (rightOperand.isLength || rightOperand.value == 0)
return false;
stack.append(SizesCalcValue(leftOperand.value / rightOperand.value, leftOperand.isLength));
break;
default:
return false;
}
return true;
}
bool SizesCalcParser::calculate(unsigned& result)
{
Vector<SizesCalcValue> stack;
for (Vector<SizesCalcValue>::iterator it = m_valueList.begin(); it != m_valueList.end(); ++it) {
if (it->operation == 0) {
stack.append(*it);
} else {
if (!operateOnStack(stack, it->operation))
return false;
}
}
if (stack.size() == 1 && stack.last().isLength) {
result = clampTo<unsigned>(stack.last().value);
return true;
}
return false;
}
} // namespace WebCore
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