CSSSupportsParser.cpp   [plain text]

// Copyright 2015 The Chromium Authors. All rights reserved.
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#include "config.h"
#include "CSSSupportsParser.h"

#include "CSSParserImpl.h"

namespace WebCore {

CSSSupportsParser::SupportsResult CSSSupportsParser::supportsCondition(CSSParserTokenRange range, CSSParserImpl& parser, SupportsParsingMode mode)
{
    // FIXME: The spec allows leading whitespace in @supports but not CSS.supports,
    // but major browser vendors allow it in CSS.supports also.
    range.consumeWhitespace();
    CSSSupportsParser supportsParser(parser);
    auto result = supportsParser.consumeCondition(range);
    if (mode != ForWindowCSS || result != Invalid)
        return result;
    // window.CSS.supports requires parsing as-if the condition was wrapped in
    // parenthesis. The only productions that wouldn't have parsed above are the
    // declaration condition or the general enclosed productions.
    return supportsParser.consumeDeclarationConditionOrGeneralEnclosed(range);
}

enum ClauseType { Unresolved, Conjunction, Disjunction };

CSSSupportsParser::SupportsResult CSSSupportsParser::consumeCondition(CSSParserTokenRange range)
{
    if (range.peek().type() == IdentToken || range.peek().type() == FunctionToken)
        return consumeNegation(range);

    bool result;
    ClauseType clauseType = Unresolved;
    
    auto previousTokenType = IdentToken;

    while (true) {
        SupportsResult nextResult = consumeConditionInParenthesis(range, previousTokenType);
        if (nextResult == Invalid)
            return Invalid;
        bool nextSupported = nextResult;
        if (clauseType == Unresolved)
            result = nextSupported;
        else if (clauseType == Conjunction)
            result &= nextSupported;
        else
            result |= nextSupported;

        if (range.atEnd())
            break;
        range.consumeWhitespace();
        if (range.atEnd())
            break;

        const CSSParserToken& token = range.peek();
        if (token.type() != IdentToken && token.type() != FunctionToken)
            return Invalid;
        
        previousTokenType = token.type();
        
        if (clauseType == Unresolved)
            clauseType = token.value().length() == 3 ? Conjunction : Disjunction;
        if ((clauseType == Conjunction && !equalIgnoringASCIICase(token.value(), "and"))
            || (clauseType == Disjunction && !equalIgnoringASCIICase(token.value(), "or")))
            return Invalid;

        if (token.type() == IdentToken)
            range.consumeIncludingWhitespace();
    }
    return result ? Supported : Unsupported;
}

CSSSupportsParser::SupportsResult CSSSupportsParser::consumeNegation(CSSParserTokenRange range)
{
    ASSERT(range.peek().type() == IdentToken || range.peek().type() == FunctionToken);
    auto tokenType = range.peek().type();
    if (!equalIgnoringASCIICase(range.peek().value(), "not"))
        return Invalid;
    if (range.peek().type() == IdentToken)
        range.consumeIncludingWhitespace();
    SupportsResult result = consumeConditionInParenthesis(range, tokenType);
    range.consumeWhitespace();
    if (!range.atEnd() || result == Invalid)
        return Invalid;
    return result ? Unsupported : Supported;
}

CSSSupportsParser::SupportsResult CSSSupportsParser::consumeDeclarationConditionOrGeneralEnclosed(CSSParserTokenRange& range)
{
    if (range.peek().type() == FunctionToken) {
        range.consumeComponentValue();
        return Unsupported;
    }

    return range.peek().type() == IdentToken && m_parser.supportsDeclaration(range) ? Supported : Unsupported;
}

CSSSupportsParser::SupportsResult CSSSupportsParser::consumeConditionInParenthesis(CSSParserTokenRange& range, CSSParserTokenType startTokenType)
{
    if (startTokenType == IdentToken && range.peek().type() != LeftParenthesisToken)
        return Invalid;

    CSSParserTokenRange innerRange = range.consumeBlock();
    innerRange.consumeWhitespace();
    SupportsResult result = consumeCondition(innerRange);
    if (result != Invalid)
        return result;
    return consumeDeclarationConditionOrGeneralEnclosed(innerRange);
}

} // namespace WebCore