A thread-safe Media Query Parser

Source/core/css/parser/MediaQueryParser.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/MediaQueryParser.h"
+
+#include "core/css/CSSParserValues.h"
+#include "core/css/MediaList.h"
+#include "core/css/MediaQuery.h"
+#include "core/css/MediaQueryExp.h"
+#include "core/css/parser/NewCSSTokenizer.h"
+
+namespace WebCore {
+
+PassRefPtr<MediaQuerySet> MediaQueryParser::parse(String queryString)
+{
+    MediaQueryParser parser(queryString);
+    return parser.parseImpl();
+}
+
+MediaQueryParser::MediaQueryParser(String queryString)
+    : m_state(ReadRestrictor)
+{
+    NewCSSTokenizer::tokenize(queryString, m_tokens);
+}
+
+PassRefPtr<MediaQuerySet> MediaQueryParser::parseImpl()
+{
+    RefPtr<MediaQuerySet> querySet = MediaQuerySet::create();
+    MediaQuery::Restrictor restrictor = MediaQuery::None;
+    String mediaType("all");
+    OwnPtr<ExpressionVector> expressions = adoptPtr(new ExpressionVector());
+    String mediaFeature;
+    CSSParserValueList valueList;
+    CSSTokenType type;
+
+    for (Vector<CSSToken>::iterator it = m_tokens.begin(); it != m_tokens.end(); ++it) {
+        type = it->type();
+        // FIXME - turn this into a lookup table
+        if (type == WhitespaceToken) {
+            continue;
+        }
+        /*
+        if (type == WhitespaceToken || type == DelimToken) {
+            continue;
+        }
+        */
+        if (m_state <= ReadMediaType) {
+            if (type == LeftParenToken) {
+                m_state = ReadFeature;
+            } else if (type == IdentToken) {
+                if (m_state == ReadRestrictor && it->value() == "not") {
+                    restrictor = MediaQuery::Not;
+                    m_state = ReadMediaType;
+                } else if (m_state == ReadRestrictor && it->value() == "only") {
+                    restrictor = MediaQuery::Only;
+                    m_state = ReadMediaType;
+                } else {
+                    mediaType = it->value();
+                    m_state = ReadAnd;
+                }
+            } else {
+                m_state = SkipTillComma;
+            }
+        } else if (m_state == ReadAnd) {
+            if (type == IdentToken && it->value() == "and") {
+                m_state = ReadFeatureStart;
+            } else if (type == CommaToken) {
+                // Append the current MediaQuery and initialize a new one
+                mediaType.ensure16Bit();
+                querySet->addMediaQuery(adoptPtr(new MediaQuery(restrictor, mediaType, expressions.release())));
+                expressions = adoptPtr(new ExpressionVector());
+                m_state = ReadRestrictor;
+                mediaType = "all";
+                mediaFeature = "";
+                restrictor = MediaQuery::None;
+                valueList.clear();
+            } else {
+                m_state = SkipTillComma;
+            }
+        } else if (m_state == ReadFeatureStart) {
+            if (type == LeftParenToken) {
+                m_state = ReadFeature;
+            } else {
+                m_state = SkipTillComma;
+            }
+        } else if (m_state == ReadFeature) {
+            if (type == IdentToken) {
+                mediaFeature = it->value();
+                m_state = ReadFeatureColon;
+            } else {
+                m_state = SkipTillComma;
+            }
+        } else if (m_state == ReadFeatureColon) {
+            if (type == ColonToken) {
+                m_state = ReadFeatureValue;
+            } else if (type == RightParenToken) {
+                --it;
+                m_state = ReadFeatureEnd;
+            } else {
+                m_state = SkipTillParen;
+            }
+        } else if (m_state == ReadFeatureValue) {
+            // Read the value and unit
+            CSSParserValue value;
+            if (type == NumberToken || type == PercentageToken || type == DimensionToken) {
+                value.setFromNumber(it->numericValue(), it->unitType());
+                value.isInt = (it->numericValueType() == IntegerValueType);
+            } else {
+                CSSParserFunction function;
+                function.name.init(it->value());
+                value.setFromFunction(&function);
+            }
+            valueList.addValue(value);
+            m_state = ReadFeatureEnd;
+        } else if (m_state == ReadFeatureEnd) {
+            if (type == RightParenToken) {
+                OwnPtr<MediaQueryExp> expression = MediaQueryExp::create(mediaFeature, &valueList);
+                if (expression) {
+                    expressions->append(expression.release());
+                    m_state = ReadAnd;
+                } else {
+                    m_state = SkipTillComma;
+                }
+
+                valueList.clear();
+            } else if (type == DelimToken && it->delimiter() == '/') {
+                CSSParserValue value;
+                value.unit = CSSParserValue::Operator;
+                value.iValue = '/';
+                valueList.addValue(value);
+                m_state = ReadFeatureValue;
+            } else {
+                m_state = SkipTillParen;
+            }
+        } else if (m_state == SkipTillComma) {
+            if (type == CommaToken || type == EOFToken) {
+                m_state = ReadRestrictor;
+                mediaType = "all";
+                mediaFeature = "";
+                valueList.clear();
+                expressions = adoptPtr(new ExpressionVector());
+                mediaType.ensure16Bit();
+                querySet->addMediaQuery(adoptPtr(new MediaQuery(MediaQuery::Not, mediaType, nullptr)));
+                restrictor = MediaQuery::None;
+            }
+            // FIXME - Should dump previousely gathered results???
+        } else if (m_state == SkipTillParen) {
+            if (type == RightParenToken) {
+                m_state = ReadAnd;
+                mediaType = "all";
+                restrictor = MediaQuery::Not;
+                mediaFeature = "";
+                expressions = adoptPtr(new ExpressionVector());
+            }
+            // FIXME - Should dump previousely gathered results???
+        }
+    }
+    // Write down the last MQ, if there was one
+    if (restrictor != MediaQuery::None || mediaType != "all" || expressions->size() > 0) {
+        mediaType.ensure16Bit();
+        querySet->addMediaQuery(adoptPtr(new MediaQuery(restrictor, mediaType, expressions.release())));
+    }
+    return querySet;
+}
+
+} // namespace WebCore