com.google.common.css.compiler.passes.EliminateUnitsFromZeroNumericValues.java Source code

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Here is the source code for com.google.common.css.compiler.passes.EliminateUnitsFromZeroNumericValues.java

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/*
 * Copyright 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.css.compiler.passes;

import com.google.common.collect.ImmutableSet;
import com.google.common.css.compiler.ast.CssCompilerPass;
import com.google.common.css.compiler.ast.CssNumericNode;
import com.google.common.css.compiler.ast.CssValueNode;
import com.google.common.css.compiler.ast.DefaultTreeVisitor;
import com.google.common.css.compiler.ast.MutatingVisitController;

import java.util.logging.Logger;

/**
 * A compiler pass that eliminates useless units from 0.
 *
 * <p>It is only allowed to eliminate units from relative or absolute length
 * units. See:
 * <a href="http://www.w3.org/TR/1998/WD-css2-19980128/syndata.html#length-units">
 * CSS 2 length units</a> and
 * <a href="http://www.w3.org/TR/css3-values/#lengths">CSS 3 length units</a>
 *
 * @author oana@google.com (Oana Florescu)
 * @author fbenz@google.com (Florian Benz)
 */
public class EliminateUnitsFromZeroNumericValues extends DefaultTreeVisitor implements CssCompilerPass {
    private static final ImmutableSet<String> REMOVABLE_LENGTH_UNITS = ImmutableSet.of("em", "ex", "px", "gd",
            "rem", "vw", "vh", "vm", "ch", "in", "cm", "mm", "pt", "pc");

    private static final Logger logger = Logger.getLogger(EliminateUnitsFromZeroNumericValues.class.getName());

    private final MutatingVisitController visitController;

    public EliminateUnitsFromZeroNumericValues(MutatingVisitController visitController) {
        this.visitController = visitController;
    }

    @Override
    public boolean enterValueNode(CssValueNode node) {
        if (node instanceof CssNumericNode) {
            CssNumericNode numericNode = (CssNumericNode) node;
            String numericValue = numericNode.getNumericPart();
            try {
                float value = Float.parseFloat(numericValue);
                if (value == 0.0) {
                    if (REMOVABLE_LENGTH_UNITS.contains(numericNode.getUnit())) {
                        numericNode.setUnit("");
                    }
                    numericNode.setNumericPart("0");
                } else {
                    // Removes the 0s at the left of the dot.
                    int stripFront = 0;
                    while (numericValue.charAt(stripFront) == '0') {
                        stripFront++;
                    }

                    int stripBack = numericValue.length() - 1;
                    if (numericValue.indexOf(".") >= 0) {
                        // Remove the 0s at the right of the dot.
                        while (numericValue.charAt(stripBack) == '0') {
                            stripBack--;
                        }
                        // Maybe remove the dot.
                        if (numericValue.charAt(stripBack) == '.') {
                            stripBack--;
                        }
                        numericValue = numericValue.substring(stripFront, stripBack + 1);
                    }
                    numericNode.setNumericPart(numericValue);
                }
            } catch (NumberFormatException e) {
                logger.warning("Numeric part of the numeric value node could not be " + "parsed: " + node.toString()
                        + ((node.getSourceCodeLocation() != null)
                                ? "@" + node.getSourceCodeLocation().getLineNumber()
                                : ""));
            }
        }
        return true;
    }

    @Override
    public void runPass() {
        visitController.startVisit(this);
    }
}