com.google.collide.shared.grok.PositionTranslator.java Source code

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Here is the source code for com.google.collide.shared.grok.PositionTranslator.java

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// Copyright 2012 Google Inc. All Rights Reserved.
//
// 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.collide.shared.grok;

import com.google.collide.shared.document.LineNumberAndColumn;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;

import java.util.Collections;
import java.util.List;

/**
 * A class to translate between position representations, such as (line number,
 * column) and text offset.
 *
 */
@GwtCompatible
public class PositionTranslator {

    private static List<Integer> calculateNewlineOffsets(String fileContents) {
        Preconditions.checkNotNull(fileContents);
        List<Integer> newlineOffsets = Lists.newArrayList();
        for (int i = -1; (i = fileContents.indexOf('\n', i + 1)) >= 0;) {
            newlineOffsets.add(i);
        }

        return newlineOffsets;
    }

    /**
     * Stores the offset for the newline character on line i, where i is the index
     */
    private final List<Integer> newlineOffsets;

    public PositionTranslator(String fileContents) {
        this.newlineOffsets = calculateNewlineOffsets(fileContents);
    }

    public LineNumberAndColumn getLineNumberAndColumn(int offset) {
        int binarySearchResult = Collections.binarySearch(newlineOffsets, offset);
        int lineNumber = binarySearchResult >= 0 ? binarySearchResult : -(binarySearchResult + 1);
        int offsetOfFirstCharacterOnLine = getOffsetOfPreviousNewline(lineNumber) + 1;
        return new LineNumberAndColumn(lineNumber, offset - offsetOfFirstCharacterOnLine);
    }

    public int getOffset(int lineNumber, int column) {
        int offsetOfPreviousNewline = getOffsetOfPreviousNewline(lineNumber);
        return offsetOfPreviousNewline + 1 + column;
    }

    /**
     * Returns -1 if this is the first line.
     */
    private int getOffsetOfPreviousNewline(int lineNumber) {
        return lineNumber > 0 ? newlineOffsets.get(lineNumber - 1) : -1;
    }
}