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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2011 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp.parsing.parser;

import com.google.javascript.jscomp.parsing.parser.util.SourcePosition;
import com.google.javascript.jscomp.parsing.parser.util.SourceRange;
import java.util.ArrayList;
import java.util.Arrays;

/**
 * Maps offsets into a source string into line/column positions.
 *
 * Immutable.
 */
public class LineNumberTable {

  private final SourceFile sourceFile;
  private final int[] lineStartOffsets;

  public LineNumberTable(SourceFile sourceFile) {
    this.sourceFile = sourceFile;
    this.lineStartOffsets = computeLineStartOffsets(sourceFile.contents);
  }

  private static int[] computeLineStartOffsets(String source) {
    // TODO(johnlenz): do this more efficiently.
    ArrayList lineStartOffsets = new ArrayList<>();
    lineStartOffsets.add(0);
    for (int index = 0; index < source.length(); index++) {
      char ch = source.charAt(index);
      if (isLineTerminator(ch)) {
        if (index + 1 < source.length() && ch == '\r'
            && source.charAt(index + 1) == '\n') {
          index++;
        }
        lineStartOffsets.add(index + 1);
      }
    }
    lineStartOffsets.add(Integer.MAX_VALUE);
    return toIntArray(lineStartOffsets);
  }

  public static int[] toIntArray(ArrayList integers) {
    int[] ret = new int[integers.size()];
    Arrays.setAll(ret, (i) -> integers.get(i).intValue());
    return ret;
  }

  private static boolean isLineTerminator(char ch) {
    switch (ch) {
    case '\n': // Line Feed
    case '\r':  // Carriage Return
    case '\u2028':  // Line Separator
    case '\u2029':  // Paragraph Separator
      return true;
    default:
      return false;
    }
  }

  public SourcePosition getSourcePosition(int offset) {
    int line = getLine(offset);
    return new SourcePosition(sourceFile, offset, line, getColumn(line, offset));
  }

  public int getLine(int offset) {
    int index = Arrays.binarySearch(lineStartOffsets, offset);
    // start of line
    if (index >= 0) {
      return index;
    }
    return -index - 2;
  }

  public int offsetOfLine(int line) {
    return lineStartOffsets[line];
  }

  private int getColumn(int line, int offset) {
    return offset - offsetOfLine(line);
  }

  public SourceRange getSourceRange(int startOffset, int endOffset) {
    return new SourceRange(getSourcePosition(startOffset), getSourcePosition(endOffset));
  }
}