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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.

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/*
 * Copyright 2009 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;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.primitives.UnsignedBytes;

import java.util.BitSet;

/**
 * Holds instrumentation details related to a file, namely, the filename,
 * the array name used in instrumentation, and the lines which were
 * instrumented (in encoded form).
 * @author [email protected] (Praveen Kumashi)
 */
@GwtIncompatible("com.google.common.primitives.UnsignedBytes")
class FileInstrumentationData {
  private final BitSet instrumentedBits;
  private final String arrayName;
  private final String fileName;

  FileInstrumentationData(String fileName, String arrayName) {
    this.fileName = fileName;
    this.arrayName = arrayName;
    instrumentedBits = new BitSet();
  }

  String getArrayName() {
    return arrayName;
  }

  String getFileName() {
    return fileName;
  }

  /**
   * Returns a byte-wise hex string representation of the BitField from
   * MSB (Most Significant Byte) to LSB (Least Significant Byte).
   * Eg. Single byte: a setting of "0001 1111", returns "1f"
   * Eg. Multiple bytes: a setting of "0000 0010 0001 1111", returns "1f02"
   *
   * @return string representation of bits set
   */
  String getInstrumentedLinesAsHexString() {
    StringBuilder builder = new StringBuilder();

    // Build the hex string.
    for (byte byteEntry : instrumentedBits.toByteArray()) {
      // Java bytes are signed, but we want the value as if it were unsigned.
      int value = UnsignedBytes.toInt(byteEntry);
      String hexString = Integer.toHexString(value);

      // Pad string to be two characters (if it isn't already).
      hexString = Strings.padStart(hexString, 2, '0');

      builder.append(hexString);
    }

    return builder.toString();
  }


  /**
   * Mark given 1-based line number as instrumented. Zero, Negative numbers
   * are not allowed.
   * @param lineNumber the line number which was instrumented
   */
  void setLineAsInstrumented(int lineNumber) {
    Preconditions.checkArgument(
        lineNumber > 0, "Expected non-zero positive integer as line number: %s", lineNumber);

    // Map the 1-based line number to 0-based bit position
    instrumentedBits.set(lineNumber - 1);
  }
}