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PlantUML is a component that allows to quickly write diagrams from text.
There is a newer version: 1.2024.8
// THIS FILE HAS BEEN GENERATED BY A PREPROCESSOR.
/* +=======================================================================
 * |
 * |      PlantUML : a free UML diagram generator
 * |
 * +=======================================================================
 *
 * (C) Copyright 2009-2024, Arnaud Roques
 *
 * Project Info:  https://plantuml.com
 *
 * If you like this project or if you find it useful, you can support us at:
 *
 * https://plantuml.com/patreon (only 1$ per month!)
 * https://plantuml.com/liberapay (only 1€ per month!)
 * https://plantuml.com/paypal
 *
 *
 * PlantUML is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License V2.
 *
 * THE ACCOMPANYING PROGRAM IS PROVIDED UNDER THE TERMS OF THIS ECLIPSE PUBLIC
 * LICENSE ("AGREEMENT"). [GNU General Public License V2]
 *
 * ANY USE, REPRODUCTION OR DISTRIBUTION OF THE PROGRAM CONSTITUTES
 * RECIPIENT'S ACCEPTANCE OF THIS AGREEMENT.
 *
 * You may obtain a copy of the License at
 *
 * https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *
 * 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.
 *
 * PlantUML can occasionally display sponsored or advertising messages. Those
 * messages are usually generated on welcome or error images and never on
 * functional diagrams.
 * See https://plantuml.com/professional if you want to remove them
 *
 * Images (whatever their format : PNG, SVG, EPS...) generated by running PlantUML
 * are owned by the author of their corresponding sources code (that is, their
 * textual description in PlantUML language). Those images are not covered by
 * this GPL v2 license.
 *
 * The generated images can then be used without any reference to the GPL v2 license.
 * It is not even necessary to stipulate that they have been generated with PlantUML,
 * although this will be appreciated by the PlantUML team.
 *
 * There is an exception : if the textual description in PlantUML language is also covered
 * by any license, then the generated images are logically covered
 * by the very same license.
 *
 * This is the IGY distribution (Install GraphViz by Yourself).
 * You have to install GraphViz and to setup the GRAPHVIZ_DOT environment variable
 * (see https://plantuml.com/graphviz-dot )
 *
 * Icons provided by OpenIconic :  https://useiconic.com/open
 * Archimate sprites provided by Archi :  http://www.archimatetool.com
 * Stdlib AWS provided by https://github.com/milo-minderbinder/AWS-PlantUML
 * Stdlib Icons provided https://github.com/tupadr3/plantuml-icon-font-sprites
 * ASCIIMathML (c) Peter Jipsen http://www.chapman.edu/~jipsen
 * ASCIIMathML (c) David Lippman http://www.pierce.ctc.edu/dlippman
 * CafeUndZopfli ported by Eugene Klyuchnikov https://github.com/eustas/CafeUndZopfli
 * Brotli (c) by the Brotli Authors https://github.com/google/brotli
 * Themes (c) by Brett Schwarz https://github.com/bschwarz/puml-themes
 * Twemoji (c) by Twitter at https://twemoji.twitter.com/
 *
 */

package ext.plantuml.com.google.zxing.common;

/**
 * This provides an easy abstraction to read bits at a time from a sequence of bytes, where the
 * number of bits read is not often a multiple of 8.
 *
 * This class is thread-safe but not reentrant. Unless the caller modifies the bytes array
 * it passed in, in which case all bets are off.
 *
 * @author Sean Owen
 */
public final class BitSource {

  private final byte[] bytes;
  private int byteOffset;
  private int bitOffset;

  /**
   * @param bytes bytes from which this will read bits. Bits will be read from the first byte first.
   * Bits are read within a byte from most-significant to least-significant bit.
   */
  public BitSource(byte[] bytes) {
    this.bytes = bytes;
  }

  /**
   * @param numBits number of bits to read
   * @return int representing the bits read. The bits will appear as the least-significant
   *         bits of the int
   * @throws IllegalArgumentException if numBits isn't in [1,32]
   */
  public int readBits(int numBits) {
    if (numBits < 1 || numBits > 32) {
      throw new IllegalArgumentException();
    }

    int result = 0;

    // First, read remainder from current byte
    if (bitOffset > 0) {
      int bitsLeft = 8 - bitOffset;
      int toRead = numBits < bitsLeft ? numBits : bitsLeft;
      int bitsToNotRead = bitsLeft - toRead;
      int mask = (0xFF >> (8 - toRead)) << bitsToNotRead;
      result = (bytes[byteOffset] & mask) >> bitsToNotRead;
      numBits -= toRead;
      bitOffset += toRead;
      if (bitOffset == 8) {
        bitOffset = 0;
        byteOffset++;
      }
    }

    // Next read whole bytes
    if (numBits > 0) {
      while (numBits >= 8) {
        result = (result << 8) | (bytes[byteOffset] & 0xFF);
        byteOffset++;
        numBits -= 8;
      }

      // Finally read a partial byte
      if (numBits > 0) {
        int bitsToNotRead = 8 - numBits;
        int mask = (0xFF >> bitsToNotRead) << bitsToNotRead;
        result = (result << numBits) | ((bytes[byteOffset] & mask) >> bitsToNotRead);
        bitOffset += numBits;
      }
    }

    return result;
  }

  /**
   * @return number of bits that can be read successfully
   */
  public int available() {
    return 8 * (bytes.length - byteOffset) - bitOffset;
  }

}