code: // ASM: a very small and fast Java bytecode manipulation framework
  // Copyright (c) 2000-2011 INRIA, France Telecom
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  //
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  //    notice, this list of conditions and the following disclaimer in the
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  //    contributors may be used to endorse or promote products derived from
  //    this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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  // THE POSSIBILITY OF SUCH DAMAGE.
  package clojure.asm;
  
  /**
   * A dynamically extensible vector of bytes. This class is roughly equivalent to a DataOutputStream
   * on top of a ByteArrayOutputStream, but is more efficient.
   *
   * @author Eric Bruneton
   */
  public class ByteVector {
  
    /** The content of this vector. Only the first {@link #length} bytes contain real data. */
    byte[] data;
  
    /** The actual number of bytes in this vector. */
    int length;
  
    /** Constructs a new {@link ByteVector} with a default initial capacity. */
    public ByteVector() {
      data = new byte[64];
    }
  
    /**
     * Constructs a new {@link ByteVector} with the given initial capacity.
     *
     * @param initialCapacity the initial capacity of the byte vector to be constructed.
     */
    public ByteVector(final int initialCapacity) {
      data = new byte[initialCapacity];
    }
  
    /**
     * Constructs a new {@link ByteVector} from the given initial data.
     *
     * @param data the initial data of the new byte vector.
     */
    ByteVector(final byte[] data) {
      this.data = data;
      this.length = data.length;
    }
  
    /**
     * Puts a byte into this byte vector. The byte vector is automatically enlarged if necessary.
     *
     * @param byteValue a byte.
     * @return this byte vector.
     */
    public ByteVector putByte(final int byteValue) {
      int currentLength = length;
      if (currentLength + 1 > data.length) {
        enlarge(1);
      }
      data[currentLength++] = (byte) byteValue;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts two bytes into this byte vector. The byte vector is automatically enlarged if necessary.
     *
     * @param byteValue1 a byte.
     * @param byteValue2 another byte.
     * @return this byte vector.
     */
    final ByteVector put11(final int byteValue1, final int byteValue2) {
      int currentLength = length;
      if (currentLength + 2 > data.length) {
        enlarge(2);
      }
      byte[] currentData = data;
      currentData[currentLength++] = (byte) byteValue1;
      currentData[currentLength++] = (byte) byteValue2;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts a short into this byte vector. The byte vector is automatically enlarged if necessary.
     *
     * @param shortValue a short.
     * @return this byte vector.
     */
    public ByteVector putShort(final int shortValue) {
      int currentLength = length;
      if (currentLength + 2 > data.length) {
        enlarge(2);
      }
      byte[] currentData = data;
      currentData[currentLength++] = (byte) (shortValue >>> 8);
      currentData[currentLength++] = (byte) shortValue;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts a byte and a short into this byte vector. The byte vector is automatically enlarged if
     * necessary.
     *
     * @param byteValue a byte.
     * @param shortValue a short.
     * @return this byte vector.
     */
    final ByteVector put12(final int byteValue, final int shortValue) {
      int currentLength = length;
      if (currentLength + 3 > data.length) {
        enlarge(3);
      }
      byte[] currentData = data;
      currentData[currentLength++] = (byte) byteValue;
      currentData[currentLength++] = (byte) (shortValue >>> 8);
      currentData[currentLength++] = (byte) shortValue;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts two bytes and a short into this byte vector. The byte vector is automatically enlarged if
     * necessary.
     *
     * @param byteValue1 a byte.
     * @param byteValue2 another byte.
     * @param shortValue a short.
     * @return this byte vector.
     */
    final ByteVector put112(final int byteValue1, final int byteValue2, final int shortValue) {
      int currentLength = length;
      if (currentLength + 4 > data.length) {
        enlarge(4);
      }
      byte[] currentData = data;
      currentData[currentLength++] = (byte) byteValue1;
      currentData[currentLength++] = (byte) byteValue2;
      currentData[currentLength++] = (byte) (shortValue >>> 8);
      currentData[currentLength++] = (byte) shortValue;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts an int into this byte vector. The byte vector is automatically enlarged if necessary.
     *
     * @param intValue an int.
     * @return this byte vector.
     */
    public ByteVector putInt(final int intValue) {
      int currentLength = length;
      if (currentLength + 4 > data.length) {
        enlarge(4);
      }
      byte[] currentData = data;
      currentData[currentLength++] = (byte) (intValue >>> 24);
      currentData[currentLength++] = (byte) (intValue >>> 16);
      currentData[currentLength++] = (byte) (intValue >>> 8);
      currentData[currentLength++] = (byte) intValue;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts one byte and two shorts into this byte vector. The byte vector is automatically enlarged
     * if necessary.
     *
     * @param byteValue a byte.
     * @param shortValue1 a short.
     * @param shortValue2 another short.
     * @return this byte vector.
     */
    final ByteVector put122(final int byteValue, final int shortValue1, final int shortValue2) {
      int currentLength = length;
      if (currentLength + 5 > data.length) {
        enlarge(5);
      }
      byte[] currentData = data;
      currentData[currentLength++] = (byte) byteValue;
      currentData[currentLength++] = (byte) (shortValue1 >>> 8);
      currentData[currentLength++] = (byte) shortValue1;
      currentData[currentLength++] = (byte) (shortValue2 >>> 8);
      currentData[currentLength++] = (byte) shortValue2;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts a long into this byte vector. The byte vector is automatically enlarged if necessary.
     *
     * @param longValue a long.
     * @return this byte vector.
     */
    public ByteVector putLong(final long longValue) {
      int currentLength = length;
      if (currentLength + 8 > data.length) {
        enlarge(8);
      }
      byte[] currentData = data;
      int intValue = (int) (longValue >>> 32);
      currentData[currentLength++] = (byte) (intValue >>> 24);
      currentData[currentLength++] = (byte) (intValue >>> 16);
      currentData[currentLength++] = (byte) (intValue >>> 8);
      currentData[currentLength++] = (byte) intValue;
      intValue = (int) longValue;
      currentData[currentLength++] = (byte) (intValue >>> 24);
      currentData[currentLength++] = (byte) (intValue >>> 16);
      currentData[currentLength++] = (byte) (intValue >>> 8);
      currentData[currentLength++] = (byte) intValue;
      length = currentLength;
      return this;
    }
  
    /**
     * Puts an UTF8 string into this byte vector. The byte vector is automatically enlarged if
     * necessary.
     *
     * @param stringValue a String whose UTF8 encoded length must be less than 65536.
     * @return this byte vector.
     */
    public ByteVector putUTF8(final String stringValue) {
      int charLength = stringValue.length();
      if (charLength > 65535) {
        throw new IllegalArgumentException();
      }
      int currentLength = length;
      if (currentLength + 2 + charLength > data.length) {
        enlarge(2 + charLength);
      }
      byte[] currentData = data;
      // Optimistic algorithm: instead of computing the byte length and then serializing the string
      // (which requires two loops), we assume the byte length is equal to char length (which is the
      // most frequent case), and we start serializing the string right away. During the
      // serialization, if we find that this assumption is wrong, we continue with the general method.
      currentData[currentLength++] = (byte) (charLength >>> 8);
      currentData[currentLength++] = (byte) charLength;
      for (int i = 0; i < charLength; ++i) {
        char charValue = stringValue.charAt(i);
        if (charValue >= '\u0001' && charValue <= '\u007F') {
          currentData[currentLength++] = (byte) charValue;
        } else {
          length = currentLength;
          return encodeUTF8(stringValue, i, 65535);
        }
      }
      length = currentLength;
      return this;
    }
  
    /**
     * Puts an UTF8 string into this byte vector. The byte vector is automatically enlarged if
     * necessary. The string length is encoded in two bytes before the encoded characters, if there is
     * space for that (i.e. if this.length - offset - 2 &gt;= 0).
     *
     * @param stringValue the String to encode.
     * @param offset the index of the first character to encode. The previous characters are supposed
     *     to have already been encoded, using only one byte per character.
     * @param maxByteLength the maximum byte length of the encoded string, including the already
     *     encoded characters.
     * @return this byte vector.
     */
    final ByteVector encodeUTF8(final String stringValue, final int offset, final int maxByteLength) {
      int charLength = stringValue.length();
      int byteLength = offset;
      for (int i = offset; i < charLength; ++i) {
        char charValue = stringValue.charAt(i);
        if (charValue >= '\u0001' && charValue <= '\u007F') {
          byteLength++;
        } else if (charValue <= '\u07FF') {
          byteLength += 2;
        } else {
          byteLength += 3;
        }
      }
      if (byteLength > maxByteLength) {
        throw new IllegalArgumentException();
      }
      // Compute where 'byteLength' must be stored in 'data', and store it at this location.
      int byteLengthOffset = length - offset - 2;
      if (byteLengthOffset >= 0) {
        data[byteLengthOffset] = (byte) (byteLength >>> 8);
        data[byteLengthOffset + 1] = (byte) byteLength;
      }
      if (length + byteLength - offset > data.length) {
        enlarge(byteLength - offset);
      }
      int currentLength = length;
      for (int i = offset; i < charLength; ++i) {
        char charValue = stringValue.charAt(i);
        if (charValue >= '\u0001' && charValue <= '\u007F') {
          data[currentLength++] = (byte) charValue;
        } else if (charValue <= '\u07FF') {
          data[currentLength++] = (byte) (0xC0 | charValue >> 6 & 0x1F);
          data[currentLength++] = (byte) (0x80 | charValue & 0x3F);
        } else {
          data[currentLength++] = (byte) (0xE0 | charValue >> 12 & 0xF);
          data[currentLength++] = (byte) (0x80 | charValue >> 6 & 0x3F);
          data[currentLength++] = (byte) (0x80 | charValue & 0x3F);
        }
      }
      length = currentLength;
      return this;
    }
  
    /**
     * Puts an array of bytes into this byte vector. The byte vector is automatically enlarged if
     * necessary.
     *
     * @param byteArrayValue an array of bytes. May be <tt>null</tt> to put <tt>byteLength</tt> null
     *     bytes into this byte vector.
     * @param byteOffset index of the first byte of byteArrayValue that must be copied.
     * @param byteLength number of bytes of byteArrayValue that must be copied.
     * @return this byte vector.
     */
    public ByteVector putByteArray(
        final byte[] byteArrayValue, final int byteOffset, final int byteLength) {
      if (length + byteLength > data.length) {
        enlarge(byteLength);
      }
      if (byteArrayValue != null) {
        System.arraycopy(byteArrayValue, byteOffset, data, length, byteLength);
      }
      length += byteLength;
      return this;
    }
  
    /**
     * Enlarges this byte vector so that it can receive 'size' more bytes.
     *
     * @param size number of additional bytes that this byte vector should be able to receive.
     */
    private void enlarge(final int size) {
      int doubleCapacity = 2 * data.length;
      int minimalCapacity = length + size;
      byte[] newData = new byte[doubleCapacity > minimalCapacity ? doubleCapacity : minimalCapacity];
      System.arraycopy(data, 0, newData, 0, length);
      data = newData;
    }
  }
  