http://asm.objectweb.org/asm/: A very small and fast Java bytecode manipulation framework (ObjectWeb)
  • Eric Bruneton
  • Eugene Kuleshov
  • Remi Forax 
ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. Neither the name of the copyright holders nor the names of its
   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"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    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"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.objectweb.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
/**
 * 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.

/**
     * The content of this vector.
     */
    byte[] data;

    
Actual number of bytes in this vector.

/**
     * Actual number of bytes in this vector.
     */
    int length;

    
Constructs a new ByteVector with a default initial size. 
/**
     * Constructs a new {@link ByteVector ByteVector} with a default initial
     * size.
     */
    public ByteVector() {
        data = new byte[64];
    }

    
Constructs a new ByteVector with the given initial size. 
Params:
  • initialSize – 
           the initial size of the byte vector to be constructed.
/**
     * Constructs a new {@link ByteVector ByteVector} with the given initial
     * size.
     * 
     * @param initialSize
     *            the initial size of the byte vector to be constructed.
     */
    public ByteVector(final int initialSize) {
        data = new byte[initialSize];
    }

    
Puts a byte into this byte vector. The byte vector is automatically
enlarged if necessary.

Params:
  • b – 
           a byte.
Returns:this byte vector.
/**
     * Puts a byte into this byte vector. The byte vector is automatically
     * enlarged if necessary.
     * 
     * @param b
     *            a byte.
     * @return this byte vector.
     */
    public ByteVector putByte(final int b) {
        int length = this.length;
        if (length + 1 > data.length) {
            enlarge(1);
        }
        data[length++] = (byte) b;
        this.length = length;
        return this;
    }

    
Puts two bytes into this byte vector. The byte vector is automatically
enlarged if necessary.

Params:
  • b1 – 
           a byte.
  • b2 – 
           another byte.
Returns:this byte vector.
/**
     * Puts two bytes into this byte vector. The byte vector is automatically
     * enlarged if necessary.
     * 
     * @param b1
     *            a byte.
     * @param b2
     *            another byte.
     * @return this byte vector.
     */
    ByteVector put11(final int b1, final int b2) {
        int length = this.length;
        if (length + 2 > data.length) {
            enlarge(2);
        }
        byte[] data = this.data;
        data[length++] = (byte) b1;
        data[length++] = (byte) b2;
        this.length = length;
        return this;
    }

    
Puts a short into this byte vector. The byte vector is automatically
enlarged if necessary.

Params:
  • s – 
           a short.
Returns:this byte vector.
/**
     * Puts a short into this byte vector. The byte vector is automatically
     * enlarged if necessary.
     * 
     * @param s
     *            a short.
     * @return this byte vector.
     */
    public ByteVector putShort(final int s) {
        int length = this.length;
        if (length + 2 > data.length) {
            enlarge(2);
        }
        byte[] data = this.data;
        data[length++] = (byte) (s >>> 8);
        data[length++] = (byte) s;
        this.length = length;
        return this;
    }

    
Puts a byte and a short into this byte vector. The byte vector is
automatically enlarged if necessary.

Params:
  • b – 
           a byte.
  • s – 
           a short.
Returns:this byte vector.
/**
     * Puts a byte and a short into this byte vector. The byte vector is
     * automatically enlarged if necessary.
     * 
     * @param b
     *            a byte.
     * @param s
     *            a short.
     * @return this byte vector.
     */
    ByteVector put12(final int b, final int s) {
        int length = this.length;
        if (length + 3 > data.length) {
            enlarge(3);
        }
        byte[] data = this.data;
        data[length++] = (byte) b;
        data[length++] = (byte) (s >>> 8);
        data[length++] = (byte) s;
        this.length = length;
        return this;
    }

    
Puts an int into this byte vector. The byte vector is automatically
enlarged if necessary.

Params:
  • i – 
           an int.
Returns:this byte vector.
/**
     * Puts an int into this byte vector. The byte vector is automatically
     * enlarged if necessary.
     * 
     * @param i
     *            an int.
     * @return this byte vector.
     */
    public ByteVector putInt(final int i) {
        int length = this.length;
        if (length + 4 > data.length) {
            enlarge(4);
        }
        byte[] data = this.data;
        data[length++] = (byte) (i >>> 24);
        data[length++] = (byte) (i >>> 16);
        data[length++] = (byte) (i >>> 8);
        data[length++] = (byte) i;
        this.length = length;
        return this;
    }

    
Puts a long into this byte vector. The byte vector is automatically
enlarged if necessary.

Params:
  • l – 
           a long.
Returns:this byte vector.
/**
     * Puts a long into this byte vector. The byte vector is automatically
     * enlarged if necessary.
     * 
     * @param l
     *            a long.
     * @return this byte vector.
     */
    public ByteVector putLong(final long l) {
        int length = this.length;
        if (length + 8 > data.length) {
            enlarge(8);
        }
        byte[] data = this.data;
        int i = (int) (l >>> 32);
        data[length++] = (byte) (i >>> 24);
        data[length++] = (byte) (i >>> 16);
        data[length++] = (byte) (i >>> 8);
        data[length++] = (byte) i;
        i = (int) l;
        data[length++] = (byte) (i >>> 24);
        data[length++] = (byte) (i >>> 16);
        data[length++] = (byte) (i >>> 8);
        data[length++] = (byte) i;
        this.length = length;
        return this;
    }

    
Puts an UTF8 string into this byte vector. The byte vector is
automatically enlarged if necessary.

Params:
  • s – 
           a String whose UTF8 encoded length must be less than 65536.
Returns:this byte vector.
/**
     * Puts an UTF8 string into this byte vector. The byte vector is
     * automatically enlarged if necessary.
     * 
     * @param s
     *            a String whose UTF8 encoded length must be less than 65536.
     * @return this byte vector.
     */
    public ByteVector putUTF8(final String s) {
        int charLength = s.length();
        if (charLength > 65535) {
            throw new IllegalArgumentException();
        }
        int len = length;
        if (len + 2 + charLength > data.length) {
            enlarge(2 + charLength);
        }
        byte[] data = this.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.
        data[len++] = (byte) (charLength >>> 8);
        data[len++] = (byte) charLength;
        for (int i = 0; i < charLength; ++i) {
            char c = s.charAt(i);
            if (c >= '\001' && c <= '\177') {
                data[len++] = (byte) c;
            } else {
                length = len;
                return encodeUTF8(s, i, 65535);
            }
        }
        length = len;
        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 - i - 2 >= 0).

Params:
  • s – 
           the String to encode.
  • i – 
           the index of the first character to encode. The previous
           characters are supposed to have already been encoded, using
           only one byte per character.
  • maxByteLength – 
           the maximum byte length of the encoded string, including the
           already encoded characters.
Returns:this byte vector.
/**
     * 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 - i - 2 >= 0).
     * 
     * @param s
     *            the String to encode.
     * @param i
     *            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.
     */
    ByteVector encodeUTF8(final String s, int i, int maxByteLength) {
        int charLength = s.length();
        int byteLength = i;
        char c;
        for (int j = i; j < charLength; ++j) {
            c = s.charAt(j);
            if (c >= '\001' && c <= '\177') {
                byteLength++;
            } else if (c > '\u07FF') {
                byteLength += 3;
            } else {
                byteLength += 2;
            }
        }
        if (byteLength > maxByteLength) {
            throw new IllegalArgumentException();
        }
        int start = length - i - 2;
        if (start >= 0) {
          data[start] = (byte) (byteLength >>> 8);
          data[start + 1] = (byte) byteLength;
        }
        if (length + byteLength - i > data.length) {
            enlarge(byteLength - i);
        }
        int len = length;
        for (int j = i; j < charLength; ++j) {
            c = s.charAt(j);
            if (c >= '\001' && c <= '\177') {
                data[len++] = (byte) c;
            } else if (c > '\u07FF') {
                data[len++] = (byte) (0xE0 | c >> 12 & 0xF);
                data[len++] = (byte) (0x80 | c >> 6 & 0x3F);
                data[len++] = (byte) (0x80 | c & 0x3F);
            } else {
                data[len++] = (byte) (0xC0 | c >> 6 & 0x1F);
                data[len++] = (byte) (0x80 | c & 0x3F);
            }
        }
        length = len;
        return this;
    }

    
Puts an array of bytes into this byte vector. The byte vector is
automatically enlarged if necessary.

Params:
  • b – 
           an array of bytes. May be null to put len
           null bytes into this byte vector.
  • off – 
           index of the fist byte of b that must be copied.
  • len – 
           number of bytes of b that must be copied.
Returns:this byte vector.
/**
     * Puts an array of bytes into this byte vector. The byte vector is
     * automatically enlarged if necessary.
     * 
     * @param b
     *            an array of bytes. May be <tt>null</tt> to put <tt>len</tt>
     *            null bytes into this byte vector.
     * @param off
     *            index of the fist byte of b that must be copied.
     * @param len
     *            number of bytes of b that must be copied.
     * @return this byte vector.
     */
    public ByteVector putByteArray(final byte[] b, final int off, final int len) {
        if (length + len > data.length) {
            enlarge(len);
        }
        if (b != null) {
            System.arraycopy(b, off, data, length, len);
        }
        length += len;
        return this;
    }

    
Enlarge this byte vector so that it can receive n more bytes.

Params:
  • size – 
           number of additional bytes that this byte vector should be
           able to receive.
/**
     * Enlarge this byte vector so that it can receive n more bytes.
     * 
     * @param size
     *            number of additional bytes that this byte vector should be
     *            able to receive.
     */
    private void enlarge(final int size) {
        int length1 = 2 * data.length;
        int length2 = length + size;
        byte[] newData = new byte[length1 > length2 ? length1 : length2];
        System.arraycopy(data, 0, newData, 0, length);
        data = newData;
    }
}