/***

 * 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 non standard class, field, method or code attribute.

 * 

 * @author Eric Bruneton

 * @author Eugene Kuleshov

 */

public class Attribute {

    /**

     * The type of this attribute.

     */

    public final String type;

    /**

     * The raw value of this attribute, used only for unknown attributes.

     */

    byte[] value;

    /**

     * The next attribute in this attribute list. May be <tt>null</tt>.

     */

    Attribute next;

    /**

     * Constructs a new empty attribute.

     * 

     * @param type

     *            the type of the attribute.

     */

    protected Attribute(final String type) {

        this.type = type;

    }

    /**

     * Returns <tt>true</tt> if this type of attribute is unknown. The default

     * implementation of this method always returns <tt>true</tt>.

     * 

     * @return <tt>true</tt> if this type of attribute is unknown.

     */

    public boolean isUnknown() {

        return true;

    }

    /**

     * Returns <tt>true</tt> if this type of attribute is a code attribute.

     * 

     * @return <tt>true</tt> if this type of attribute is a code attribute.

     */

    public boolean isCodeAttribute() {

        return false;

    }

    /**

     * Returns the labels corresponding to this attribute.

     * 

     * @return the labels corresponding to this attribute, or <tt>null</tt> if

     *         this attribute is not a code attribute that contains labels.

     */

    protected Label[] getLabels() {

        return null;

    }

    /**

     * Reads a {@link #type type} attribute. This method must return a

     * new {@link Attribute} object, of type {@link #type type},

     * corresponding to the <tt>len</tt> bytes starting at the given offset, in

     * the given class reader.

     * 

     * @param cr

     *            the class that contains the attribute to be read.

     * @param off

     *            index of the first byte of the attribute's content in

     *            {@link ClassReader#b cr.b}. The 6 attribute header bytes,

     *            containing the type and the length of the attribute, are not

     *            taken into account here.

     * @param len

     *            the length of the attribute's content.

     * @param buf

     *            buffer to be used to call {@link ClassReader#readUTF8

     *            readUTF8}, {@link ClassReader#readClass(int,char[]) readClass}

     *            or {@link ClassReader#readConst readConst}.

     * @param codeOff

     *            index of the first byte of code's attribute content in

     *            {@link ClassReader#b cr.b}, or -1 if the attribute to be read

     *            is not a code attribute. The 6 attribute header bytes,

     *            containing the type and the length of the attribute, are not

     *            taken into account here.

     * @param labels

     *            the labels of the method's code, or <tt>null</tt> if the

     *            attribute to be read is not a code attribute.

     * @return a new {@link Attribute} object corresponding to the given

     *         bytes.

     */

    protected Attribute read(final ClassReader cr, final int off,

            final int len, final char[] buf, final int codeOff,

            final Label[] labels) {

        Attribute attr = new Attribute(type);

        attr.value = new byte[len];

        System.arraycopy(cr.b, off, attr.value, 0, len);

        return attr;

    }

    /**

     * Returns the byte array form of this attribute.

     * 

     * @param cw

     *            the class to which this attribute must be added. This

     *            parameter can be used to add to the constant pool of this

     *            class the items that corresponds to this attribute.

     * @param code

     *            the bytecode of the method corresponding to this code

     *            attribute, or <tt>null</tt> if this attribute is not a code

     *            attributes.

     * @param len

     *            the length of the bytecode of the method corresponding to this

     *            code attribute, or <tt>null</tt> if this attribute is not a

     *            code attribute.

     * @param maxStack

     *            the maximum stack size of the method corresponding to this

     *            code attribute, or -1 if this attribute is not a code

     *            attribute.

     * @param maxLocals

     *            the maximum number of local variables of the method

     *            corresponding to this code attribute, or -1 if this attribute

     *            is not a code attribute.

     * @return the byte array form of this attribute.

     */

    protected ByteVector write(final ClassWriter cw, final byte[] code,

            final int len, final int maxStack, final int maxLocals) {

        ByteVector v = new ByteVector();

        v.data = value;

        v.length = value.length;

        return v;

    }

    /**

     * Returns the length of the attribute list that begins with this attribute.

     * 

     * @return the length of the attribute list that begins with this attribute.

     */

    final int getCount() {

        int count = 0;

        Attribute attr = this;

        while (attr != null) {

            count += 1;

            attr = attr.next;

        }

        return count;

    }

    /**

     * Returns the size of all the attributes in this attribute list.

     * 

     * @param cw

     *            the class writer to be used to convert the attributes into

     *            byte arrays, with the {@link #write write} method.

     * @param code

     *            the bytecode of the method corresponding to these code

     *            attributes, or <tt>null</tt> if these attributes are not code

     *            attributes.

     * @param len

     *            the length of the bytecode of the method corresponding to

     *            these code attributes, or <tt>null</tt> if these attributes

     *            are not code attributes.

     * @param maxStack

     *            the maximum stack size of the method corresponding to these

     *            code attributes, or -1 if these attributes are not code

     *            attributes.

     * @param maxLocals

     *            the maximum number of local variables of the method

     *            corresponding to these code attributes, or -1 if these

     *            attributes are not code attributes.

     * @return the size of all the attributes in this attribute list. This size

     *         includes the size of the attribute headers.

     */

    final int getSize(final ClassWriter cw, final byte[] code, final int len,

            final int maxStack, final int maxLocals) {

        Attribute attr = this;

        int size = 0;

        while (attr != null) {

            cw.newUTF8(attr.type);

            size += attr.write(cw, code, len, maxStack, maxLocals).length + 6;

            attr = attr.next;

        }

        return size;

    }

    /**

     * Writes all the attributes of this attribute list in the given byte

     * vector.

     * 

     * @param cw

     *            the class writer to be used to convert the attributes into

     *            byte arrays, with the {@link #write write} method.

     * @param code

     *            the bytecode of the method corresponding to these code

     *            attributes, or <tt>null</tt> if these attributes are not code

     *            attributes.

     * @param len

     *            the length of the bytecode of the method corresponding to

     *            these code attributes, or <tt>null</tt> if these attributes

     *            are not code attributes.

     * @param maxStack

     *            the maximum stack size of the method corresponding to these

     *            code attributes, or -1 if these attributes are not code

     *            attributes.

     * @param maxLocals

     *            the maximum number of local variables of the method

     *            corresponding to these code attributes, or -1 if these

     *            attributes are not code attributes.

     * @param out

     *            where the attributes must be written.

     */

    final void put(final ClassWriter cw, final byte[] code, final int len,

            final int maxStack, final int maxLocals, final ByteVector out) {

        Attribute attr = this;

        while (attr != null) {

            ByteVector b = attr.write(cw, code, len, maxStack, maxLocals);

            out.putShort(cw.newUTF8(attr.type)).putInt(b.length);

            out.putByteArray(b.data, 0, b.length);

            attr = attr.next;

        }

    }

}