/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2007 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 alterrs.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
	 * <i>new</i> {@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 <i>new</i> {@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;
		}
	}
}
