// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
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package net.hasor.utils.asm;
/**
 * A non standard class, field, method or Code attribute, as defined in the Java Virtual Machine
 * Specification (JVMS).
 *
 * @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7">JVMS 4.7</a>
 * @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.3">JVMS 4.7.3</a>
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public class Attribute {
    /** The type of this attribute, also called its name in the JVMS. */
    public final String type;
    /**
     * The raw content of this attribute, only used for unknown attributes (see {@link #isUnknown()}).
     * The 6 header bytes of the attribute (attribute_name_index and attribute_length) are <i>not</i>
     * included.
     */
    private      byte[] content;
    /**
     * The next attribute in this attribute list (Attribute instances can be linked via this field to
     * store a list of class, field, method or Code attributes). May be {@literal null}.
     */
    Attribute nextAttribute;

    /**
     * Constructs a new empty attribute.
     *
     * @param type the type of the attribute.
     */
    protected Attribute(final String type) {
        this.type = type;
    }

    /**
     * Returns {@literal true} if this type of attribute is unknown. This means that the attribute
     * content can't be parsed to extract constant pool references, labels, etc. Instead, the
     * attribute content is read as an opaque byte array, and written back as is. This can lead to
     * invalid attributes, if the content actually contains constant pool references, labels, or other
     * symbolic references that need to be updated when there are changes to the constant pool, the
     * method bytecode, etc. The default implementation of this method always returns {@literal true}.
     *
     * @return {@literal true} if this type of attribute is unknown.
     */
    public boolean isUnknown() {
        return true;
    }

    /**
     * Returns {@literal true} if this type of attribute is a Code attribute.
     *
     * @return {@literal true} 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 {@literal null} if this attribute is not
     *     a Code attribute that contains labels.
     */
    protected Label[] getLabels() {
        return new Label[0];
    }

    /**
     * Reads a {@link #type} attribute. This method must return a <i>new</i> {@link Attribute} object,
     * of type {@link #type}, corresponding to the 'length' bytes starting at 'offset', in the given
     * ClassReader.
     *
     * @param classReader the class that contains the attribute to be read.
     * @param offset index of the first byte of the attribute's content in {@link ClassReader}. The 6
     *     attribute header bytes (attribute_name_index and attribute_length) are not taken into
     *     account here.
     * @param length the length of the attribute's content (excluding the 6 attribute header bytes).
     * @param charBuffer the buffer to be used to call the ClassReader methods requiring a
     *     'charBuffer' parameter.
     * @param codeAttributeOffset index of the first byte of content of the enclosing Code attribute
     *     in {@link ClassReader}, or -1 if the attribute to be read is not a Code attribute. The 6
     *     attribute header bytes (attribute_name_index and attribute_length) are not taken into
     *     account here.
     * @param labels the labels of the method's code, or {@literal null} if the attribute to be read
     *     is not a Code attribute.
     * @return a <i>new</i> {@link Attribute} object corresponding to the specified bytes.
     */
    protected Attribute read(final ClassReader classReader, final int offset, final int length, final char[] charBuffer, final int codeAttributeOffset, final Label[] labels) {
        Attribute attribute = new Attribute(type);
        attribute.content = new byte[length];
        System.arraycopy(classReader.classFileBuffer, offset, attribute.content, 0, length);
        return attribute;
    }

    /**
     * Returns the byte array form of the content of this attribute. The 6 header bytes
     * (attribute_name_index and attribute_length) must <i>not</i> be added in the returned
     * ByteVector.
     *
     * @param classWriter the class to which this attribute must be added. This parameter can be used
     *     to add the items that corresponds to this attribute to the constant pool of this class.
     * @param code the bytecode of the method corresponding to this Code attribute, or {@literal null}
     *     if this attribute is not a Code attribute. Corresponds to the 'code' field of the Code
     *     attribute.
     * @param codeLength the length of the bytecode of the method corresponding to this code
     *     attribute, or 0 if this attribute is not a Code attribute. Corresponds to the 'code_length'
     *     field of the 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 classWriter, final byte[] code, final int codeLength, final int maxStack, final int maxLocals) {
        return new ByteVector(content);
    }

    /**
     * Returns the number of attributes of the attribute list that begins with this attribute.
     *
     * @return the number of attributes of the attribute list that begins with this attribute.
     */
    final int getAttributeCount() {
        int count = 0;
        Attribute attribute = this;
        while (attribute != null) {
            count += 1;
            attribute = attribute.nextAttribute;
        }
        return count;
    }

    /**
     * Returns the total size in bytes of all the attributes in the attribute list that begins with
     * this attribute. This size includes the 6 header bytes (attribute_name_index and
     * attribute_length) per attribute. Also adds the attribute type names to the constant pool.
     *
     * @param symbolTable where the constants used in the attributes must be stored.
     * @return the size of all the attributes in this attribute list. This size includes the size of
     *     the attribute headers.
     */
    final int computeAttributesSize(final SymbolTable symbolTable) {
        final byte[] code = null;
        final int codeLength = 0;
        final int maxStack = -1;
        final int maxLocals = -1;
        return computeAttributesSize(symbolTable, code, codeLength, maxStack, maxLocals);
    }

    /**
     * Returns the total size in bytes of all the attributes in the attribute list that begins with
     * this attribute. This size includes the 6 header bytes (attribute_name_index and
     * attribute_length) per attribute. Also adds the attribute type names to the constant pool.
     *
     * @param symbolTable where the constants used in the attributes must be stored.
     * @param code the bytecode of the method corresponding to these Code attributes, or {@literal
     *     null} if they are not Code attributes. Corresponds to the 'code' field of the Code
     *     attribute.
     * @param codeLength the length of the bytecode of the method corresponding to these code
     *     attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of
     *     the Code attribute.
     * @param maxStack the maximum stack size of the method corresponding to these Code attributes, or
     *     -1 if they are not Code attributes.
     * @param maxLocals the maximum number of local variables of the method corresponding to these
     *     Code attributes, or -1 if they are not Code attribute.
     * @return the size of all the attributes in this attribute list. This size includes the size of
     *     the attribute headers.
     */
    final int computeAttributesSize(final SymbolTable symbolTable, final byte[] code, final int codeLength, final int maxStack, final int maxLocals) {
        final ClassWriter classWriter = symbolTable.classWriter;
        int size = 0;
        Attribute attribute = this;
        while (attribute != null) {
            symbolTable.addConstantUtf8(attribute.type);
            size += 6 + attribute.write(classWriter, code, codeLength, maxStack, maxLocals).length;
            attribute = attribute.nextAttribute;
        }
        return size;
    }

    /**
     * Returns the total size in bytes of all the attributes that correspond to the given field,
     * method or class access flags and signature. This size includes the 6 header bytes
     * (attribute_name_index and attribute_length) per attribute. Also adds the attribute type names
     * to the constant pool.
     *
     * @param symbolTable where the constants used in the attributes must be stored.
     * @param accessFlags some field, method or class access flags.
     * @param signatureIndex the constant pool index of a field, method of class signature.
     * @return the size of all the attributes in bytes. This size includes the size of the attribute
     *     headers.
     */
    static int computeAttributesSize(final SymbolTable symbolTable, final int accessFlags, final int signatureIndex) {
        int size = 0;
        // Before Java 1.5, synthetic fields are represented with a Synthetic attribute.
        if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0 && symbolTable.getMajorVersion() < Opcodes.V1_5) {
            // Synthetic attributes always use 6 bytes.
            symbolTable.addConstantUtf8(Constants.SYNTHETIC);
            size += 6;
        }
        if (signatureIndex != 0) {
            // Signature attributes always use 8 bytes.
            symbolTable.addConstantUtf8(Constants.SIGNATURE);
            size += 8;
        }
        // ACC_DEPRECATED is ASM specific, the ClassFile format uses a Deprecated attribute instead.
        if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) {
            // Deprecated attributes always use 6 bytes.
            symbolTable.addConstantUtf8(Constants.DEPRECATED);
            size += 6;
        }
        return size;
    }

    /**
     * Puts all the attributes of the attribute list that begins with this attribute, in the given
     * byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
     * attribute.
     *
     * @param symbolTable where the constants used in the attributes must be stored.
     * @param output where the attributes must be written.
     */
    final void putAttributes(final SymbolTable symbolTable, final ByteVector output) {
        final byte[] code = null;
        final int codeLength = 0;
        final int maxStack = -1;
        final int maxLocals = -1;
        putAttributes(symbolTable, code, codeLength, maxStack, maxLocals, output);
    }

    /**
     * Puts all the attributes of the attribute list that begins with this attribute, in the given
     * byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
     * attribute.
     *
     * @param symbolTable where the constants used in the attributes must be stored.
     * @param code the bytecode of the method corresponding to these Code attributes, or {@literal
     *     null} if they are not Code attributes. Corresponds to the 'code' field of the Code
     *     attribute.
     * @param codeLength the length of the bytecode of the method corresponding to these code
     *     attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of
     *     the Code attribute.
     * @param maxStack the maximum stack size of the method corresponding to these Code attributes, or
     *     -1 if they are not Code attributes.
     * @param maxLocals the maximum number of local variables of the method corresponding to these
     *     Code attributes, or -1 if they are not Code attribute.
     * @param output where the attributes must be written.
     */
    final void putAttributes(final SymbolTable symbolTable, final byte[] code, final int codeLength, final int maxStack, final int maxLocals, final ByteVector output) {
        final ClassWriter classWriter = symbolTable.classWriter;
        Attribute attribute = this;
        while (attribute != null) {
            ByteVector attributeContent = attribute.write(classWriter, code, codeLength, maxStack, maxLocals);
            // Put attribute_name_index and attribute_length.
            output.putShort(symbolTable.addConstantUtf8(attribute.type)).putInt(attributeContent.length);
            output.putByteArray(attributeContent.data, 0, attributeContent.length);
            attribute = attribute.nextAttribute;
        }
    }

    /**
     * Puts all the attributes that correspond to the given field, method or class access flags and
     * signature, in the given byte vector. This includes the 6 header bytes (attribute_name_index and
     * attribute_length) per attribute.
     *
     * @param symbolTable where the constants used in the attributes must be stored.
     * @param accessFlags some field, method or class access flags.
     * @param signatureIndex the constant pool index of a field, method of class signature.
     * @param output where the attributes must be written.
     */
    static void putAttributes(final SymbolTable symbolTable, final int accessFlags, final int signatureIndex, final ByteVector output) {
        // Before Java 1.5, synthetic fields are represented with a Synthetic attribute.
        if ((accessFlags & Opcodes.ACC_SYNTHETIC) != 0 && symbolTable.getMajorVersion() < Opcodes.V1_5) {
            output.putShort(symbolTable.addConstantUtf8(Constants.SYNTHETIC)).putInt(0);
        }
        if (signatureIndex != 0) {
            output.putShort(symbolTable.addConstantUtf8(Constants.SIGNATURE)).putInt(2).putShort(signatureIndex);
        }
        if ((accessFlags & Opcodes.ACC_DEPRECATED) != 0) {
            output.putShort(symbolTable.addConstantUtf8(Constants.DEPRECATED)).putInt(0);
        }
    }

    /** A set of attribute prototypes (attributes with the same type are considered equal). */
    static final class Set {
        private static final int         SIZE_INCREMENT = 6;
        private              int         size;
        private              Attribute[] data           = new Attribute[SIZE_INCREMENT];

        void addAttributes(final Attribute attributeList) {
            Attribute attribute = attributeList;
            while (attribute != null) {
                if (!contains(attribute)) {
                    add(attribute);
                }
                attribute = attribute.nextAttribute;
            }
        }

        Attribute[] toArray() {
            Attribute[] result = new Attribute[size];
            System.arraycopy(data, 0, result, 0, size);
            return result;
        }

        private boolean contains(final Attribute attribute) {
            for (int i = 0; i < size; ++i) {
                if (data[i].type.equals(attribute.type)) {
                    return true;
                }
            }
            return false;
        }

        private void add(final Attribute attribute) {
            if (size >= data.length) {
                Attribute[] newData = new Attribute[data.length + SIZE_INCREMENT];
                System.arraycopy(data, 0, newData, 0, size);
                data = newData;
            }
            data[size++] = attribute;
        }
    }
}
