src/main/java/org/apache/bcel/classfile/StackMapEntry.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.bcel.classfile;

import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.Arrays;

import org.apache.bcel.Const;

/**
 * This class represents a stack map entry recording the types of local variables and the of stack items at a given
 * byte code offset. See CLDC specification 5.3.1.2.
 *
 * See also https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.4
 *
 * <pre>
 * union stack_map_frame {
 *   same_frame;
 *   same_locals_1_stack_item_frame;
 *   same_locals_1_stack_item_frame_extended;
 *   chop_frame;
 *   same_frame_extended;
 *   append_frame;
 *   full_frame;
 * }
 * </pre>
 * @see StackMap
 * @see StackMapType
 */
public final class StackMapEntry implements Node, Cloneable {

    static final StackMapEntry[] EMPTY_ARRAY = {};

    private int frameType;
    private int byteCodeOffset;
    private StackMapType[] typesOfLocals;
    private StackMapType[] typesOfStackItems;
    private ConstantPool constantPool;

    /**
     * Constructs object from input stream.
     *
     * @param dataInput Input stream
     * @throws IOException if an I/O error occurs.
     */
    StackMapEntry(final DataInput dataInput, final ConstantPool constantPool) throws IOException {
        this(dataInput.readByte() & 0xFF, -1, null, null, constantPool);

        if (frameType >= Const.SAME_FRAME && frameType <= Const.SAME_FRAME_MAX) {
            byteCodeOffset = frameType - Const.SAME_FRAME;
        } else if (frameType >= Const.SAME_LOCALS_1_STACK_ITEM_FRAME && frameType <= Const.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
            byteCodeOffset = frameType - Const.SAME_LOCALS_1_STACK_ITEM_FRAME;
            typesOfStackItems = new StackMapType[] { new StackMapType(dataInput, constantPool) };
        } else if (frameType == Const.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED) {
            byteCodeOffset = dataInput.readUnsignedShort();
            typesOfStackItems = new StackMapType[] { new StackMapType(dataInput, constantPool) };
        } else if (frameType >= Const.CHOP_FRAME && frameType <= Const.CHOP_FRAME_MAX) {
            byteCodeOffset = dataInput.readUnsignedShort();
        } else if (frameType == Const.SAME_FRAME_EXTENDED) {
            byteCodeOffset = dataInput.readUnsignedShort();
        } else if (frameType >= Const.APPEND_FRAME && frameType <= Const.APPEND_FRAME_MAX) {
            byteCodeOffset = dataInput.readUnsignedShort();
            final int numberOfLocals = frameType - 251;
            typesOfLocals = new StackMapType[numberOfLocals];
            for (int i = 0; i < numberOfLocals; i++) {
                typesOfLocals[i] = new StackMapType(dataInput, constantPool);
            }
        } else if (frameType == Const.FULL_FRAME) {
            byteCodeOffset = dataInput.readUnsignedShort();
            final int numberOfLocals = dataInput.readUnsignedShort();
            typesOfLocals = new StackMapType[numberOfLocals];
            for (int i = 0; i < numberOfLocals; i++) {
                typesOfLocals[i] = new StackMapType(dataInput, constantPool);
            }
            final int numberOfStackItems = dataInput.readUnsignedShort();
            typesOfStackItems = new StackMapType[numberOfStackItems];
            for (int i = 0; i < numberOfStackItems; i++) {
                typesOfStackItems[i] = new StackMapType(dataInput, constantPool);
            }
        } else {
            /* Can't happen */
            throw new ClassFormatException("Invalid frame type found while parsing stack map table: " + frameType);
        }
    }

    /**
     * DO NOT USE
     *
     * @param byteCodeOffset
     * @param numberOfLocals NOT USED
     * @param typesOfLocals array of {@link StackMapType}s of locals
     * @param numberOfStackItems NOT USED
     * @param typesOfStackItems array ot {@link StackMapType}s of stack items
     * @param constantPool the constant pool
     * @deprecated Since 6.0, use {@link #StackMapEntry(int, int, StackMapType[], StackMapType[], ConstantPool)} instead
     */
    @java.lang.Deprecated
    public StackMapEntry(final int byteCodeOffset, final int numberOfLocals, final StackMapType[] typesOfLocals, final int numberOfStackItems,
        final StackMapType[] typesOfStackItems, final ConstantPool constantPool) {
        this.byteCodeOffset = byteCodeOffset;
        this.typesOfLocals = typesOfLocals != null ? typesOfLocals : StackMapType.EMPTY_ARRAY;
        this.typesOfStackItems = typesOfStackItems != null ? typesOfStackItems : StackMapType.EMPTY_ARRAY;
        this.constantPool = constantPool;
        if (numberOfLocals < 0) {
            throw new IllegalArgumentException("numberOfLocals < 0");
        }
        if (numberOfStackItems < 0) {
            throw new IllegalArgumentException("numberOfStackItems < 0");
        }
    }

    /**
     * Create an instance
     *
     * @param tag the frameType to use
     * @param byteCodeOffset
     * @param typesOfLocals array of {@link StackMapType}s of locals
     * @param typesOfStackItems array ot {@link StackMapType}s of stack items
     * @param constantPool the constant pool
     */
    public StackMapEntry(final int tag, final int byteCodeOffset, final StackMapType[] typesOfLocals, final StackMapType[] typesOfStackItems,
        final ConstantPool constantPool) {
        this.frameType = tag;
        this.byteCodeOffset = byteCodeOffset;
        this.typesOfLocals = typesOfLocals != null ? typesOfLocals : StackMapType.EMPTY_ARRAY;
        this.typesOfStackItems = typesOfStackItems != null ? typesOfStackItems : StackMapType.EMPTY_ARRAY;
        this.constantPool = constantPool;
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object
     */
    @Override
    public void accept(final Visitor v) {
        v.visitStackMapEntry(this);
    }

    /**
     * @return deep copy of this object
     */
    public StackMapEntry copy() {
        StackMapEntry e;
        try {
            e = (StackMapEntry) clone();
        } catch (final CloneNotSupportedException ex) {
            throw new UnsupportedOperationException("Clone Not Supported", ex);
        }

        e.typesOfLocals = new StackMapType[typesOfLocals.length];
        Arrays.setAll(e.typesOfLocals, i -> typesOfLocals[i].copy());
        e.typesOfStackItems = new StackMapType[typesOfStackItems.length];
        Arrays.setAll(e.typesOfStackItems, i -> typesOfStackItems[i].copy());
        return e;
    }

    /**
     * Dump stack map entry
     *
     * @param file Output file stream
     * @throws IOException if an I/O error occurs.
     */
    public void dump(final DataOutputStream file) throws IOException {
        file.write(frameType);
        if (frameType >= Const.SAME_LOCALS_1_STACK_ITEM_FRAME && frameType <= Const.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
            typesOfStackItems[0].dump(file);
        } else if (frameType == Const.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED) {
            file.writeShort(byteCodeOffset);
            typesOfStackItems[0].dump(file);
        } else if (frameType >= Const.CHOP_FRAME && frameType <= Const.CHOP_FRAME_MAX) {
            file.writeShort(byteCodeOffset);
        } else if (frameType == Const.SAME_FRAME_EXTENDED) {
            file.writeShort(byteCodeOffset);
        } else if (frameType >= Const.APPEND_FRAME && frameType <= Const.APPEND_FRAME_MAX) {
            file.writeShort(byteCodeOffset);
            for (final StackMapType type : typesOfLocals) {
                type.dump(file);
            }
        } else if (frameType == Const.FULL_FRAME) {
            file.writeShort(byteCodeOffset);
            file.writeShort(typesOfLocals.length);
            for (final StackMapType type : typesOfLocals) {
                type.dump(file);
            }
            file.writeShort(typesOfStackItems.length);
            for (final StackMapType type : typesOfStackItems) {
                type.dump(file);
            }
        } else if (!(frameType >= Const.SAME_FRAME && frameType <= Const.SAME_FRAME_MAX)) {
            /* Can't happen */
            throw new ClassFormatException("Invalid Stack map table tag: " + frameType);
        }
    }

    public int getByteCodeOffset() {
        return byteCodeOffset;
    }

    /**
     * @return Constant pool used by this object.
     */
    public ConstantPool getConstantPool() {
        return constantPool;
    }

    public int getFrameType() {
        return frameType;
    }

    /**
     * Calculate stack map entry size
     *
     */
    int getMapEntrySize() {
        if (frameType >= Const.SAME_FRAME && frameType <= Const.SAME_FRAME_MAX) {
            return 1;
        }
        if (frameType >= Const.SAME_LOCALS_1_STACK_ITEM_FRAME && frameType <= Const.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
            return 1 + (typesOfStackItems[0].hasIndex() ? 3 : 1);
        }
        if (frameType == Const.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED) {
            return 3 + (typesOfStackItems[0].hasIndex() ? 3 : 1);
        }
        if (frameType >= Const.CHOP_FRAME && frameType <= Const.CHOP_FRAME_MAX || frameType == Const.SAME_FRAME_EXTENDED) {
            return 3;
        }
        if (frameType >= Const.APPEND_FRAME && frameType <= Const.APPEND_FRAME_MAX) {
            int len = 3;
            for (final StackMapType typesOfLocal : typesOfLocals) {
                len += typesOfLocal.hasIndex() ? 3 : 1;
            }
            return len;
        }
        if (frameType != Const.FULL_FRAME) {
            throw new IllegalStateException("Invalid StackMap frameType: " + frameType);
        }
        int len = 7;
        for (final StackMapType typesOfLocal : typesOfLocals) {
            len += typesOfLocal.hasIndex() ? 3 : 1;
        }
        for (final StackMapType typesOfStackItem : typesOfStackItems) {
            len += typesOfStackItem.hasIndex() ? 3 : 1;
        }
        return len;
    }

    public int getNumberOfLocals() {
        return typesOfLocals.length;
    }

    public int getNumberOfStackItems() {
        return typesOfStackItems.length;
    }

    public StackMapType[] getTypesOfLocals() {
        return typesOfLocals;
    }

    public StackMapType[] getTypesOfStackItems() {
        return typesOfStackItems;
    }

    private boolean invalidFrameType(final int f) {
        // @formatter:off
        return f != Const.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED
            && !(f >= Const.CHOP_FRAME && f <= Const.CHOP_FRAME_MAX)
            && f != Const.SAME_FRAME_EXTENDED
            && !(f >= Const.APPEND_FRAME && f <= Const.APPEND_FRAME_MAX)
            && f != Const.FULL_FRAME;
        // @formatter:on
    }

    public void setByteCodeOffset(final int newOffset) {
        if (newOffset < 0 || newOffset > 32767) {
            throw new IllegalArgumentException("Invalid StackMap offset: " + newOffset);
        }

        if (frameType >= Const.SAME_FRAME && frameType <= Const.SAME_FRAME_MAX) {
            if (newOffset > Const.SAME_FRAME_MAX) {
                frameType = Const.SAME_FRAME_EXTENDED;
            } else {
                frameType = newOffset;
            }
        } else if (frameType >= Const.SAME_LOCALS_1_STACK_ITEM_FRAME && frameType <= Const.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
            if (newOffset > Const.SAME_FRAME_MAX) {
                frameType = Const.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED;
            } else {
                frameType = Const.SAME_LOCALS_1_STACK_ITEM_FRAME + newOffset;
            }
        } else if (invalidFrameType(frameType)) {
            throw new IllegalStateException("Invalid StackMap frameType: " + frameType);
        }
        byteCodeOffset = newOffset;
    }

    /**
     * @param constantPool Constant pool to be used for this object.
     */
    public void setConstantPool(final ConstantPool constantPool) {
        this.constantPool = constantPool;
    }

    public void setFrameType(final int ft) {
        if (ft >= Const.SAME_FRAME && ft <= Const.SAME_FRAME_MAX) {
            byteCodeOffset = ft - Const.SAME_FRAME;
        } else if (ft >= Const.SAME_LOCALS_1_STACK_ITEM_FRAME && ft <= Const.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
            byteCodeOffset = ft - Const.SAME_LOCALS_1_STACK_ITEM_FRAME;
        } else if (invalidFrameType(ft)) {
            throw new IllegalArgumentException("Invalid StackMap frameType");
        }
        frameType = ft;
    }

    /**
     *
     * @deprecated since 6.0
     */
    @java.lang.Deprecated
    public void setNumberOfLocals(final int n) { // TODO unused
    }

    /**
     *
     * @deprecated since 6.0
     */
    @java.lang.Deprecated
    public void setNumberOfStackItems(final int n) { // TODO unused
    }

    public void setTypesOfLocals(final StackMapType[] types) {
        typesOfLocals = types != null ? types : StackMapType.EMPTY_ARRAY;
    }

    public void setTypesOfStackItems(final StackMapType[] types) {
        typesOfStackItems = types != null ? types : StackMapType.EMPTY_ARRAY;
    }

    /**
     * @return String representation.
     */
    @Override
    public String toString() {
        final StringBuilder buf = new StringBuilder(64);
        buf.append("(");
        if (frameType >= Const.SAME_FRAME && frameType <= Const.SAME_FRAME_MAX) {
            buf.append("SAME");
        } else if (frameType >= Const.SAME_LOCALS_1_STACK_ITEM_FRAME && frameType <= Const.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
            buf.append("SAME_LOCALS_1_STACK");
        } else if (frameType == Const.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED) {
            buf.append("SAME_LOCALS_1_STACK_EXTENDED");
        } else if (frameType >= Const.CHOP_FRAME && frameType <= Const.CHOP_FRAME_MAX) {
            buf.append("CHOP ").append(String.valueOf(251 - frameType));
        } else if (frameType == Const.SAME_FRAME_EXTENDED) {
            buf.append("SAME_EXTENDED");
        } else if (frameType >= Const.APPEND_FRAME && frameType <= Const.APPEND_FRAME_MAX) {
            buf.append("APPEND ").append(String.valueOf(frameType - 251));
        } else if (frameType == Const.FULL_FRAME) {
            buf.append("FULL");
        } else {
            buf.append("UNKNOWN (").append(frameType).append(")");
        }
        buf.append(", offset delta=").append(byteCodeOffset);
        if (typesOfLocals.length > 0) {
            buf.append(", locals={");
            for (int i = 0; i < typesOfLocals.length; i++) {
                buf.append(typesOfLocals[i]);
                if (i < typesOfLocals.length - 1) {
                    buf.append(", ");
                }
            }
            buf.append("}");
        }
        if (typesOfStackItems.length > 0) {
            buf.append(", stack items={");
            for (int i = 0; i < typesOfStackItems.length; i++) {
                buf.append(typesOfStackItems[i]);
                if (i < typesOfStackItems.length - 1) {
                    buf.append(", ");
                }
            }
            buf.append("}");
        }
        buf.append(")");
        return buf.toString();
    }

    /**
     * Update the distance (as an offset delta) from this StackMap entry to the next. Note that this might cause the
     * frame type to change. Note also that delta may be negative.
     *
     * @param delta offset delta
     */
    public void updateByteCodeOffset(final int delta) {
        setByteCodeOffset(byteCodeOffset + delta);
    }
}