src/java.base/share/classes/jdk/internal/jimage/ImageLocation.java

/*
 * Copyright (c) 2014, 2021, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.internal.jimage;

import java.nio.ByteBuffer;
import java.util.Objects;

/**
 * @implNote This class needs to maintain JDK 8 source compatibility.
 *
 * It is used internally in the JDK to implement jimage/jrtfs access,
 * but also compiled and delivered as part of the jrtfs.jar to support access
 * to the jimage file provided by the shipped JDK by tools running on JDK 8.
 */
public class ImageLocation {
    public static final int ATTRIBUTE_END = 0;
    public static final int ATTRIBUTE_MODULE = 1;
    public static final int ATTRIBUTE_PARENT = 2;
    public static final int ATTRIBUTE_BASE = 3;
    public static final int ATTRIBUTE_EXTENSION = 4;
    public static final int ATTRIBUTE_OFFSET = 5;
    public static final int ATTRIBUTE_COMPRESSED = 6;
    public static final int ATTRIBUTE_UNCOMPRESSED = 7;
    public static final int ATTRIBUTE_COUNT = 8;

    protected final long[] attributes;

    protected final ImageStrings strings;

    public ImageLocation(long[] attributes, ImageStrings strings) {
        this.attributes = Objects.requireNonNull(attributes);
        this.strings = Objects.requireNonNull(strings);
    }

    ImageStrings getStrings() {
        return strings;
    }

    static long[] decompress(ByteBuffer bytes, int offset) {
        Objects.requireNonNull(bytes);
        long[] attributes = new long[ATTRIBUTE_COUNT];

        int limit = bytes.limit();
        while (offset < limit) {
            int data = bytes.get(offset++) & 0xFF;
            if (data <= 0x7) { // ATTRIBUTE_END
                break;
            }
            int kind = data >>> 3;
            if (ATTRIBUTE_COUNT <= kind) {
                throw new InternalError(
                    "Invalid jimage attribute kind: " + kind);
            }

            int length = (data & 0x7) + 1;
            attributes[kind] = readValue(length, bytes, offset, limit);
            offset += length;
        }
        return attributes;
    }

    public static byte[] compress(long[] attributes) {
        Objects.requireNonNull(attributes);
        ImageStream stream = new ImageStream(16);

        for (int kind = ATTRIBUTE_END + 1; kind < ATTRIBUTE_COUNT; kind++) {
            long value = attributes[kind];

            if (value != 0) {
                int n = (63 - Long.numberOfLeadingZeros(value)) >> 3;
                stream.put((kind << 3) | n);

                for (int i = n; i >= 0; i--) {
                    stream.put((int)(value >> (i << 3)));
                }
            }
        }

        stream.put(ATTRIBUTE_END << 3);

        return stream.toArray();
     }

    public boolean verify(String name) {
        return verify(name, attributes, strings);
    }

    /**
     * A simpler verification would be {@code name.equals(getFullName())}, but
     * by not creating the full name and enabling early returns we allocate
     * fewer objects.
     */
    static boolean verify(String name, long[] attributes, ImageStrings strings) {
        Objects.requireNonNull(name);
        final int length = name.length();
        int index = 0;
        int moduleOffset = (int)attributes[ATTRIBUTE_MODULE];
        if (moduleOffset != 0 && length >= 1) {
            int moduleLen = strings.match(moduleOffset, name, 1);
            index = moduleLen + 1;
            if (moduleLen < 0
                    || length <= index
                    || name.charAt(0) != '/'
                    || name.charAt(index++) != '/') {
                return false;
            }
        }
        return verifyName(null, name, index, length, 0,
                (int) attributes[ATTRIBUTE_PARENT],
                (int) attributes[ATTRIBUTE_BASE],
                (int) attributes[ATTRIBUTE_EXTENSION],
                strings);
    }

    static boolean verify(String module, String name, ByteBuffer locations,
                          int locationOffset, ImageStrings strings) {
        int moduleOffset = 0;
        int parentOffset = 0;
        int baseOffset = 0;
        int extOffset = 0;

        int limit = locations.limit();
        while (locationOffset < limit) {
            int data = locations.get(locationOffset++) & 0xFF;
            if (data <= 0x7) { // ATTRIBUTE_END
                break;
            }
            int kind = data >>> 3;
            if (ATTRIBUTE_COUNT <= kind) {
                throw new InternalError(
                        "Invalid jimage attribute kind: " + kind);
            }

            int length = (data & 0x7) + 1;
            switch (kind) {
                case ATTRIBUTE_MODULE:
                    moduleOffset = (int) readValue(length, locations, locationOffset, limit);
                    break;
                case ATTRIBUTE_BASE:
                    baseOffset = (int) readValue(length, locations, locationOffset, limit);
                    break;
                case ATTRIBUTE_PARENT:
                    parentOffset = (int) readValue(length, locations, locationOffset, limit);
                    break;
                case ATTRIBUTE_EXTENSION:
                    extOffset = (int) readValue(length, locations, locationOffset, limit);
                    break;
            }
            locationOffset += length;
        }
        return verifyName(module, name, 0, name.length(),
                moduleOffset, parentOffset, baseOffset, extOffset, strings);
    }

    private static long readValue(int length, ByteBuffer buffer, int offset, int limit) {
        long value = 0;
        for (int j = 0; j < length; j++) {
            value <<= 8;
            if (offset >= limit) {
                throw new InternalError("Missing jimage attribute data");
            }
            value |= buffer.get(offset++) & 0xFF;
        }
        return value;
    }

    static boolean verify(String module, String name, long[] attributes,
            ImageStrings strings) {
        Objects.requireNonNull(module);
        Objects.requireNonNull(name);
        return verifyName(module, name, 0, name.length(),
                (int) attributes[ATTRIBUTE_MODULE],
                (int) attributes[ATTRIBUTE_PARENT],
                (int) attributes[ATTRIBUTE_BASE],
                (int) attributes[ATTRIBUTE_EXTENSION],
                strings);
    }

    private static boolean verifyName(String module, String name, int index, int length,
            int moduleOffset, int parentOffset, int baseOffset, int extOffset, ImageStrings strings) {

        if (moduleOffset != 0) {
            if (strings.match(moduleOffset, module, 0) != module.length()) {
                return false;
            }
        }
        if (parentOffset != 0) {
            int parentLen = strings.match(parentOffset, name, index);
            if (parentLen < 0) {
                return false;
            }
            index += parentLen;
            if (length <= index || name.charAt(index++) != '/') {
                return false;
            }
        }
        int baseLen = strings.match(baseOffset, name, index);
        if (baseLen < 0) {
            return false;
        }
        index += baseLen;
        if (extOffset != 0) {
            if (length <= index
                    || name.charAt(index++) != '.') {
                return false;
            }

            int extLen = strings.match(extOffset, name, index);
            if (extLen < 0) {
                return false;
            }
            index += extLen;
        }
        return length == index;
    }

    long getAttribute(int kind) {
        if (kind < ATTRIBUTE_END || ATTRIBUTE_COUNT <= kind) {
            throw new InternalError(
                "Invalid jimage attribute kind: " + kind);
        }
        return attributes[kind];
    }

    String getAttributeString(int kind) {
        if (kind < ATTRIBUTE_END || ATTRIBUTE_COUNT <= kind) {
            throw new InternalError(
                "Invalid jimage attribute kind: " + kind);
        }
        return getStrings().get((int)attributes[kind]);
    }

    public String getModule() {
        return getAttributeString(ATTRIBUTE_MODULE);
    }

    public int getModuleOffset() {
        return (int)getAttribute(ATTRIBUTE_MODULE);
    }

    public String getBase() {
        return getAttributeString(ATTRIBUTE_BASE);
    }

    public int getBaseOffset() {
        return (int)getAttribute(ATTRIBUTE_BASE);
    }

    public String getParent() {
        return getAttributeString(ATTRIBUTE_PARENT);
    }

    public int getParentOffset() {
        return (int)getAttribute(ATTRIBUTE_PARENT);
    }

    public String getExtension() {
        return getAttributeString(ATTRIBUTE_EXTENSION);
    }

    public int getExtensionOffset() {
        return (int)getAttribute(ATTRIBUTE_EXTENSION);
    }

    public String getFullName() {
        return getFullName(false);
    }

    public String getFullName(boolean modulesPrefix) {
        StringBuilder builder = new StringBuilder();

        if (getModuleOffset() != 0) {
            if (modulesPrefix) {
                builder.append("/modules");
            }

            builder.append('/');
            builder.append(getModule());
            builder.append('/');
        }

        if (getParentOffset() != 0) {
            builder.append(getParent());
            builder.append('/');
        }

        builder.append(getBase());

        if (getExtensionOffset() != 0) {
            builder.append('.');
            builder.append(getExtension());
        }

        return builder.toString();
    }

    String buildName(boolean includeModule, boolean includeParent,
            boolean includeName) {
        StringBuilder builder = new StringBuilder();

        if (includeModule && getModuleOffset() != 0) {
            builder.append("/modules/");
            builder.append(getModule());
         }

        if (includeParent && getParentOffset() != 0) {
            builder.append('/');
            builder.append(getParent());
        }

        if (includeName) {
            if (includeModule || includeParent) {
                builder.append('/');
            }

            builder.append(getBase());

            if (getExtensionOffset() != 0) {
                builder.append('.');
                builder.append(getExtension());
            }
        }

        return builder.toString();
   }

    public long getContentOffset() {
        return getAttribute(ATTRIBUTE_OFFSET);
    }

    public long getCompressedSize() {
        return getAttribute(ATTRIBUTE_COMPRESSED);
    }

    public long getUncompressedSize() {
        return getAttribute(ATTRIBUTE_UNCOMPRESSED);
    }

    static ImageLocation readFrom(BasicImageReader reader, int offset) {
        Objects.requireNonNull(reader);
        long[] attributes = reader.getAttributes(offset);
        ImageStringsReader strings = reader.getStrings();

        return new ImageLocation(attributes, strings);
    }
}