content: /*
   * Copyright (c) 2022, 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 javac.internal.jimage;
  
  import java.nio.ByteBuffer;
  import java.nio.IntBuffer;
  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 final class ImageHeader {
      public static final int MAGIC = 0xCAFEDADA;
      public static final int MAJOR_VERSION = 1;
      public static final int MINOR_VERSION = 0;
      private static final int HEADER_SLOTS = 7;
  
      private final int magic;
      private final int majorVersion;
      private final int minorVersion;
      private final int flags;
      private final int resourceCount;
      private final int tableLength;
      private final int locationsSize;
      private final int stringsSize;
  
      public ImageHeader(int resourceCount, int tableCount,
              int locationsSize, int stringsSize) {
          this(MAGIC, MAJOR_VERSION, MINOR_VERSION, 0, resourceCount,
                  tableCount, locationsSize, stringsSize);
      }
  
      public ImageHeader(int magic, int majorVersion, int minorVersion,
                  int flags, int resourceCount,
                  int tableLength, int locationsSize, int stringsSize)
      {
          this.magic = magic;
          this.majorVersion = majorVersion;
          this.minorVersion = minorVersion;
          this.flags = flags;
          this.resourceCount = resourceCount;
          this.tableLength = tableLength;
          this.locationsSize = locationsSize;
          this.stringsSize = stringsSize;
      }
  
      public static int getHeaderSize() {
         return HEADER_SLOTS * 4;
      }
  
      static ImageHeader readFrom(IntBuffer buffer) {
          Objects.requireNonNull(buffer);
  
          if (buffer.capacity() != HEADER_SLOTS) {
              throw new InternalError(
                  "jimage header not the correct size: " + buffer.capacity());
          }
  
          int magic = buffer.get(0);
          int version = buffer.get(1);
          int majorVersion = version >>> 16;
          int minorVersion = version & 0xFFFF;
          int flags = buffer.get(2);
          int resourceCount = buffer.get(3);
          int tableLength = buffer.get(4);
          int locationsSize = buffer.get(5);
          int stringsSize = buffer.get(6);
  
          return new ImageHeader(magic, majorVersion, minorVersion, flags,
              resourceCount, tableLength, locationsSize, stringsSize);
      }
  
      public void writeTo(ImageStream stream) {
          Objects.requireNonNull(stream);
          stream.ensure(getHeaderSize());
          writeTo(stream.getBuffer());
      }
  
      public void writeTo(ByteBuffer buffer) {
          Objects.requireNonNull(buffer);
          buffer.putInt(magic);
          buffer.putInt(majorVersion << 16 | minorVersion);
          buffer.putInt(flags);
          buffer.putInt(resourceCount);
          buffer.putInt(tableLength);
          buffer.putInt(locationsSize);
          buffer.putInt(stringsSize);
      }
  
      public int getMagic() {
          return magic;
      }
  
      public int getMajorVersion() {
          return majorVersion;
      }
  
      public int getMinorVersion() {
          return minorVersion;
      }
  
      public int getFlags() {
          return flags;
      }
  
      public int getResourceCount() {
          return resourceCount;
      }
  
      public int getTableLength() {
          return tableLength;
      }
  
      public int getRedirectSize() {
          return tableLength * 4;
      }
  
      public int getOffsetsSize() {
          return tableLength * 4;
      }
  
      public int getLocationsSize() {
          return locationsSize;
      }
  
      public int getStringsSize() {
          return stringsSize;
      }
  
      public int getIndexSize() {
          return getHeaderSize() +
                 getRedirectSize() +
                 getOffsetsSize() +
                 getLocationsSize() +
                 getStringsSize();
      }
  
      int getRedirectOffset() {
          return getHeaderSize();
      }
  
      int getOffsetsOffset() {
          return getRedirectOffset() +
                 getRedirectSize();
      }
  
      int getLocationsOffset() {
          return getOffsetsOffset() +
                 getOffsetsSize();
      }
  
      int getStringsOffset() {
          return getLocationsOffset() +
                 getLocationsSize();
      }
  }
  