/*

 * Copyright (c) 2000, 2018, 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.

 *

 * 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 sun.jvm.hotspot.oops;

import java.io.*;

import java.util.*;

import sun.jvm.hotspot.debugger.*;

import sun.jvm.hotspot.runtime.*;

import sun.jvm.hotspot.types.*;

import sun.jvm.hotspot.utilities.*;

// A Symbol is a canonicalized string.

// All Symbols reside in global symbolTable.

public class Symbol extends VMObject {

  static {

    VM.registerVMInitializedObserver(new Observer() {

        public void update(Observable o, Object data) {

          initialize(VM.getVM().getTypeDataBase());

        }

      });

  }

  private static synchronized void initialize(TypeDataBase db) throws WrongTypeException {

    Type type  = db.lookupType("Symbol");

    lengthAndRefcount = type.getCIntegerField("_length_and_refcount");

    baseOffset = type.getField("_body").getOffset();

    idHash = type.getCIntegerField("_identity_hash");

  }

  public static Symbol create(Address addr) {

    if (addr == null) {

      return null;

    }

    return new Symbol(addr);

  }

  Symbol(Address addr) {

    super(addr);

  }

  public boolean isSymbol()            { return true; }

  private static long baseOffset; // tells where the array part starts

  // Fields

  private static CIntegerField lengthAndRefcount;

  // Accessors for declared fields

  public long getLength() {

    long i = lengthAndRefcount.getValue(this.addr);

    return (i >> 16) & 0xffff;

  }

  public byte getByteAt(long index) {

    return addr.getJByteAt(baseOffset + index);

  }

  // _identity_hash is a short

  private static CIntegerField idHash;

  public long identityHash() {

    long addr_value = getAddress().asLongValue();

    long addr_bits =

      (addr_value >> (VM.getVM().getLogMinObjAlignmentInBytes() + 3)) & 0xffffffffL;

    int  length = (int)getLength();

    int  byte0 = getByteAt(0);

    int  byte1 = getByteAt(1);

    long id_hash = 0xffffL & (long)idHash.getValue(this.addr);

    return (id_hash |

      ((addr_bits ^ (length << 8) ^ ((byte0 << 8) | byte1)) << 16)) & 0xffffffffL;

  }

  public boolean equals(byte[] modUTF8Chars) {

    int l = (int) getLength();

    if (l != modUTF8Chars.length) return false;

    while (l-- > 0) {

      if (modUTF8Chars[l] != getByteAt(l)) return false;

    }

    if (Assert.ASSERTS_ENABLED) {

      Assert.that(l == -1, "we should be at the beginning");

    }

    return true;

  }

  public boolean equals(String string) {

    return asString().equals(string);

  }

  public byte[] asByteArray() {

    int length = (int) getLength();

    byte [] result = new byte [length];

    for (int index = 0; index < length; index++) {

      result[index] = getByteAt(index);

    }

    return result;

  }

  public String asString() {

    // Decode the byte array and return the string.

    try {

      return readModifiedUTF8(asByteArray());

    } catch(Exception e) {

      System.err.println(addr);

      e.printStackTrace();

      return null;

    }

  }

  public boolean startsWith(String str) {

    return asString().startsWith(str);

  }

  public void printValueOn(PrintStream tty) {

    tty.print("#" + asString());

  }

  /** Note: this comparison is used for vtable sorting only; it

      doesn't matter what order it defines, as long as it is a total,

      time-invariant order Since Symbol* are in C_HEAP, their

      relative order in memory never changes, so use address

      comparison for speed. */

  public long fastCompare(Symbol other) {

    return addr.minus(other.addr);

  }

  private static String readModifiedUTF8(byte[] buf) throws IOException {

    final int len = buf.length;

    byte[] tmp = new byte[len + 2];

    // write modified UTF-8 length as short in big endian

    tmp[0] = (byte) ((len >>> 8) & 0xFF);

    tmp[1] = (byte) ((len >>> 0) & 0xFF);

    // copy the data

    System.arraycopy(buf, 0, tmp, 2, len);

    DataInputStream dis = new DataInputStream(new ByteArrayInputStream(tmp));

    return dis.readUTF();

  }

}