/*

 * Copyright (c) 2012, 2017, 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

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 */

#include "precompiled.hpp"

#include "classfile/altHashing.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "oops/markOop.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/thread.hpp"

// Get the hash code of the classes mirror if it exists, otherwise just

// return a random number, which is one of the possible hash code used for

// objects.  We don't want to call the synchronizer hash code to install

// this value because it may safepoint.

static intptr_t object_hash(Klass* k) {

  intptr_t hc = k->java_mirror()->mark()->hash();

  return hc != markOopDesc::no_hash ? hc : os::random();

}

// Seed value used for each alternative hash calculated.

juint AltHashing::compute_seed() {

  jlong nanos = os::javaTimeNanos();

  jlong now = os::javaTimeMillis();

  jint SEED_MATERIAL[8] = {

            (jint) object_hash(SystemDictionary::String_klass()),

            (jint) object_hash(SystemDictionary::System_klass()),

            (jint) os::random(),  // current thread isn't a java thread

            (jint) (((julong)nanos) >> 32),

            (jint) nanos,

            (jint) (((julong)now) >> 32),

            (jint) now,

            (jint) (os::javaTimeNanos() >> 2)

  };

  return murmur3_32(SEED_MATERIAL, 8);

}

// Murmur3 hashing for Symbol

juint AltHashing::murmur3_32(juint seed, const jbyte* data, int len) {

  juint h1 = seed;

  int count = len;

  int offset = 0;

  // body

  while (count >= 4) {

    juint k1 = (data[offset] & 0x0FF)

        | (data[offset + 1] & 0x0FF) << 8

        | (data[offset + 2] & 0x0FF) << 16

        | data[offset + 3] << 24;

    count -= 4;

    offset += 4;

    k1 *= 0xcc9e2d51;

    k1 = Integer_rotateLeft(k1, 15);

    k1 *= 0x1b873593;

    h1 ^= k1;

    h1 = Integer_rotateLeft(h1, 13);

    h1 = h1 * 5 + 0xe6546b64;

  }

  // tail

  if (count > 0) {

    juint k1 = 0;

    switch (count) {

      case 3:

        k1 ^= (data[offset + 2] & 0xff) << 16;

      // fall through

      case 2:

        k1 ^= (data[offset + 1] & 0xff) << 8;

      // fall through

      case 1:

        k1 ^= (data[offset] & 0xff);

      // fall through

      default:

        k1 *= 0xcc9e2d51;

        k1 = Integer_rotateLeft(k1, 15);

        k1 *= 0x1b873593;

        h1 ^= k1;

    }

  }

  // finalization

  h1 ^= len;

  // finalization mix force all bits of a hash block to avalanche

  h1 ^= h1 >> 16;

  h1 *= 0x85ebca6b;

  h1 ^= h1 >> 13;

  h1 *= 0xc2b2ae35;

  h1 ^= h1 >> 16;

  return h1;

}

// Murmur3 hashing for Strings

juint AltHashing::murmur3_32(juint seed, const jchar* data, int len) {

  juint h1 = seed;

  int off = 0;

  int count = len;

  // body

  while (count >= 2) {

    jchar d1 = data[off++] & 0xFFFF;

    jchar d2 = data[off++];

    juint k1 = (d1 | d2 << 16);

    count -= 2;

    k1 *= 0xcc9e2d51;

    k1 = Integer_rotateLeft(k1, 15);

    k1 *= 0x1b873593;

    h1 ^= k1;

    h1 = Integer_rotateLeft(h1, 13);

    h1 = h1 * 5 + 0xe6546b64;

  }

  // tail

  if (count > 0) {

    juint k1 = (juint)data[off];

    k1 *= 0xcc9e2d51;

    k1 = Integer_rotateLeft(k1, 15);

    k1 *= 0x1b873593;

    h1 ^= k1;

  }

  // finalization

  h1 ^= len * 2; // (Character.SIZE / Byte.SIZE);

  // finalization mix force all bits of a hash block to avalanche

  h1 ^= h1 >> 16;

  h1 *= 0x85ebca6b;

  h1 ^= h1 >> 13;

  h1 *= 0xc2b2ae35;

  h1 ^= h1 >> 16;

  return h1;

}

// Hash used for the seed.

juint AltHashing::murmur3_32(juint seed, const jint* data, int len) {

  juint h1 = seed;

  int off = 0;

  int end = len;

  // body

  while (off < end) {

    juint k1 = (juint)data[off++];

    k1 *= 0xcc9e2d51;

    k1 = Integer_rotateLeft(k1, 15);

    k1 *= 0x1b873593;

    h1 ^= k1;

    h1 = Integer_rotateLeft(h1, 13);

    h1 = h1 * 5 + 0xe6546b64;

  }

  // tail (always empty, as body is always 32-bit chunks)

  // finalization

  h1 ^= len * 4; // (Integer.SIZE / Byte.SIZE);

  // finalization mix force all bits of a hash block to avalanche

  h1 ^= h1 >> 16;

  h1 *= 0x85ebca6b;

  h1 ^= h1 >> 13;

  h1 *= 0xc2b2ae35;

  h1 ^= h1 >> 16;

  return h1;

}

juint AltHashing::murmur3_32(const jint* data, int len) {

  return murmur3_32(0, data, len);

}