/*

 * Copyright (c) 2012, 2014, 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.

 *

 */

#include "precompiled.hpp"

#include "classfile/altHashing.hpp"

#include "classfile/symbolTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "oops/markOop.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.

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();

  int SEED_MATERIAL[8] = {

            (int) object_hash(SystemDictionary::String_klass()),

            (int) object_hash(SystemDictionary::System_klass()),

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

            (int) (((julong)nanos) >> 32),

            (int) nanos,

            (int) (((julong)now) >> 32),

            (int) now,

            (int) (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 int* 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 int* data, int len) {

  return murmur3_32(0, data, len);

}

#ifndef PRODUCT

// Overloaded versions for internal test.

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

  return murmur3_32(0, data, len);

}

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

  return murmur3_32(0, data, len);

}

// Internal test for alternate hashing.  Translated from JDK version

// test/sun/misc/Hashing.java

static const jbyte ONE_BYTE[] = { (jbyte) 0x80};

static const jbyte TWO_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81};

static const jchar ONE_CHAR[] = { (jchar) 0x8180};

static const jbyte THREE_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82};

static const jbyte FOUR_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82, (jbyte) 0x83};

static const jchar TWO_CHAR[] = { (jchar) 0x8180, (jchar) 0x8382};

static const jint ONE_INT[] = { 0x83828180};

static const jbyte SIX_BYTE[] = { (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82, (jbyte) 0x83, (jbyte) 0x84, (jbyte) 0x85};

static const jchar THREE_CHAR[] = { (jchar) 0x8180, (jchar) 0x8382, (jchar) 0x8584};

static const jbyte EIGHT_BYTE[] = {

  (jbyte) 0x80, (jbyte) 0x81, (jbyte) 0x82,

  (jbyte) 0x83, (jbyte) 0x84, (jbyte) 0x85,

  (jbyte) 0x86, (jbyte) 0x87};

static const jchar FOUR_CHAR[] = {

  (jchar) 0x8180, (jchar) 0x8382,

  (jchar) 0x8584, (jchar) 0x8786};

static const jint TWO_INT[] = { 0x83828180, 0x87868584};

static const juint MURMUR3_32_X86_CHECK_VALUE = 0xB0F57EE3;

void AltHashing::testMurmur3_32_ByteArray() {

  // printf("testMurmur3_32_ByteArray\n");

  jbyte vector[256];

  jbyte hashes[4 * 256];

  for (int i = 0; i < 256; i++) {

    vector[i] = (jbyte) i;

  }

  // Hash subranges {}, {0}, {0,1}, {0,1,2}, ..., {0,...,255}

  for (int i = 0; i < 256; i++) {

    juint hash = murmur3_32(256 - i, vector, i);

    hashes[i * 4] = (jbyte) hash;

    hashes[i * 4 + 1] = (jbyte)(hash >> 8);

    hashes[i * 4 + 2] = (jbyte)(hash >> 16);

    hashes[i * 4 + 3] = (jbyte)(hash >> 24);

  }

  // hash to get const result.

  juint final_hash = murmur3_32(hashes, 4*256);

  assert (MURMUR3_32_X86_CHECK_VALUE == final_hash,

    err_msg(

        "Calculated hash result not as expected. Expected %08X got %08X\n",

        MURMUR3_32_X86_CHECK_VALUE,

        final_hash));

}

void AltHashing::testEquivalentHashes() {

  juint jbytes, jchars, ints;

  // printf("testEquivalentHashes\n");

  jbytes = murmur3_32(TWO_BYTE, 2);

  jchars = murmur3_32(ONE_CHAR, 1);

  assert (jbytes == jchars,

    err_msg("Hashes did not match. b:%08x != c:%08x\n", jbytes, jchars));

  jbytes = murmur3_32(FOUR_BYTE, 4);

  jchars = murmur3_32(TWO_CHAR, 2);

  ints = murmur3_32(ONE_INT, 1);

  assert ((jbytes == jchars) && (jbytes == ints),

    err_msg("Hashes did not match. b:%08x != c:%08x != i:%08x\n", jbytes, jchars, ints));

  jbytes = murmur3_32(SIX_BYTE, 6);

  jchars = murmur3_32(THREE_CHAR, 3);

  assert (jbytes == jchars,

    err_msg("Hashes did not match. b:%08x != c:%08x\n", jbytes, jchars));

  jbytes = murmur3_32(EIGHT_BYTE, 8);

  jchars = murmur3_32(FOUR_CHAR, 4);

  ints = murmur3_32(TWO_INT, 2);

  assert ((jbytes == jchars) && (jbytes == ints),

    err_msg("Hashes did not match. b:%08x != c:%08x != i:%08x\n", jbytes, jchars, ints));

}

// Returns true if the alternate hashcode is correct

void AltHashing::test_alt_hash() {

  testMurmur3_32_ByteArray();

  testEquivalentHashes();

}

#endif // PRODUCT