/*

 * Copyright (c) 1997, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "code/compressedStream.hpp"

#include "utilities/ostream.hpp"

// 32-bit self-inverse encoding of float bits

// converts trailing zeroes (common in floats) to leading zeroes

inline juint CompressedStream::reverse_int(juint i) {

  // Hacker's Delight, Figure 7-1

  i = (i & 0x55555555) << 1 | ((i >> 1) & 0x55555555);

  i = (i & 0x33333333) << 2 | ((i >> 2) & 0x33333333);

  i = (i & 0x0f0f0f0f) << 4 | ((i >> 4) & 0x0f0f0f0f);

  i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);

  return i;

}

jint CompressedReadStream::read_signed_int() {

  return decode_sign(read_int());

}

// Compressing floats is simple, because the only common pattern

// is trailing zeroes.  (Compare leading sign bits on ints.)

// Since floats are left-justified, as opposed to right-justified

// ints, we can bit-reverse them in order to take advantage of int

// compression.

jfloat CompressedReadStream::read_float() {

  int rf = read_int();

  int f  = reverse_int(rf);

  return jfloat_cast(f);

}

jdouble CompressedReadStream::read_double() {

  jint rh = read_int();

  jint rl = read_int();

  jint h  = reverse_int(rh);

  jint l  = reverse_int(rl);

  return jdouble_cast(jlong_from(h, l));

}

jlong CompressedReadStream::read_long() {

  jint low  = read_signed_int();

  jint high = read_signed_int();

  return jlong_from(high, low);

}

CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {

  _buffer   = NEW_RESOURCE_ARRAY(u_char, initial_size);

  _size     = initial_size;

  _position = 0;

}

void CompressedWriteStream::grow() {

  u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);

  memcpy(_new_buffer, _buffer, _position);

  _buffer = _new_buffer;

  _size   = _size * 2;

}

void CompressedWriteStream::write_float(jfloat value) {

  juint f = jint_cast(value);

  juint rf = reverse_int(f);

  assert(f == reverse_int(rf), "can re-read same bits");

  write_int(rf);

}

void CompressedWriteStream::write_double(jdouble value) {

  juint h  = high(jlong_cast(value));

  juint l  = low( jlong_cast(value));

  juint rh = reverse_int(h);

  juint rl = reverse_int(l);

  assert(h == reverse_int(rh), "can re-read same bits");

  assert(l == reverse_int(rl), "can re-read same bits");

  write_int(rh);

  write_int(rl);

}

void CompressedWriteStream::write_long(jlong value) {

  write_signed_int(low(value));

  write_signed_int(high(value));

}