1 /*
   2  * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "code/compressedStream.hpp"
  27 #include "utilities/ostream.hpp"
  28 
  29 // 32-bit one-to-one sign encoding taken from Pack200
  30 // converts leading sign bits into leading zeroes with trailing sign bit
  31 inline juint CompressedStream::encode_sign(jint  value) {
  32   return (value << 1) ^ (value >> 31);
  33 }
  34 inline jint  CompressedStream::decode_sign(juint value) {
  35   return (value >> 1) ^ -(jint)(value & 1);
  36 }
  37 
  38 // 32-bit self-inverse encoding of float bits
  39 // converts trailing zeroes (common in floats) to leading zeroes
  40 inline juint CompressedStream::reverse_int(juint i) {
  41   // Hacker's Delight, Figure 7-1
  42   i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555;
  43   i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333;
  44   i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f;
  45   i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);
  46   return i;
  47 }
  48 
  49 
  50 jint CompressedReadStream::read_signed_int() {
  51   return decode_sign(read_int());
  52 }
  53 
  54 // Compressing floats is simple, because the only common pattern
  55 // is trailing zeroes.  (Compare leading sign bits on ints.)
  56 // Since floats are left-justified, as opposed to right-justified
  57 // ints, we can bit-reverse them in order to take advantage of int
  58 // compression.
  59 
  60 jfloat CompressedReadStream::read_float() {
  61   int rf = read_int();
  62   int f  = reverse_int(rf);
  63   return jfloat_cast(f);
  64 }

   1 /*
   2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "code/compressedStream.hpp"
  27 #include "utilities/ostream.hpp"
  28 
  29 // 32-bit one-to-one sign encoding taken from Pack200
  30 // converts leading sign bits into leading zeroes with trailing sign bit
  31 inline juint CompressedStream::encode_sign(jint  value) {
  32   return (value << 1) ^ (value >> 31);
  33 }
  34 inline jint  CompressedStream::decode_sign(juint value) {
  35   return (value >> 1) ^ -(jint)(value & 1);
  36 }
  37 
  38 // 32-bit self-inverse encoding of float bits
  39 // converts trailing zeroes (common in floats) to leading zeroes
  40 inline juint CompressedStream::reverse_int(juint i) {
  41   // Hacker's Delight, Figure 7-1
  42   i = (i & 0x55555555) << 1 | ((i >> 1) & 0x55555555);
  43   i = (i & 0x33333333) << 2 | ((i >> 2) & 0x33333333);
  44   i = (i & 0x0f0f0f0f) << 4 | ((i >> 4) & 0x0f0f0f0f);
  45   i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);
  46   return i;
  47 }
  48 
  49 
  50 jint CompressedReadStream::read_signed_int() {
  51   return decode_sign(read_int());
  52 }
  53 
  54 // Compressing floats is simple, because the only common pattern
  55 // is trailing zeroes.  (Compare leading sign bits on ints.)
  56 // Since floats are left-justified, as opposed to right-justified
  57 // ints, we can bit-reverse them in order to take advantage of int
  58 // compression.
  59 
  60 jfloat CompressedReadStream::read_float() {
  61   int rf = read_int();
  62   int f  = reverse_int(rf);
  63   return jfloat_cast(f);
  64 }