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 self-inverse encoding of float bits
30// converts trailing zeroes (common in floats) to leading zeroes
31inline juint CompressedStream::reverse_int(juint i) {
32 // Hacker's Delight, Figure 7-1
33 i = (i & 0x55555555) << 1 | ((i >> 1) & 0x55555555);
34 i = (i & 0x33333333) << 2 | ((i >> 2) & 0x33333333);
35 i = (i & 0x0f0f0f0f) << 4 | ((i >> 4) & 0x0f0f0f0f);
36 i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);
37 return i;
38}
39
40jint CompressedReadStream::read_signed_int() {
41 return decode_sign(read_int());
42}
43
44// Compressing floats is simple, because the only common pattern
45// is trailing zeroes. (Compare leading sign bits on ints.)
46// Since floats are left-justified, as opposed to right-justified
47// ints, we can bit-reverse them in order to take advantage of int
48// compression.
49
50jfloat CompressedReadStream::read_float() {
51 int rf = read_int();
52 int f = reverse_int(rf);
53 return jfloat_cast(f);
54}
55
56jdouble CompressedReadStream::read_double() {
57 jint rh = read_int();
58 jint rl = read_int();
59 jint h = reverse_int(rh);
60 jint l = reverse_int(rl);
61 return jdouble_cast(jlong_from(h, l));
62}
63
64jlong CompressedReadStream::read_long() {
65 jint low = read_signed_int();
66 jint high = read_signed_int();
67 return jlong_from(high, low);
68}
69
70CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {
71 _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size);
72 _size = initial_size;
73 _position = 0;
74}
75
76void CompressedWriteStream::grow() {
77 u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);
78 memcpy(_new_buffer, _buffer, _position);
79 _buffer = _new_buffer;
80 _size = _size * 2;
81}
82
83void CompressedWriteStream::write_float(jfloat value) {
84 juint f = jint_cast(value);
85 juint rf = reverse_int(f);
86 assert(f == reverse_int(rf), "can re-read same bits");
87 write_int(rf);
88}
89
90void CompressedWriteStream::write_double(jdouble value) {
91 juint h = high(jlong_cast(value));
92 juint l = low( jlong_cast(value));
93 juint rh = reverse_int(h);
94 juint rl = reverse_int(l);
95 assert(h == reverse_int(rh), "can re-read same bits");
96 assert(l == reverse_int(rl), "can re-read same bits");
97 write_int(rh);
98 write_int(rl);
99}
100
101void CompressedWriteStream::write_long(jlong value) {
102 write_signed_int(low(value));
103 write_signed_int(high(value));
104}
105