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 }
65
66 jdouble CompressedReadStream::read_double() {
67 jint rh = read_int();
68 jint rl = read_int();
69 jint h = reverse_int(rh);
70 jint l = reverse_int(rl);
71 return jdouble_cast(jlong_from(h, l));
72 }
73
74 jlong CompressedReadStream::read_long() {
75 jint low = read_signed_int();
76 jint high = read_signed_int();
77 return jlong_from(high, low);
78 }
79
80 CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {
81 _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size);
82 _size = initial_size;
83 _position = 0;
84 }
85
86 void CompressedWriteStream::grow() {
87 u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);
88 memcpy(_new_buffer, _buffer, _position);
89 _buffer = _new_buffer;
90 _size = _size * 2;
91 }
92
93 void CompressedWriteStream::write_signed_int(jint value) {
94 // this encoding, called SIGNED5, is taken from Pack200
95 write_int(encode_sign(value));
96 }
97
98 void CompressedWriteStream::write_float(jfloat value) {
99 juint f = jint_cast(value);
100 juint rf = reverse_int(f);
101 assert(f == reverse_int(rf), "can re-read same bits");
102 write_int(rf);
103 }
104
105 void CompressedWriteStream::write_double(jdouble value) {
106 juint h = high(jlong_cast(value));
107 juint l = low( jlong_cast(value));
108 juint rh = reverse_int(h);
109 juint rl = reverse_int(l);
110 assert(h == reverse_int(rh), "can re-read same bits");
111 assert(l == reverse_int(rl), "can re-read same bits");
112 write_int(rh);
113 write_int(rl);
114 }
115
116 void CompressedWriteStream::write_long(jlong value) {
117 write_signed_int(low(value));
118 write_signed_int(high(value));
119 }
120
121
122 /// The remaining details
123
124 #ifndef PRODUCT
125 // set this to trigger unit test
126 void test_compressed_stream(int trace);
127 bool test_compressed_stream_enabled = false;
128 #endif
129
130 // This encoding, called UNSIGNED5, is taken from J2SE Pack200.
131 // It assumes that most values have lots of leading zeroes.
132 // Very small values, in the range [0..191], code in one byte.
133 // Any 32-bit value (including negatives) can be coded, in
134 // up to five bytes. The grammar is:
135 // low_byte = [0..191]
136 // high_byte = [192..255]
137 // any_byte = low_byte | high_byte
138 // coding = low_byte
139 // | high_byte low_byte
140 // | high_byte high_byte low_byte
141 // | high_byte high_byte high_byte low_byte
142 // | high_byte high_byte high_byte high_byte any_byte
143 // Each high_byte contributes six bits of payload.
144 // The encoding is one-to-one (except for integer overflow)
145 // and easy to parse and unparse.
146
147 jint CompressedReadStream::read_int_mb(jint b0) {
148 int pos = position() - 1;
149 u_char* buf = buffer() + pos;
150 assert(buf[0] == b0 && b0 >= L, "correctly called");
151 jint sum = b0;
152 // must collect more bytes: b[1]...b[4]
153 int lg_H_i = lg_H;
154 for (int i = 0; ; ) {
155 jint b_i = buf[++i]; // b_i = read(); ++i;
156 sum += b_i << lg_H_i; // sum += b[i]*(64**i)
157 if (b_i < L || i == MAX_i) {
158 set_position(pos+i+1);
159 return sum;
160 }
161 lg_H_i += lg_H;
162 }
163 }
164
165 void CompressedWriteStream::write_int_mb(jint value) {
166 debug_only(int pos1 = position());
167 juint sum = value;
168 for (int i = 0; ; ) {
169 if (sum < L || i == MAX_i) {
170 // remainder is either a "low code" or the 5th byte
171 assert(sum == (u_char)sum, "valid byte");
172 write((u_char)sum);
173 break;
174 }
175 sum -= L;
176 int b_i = L + (sum % H); // this is a "high code"
177 sum >>= lg_H; // extracted 6 bits
178 write(b_i); ++i;
179 }
180
181 #ifndef PRODUCT
182 if (test_compressed_stream_enabled) { // hack to enable this stress test
183 test_compressed_stream_enabled = false;
184 test_compressed_stream(0);
185 }
186 #endif
187 }
188
189
190 #ifndef PRODUCT
191 /// a unit test (can be run by hand from a debugger)
192
193 // Avoid a VS2005 compiler stack overflow w/ fastdebug build.
194 // The following pragma optimize turns off optimization ONLY
195 // for this block (a matching directive turns it back on later).
196 // These directives can be removed once the MS VS.NET 2005
197 // compiler stack overflow is fixed.
198 #if defined(_MSC_VER) && _MSC_VER >=1400 && !defined(_WIN64)
199 #pragma optimize("", off)
200 #pragma warning(disable: 4748)
201 #endif
202
203 // generator for an "interesting" set of critical values
204 enum { stretch_limit = (1<<16) * (64-16+1) };
205 static jlong stretch(jint x, int bits) {
206 // put x[high 4] into place
207 jlong h = (jlong)((x >> (16-4))) << (bits - 4);
208 // put x[low 12] into place, sign extended
209 jlong l = ((jlong)x << (64-12)) >> (64-12);
210 // move l upwards, maybe
211 l <<= (x >> 16);
212 return h ^ l;
213 }
214
215 PRAGMA_DIAG_PUSH
216 PRAGMA_FORMAT_IGNORED // Someone needs to deal with this.
217 void test_compressed_stream(int trace) {
218 CompressedWriteStream bytes(stretch_limit * 100);
219 jint n;
220 int step = 0, fails = 0;
221 #define CHECKXY(x, y, fmt) { \
222 ++step; \
223 int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \
224 if (trace > 0 && (step % trace) == 0) { \
225 tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \
226 step, n, x, xlen); } \
227 if (x != y) { \
228 tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \
229 fails++; \
230 } }
231 for (n = 0; n < (1<<8); n++) {
232 jbyte x = (jbyte)n;
233 bytes.write_byte(x); ++step;
234 }
235 for (n = 0; n < stretch_limit; n++) {
236 jint x = (jint)stretch(n, 32);
237 bytes.write_int(x); ++step;
238 bytes.write_signed_int(x); ++step;
239 bytes.write_float(jfloat_cast(x)); ++step;
240 }
241 for (n = 0; n < stretch_limit; n++) {
242 jlong x = stretch(n, 64);
243 bytes.write_long(x); ++step;
244 bytes.write_double(jdouble_cast(x)); ++step;
245 }
246 int length = bytes.position();
247 if (trace != 0)
248 tty->print_cr("set up test of %d stream values, size %d", step, length);
249 step = 0;
250 // now decode it all
251 CompressedReadStream decode(bytes.buffer());
252 int pos, lastpos = decode.position();
253 for (n = 0; n < (1<<8); n++) {
254 jbyte x = (jbyte)n;
255 jbyte y = decode.read_byte();
256 CHECKXY(x, y, "%db");
257 }
258 for (n = 0; n < stretch_limit; n++) {
259 jint x = (jint)stretch(n, 32);
260 jint y1 = decode.read_int();
261 CHECKXY(x, y1, "%du");
262 jint y2 = decode.read_signed_int();
263 CHECKXY(x, y2, "%di");
264 jint y3 = jint_cast(decode.read_float());
265 CHECKXY(x, y3, "%df");
266 }
267 for (n = 0; n < stretch_limit; n++) {
268 jlong x = stretch(n, 64);
269 jlong y1 = decode.read_long();
270 CHECKXY(x, y1, INT64_FORMAT "l");
271 jlong y2 = jlong_cast(decode.read_double());
272 CHECKXY(x, y2, INT64_FORMAT "d");
273 }
274 int length2 = decode.position();
275 if (trace != 0)
276 tty->print_cr("finished test of %d stream values, size %d", step, length2);
277 guarantee(length == length2, "bad length");
278 guarantee(fails == 0, "test failures");
279 }
280 PRAGMA_DIAG_POP
281
282 #if defined(_MSC_VER) &&_MSC_VER >=1400 && !defined(_WIN64)
283 #pragma warning(default: 4748)
284 #pragma optimize("", on)
285 #endif
286
287 #endif // PRODUCT