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annotate src/share/vm/code/compressedStream.cpp @ 3763:e66f38dd58a9
Merge
author | ysr |
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date | Wed, 08 Jun 2011 08:39:53 -0700 |
parents | 5fa559508216 |
children | 47bc9800972c |
rev | line source |
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0 | 1 /* |
1972 | 2 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
1552
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
26 #include "code/compressedStream.hpp" | |
27 #include "utilities/ostream.hpp" | |
0 | 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 _MSC_VER >=1400 && !defined(_WIN64) | |
199 #pragma optimize("", off) | |
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200 #pragma warning(disable: 4748) |
0 | 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 void test_compressed_stream(int trace) { | |
216 CompressedWriteStream bytes(stretch_limit * 100); | |
217 jint n; | |
218 int step = 0, fails = 0; | |
219 #define CHECKXY(x, y, fmt) { \ | |
220 ++step; \ | |
221 int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \ | |
222 if (trace > 0 && (step % trace) == 0) { \ | |
223 tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \ | |
224 step, n, x, xlen); } \ | |
225 if (x != y) { \ | |
226 tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \ | |
227 fails++; \ | |
228 } } | |
229 for (n = 0; n < (1<<8); n++) { | |
230 jbyte x = (jbyte)n; | |
231 bytes.write_byte(x); ++step; | |
232 } | |
233 for (n = 0; n < stretch_limit; n++) { | |
234 jint x = (jint)stretch(n, 32); | |
235 bytes.write_int(x); ++step; | |
236 bytes.write_signed_int(x); ++step; | |
237 bytes.write_float(jfloat_cast(x)); ++step; | |
238 } | |
239 for (n = 0; n < stretch_limit; n++) { | |
240 jlong x = stretch(n, 64); | |
241 bytes.write_long(x); ++step; | |
242 bytes.write_double(jdouble_cast(x)); ++step; | |
243 } | |
244 int length = bytes.position(); | |
245 if (trace != 0) | |
246 tty->print_cr("set up test of %d stream values, size %d", step, length); | |
247 step = 0; | |
248 // now decode it all | |
249 CompressedReadStream decode(bytes.buffer()); | |
250 int pos, lastpos = decode.position(); | |
251 for (n = 0; n < (1<<8); n++) { | |
252 jbyte x = (jbyte)n; | |
253 jbyte y = decode.read_byte(); | |
254 CHECKXY(x, y, "%db"); | |
255 } | |
256 for (n = 0; n < stretch_limit; n++) { | |
257 jint x = (jint)stretch(n, 32); | |
258 jint y1 = decode.read_int(); | |
259 CHECKXY(x, y1, "%du"); | |
260 jint y2 = decode.read_signed_int(); | |
261 CHECKXY(x, y2, "%di"); | |
262 jint y3 = jint_cast(decode.read_float()); | |
263 CHECKXY(x, y3, "%df"); | |
264 } | |
265 for (n = 0; n < stretch_limit; n++) { | |
266 jlong x = stretch(n, 64); | |
267 jlong y1 = decode.read_long(); | |
268 CHECKXY(x, y1, INT64_FORMAT "l"); | |
269 jlong y2 = jlong_cast(decode.read_double()); | |
270 CHECKXY(x, y2, INT64_FORMAT "d"); | |
271 } | |
272 int length2 = decode.position(); | |
273 if (trace != 0) | |
274 tty->print_cr("finished test of %d stream values, size %d", step, length2); | |
275 guarantee(length == length2, "bad length"); | |
276 guarantee(fails == 0, "test failures"); | |
277 } | |
278 | |
279 #if _MSC_VER >=1400 && !defined(_WIN64) | |
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280 #pragma warning(default: 4748) |
0 | 281 #pragma optimize("", on) |
282 #endif | |
283 | |
284 #endif // PRODUCT |