Mercurial > hg > graal-jvmci-8

comparison src/share/vm/code/compressedStream.cpp @ 0:a61af66fc99e jdk7-b24

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children c18cbe5936b8
comparison
equal deleted inserted replaced
-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 1997-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 #include "incls/_precompiled.incl"
26 #include "incls/_compressedStream.cpp.incl"
27
28 // 32-bit one-to-one sign encoding taken from Pack200
29 // converts leading sign bits into leading zeroes with trailing sign bit
30 inline juint CompressedStream::encode_sign(jint value) {
31 return (value << 1) ^ (value >> 31);
32 }
33 inline jint CompressedStream::decode_sign(juint value) {
34 return (value >> 1) ^ -(jint)(value & 1);
35 }
36
37 // 32-bit self-inverse encoding of float bits
38 // converts trailing zeroes (common in floats) to leading zeroes
39 inline juint CompressedStream::reverse_int(juint i) {
40 // Hacker's Delight, Figure 7-1
41 i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555;
42 i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333;
43 i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f;
44 i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);
45 return i;
46 }
47
48
49 jint CompressedReadStream::read_signed_int() {
50 return decode_sign(read_int());
51 }
52
53 // Compressing floats is simple, because the only common pattern
54 // is trailing zeroes. (Compare leading sign bits on ints.)
55 // Since floats are left-justified, as opposed to right-justified
56 // ints, we can bit-reverse them in order to take advantage of int
57 // compression.
58
59 jfloat CompressedReadStream::read_float() {
60 int rf = read_int();
61 int f = reverse_int(rf);
62 return jfloat_cast(f);
63 }
64
65 jdouble CompressedReadStream::read_double() {
66 jint rh = read_int();
67 jint rl = read_int();
68 jint h = reverse_int(rh);
69 jint l = reverse_int(rl);
70 return jdouble_cast(jlong_from(h, l));
71 }
72
73 jlong CompressedReadStream::read_long() {
74 jint low = read_signed_int();
75 jint high = read_signed_int();
76 return jlong_from(high, low);
77 }
78
79 CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {
80 _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size);
81 _size = initial_size;
82 _position = 0;
83 }
84
85 void CompressedWriteStream::grow() {
86 u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);
87 memcpy(_new_buffer, _buffer, _position);
88 _buffer = _new_buffer;
89 _size = _size * 2;
90 }
91
92 void CompressedWriteStream::write_signed_int(jint value) {
93 // this encoding, called SIGNED5, is taken from Pack200
94 write_int(encode_sign(value));
95 }
96
97 void CompressedWriteStream::write_float(jfloat value) {
98 juint f = jint_cast(value);
99 juint rf = reverse_int(f);
100 assert(f == reverse_int(rf), "can re-read same bits");
101 write_int(rf);
102 }
103
104 void CompressedWriteStream::write_double(jdouble value) {
105 juint h = high(jlong_cast(value));
106 juint l = low( jlong_cast(value));
107 juint rh = reverse_int(h);
108 juint rl = reverse_int(l);
109 assert(h == reverse_int(rh), "can re-read same bits");
110 assert(l == reverse_int(rl), "can re-read same bits");
111 write_int(rh);
112 write_int(rl);
113 }
114
115 void CompressedWriteStream::write_long(jlong value) {
116 write_signed_int(low(value));
117 write_signed_int(high(value));
118 }
119
120
121 /// The remaining details
122
123 #ifndef PRODUCT
124 // set this to trigger unit test
125 void test_compressed_stream(int trace);
126 bool test_compressed_stream_enabled = false;
127 #endif
128
129 // This encoding, called UNSIGNED5, is taken from J2SE Pack200.
130 // It assumes that most values have lots of leading zeroes.
131 // Very small values, in the range [0..191], code in one byte.
132 // Any 32-bit value (including negatives) can be coded, in
133 // up to five bytes. The grammar is:
134 // low_byte = [0..191]
135 // high_byte = [192..255]
136 // any_byte = low_byte | high_byte
137 // coding = low_byte
138 // | high_byte low_byte
139 // | high_byte high_byte low_byte
140 // | high_byte high_byte high_byte low_byte
141 // | high_byte high_byte high_byte high_byte any_byte
142 // Each high_byte contributes six bits of payload.
143 // The encoding is one-to-one (except for integer overflow)
144 // and easy to parse and unparse.
145
146 jint CompressedReadStream::read_int_mb(jint b0) {
147 int pos = position() - 1;
148 u_char* buf = buffer() + pos;
149 assert(buf[0] == b0 && b0 >= L, "correctly called");
150 jint sum = b0;
151 // must collect more bytes: b[1]...b[4]
152 int lg_H_i = lg_H;
153 for (int i = 0; ; ) {
154 jint b_i = buf[++i]; // b_i = read(); ++i;
155 sum += b_i << lg_H_i; // sum += b[i]*(64**i)
156 if (b_i < L || i == MAX_i) {
157 set_position(pos+i+1);
158 return sum;
159 }
160 lg_H_i += lg_H;
161 }
162 }
163
164 void CompressedWriteStream::write_int_mb(jint value) {
165 debug_only(int pos1 = position());
166 juint sum = value;
167 for (int i = 0; ; ) {
168 if (sum < L || i == MAX_i) {
169 // remainder is either a "low code" or the 5th byte
170 assert(sum == (u_char)sum, "valid byte");
171 write((u_char)sum);
172 break;
173 }
174 sum -= L;
175 int b_i = L + (sum % H); // this is a "high code"
176 sum >>= lg_H; // extracted 6 bits
177 write(b_i); ++i;
178 }
179
180 #ifndef PRODUCT
181 if (test_compressed_stream_enabled) { // hack to enable this stress test
182 test_compressed_stream_enabled = false;
183 test_compressed_stream(0);
184 }
185 #endif
186 }
187
188
189 #ifndef PRODUCT
190 /// a unit test (can be run by hand from a debugger)
191
192 // Avoid a VS2005 compiler stack overflow w/ fastdebug build.
193 // The following pragma optimize turns off optimization ONLY
194 // for this block (a matching directive turns it back on later).
195 // These directives can be removed once the MS VS.NET 2005
196 // compiler stack overflow is fixed.
197 #if _MSC_VER >=1400 && !defined(_WIN64)
198 #pragma optimize("", off)
199 #endif
200
201 // generator for an "interesting" set of critical values
202 enum { stretch_limit = (1<<16) * (64-16+1) };
203 static jlong stretch(jint x, int bits) {
204 // put x[high 4] into place
205 jlong h = (jlong)((x >> (16-4))) << (bits - 4);
206 // put x[low 12] into place, sign extended
207 jlong l = ((jlong)x << (64-12)) >> (64-12);
208 // move l upwards, maybe
209 l <<= (x >> 16);
210 return h ^ l;
211 }
212
213 void test_compressed_stream(int trace) {
214 CompressedWriteStream bytes(stretch_limit * 100);
215 jint n;
216 int step = 0, fails = 0;
217 #define CHECKXY(x, y, fmt) { \
218 ++step; \
219 int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \
220 if (trace > 0 && (step % trace) == 0) { \
221 tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \
222 step, n, x, xlen); } \
223 if (x != y) { \
224 tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \
225 fails++; \
226 } }
227 for (n = 0; n < (1<<8); n++) {
228 jbyte x = (jbyte)n;
229 bytes.write_byte(x); ++step;
230 }
231 for (n = 0; n < stretch_limit; n++) {
232 jint x = (jint)stretch(n, 32);
233 bytes.write_int(x); ++step;
234 bytes.write_signed_int(x); ++step;
235 bytes.write_float(jfloat_cast(x)); ++step;
236 }
237 for (n = 0; n < stretch_limit; n++) {
238 jlong x = stretch(n, 64);
239 bytes.write_long(x); ++step;
240 bytes.write_double(jdouble_cast(x)); ++step;
241 }
242 int length = bytes.position();
243 if (trace != 0)
244 tty->print_cr("set up test of %d stream values, size %d", step, length);
245 step = 0;
246 // now decode it all
247 CompressedReadStream decode(bytes.buffer());
248 int pos, lastpos = decode.position();
249 for (n = 0; n < (1<<8); n++) {
250 jbyte x = (jbyte)n;
251 jbyte y = decode.read_byte();
252 CHECKXY(x, y, "%db");
253 }
254 for (n = 0; n < stretch_limit; n++) {
255 jint x = (jint)stretch(n, 32);
256 jint y1 = decode.read_int();
257 CHECKXY(x, y1, "%du");
258 jint y2 = decode.read_signed_int();
259 CHECKXY(x, y2, "%di");
260 jint y3 = jint_cast(decode.read_float());
261 CHECKXY(x, y3, "%df");
262 }
263 for (n = 0; n < stretch_limit; n++) {
264 jlong x = stretch(n, 64);
265 jlong y1 = decode.read_long();
266 CHECKXY(x, y1, INT64_FORMAT "l");
267 jlong y2 = jlong_cast(decode.read_double());
268 CHECKXY(x, y2, INT64_FORMAT "d");
269 }
270 int length2 = decode.position();
271 if (trace != 0)
272 tty->print_cr("finished test of %d stream values, size %d", step, length2);
273 guarantee(length == length2, "bad length");
274 guarantee(fails == 0, "test failures");
275 }
276
277 #if _MSC_VER >=1400 && !defined(_WIN64)
278 #pragma optimize("", on)
279 #endif
280
281 #endif // PRODUCT