1 /* 2 * Copyright (c) 1997, 2010, 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 _MSC_VER >=1400 && !defined(_WIN64) 199 #pragma optimize("", off) 200 #endif 201 202 // generator for an "interesting" set of critical values 203 enum { stretch_limit = (1<<16) * (64-16+1) }; 204 static jlong stretch(jint x, int bits) { 205 // put x[high 4] into place 206 jlong h = (jlong)((x >> (16-4))) << (bits - 4); 207 // put x[low 12] into place, sign extended 208 jlong l = ((jlong)x << (64-12)) >> (64-12); 209 // move l upwards, maybe 210 l <<= (x >> 16); 211 return h ^ l; 212 } 213 214 void test_compressed_stream(int trace) { 215 CompressedWriteStream bytes(stretch_limit * 100); 216 jint n; 217 int step = 0, fails = 0; 218 #define CHECKXY(x, y, fmt) { \ 219 ++step; \ 220 int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \ 221 if (trace > 0 && (step % trace) == 0) { \ 222 tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \ 223 step, n, x, xlen); } \ 224 if (x != y) { \ 225 tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \ 226 fails++; \ 227 } } 228 for (n = 0; n < (1<<8); n++) { 229 jbyte x = (jbyte)n; 230 bytes.write_byte(x); ++step; 231 } 232 for (n = 0; n < stretch_limit; n++) { 233 jint x = (jint)stretch(n, 32); 234 bytes.write_int(x); ++step; 235 bytes.write_signed_int(x); ++step; 236 bytes.write_float(jfloat_cast(x)); ++step; 237 } 238 for (n = 0; n < stretch_limit; n++) { 239 jlong x = stretch(n, 64); 240 bytes.write_long(x); ++step; 241 bytes.write_double(jdouble_cast(x)); ++step; 242 } 243 int length = bytes.position(); 244 if (trace != 0) 245 tty->print_cr("set up test of %d stream values, size %d", step, length); 246 step = 0; 247 // now decode it all 248 CompressedReadStream decode(bytes.buffer()); 249 int pos, lastpos = decode.position(); 250 for (n = 0; n < (1<<8); n++) { 251 jbyte x = (jbyte)n; 252 jbyte y = decode.read_byte(); 253 CHECKXY(x, y, "%db"); 254 } 255 for (n = 0; n < stretch_limit; n++) { 256 jint x = (jint)stretch(n, 32); 257 jint y1 = decode.read_int(); 258 CHECKXY(x, y1, "%du"); 259 jint y2 = decode.read_signed_int(); 260 CHECKXY(x, y2, "%di"); 261 jint y3 = jint_cast(decode.read_float()); 262 CHECKXY(x, y3, "%df"); 263 } 264 for (n = 0; n < stretch_limit; n++) { 265 jlong x = stretch(n, 64); 266 jlong y1 = decode.read_long(); 267 CHECKXY(x, y1, INT64_FORMAT "l"); 268 jlong y2 = jlong_cast(decode.read_double()); 269 CHECKXY(x, y2, INT64_FORMAT "d"); 270 } 271 int length2 = decode.position(); 272 if (trace != 0) 273 tty->print_cr("finished test of %d stream values, size %d", step, length2); 274 guarantee(length == length2, "bad length"); 275 guarantee(fails == 0, "test failures"); 276 } 277 278 #if _MSC_VER >=1400 && !defined(_WIN64) 279 #pragma optimize("", on) 280 #endif 281 282 #endif // PRODUCT