1 /* 2 * Copyright (c) 1997, 2006, 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 "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