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