1 /*

     2  * Copyright (c) 1997, 2017, 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 void CompressedWriteStream::write_int_mb(jint value) {

   131   debug_only(int pos1 = position());

   132   juint sum = value;

   133   for (int i = 0; ; ) {

   134     if (sum < L || i == MAX_i) {

   135       // remainder is either a "low code" or the 5th byte

   136       assert(sum == (u_char)sum, "valid byte");

   137       write((u_char)sum);

   138       break;

   139     }

   140     sum -= L;

   141     int b_i = L + (sum % H);  // this is a "high code"

   142     sum >>= lg_H;             // extracted 6 bits

   143     write(b_i); ++i;

   144   }

   145 

   146 #ifndef PRODUCT

   147   if (test_compressed_stream_enabled) {  // hack to enable this stress test

   148     test_compressed_stream_enabled = false;

   149     test_compressed_stream(0);

   150   }

   151 #endif

   152 }

   153 

   154 

   155 #ifndef PRODUCT

   156 /// a unit test (can be run by hand from a debugger)

   157 

   158 // Avoid a VS2005 compiler stack overflow w/ fastdebug build.

   159 // The following pragma optimize turns off optimization ONLY

   160 // for this block (a matching directive turns it back on later).

   161 // These directives can be removed once the MS VS.NET 2005

   162 // compiler stack overflow is fixed.

   163 #if defined(_MSC_VER) && _MSC_VER >=1400 && !defined(_WIN64)

   164 #pragma optimize("", off)

   165 #pragma warning(disable: 4748)

   166 #endif

   167 

   168 // generator for an "interesting" set of critical values

   169 enum { stretch_limit = (1<<16) * (64-16+1) };

   170 static jlong stretch(jint x, int bits) {

   171   // put x[high 4] into place

   172   jlong h = (jlong)((x >> (16-4))) << (bits - 4);

   173   // put x[low 12] into place, sign extended

   174   jlong l = ((jlong)x << (64-12)) >> (64-12);

   175   // move l upwards, maybe

   176   l <<= (x >> 16);

   177   return h ^ l;

   178 }

   179 

   180 PRAGMA_DIAG_PUSH

   181 PRAGMA_FORMAT_IGNORED // Someone needs to deal with this.

   182 void test_compressed_stream(int trace) {

   183   CompressedWriteStream bytes(stretch_limit * 100);

   184   jint n;

   185   int step = 0, fails = 0;

   186 #define CHECKXY(x, y, fmt) { \

   187     ++step; \

   188     int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \

   189     if (trace > 0 && (step % trace) == 0) { \

   190       tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \

   191                     step, n, x, xlen); } \

   192     if (x != y) {                                                     \

   193       tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \

   194       fails++; \

   195     } }

   196   for (n = 0; n < (1<<8); n++) {

   197     jbyte x = (jbyte)n;

   198     bytes.write_byte(x); ++step;

   199   }

   200   for (n = 0; n < stretch_limit; n++) {

   201     jint x = (jint)stretch(n, 32);

   202     bytes.write_int(x); ++step;

   203     bytes.write_signed_int(x); ++step;

   204     bytes.write_float(jfloat_cast(x)); ++step;

   205   }

   206   for (n = 0; n < stretch_limit; n++) {

   207     jlong x = stretch(n, 64);

   208     bytes.write_long(x); ++step;

   209     bytes.write_double(jdouble_cast(x)); ++step;

   210   }

   211   int length = bytes.position();

   212   if (trace != 0)

   213     tty->print_cr("set up test of %d stream values, size %d", step, length);

   214   step = 0;

   215   // now decode it all

   216   CompressedReadStream decode(bytes.buffer());

   217   int pos, lastpos = decode.position();

   218   for (n = 0; n < (1<<8); n++) {

   219     jbyte x = (jbyte)n;

   220     jbyte y = decode.read_byte();

   221     CHECKXY(x, y, "%db");

   222   }

   223   for (n = 0; n < stretch_limit; n++) {

   224     jint x = (jint)stretch(n, 32);

   225     jint y1 = decode.read_int();

   226     CHECKXY(x, y1, "%du");

   227     jint y2 = decode.read_signed_int();

   228     CHECKXY(x, y2, "%di");

   229     jint y3 = jint_cast(decode.read_float());

   230     CHECKXY(x, y3, "%df");

   231   }

   232   for (n = 0; n < stretch_limit; n++) {

   233     jlong x = stretch(n, 64);

   234     jlong y1 = decode.read_long();

   235     CHECKXY(x, y1, INT64_FORMAT "l");

   236     jlong y2 = jlong_cast(decode.read_double());

   237     CHECKXY(x, y2, INT64_FORMAT "d");

   238   }

   239   int length2 = decode.position();

   240   if (trace != 0)

   241     tty->print_cr("finished test of %d stream values, size %d", step, length2);

   242   guarantee(length == length2, "bad length");

   243   guarantee(fails == 0, "test failures");

   244 }

   245 PRAGMA_DIAG_POP

   246 

   247 #if defined(_MSC_VER) &&_MSC_VER >=1400 && !defined(_WIN64)

   248 #pragma warning(default: 4748)

   249 #pragma optimize("", on)

   250 #endif

   251 

   252 #endif // PRODUCT