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 /*

  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "code/compressedStream.hpp"

 #include "utilities/ostream.hpp"

 // 32-bit one-to-one sign encoding taken from Pack200

 // converts leading sign bits into leading zeroes with trailing sign bit

 inline juint CompressedStream::encode_sign(jint  value) {

   return (value << 1) ^ (value >> 31);

 }

 inline jint  CompressedStream::decode_sign(juint value) {

   return (value >> 1) ^ -(jint)(value & 1);

 }

 // 32-bit self-inverse encoding of float bits

 // converts trailing zeroes (common in floats) to leading zeroes

 inline juint CompressedStream::reverse_int(juint i) {

   // Hacker's Delight, Figure 7-1

   i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555;

   i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333;

   i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f;

   i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);

   return i;

 }

 jint CompressedReadStream::read_signed_int() {

   return decode_sign(read_int());

 }

 // Compressing floats is simple, because the only common pattern

 // is trailing zeroes.  (Compare leading sign bits on ints.)

 // Since floats are left-justified, as opposed to right-justified

 // ints, we can bit-reverse them in order to take advantage of int

 // compression.

 jfloat CompressedReadStream::read_float() {

   int rf = read_int();

   int f  = reverse_int(rf);

   return jfloat_cast(f);

 }

 jdouble CompressedReadStream::read_double() {

   jint rh = read_int();

   jint rl = read_int();

   jint h  = reverse_int(rh);

   jint l  = reverse_int(rl);

   return jdouble_cast(jlong_from(h, l));

 }

 jlong CompressedReadStream::read_long() {

   jint low  = read_signed_int();

   jint high = read_signed_int();

   return jlong_from(high, low);

 }

 CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {

   _buffer   = NEW_RESOURCE_ARRAY(u_char, initial_size);

   _size     = initial_size;

   _position = 0;

 }

 void CompressedWriteStream::grow() {

   u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);

   memcpy(_new_buffer, _buffer, _position);

   _buffer = _new_buffer;

   _size   = _size * 2;

 }

 void CompressedWriteStream::write_signed_int(jint value) {

   // this encoding, called SIGNED5, is taken from Pack200

   write_int(encode_sign(value));

 }

 void CompressedWriteStream::write_float(jfloat value) {

   juint f = jint_cast(value);

   juint rf = reverse_int(f);

   assert(f == reverse_int(rf), "can re-read same bits");

   write_int(rf);

 }

 void CompressedWriteStream::write_double(jdouble value) {

   juint h  = high(jlong_cast(value));

   juint l  = low( jlong_cast(value));

   juint rh = reverse_int(h);

   juint rl = reverse_int(l);

   assert(h == reverse_int(rh), "can re-read same bits");

   assert(l == reverse_int(rl), "can re-read same bits");

   write_int(rh);

   write_int(rl);

 }

 void CompressedWriteStream::write_long(jlong value) {

   write_signed_int(low(value));

   write_signed_int(high(value));

 }

 /// The remaining details

 #ifndef PRODUCT

 // set this to trigger unit test

 void test_compressed_stream(int trace);

 bool test_compressed_stream_enabled = false;

 #endif

 // This encoding, called UNSIGNED5, is taken from J2SE Pack200.

 // It assumes that most values have lots of leading zeroes.

 // Very small values, in the range [0..191], code in one byte.

 // Any 32-bit value (including negatives) can be coded, in

 // up to five bytes.  The grammar is:

 //    low_byte  = [0..191]

 //    high_byte = [192..255]

 //    any_byte  = low_byte | high_byte

 //    coding = low_byte

 //           | high_byte low_byte

 //           | high_byte high_byte low_byte

 //           | high_byte high_byte high_byte low_byte

 //           | high_byte high_byte high_byte high_byte any_byte

 // Each high_byte contributes six bits of payload.

 // The encoding is one-to-one (except for integer overflow)

 // and easy to parse and unparse.

 jint CompressedReadStream::read_int_mb(jint b0) {

   int     pos = position() - 1;

   u_char* buf = buffer() + pos;

   assert(buf[0] == b0 && b0 >= L, "correctly called");

   jint    sum = b0;

   // must collect more bytes:  b[1]...b[4]

   int lg_H_i = lg_H;

   for (int i = 0; ; ) {

     jint b_i = buf[++i]; // b_i = read(); ++i;

     sum += b_i << lg_H_i;  // sum += b[i]*(64**i)

     if (b_i < L || i == MAX_i) {

       set_position(pos+i+1);

       return sum;

     }

     lg_H_i += lg_H;

   }

 }

 void CompressedWriteStream::write_int_mb(jint value) {

   debug_only(int pos1 = position());

   juint sum = value;

   for (int i = 0; ; ) {

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

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

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

       write((u_char)sum);

       break;

     }

     sum -= L;

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

     sum >>= lg_H;             // extracted 6 bits

     write(b_i); ++i;

   }

 #ifndef PRODUCT

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

     test_compressed_stream_enabled = false;

     test_compressed_stream(0);

   }

 #endif

 }

 #ifndef PRODUCT

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

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

 // The following pragma optimize turns off optimization ONLY

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

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

 // compiler stack overflow is fixed.

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

 #pragma optimize("", off)

 #pragma warning(disable: 4748)

 #endif

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

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

 static jlong stretch(jint x, int bits) {

   // put x[high 4] into place

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

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

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

   // move l upwards, maybe

   l <<= (x >> 16);

   return h ^ l;

 }

 void test_compressed_stream(int trace) {

   CompressedWriteStream bytes(stretch_limit * 100);

   jint n;

   int step = 0, fails = 0;

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

     ++step; \

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

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

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

                     step, n, x, xlen); } \

     if (x != y) {                                                     \

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

       fails++; \

     } }

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

     jbyte x = (jbyte)n;

     bytes.write_byte(x); ++step;

   }

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

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

     bytes.write_int(x); ++step;

     bytes.write_signed_int(x); ++step;

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

   }

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

     jlong x = stretch(n, 64);

     bytes.write_long(x); ++step;

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

   }

   int length = bytes.position();

   if (trace != 0)

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

   step = 0;

   // now decode it all

   CompressedReadStream decode(bytes.buffer());

   int pos, lastpos = decode.position();

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

     jbyte x = (jbyte)n;

     jbyte y = decode.read_byte();

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

   }

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

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

     jint y1 = decode.read_int();

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

     jint y2 = decode.read_signed_int();

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

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

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

   }

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

     jlong x = stretch(n, 64);

     jlong y1 = decode.read_long();

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

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

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

   }

   int length2 = decode.position();

   if (trace != 0)

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

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

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

 }

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

 #pragma warning(default: 4748)

 #pragma optimize("", on)

 #endif

 #endif // PRODUCT