/*

 * Copyright 1997-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

#include "incls/_precompiled.incl"

#include "incls/_compressedStream.cpp.incl"

// 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)

#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 optimize("", on)

#endif

#endif // PRODUCT