/*
* 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