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view src/share/vm/code/compressedStream.cpp @ 19181:9ee881900cf5
PrintFlagsWithComments should respect UnlockDiagnosticVMOptions
author | Tom Rodriguez <tom.rodriguez@oracle.com> |
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date | Fri, 06 Feb 2015 11:31:59 -0800 |
parents | 52b4284cb496 |
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/* * Copyright (c) 1997, 2014, 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 defined(_MSC_VER) && _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; } PRAGMA_DIAG_PUSH PRAGMA_FORMAT_IGNORED // Someone needs to deal with this. 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"); } PRAGMA_DIAG_POP #if defined(_MSC_VER) &&_MSC_VER >=1400 && !defined(_WIN64) #pragma warning(default: 4748) #pragma optimize("", on) #endif #endif // PRODUCT