1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/code/compressedStream.cpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,281 @@
1.4 +/*
1.5 + * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "incls/_precompiled.incl"
1.29 +#include "incls/_compressedStream.cpp.incl"
1.30 +
1.31 +// 32-bit one-to-one sign encoding taken from Pack200
1.32 +// converts leading sign bits into leading zeroes with trailing sign bit
1.33 +inline juint CompressedStream::encode_sign(jint value) {
1.34 + return (value << 1) ^ (value >> 31);
1.35 +}
1.36 +inline jint CompressedStream::decode_sign(juint value) {
1.37 + return (value >> 1) ^ -(jint)(value & 1);
1.38 +}
1.39 +
1.40 +// 32-bit self-inverse encoding of float bits
1.41 +// converts trailing zeroes (common in floats) to leading zeroes
1.42 +inline juint CompressedStream::reverse_int(juint i) {
1.43 + // Hacker's Delight, Figure 7-1
1.44 + i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555;
1.45 + i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333;
1.46 + i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f;
1.47 + i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);
1.48 + return i;
1.49 +}
1.50 +
1.51 +
1.52 +jint CompressedReadStream::read_signed_int() {
1.53 + return decode_sign(read_int());
1.54 +}
1.55 +
1.56 +// Compressing floats is simple, because the only common pattern
1.57 +// is trailing zeroes. (Compare leading sign bits on ints.)
1.58 +// Since floats are left-justified, as opposed to right-justified
1.59 +// ints, we can bit-reverse them in order to take advantage of int
1.60 +// compression.
1.61 +
1.62 +jfloat CompressedReadStream::read_float() {
1.63 + int rf = read_int();
1.64 + int f = reverse_int(rf);
1.65 + return jfloat_cast(f);
1.66 +}
1.67 +
1.68 +jdouble CompressedReadStream::read_double() {
1.69 + jint rh = read_int();
1.70 + jint rl = read_int();
1.71 + jint h = reverse_int(rh);
1.72 + jint l = reverse_int(rl);
1.73 + return jdouble_cast(jlong_from(h, l));
1.74 +}
1.75 +
1.76 +jlong CompressedReadStream::read_long() {
1.77 + jint low = read_signed_int();
1.78 + jint high = read_signed_int();
1.79 + return jlong_from(high, low);
1.80 +}
1.81 +
1.82 +CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {
1.83 + _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size);
1.84 + _size = initial_size;
1.85 + _position = 0;
1.86 +}
1.87 +
1.88 +void CompressedWriteStream::grow() {
1.89 + u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);
1.90 + memcpy(_new_buffer, _buffer, _position);
1.91 + _buffer = _new_buffer;
1.92 + _size = _size * 2;
1.93 +}
1.94 +
1.95 +void CompressedWriteStream::write_signed_int(jint value) {
1.96 + // this encoding, called SIGNED5, is taken from Pack200
1.97 + write_int(encode_sign(value));
1.98 +}
1.99 +
1.100 +void CompressedWriteStream::write_float(jfloat value) {
1.101 + juint f = jint_cast(value);
1.102 + juint rf = reverse_int(f);
1.103 + assert(f == reverse_int(rf), "can re-read same bits");
1.104 + write_int(rf);
1.105 +}
1.106 +
1.107 +void CompressedWriteStream::write_double(jdouble value) {
1.108 + juint h = high(jlong_cast(value));
1.109 + juint l = low( jlong_cast(value));
1.110 + juint rh = reverse_int(h);
1.111 + juint rl = reverse_int(l);
1.112 + assert(h == reverse_int(rh), "can re-read same bits");
1.113 + assert(l == reverse_int(rl), "can re-read same bits");
1.114 + write_int(rh);
1.115 + write_int(rl);
1.116 +}
1.117 +
1.118 +void CompressedWriteStream::write_long(jlong value) {
1.119 + write_signed_int(low(value));
1.120 + write_signed_int(high(value));
1.121 +}
1.122 +
1.123 +
1.124 +/// The remaining details
1.125 +
1.126 +#ifndef PRODUCT
1.127 +// set this to trigger unit test
1.128 +void test_compressed_stream(int trace);
1.129 +bool test_compressed_stream_enabled = false;
1.130 +#endif
1.131 +
1.132 +// This encoding, called UNSIGNED5, is taken from J2SE Pack200.
1.133 +// It assumes that most values have lots of leading zeroes.
1.134 +// Very small values, in the range [0..191], code in one byte.
1.135 +// Any 32-bit value (including negatives) can be coded, in
1.136 +// up to five bytes. The grammar is:
1.137 +// low_byte = [0..191]
1.138 +// high_byte = [192..255]
1.139 +// any_byte = low_byte | high_byte
1.140 +// coding = low_byte
1.141 +// | high_byte low_byte
1.142 +// | high_byte high_byte low_byte
1.143 +// | high_byte high_byte high_byte low_byte
1.144 +// | high_byte high_byte high_byte high_byte any_byte
1.145 +// Each high_byte contributes six bits of payload.
1.146 +// The encoding is one-to-one (except for integer overflow)
1.147 +// and easy to parse and unparse.
1.148 +
1.149 +jint CompressedReadStream::read_int_mb(jint b0) {
1.150 + int pos = position() - 1;
1.151 + u_char* buf = buffer() + pos;
1.152 + assert(buf[0] == b0 && b0 >= L, "correctly called");
1.153 + jint sum = b0;
1.154 + // must collect more bytes: b[1]...b[4]
1.155 + int lg_H_i = lg_H;
1.156 + for (int i = 0; ; ) {
1.157 + jint b_i = buf[++i]; // b_i = read(); ++i;
1.158 + sum += b_i << lg_H_i; // sum += b[i]*(64**i)
1.159 + if (b_i < L || i == MAX_i) {
1.160 + set_position(pos+i+1);
1.161 + return sum;
1.162 + }
1.163 + lg_H_i += lg_H;
1.164 + }
1.165 +}
1.166 +
1.167 +void CompressedWriteStream::write_int_mb(jint value) {
1.168 + debug_only(int pos1 = position());
1.169 + juint sum = value;
1.170 + for (int i = 0; ; ) {
1.171 + if (sum < L || i == MAX_i) {
1.172 + // remainder is either a "low code" or the 5th byte
1.173 + assert(sum == (u_char)sum, "valid byte");
1.174 + write((u_char)sum);
1.175 + break;
1.176 + }
1.177 + sum -= L;
1.178 + int b_i = L + (sum % H); // this is a "high code"
1.179 + sum >>= lg_H; // extracted 6 bits
1.180 + write(b_i); ++i;
1.181 + }
1.182 +
1.183 +#ifndef PRODUCT
1.184 + if (test_compressed_stream_enabled) { // hack to enable this stress test
1.185 + test_compressed_stream_enabled = false;
1.186 + test_compressed_stream(0);
1.187 + }
1.188 +#endif
1.189 +}
1.190 +
1.191 +
1.192 +#ifndef PRODUCT
1.193 +/// a unit test (can be run by hand from a debugger)
1.194 +
1.195 +// Avoid a VS2005 compiler stack overflow w/ fastdebug build.
1.196 +// The following pragma optimize turns off optimization ONLY
1.197 +// for this block (a matching directive turns it back on later).
1.198 +// These directives can be removed once the MS VS.NET 2005
1.199 +// compiler stack overflow is fixed.
1.200 +#if _MSC_VER >=1400 && !defined(_WIN64)
1.201 +#pragma optimize("", off)
1.202 +#endif
1.203 +
1.204 +// generator for an "interesting" set of critical values
1.205 +enum { stretch_limit = (1<<16) * (64-16+1) };
1.206 +static jlong stretch(jint x, int bits) {
1.207 + // put x[high 4] into place
1.208 + jlong h = (jlong)((x >> (16-4))) << (bits - 4);
1.209 + // put x[low 12] into place, sign extended
1.210 + jlong l = ((jlong)x << (64-12)) >> (64-12);
1.211 + // move l upwards, maybe
1.212 + l <<= (x >> 16);
1.213 + return h ^ l;
1.214 +}
1.215 +
1.216 +void test_compressed_stream(int trace) {
1.217 + CompressedWriteStream bytes(stretch_limit * 100);
1.218 + jint n;
1.219 + int step = 0, fails = 0;
1.220 +#define CHECKXY(x, y, fmt) { \
1.221 + ++step; \
1.222 + int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \
1.223 + if (trace > 0 && (step % trace) == 0) { \
1.224 + tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \
1.225 + step, n, x, xlen); } \
1.226 + if (x != y) { \
1.227 + tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \
1.228 + fails++; \
1.229 + } }
1.230 + for (n = 0; n < (1<<8); n++) {
1.231 + jbyte x = (jbyte)n;
1.232 + bytes.write_byte(x); ++step;
1.233 + }
1.234 + for (n = 0; n < stretch_limit; n++) {
1.235 + jint x = (jint)stretch(n, 32);
1.236 + bytes.write_int(x); ++step;
1.237 + bytes.write_signed_int(x); ++step;
1.238 + bytes.write_float(jfloat_cast(x)); ++step;
1.239 + }
1.240 + for (n = 0; n < stretch_limit; n++) {
1.241 + jlong x = stretch(n, 64);
1.242 + bytes.write_long(x); ++step;
1.243 + bytes.write_double(jdouble_cast(x)); ++step;
1.244 + }
1.245 + int length = bytes.position();
1.246 + if (trace != 0)
1.247 + tty->print_cr("set up test of %d stream values, size %d", step, length);
1.248 + step = 0;
1.249 + // now decode it all
1.250 + CompressedReadStream decode(bytes.buffer());
1.251 + int pos, lastpos = decode.position();
1.252 + for (n = 0; n < (1<<8); n++) {
1.253 + jbyte x = (jbyte)n;
1.254 + jbyte y = decode.read_byte();
1.255 + CHECKXY(x, y, "%db");
1.256 + }
1.257 + for (n = 0; n < stretch_limit; n++) {
1.258 + jint x = (jint)stretch(n, 32);
1.259 + jint y1 = decode.read_int();
1.260 + CHECKXY(x, y1, "%du");
1.261 + jint y2 = decode.read_signed_int();
1.262 + CHECKXY(x, y2, "%di");
1.263 + jint y3 = jint_cast(decode.read_float());
1.264 + CHECKXY(x, y3, "%df");
1.265 + }
1.266 + for (n = 0; n < stretch_limit; n++) {
1.267 + jlong x = stretch(n, 64);
1.268 + jlong y1 = decode.read_long();
1.269 + CHECKXY(x, y1, INT64_FORMAT "l");
1.270 + jlong y2 = jlong_cast(decode.read_double());
1.271 + CHECKXY(x, y2, INT64_FORMAT "d");
1.272 + }
1.273 + int length2 = decode.position();
1.274 + if (trace != 0)
1.275 + tty->print_cr("finished test of %d stream values, size %d", step, length2);
1.276 + guarantee(length == length2, "bad length");
1.277 + guarantee(fails == 0, "test failures");
1.278 +}
1.279 +
1.280 +#if _MSC_VER >=1400 && !defined(_WIN64)
1.281 +#pragma optimize("", on)
1.282 +#endif
1.283 +
1.284 +#endif // PRODUCT
