Initial load

hotspot/src/share/vm/code/compressedStream.cpp

@@ -0,0 +1,281 @@
+/*
+ * 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