1 /* 2 * Copyright (c) 2000, 2005, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, 20 * CA 94065 USA or visit www.oracle.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25 package sun.jvm.hotspot.code; 26 27 import sun.jvm.hotspot.debugger.*; 28 29 /** NOTE that this class takes the address of a buffer. This means 30 that it can read previously-generated debug information directly 31 from the target VM. However, it also means that you can't create a 32 "wrapper" object for a CompressedStream down in the VM. It looks 33 like these are only kept persistently in OopMaps, and the code has 34 been special-cased in OopMap.java to handle this. */ 35 36 public class CompressedStream { 37 protected Address buffer; 38 protected int position; 39 40 /** Equivalent to CompressedStream(buffer, 0) */ 41 public CompressedStream(Address buffer) { 42 this(buffer, 0); 43 } 44 45 public CompressedStream(Address buffer, int position) { 46 this.buffer = buffer; 47 this.position = position; 48 } 49 50 public Address getBuffer() { 51 return buffer; 52 } 53 54 public static final int LogBitsPerByte = 3; 55 public static final int BitsPerByte = 1 << 3; 56 57 // Constants for UNSIGNED5 coding of Pack200 58 public static final int lg_H = 6; 59 public static final int H = 1<<lg_H; // number of high codes (64) 60 public static final int L = (1<<BitsPerByte) - H; // number of low codes (192) 61 public static final int MAX_i = 4; // bytes are numbered in (0..4) 62 63 // Positioning 64 public int getPosition() { 65 return position; 66 } 67 public void setPosition(int position) { 68 this.position = position; 69 } 70 71 // 32-bit one-to-one sign encoding taken from Pack200 72 // converts leading sign bits into leading zeros with trailing sign bit 73 public int encodeSign(int value) { 74 return (value << 1) ^ (value >> 31); 75 } 76 77 public int decodeSign(int value) { 78 return (value >>> 1) ^ -(value & 1); 79 } 80 81 // 32-bit self-inverse encoding of float bits 82 // converts trailing zeros (common in floats) to leading zeros 83 public int reverseInt(int i) { 84 // Hacker's Delight, Figure 7-1 85 i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555; 86 i = (i & 0x33333333) << 3 | (i >>> 2) & 0x33333333; 87 i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f; 88 i = (i << 24) | ((i & 0xff00) << 8) | ((i >>> 8) & 0xff00) | (i >>> 24); 89 return i; 90 } 91 }