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, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25package sun.jvm.hotspot.code; 26 27import sun.jvm.hotspot.debugger.*; 28 29public class CompressedReadStream extends CompressedStream { 30 /** Equivalent to CompressedReadStream(buffer, 0) */ 31 public CompressedReadStream(Address buffer) { 32 this(buffer, 0); 33 } 34 35 public CompressedReadStream(Address buffer, int position) { 36 super(buffer, position); 37 } 38 39 public boolean readBoolean() { 40 return (read() != 0); 41 } 42 43 public byte readByte() { 44 return (byte) read(); 45 } 46 47 public char readChar() { 48 return (char) readInt(); 49 } 50 51 public short readShort() { 52 return (short) readSignedInt(); 53 } 54 55 public int readSignedInt() { 56 return decodeSign(readInt()); 57 } 58 59 public int readInt() { 60 int b0 = read(); 61 if (b0 < L) { 62 return b0; 63 } else { 64 return readIntMb(b0); 65 } 66 } 67 68 69 public float readFloat() { 70 return Float.intBitsToFloat(reverseInt(readInt())); 71 } 72 73 public double readDouble() { 74 int rh = readInt(); 75 int rl = readInt(); 76 int h = reverseInt(rh); 77 int l = reverseInt(rl); 78 return Double.longBitsToDouble((h << 32) | ((long)l & 0x00000000FFFFFFFFL)); 79 } 80 81 public long readLong() { 82 long low = readSignedInt() & 0x00000000FFFFFFFFL; 83 long high = readSignedInt(); 84 return (high << 32) | low; 85 } 86 87 //-------------------------------------------------------------------------------- 88 // Internals only below this point 89 // 90 91 92 // This encoding, called UNSIGNED5, is taken from J2SE Pack200. 93 // It assumes that most values have lots of leading zeroes. 94 // Very small values, in the range [0..191], code in one byte. 95 // Any 32-bit value (including negatives) can be coded, in 96 // up to five bytes. The grammar is: 97 // low_byte = [0..191] 98 // high_byte = [192..255] 99 // any_byte = low_byte | high_byte 100 // coding = low_byte 101 // | high_byte low_byte 102 // | high_byte high_byte low_byte 103 // | high_byte high_byte high_byte low_byte 104 // | high_byte high_byte high_byte high_byte any_byte 105 // Each high_byte contributes six bits of payload. 106 // The encoding is one-to-one (except for integer overflow) 107 // and easy to parse and unparse. 108 109 private int readIntMb(int b0) { 110 int pos = position - 1; 111 int sum = b0; 112 // must collect more bytes: b[1]...b[4] 113 int lg_H_i = lg_H; 114 for (int i = 0; ;) { 115 int b_i = read(pos + (++i)); 116 sum += b_i << lg_H_i; // sum += b[i]*(64**i) 117 if (b_i < L || i == MAX_i) { 118 setPosition(pos+i+1); 119 return sum; 120 } 121 lg_H_i += lg_H; 122 } 123 } 124 125 private short read(int index) { 126 return (short) buffer.getCIntegerAt(index, 1, true); 127 } 128 129 /** Reads an unsigned byte, but returns it as a short */ 130 private short read() { 131 short retval = (short) buffer.getCIntegerAt(position, 1, true); 132 ++position; 133 return retval; 134 } 135} 136