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