1/*
2
3  Copyright (C) 2000,2004 Silicon Graphics, Inc.  All Rights Reserved.
4
5  This program is free software; you can redistribute it and/or modify it
6  under the terms of version 2.1 of the GNU Lesser General Public License
7  as published by the Free Software Foundation.
8
9  This program is distributed in the hope that it would be useful, but
10  WITHOUT ANY WARRANTY; without even the implied warranty of
11  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
12
13  Further, this software is distributed without any warranty that it is
14  free of the rightful claim of any third person regarding infringement
15  or the like.  Any license provided herein, whether implied or
16  otherwise, applies only to this software file.  Patent licenses, if
17  any, provided herein do not apply to combinations of this program with
18  other software, or any other product whatsoever.
19
20  You should have received a copy of the GNU Lesser General Public
21  License along with this program; if not, write the Free Software
22  Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston MA 02110-1301,
23  USA.
24
25  Contact information:  Silicon Graphics, Inc., 1500 Crittenden Lane,
26  Mountain View, CA 94043, or:
27
28  http://www.sgi.com
29
30  For further information regarding this notice, see:
31
32  http://oss.sgi.com/projects/GenInfo/NoticeExplan
33
34*/
35
36
37
38#include "config.h"
39#include "dwarf_incl.h"
40#include <stdio.h>
41
42
43/*
44    decode ULEB
45*/
46Dwarf_Unsigned
47_dwarf_decode_u_leb128(Dwarf_Small * leb128, Dwarf_Word * leb128_length)
48{
49    unsigned char byte;
50    Dwarf_Word word_number;
51    Dwarf_Unsigned number;
52    Dwarf_Sword shift;
53    Dwarf_Sword byte_length;
54
55    /* The following unrolls-the-loop for the first few bytes and
56       unpacks into 32 bits to make this as fast as possible.
57       word_number is assumed big enough that the shift has a defined
58       result. */
59    if ((*leb128 & 0x80) == 0) {
60        if (leb128_length != NULL)
61            *leb128_length = 1;
62        return (*leb128);
63    } else if ((*(leb128 + 1) & 0x80) == 0) {
64        if (leb128_length != NULL)
65            *leb128_length = 2;
66
67        word_number = *leb128 & 0x7f;
68        word_number |= (*(leb128 + 1) & 0x7f) << 7;
69        return (word_number);
70    } else if ((*(leb128 + 2) & 0x80) == 0) {
71        if (leb128_length != NULL)
72            *leb128_length = 3;
73
74        word_number = *leb128 & 0x7f;
75        word_number |= (*(leb128 + 1) & 0x7f) << 7;
76        word_number |= (*(leb128 + 2) & 0x7f) << 14;
77        return (word_number);
78    } else if ((*(leb128 + 3) & 0x80) == 0) {
79        if (leb128_length != NULL)
80            *leb128_length = 4;
81
82        word_number = *leb128 & 0x7f;
83        word_number |= (*(leb128 + 1) & 0x7f) << 7;
84        word_number |= (*(leb128 + 2) & 0x7f) << 14;
85        word_number |= (*(leb128 + 3) & 0x7f) << 21;
86        return (word_number);
87    }
88
89    /* The rest handles long numbers Because the 'number' may be larger
90       than the default int/unsigned, we must cast the 'byte' before
91       the shift for the shift to have a defined result. */
92    number = 0;
93    shift = 0;
94    byte_length = 1;
95    byte = *(leb128);
96    for (;;) {
97        number |= ((Dwarf_Unsigned) (byte & 0x7f)) << shift;
98
99        if ((byte & 0x80) == 0) {
100            if (leb128_length != NULL)
101                *leb128_length = byte_length;
102            return (number);
103        }
104        shift += 7;
105
106        byte_length++;
107        ++leb128;
108        byte = *leb128;
109    }
110}
111
112#define BITSINBYTE 8
113
114/*
115    decode SLEB
116*/
117Dwarf_Signed
118_dwarf_decode_s_leb128(Dwarf_Small * leb128, Dwarf_Word * leb128_length)
119{
120    Dwarf_Signed number = 0;
121    Dwarf_Bool sign = 0;
122    Dwarf_Sword shift = 0;
123    unsigned char byte = *leb128;
124    Dwarf_Sword byte_length = 1;
125
126    /* byte_length being the number of bytes of data absorbed so far in
127       turning the leb into a Dwarf_Signed. */
128
129    for (;;) {
130        sign = byte & 0x40;
131        number |= ((Dwarf_Signed) ((byte & 0x7f))) << shift;
132        shift += 7;
133
134        if ((byte & 0x80) == 0) {
135            break;
136        }
137        ++leb128;
138        byte = *leb128;
139        byte_length++;
140    }
141
142    if ((shift < sizeof(Dwarf_Signed) * BITSINBYTE) && sign) {
143        number |= -((Dwarf_Signed) 1 << shift);
144    }
145
146    if (leb128_length != NULL)
147        *leb128_length = byte_length;
148    return (number);
149}
150