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4f787271 DK |
1 | // varint.cc -- variable length and unaligned integer encoding support. |
2 | ||
3 | // Copyright 2009 Free Software Foundation, Inc. | |
4 | // Written by Doug Kwan <dougkwan@google.com> by refactoring scattered | |
5 | // contents from other files in gold. Original code written by Ian | |
6 | // Lance Taylor <iant@google.com> and Caleb Howe <cshowe@google.com>. | |
7 | ||
8 | // This file is part of gold. | |
9 | ||
10 | // This program is free software; you can redistribute it and/or modify | |
11 | // it under the terms of the GNU General Public License as published by | |
12 | // the Free Software Foundation; either version 3 of the License, or | |
13 | // (at your option) any later version. | |
14 | ||
15 | // This program is distributed in the hope that it will be useful, | |
16 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | // GNU General Public License for more details. | |
19 | ||
20 | // You should have received a copy of the GNU General Public License | |
21 | // along with this program; if not, write to the Free Software | |
22 | // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, | |
23 | // MA 02110-1301, USA. | |
24 | ||
25 | #include "gold.h" | |
26 | ||
27 | #include <vector> | |
28 | ||
29 | #include "int_encoding.h" | |
30 | ||
31 | namespace gold { | |
32 | ||
33 | // Read an unsigned LEB128 number. Each byte contains 7 bits of | |
34 | // information, plus one bit saying whether the number continues or | |
35 | // not. | |
36 | ||
37 | uint64_t | |
38 | read_unsigned_LEB_128(const unsigned char* buffer, size_t* len) | |
39 | { | |
40 | uint64_t result = 0; | |
41 | size_t num_read = 0; | |
42 | unsigned int shift = 0; | |
43 | unsigned char byte; | |
44 | ||
45 | do | |
46 | { | |
47 | if (num_read >= 64 / 7) | |
48 | { | |
49 | gold_warning(_("Unusually large LEB128 decoded, " | |
50 | "debug information may be corrupted")); | |
51 | break; | |
52 | } | |
53 | byte = *buffer++; | |
54 | num_read++; | |
55 | result |= (static_cast<uint64_t>(byte & 0x7f)) << shift; | |
56 | shift += 7; | |
57 | } | |
58 | while (byte & 0x80); | |
59 | ||
60 | *len = num_read; | |
61 | ||
62 | return result; | |
63 | } | |
64 | ||
65 | // Read a signed LEB128 number. These are like regular LEB128 | |
66 | // numbers, except the last byte may have a sign bit set. | |
67 | ||
68 | int64_t | |
69 | read_signed_LEB_128(const unsigned char* buffer, size_t* len) | |
70 | { | |
71 | int64_t result = 0; | |
72 | int shift = 0; | |
73 | size_t num_read = 0; | |
74 | unsigned char byte; | |
75 | ||
76 | do | |
77 | { | |
78 | if (num_read >= 64 / 7) | |
79 | { | |
80 | gold_warning(_("Unusually large LEB128 decoded, " | |
81 | "debug information may be corrupted")); | |
82 | break; | |
83 | } | |
84 | byte = *buffer++; | |
85 | num_read++; | |
86 | result |= (static_cast<uint64_t>(byte & 0x7f) << shift); | |
87 | shift += 7; | |
88 | } | |
89 | while (byte & 0x80); | |
90 | ||
91 | if ((shift < 8 * static_cast<int>(sizeof(result))) && (byte & 0x40)) | |
92 | result |= -((static_cast<int64_t>(1)) << shift); | |
93 | *len = num_read; | |
94 | return result; | |
95 | } | |
96 | ||
97 | void | |
98 | write_unsigned_LEB_128(std::vector<unsigned char>* buffer, uint64_t value) | |
99 | { | |
100 | do | |
101 | { | |
102 | unsigned char current_byte = value & 0x7f; | |
103 | value >>= 7; | |
104 | if (value != 0) | |
105 | { | |
106 | current_byte |= 0x80; | |
107 | } | |
108 | buffer->push_back(current_byte); | |
109 | } | |
110 | while (value != 0); | |
111 | } | |
112 | ||
113 | size_t | |
114 | get_length_as_unsigned_LEB_128(uint64_t value) | |
115 | { | |
116 | size_t length = 0; | |
117 | do | |
118 | { | |
119 | unsigned char current_byte = value & 0x7f; | |
120 | value >>= 7; | |
121 | if (value != 0) | |
122 | { | |
123 | current_byte |= 0x80; | |
124 | } | |
125 | length++; | |
126 | } | |
127 | while (value != 0); | |
128 | return length; | |
129 | } | |
130 | ||
131 | } // End namespace gold. |