1 // int_encoding.h -- variable length and unaligned integers -*- C++ -*-
2
3 // Copyright (C) 2009-2023 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 #ifndef GOLD_INT_ENCODING_H
26 #define GOLD_INT_ENCODING_H
27
28 #include <vector>
29 #include "elfcpp.h"
30 #include "target.h"
31 #include "parameters.h"
32
33 namespace gold
34 {
35
36 //
37 // LEB 128 encoding support.
38 //
39
40 // Read a ULEB 128 encoded integer from BUFFER. Return the length of the
41 // encoded integer at the location PLEN. The common case of a single-byte
42 // value is handled inline, and multi-byte values are processed by the _x
43 // routine, where BYTE is the first byte of the value.
44
45 uint64_t
46 read_unsigned_LEB_128_x(const unsigned char* buffer, size_t* plen,
47 unsigned char byte);
48
49 inline uint64_t
50 read_unsigned_LEB_128(const unsigned char* buffer, size_t* plen)
51 {
52 unsigned char byte = *buffer++;
53
54 if ((byte & 0x80) != 0)
55 return read_unsigned_LEB_128_x(buffer, plen, byte);
56
57 *plen = 1;
58 return static_cast<uint64_t>(byte);
59 }
60
61 // Read an SLEB 128 encoded integer from BUFFER. Return the length of the
62 // encoded integer at the location PLEN. The common case of a single-byte
63 // value is handled inline, and multi-byte values are processed by the _x
64 // routine, where BYTE is the first byte of the value.
65
66 int64_t
67 read_signed_LEB_128_x(const unsigned char* buffer, size_t* plen,
68 unsigned char byte);
69
70 inline int64_t
71 read_signed_LEB_128(const unsigned char* buffer, size_t* plen)
72 {
73 unsigned char byte = *buffer++;
74
75 if ((byte & 0x80) != 0)
76 return read_signed_LEB_128_x(buffer, plen, byte);
77
78 *plen = 1;
79 if (byte & 0x40)
80 return -(static_cast<int64_t>(1) << 7) | static_cast<int64_t>(byte);
81 return static_cast<int64_t>(byte);
82 }
83
84 // Write a ULEB 128 encoded VALUE to BUFFER.
85
86 void
87 write_unsigned_LEB_128(std::vector<unsigned char>* buffer, uint64_t value);
88
89 // Return the ULEB 128 encoded size of VALUE.
90
91 size_t
92 get_length_as_unsigned_LEB_128(uint64_t value);
93
94 //
95 // Unaligned integer encoding support.
96 //
97
98 // Insert VALSIZE-bit integer VALUE into DESTINATION.
99
100 template <int valsize>
101 void insert_into_vector(std::vector<unsigned char>* destination,
102 typename elfcpp::Valtype_base<valsize>::Valtype value)
103 {
104 unsigned char buffer[valsize / 8];
105 if (parameters->target().is_big_endian())
106 elfcpp::Swap_unaligned<valsize, true>::writeval(buffer, value);
107 else
108 elfcpp::Swap_unaligned<valsize, false>::writeval(buffer, value);
109 destination->insert(destination->end(), buffer, buffer + valsize / 8);
110 }
111
112 // Read a possibly unaligned integer of SIZE from SOURCE.
113
114 template <int valsize>
115 typename elfcpp::Valtype_base<valsize>::Valtype
116 read_from_pointer(const unsigned char* source)
117 {
118 typename elfcpp::Valtype_base<valsize>::Valtype return_value;
119 if (parameters->target().is_big_endian())
120 return_value = elfcpp::Swap_unaligned<valsize, true>::readval(source);
121 else
122 return_value = elfcpp::Swap_unaligned<valsize, false>::readval(source);
123 return return_value;
124 }
125
126 // Read a possibly unaligned integer of SIZE. Update SOURCE after read.
127
128 template <int valsize>
129 typename elfcpp::Valtype_base<valsize>::Valtype
130 read_from_pointer(unsigned char** source)
131 {
132 typename elfcpp::Valtype_base<valsize>::Valtype return_value;
133 if (parameters->target().is_big_endian())
134 return_value = elfcpp::Swap_unaligned<valsize, true>::readval(*source);
135 else
136 return_value = elfcpp::Swap_unaligned<valsize, false>::readval(*source);
137 *source += valsize / 8;
138 return return_value;
139 }
140
141 // Same as the above except for use with const unsigned char data.
142
143 template <int valsize>
144 typename elfcpp::Valtype_base<valsize>::Valtype
145 read_from_pointer(const unsigned char** source)
146 {
147 typename elfcpp::Valtype_base<valsize>::Valtype return_value;
148 if (parameters->target().is_big_endian())
149 return_value = elfcpp::Swap_unaligned<valsize, true>::readval(*source);
150 else
151 return_value = elfcpp::Swap_unaligned<valsize, false>::readval(*source);
152 *source += valsize / 8;
153 return return_value;
154 }
155
156 } // End namespace gold.
157
158 #endif // !defined(GOLD_INT_ENCODING_H)