1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
|
/*
* This file is part of OpenTTD.
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file endian_buffer.hpp Endian-aware buffer. */
#ifndef ENDIAN_BUFFER_HPP
#define ENDIAN_BUFFER_HPP
#include <iterator>
#include <string_view>
#include "../core/span_type.hpp"
#include "../core/bitmath_func.hpp"
struct StrongTypedefBase;
/**
* Endian-aware buffer adapter that always writes values in little endian order.
* @note This class uses operator overloading (<<, just like streams) for writing
* as this allows providing custom operator overloads for more complex types
* like e.g. structs without needing to modify this class.
*/
template <typename Tcont = typename std::vector<byte>, typename Titer = typename std::back_insert_iterator<Tcont>>
class EndianBufferWriter {
/** Output iterator for the destination buffer. */
Titer buffer;
public:
EndianBufferWriter(Titer buffer) : buffer(buffer) {}
EndianBufferWriter(typename Titer::container_type &container) : buffer(std::back_inserter(container)) {}
EndianBufferWriter &operator <<(const std::string &data) { return *this << std::string_view{ data }; }
EndianBufferWriter &operator <<(const char *data) { return *this << std::string_view{ data }; }
EndianBufferWriter &operator <<(std::string_view data) { this->Write(data); return *this; }
EndianBufferWriter &operator <<(bool data) { return *this << static_cast<byte>(data ? 1 : 0); }
template <typename... Targs>
EndianBufferWriter &operator <<(const std::tuple<Targs...> &data)
{
this->WriteTuple(data, std::index_sequence_for<Targs...>{});
return *this;
}
template <class T, std::enable_if_t<std::disjunction_v<std::negation<std::is_class<T>>, std::is_base_of<StrongTypedefBase, T>>, int> = 0>
EndianBufferWriter &operator <<(const T data)
{
if constexpr (std::is_enum_v<T>) {
this->Write(static_cast<std::underlying_type_t<const T>>(data));
} else if constexpr (std::is_base_of_v<StrongTypedefBase, T>) {
this->Write(data.value);
} else {
this->Write(data);
}
return *this;
}
template <typename Tvalue, typename Tbuf = std::vector<byte>>
static Tbuf FromValue(const Tvalue &data)
{
Tbuf buffer;
EndianBufferWriter writer{ buffer };
writer << data;
return buffer;
}
private:
/** Helper function to write a tuple to the buffer. */
template<class Ttuple, size_t... Tindices>
void WriteTuple(const Ttuple &values, std::index_sequence<Tindices...>) {
((*this << std::get<Tindices>(values)), ...);
}
/** Write overload for string values. */
void Write(std::string_view value)
{
for (auto c : value) {
this->buffer++ = c;
}
this->buffer++ = '\0';
}
/** Fundamental write function. */
template <class T>
void Write(T value)
{
static_assert(sizeof(T) <= 8, "Value can't be larger than 8 bytes");
if constexpr (sizeof(T) > 1) {
this->buffer++ = GB(value, 0, 8);
this->buffer++ = GB(value, 8, 8);
if constexpr (sizeof(T) > 2) {
this->buffer++ = GB(value, 16, 8);
this->buffer++ = GB(value, 24, 8);
}
if constexpr (sizeof(T) > 4) {
this->buffer++ = GB(value, 32, 8);
this->buffer++ = GB(value, 40, 8);
this->buffer++ = GB(value, 48, 8);
this->buffer++ = GB(value, 56, 8);
}
} else {
this->buffer++ = value;
}
}
};
/**
* Endian-aware buffer adapter that always reads values in little endian order.
* @note This class uses operator overloading (>>, just like streams) for reading
* as this allows providing custom operator overloads for more complex types
* like e.g. structs without needing to modify this class.
*/
class EndianBufferReader {
/** Reference to storage buffer. */
span<const byte> buffer;
/** Current read position. */
size_t read_pos = 0;
public:
EndianBufferReader(span<const byte> buffer) : buffer(buffer) {}
void rewind() { this->read_pos = 0; }
EndianBufferReader &operator >>(std::string &data) { data = this->ReadStr(); return *this; }
EndianBufferReader &operator >>(bool &data) { data = this->Read<byte>() != 0; return *this; }
template <typename... Targs>
EndianBufferReader &operator >>(std::tuple<Targs...> &data)
{
this->ReadTuple(data, std::index_sequence_for<Targs...>{});
return *this;
}
template <class T, std::enable_if_t<std::disjunction_v<std::negation<std::is_class<T>>, std::is_base_of<StrongTypedefBase, T>>, int> = 0>
EndianBufferReader &operator >>(T &data)
{
if constexpr (std::is_enum_v<T>) {
data = static_cast<T>(this->Read<std::underlying_type_t<T>>());
} else if constexpr (std::is_base_of_v<StrongTypedefBase, T>) {
data.value = this->Read<decltype(data.value)>();
} else {
data = this->Read<T>();
}
return *this;
}
template <typename Tvalue>
static Tvalue ToValue(span<const byte> buffer)
{
Tvalue result{};
EndianBufferReader reader{ buffer };
reader >> result;
return result;
}
private:
/** Helper function to read a tuple from the buffer. */
template<class Ttuple, size_t... Tindices>
void ReadTuple(Ttuple &values, std::index_sequence<Tindices...>) {
((*this >> std::get<Tindices>(values)), ...);
}
/** Read overload for string data. */
std::string ReadStr()
{
std::string str;
while (this->read_pos < this->buffer.size()) {
char ch = this->Read<char>();
if (ch == '\0') break;
str.push_back(ch);
}
return str;
}
/** Fundamental read function. */
template <class T>
T Read()
{
static_assert(!std::is_const_v<T>, "Can't read into const variables");
static_assert(sizeof(T) <= 8, "Value can't be larger than 8 bytes");
if (read_pos + sizeof(T) > this->buffer.size()) return {};
T value = static_cast<T>(this->buffer[this->read_pos++]);
if constexpr (sizeof(T) > 1) {
value += static_cast<T>(this->buffer[this->read_pos++]) << 8;
}
if constexpr (sizeof(T) > 2) {
value += static_cast<T>(this->buffer[this->read_pos++]) << 16;
value += static_cast<T>(this->buffer[this->read_pos++]) << 24;
}
if constexpr (sizeof(T) > 4) {
value += static_cast<T>(this->buffer[this->read_pos++]) << 32;
value += static_cast<T>(this->buffer[this->read_pos++]) << 40;
value += static_cast<T>(this->buffer[this->read_pos++]) << 48;
value += static_cast<T>(this->buffer[this->read_pos++]) << 56;
}
return value;
}
};
#endif /* ENDIAN_BUFFER_HPP */
|