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1 | // elfcpp_swap.h -- Handle swapping for elfcpp -*- C++ -*- |
2 | ||
6cb15b7f ILT |
3 | // Copyright 2006, 2007, Free Software Foundation, Inc. |
4 | // Written by Ian Lance Taylor <iant@google.com>. | |
5 | ||
6 | // This file is part of elfcpp. | |
7 | ||
8 | // This program is free software; you can redistribute it and/or | |
9 | // modify it under the terms of the GNU Library General Public License | |
10 | // as published by the Free Software Foundation; either version 2, or | |
11 | // (at your option) any later version. | |
12 | ||
13 | // In addition to the permissions in the GNU Library General Public | |
14 | // License, the Free Software Foundation gives you unlimited | |
15 | // permission to link the compiled version of this file into | |
16 | // combinations with other programs, and to distribute those | |
17 | // combinations without any restriction coming from the use of this | |
18 | // file. (The Library Public License restrictions do apply in other | |
19 | // respects; for example, they cover modification of the file, and | |
20 | /// distribution when not linked into a combined executable.) | |
21 | ||
22 | // This program is distributed in the hope that it will be useful, but | |
23 | // WITHOUT ANY WARRANTY; without even the implied warranty of | |
24 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
25 | // Library General Public License for more details. | |
26 | ||
27 | // You should have received a copy of the GNU Library General Public | |
28 | // License along with this program; if not, write to the Free Software | |
29 | // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA | |
30 | // 02110-1301, USA. | |
31 | ||
8d9455b4 ILT |
32 | // This header file defines basic template classes to efficiently swap |
33 | // numbers between host form and target form. When the host and | |
34 | // target have the same endianness, these turn into no-ops. | |
35 | ||
36 | #ifndef ELFCPP_SWAP_H | |
37 | #define ELFCPP_SWAP_H | |
38 | ||
39 | #include <stdint.h> | |
40 | #include <endian.h> | |
41 | #include <byteswap.h> | |
42 | ||
43 | namespace elfcpp | |
44 | { | |
45 | ||
46 | // Endian simply indicates whether the host is big endian or not. | |
47 | ||
48 | struct Endian | |
49 | { | |
50 | public: | |
51 | // Used for template specializations. | |
52 | static const bool host_big_endian = __BYTE_ORDER == __BIG_ENDIAN; | |
53 | }; | |
54 | ||
55 | // Valtype_base is a template based on size (8, 16, 32, 64) which | |
56 | // defines the type Valtype as the unsigned integer of the specified | |
57 | // size. | |
58 | ||
59 | template<int size> | |
60 | struct Valtype_base; | |
61 | ||
62 | template<> | |
63 | struct Valtype_base<8> | |
64 | { | |
65 | typedef unsigned char Valtype; | |
66 | }; | |
67 | ||
68 | template<> | |
69 | struct Valtype_base<16> | |
70 | { | |
71 | typedef uint16_t Valtype; | |
72 | }; | |
73 | ||
74 | template<> | |
75 | struct Valtype_base<32> | |
76 | { | |
77 | typedef uint32_t Valtype; | |
78 | }; | |
79 | ||
80 | template<> | |
81 | struct Valtype_base<64> | |
82 | { | |
83 | typedef uint64_t Valtype; | |
84 | }; | |
85 | ||
86 | // Convert_endian is a template based on size and on whether the host | |
87 | // and target have the same endianness. It defines the type Valtype | |
88 | // as Valtype_base does, and also defines a function convert_host | |
89 | // which takes an argument of type Valtype and returns the same value, | |
90 | // but swapped if the host and target have different endianness. | |
91 | ||
92 | template<int size, bool same_endian> | |
93 | struct Convert_endian; | |
94 | ||
95 | template<int size> | |
96 | struct Convert_endian<size, true> | |
97 | { | |
98 | typedef typename Valtype_base<size>::Valtype Valtype; | |
99 | ||
100 | static inline Valtype | |
101 | convert_host(Valtype v) | |
102 | { return v; } | |
103 | }; | |
104 | ||
105 | template<> | |
106 | struct Convert_endian<8, false> | |
107 | { | |
108 | typedef Valtype_base<8>::Valtype Valtype; | |
109 | ||
110 | static inline Valtype | |
111 | convert_host(Valtype v) | |
112 | { return v; } | |
113 | }; | |
114 | ||
115 | template<> | |
116 | struct Convert_endian<16, false> | |
117 | { | |
118 | typedef Valtype_base<16>::Valtype Valtype; | |
119 | ||
120 | static inline Valtype | |
121 | convert_host(Valtype v) | |
122 | { return bswap_16(v); } | |
123 | }; | |
124 | ||
125 | template<> | |
126 | struct Convert_endian<32, false> | |
127 | { | |
128 | typedef Valtype_base<32>::Valtype Valtype; | |
129 | ||
130 | static inline Valtype | |
131 | convert_host(Valtype v) | |
132 | { return bswap_32(v); } | |
133 | }; | |
134 | ||
135 | template<> | |
136 | struct Convert_endian<64, false> | |
137 | { | |
138 | typedef Valtype_base<64>::Valtype Valtype; | |
139 | ||
140 | static inline Valtype | |
141 | convert_host(Valtype v) | |
142 | { return bswap_64(v); } | |
143 | }; | |
144 | ||
145 | // Convert is a template based on size and on whether the target is | |
146 | // big endian. It defines Valtype and convert_host like | |
147 | // Convert_endian. That is, it is just like Convert_endian except in | |
148 | // the meaning of the second template parameter. | |
149 | ||
150 | template<int size, bool big_endian> | |
151 | struct Convert | |
152 | { | |
153 | typedef typename Valtype_base<size>::Valtype Valtype; | |
154 | ||
155 | static inline Valtype | |
156 | convert_host(Valtype v) | |
157 | { | |
158 | return Convert_endian<size, big_endian == Endian::host_big_endian> | |
159 | ::convert_host(v); | |
160 | } | |
161 | }; | |
162 | ||
163 | // Swap is a template based on size and on whether the target is big | |
164 | // endian. It defines the type Valtype and the functions readval and | |
165 | // writeval. The functions read and write values of the appropriate | |
166 | // size out of buffers, swapping them if necessary. readval and | |
167 | // writeval are overloaded to take pointers to the appropriate type or | |
168 | // pointers to unsigned char. | |
169 | ||
170 | template<int size, bool big_endian> | |
171 | struct Swap | |
172 | { | |
173 | typedef typename Valtype_base<size>::Valtype Valtype; | |
174 | ||
175 | static inline Valtype | |
176 | readval(const Valtype* wv) | |
177 | { return Convert<size, big_endian>::convert_host(*wv); } | |
178 | ||
179 | static inline void | |
180 | writeval(Valtype* wv, Valtype v) | |
181 | { *wv = Convert<size, big_endian>::convert_host(v); } | |
182 | ||
183 | static inline Valtype | |
184 | readval(const unsigned char* wv) | |
185 | { return readval(reinterpret_cast<const Valtype*>(wv)); } | |
186 | ||
187 | static inline void | |
188 | writeval(unsigned char* wv, Valtype v) | |
189 | { writeval(reinterpret_cast<Valtype*>(wv), v); } | |
190 | }; | |
191 | ||
192 | // We need to specialize the 8-bit version of Swap to avoid | |
193 | // conflicting overloads, since both versions of readval and writeval | |
194 | // will have the same type parameters. | |
195 | ||
196 | template<bool big_endian> | |
197 | struct Swap<8, big_endian> | |
198 | { | |
199 | typedef typename Valtype_base<8>::Valtype Valtype; | |
200 | ||
201 | static inline Valtype | |
202 | readval(const Valtype* wv) | |
203 | { return *wv; } | |
204 | ||
205 | static inline void | |
206 | writeval(Valtype* wv, Valtype v) | |
207 | { *wv = v; } | |
208 | }; | |
209 | ||
210 | // Swap_unaligned is a template based on size and on whether the | |
211 | // target is big endian. It defines the type Valtype and the | |
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212 | // functions readval and writeval. The functions read and write |
213 | // values of the appropriate size out of buffers which may be | |
214 | // misaligned. | |
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215 | |
216 | template<int size, bool big_endian> | |
217 | struct Swap_unaligned; | |
218 | ||
219 | template<bool big_endian> | |
220 | struct Swap_unaligned<8, big_endian> | |
221 | { | |
222 | typedef typename Valtype_base<8>::Valtype Valtype; | |
223 | ||
224 | static inline Valtype | |
a3ad94ed | 225 | readval(const unsigned char* wv) |
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226 | { return *wv; } |
227 | ||
228 | static inline void | |
a3ad94ed | 229 | writeval(unsigned char* wv, Valtype v) |
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230 | { *wv = v; } |
231 | }; | |
232 | ||
233 | template<> | |
234 | struct Swap_unaligned<16, false> | |
235 | { | |
236 | typedef Valtype_base<16>::Valtype Valtype; | |
237 | ||
238 | static inline Valtype | |
a3ad94ed | 239 | readval(const unsigned char* wv) |
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240 | { |
241 | return (wv[1] << 8) | wv[0]; | |
242 | } | |
243 | ||
244 | static inline void | |
a3ad94ed | 245 | writeval(unsigned char* wv, Valtype v) |
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246 | { |
247 | wv[1] = v >> 8; | |
248 | wv[0] = v; | |
249 | } | |
250 | }; | |
251 | ||
252 | template<> | |
253 | struct Swap_unaligned<16, true> | |
254 | { | |
255 | typedef Valtype_base<16>::Valtype Valtype; | |
256 | ||
257 | static inline Valtype | |
a3ad94ed | 258 | readval(const unsigned char* wv) |
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259 | { |
260 | return (wv[0] << 8) | wv[1]; | |
261 | } | |
262 | ||
263 | static inline void | |
a3ad94ed | 264 | writeval(unsigned char* wv, Valtype v) |
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265 | { |
266 | wv[0] = v >> 8; | |
267 | wv[1] = v; | |
268 | } | |
269 | }; | |
270 | ||
271 | template<> | |
272 | struct Swap_unaligned<32, false> | |
273 | { | |
274 | typedef Valtype_base<32>::Valtype Valtype; | |
275 | ||
276 | static inline Valtype | |
a3ad94ed | 277 | readval(const unsigned char* wv) |
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278 | { |
279 | return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0]; | |
280 | } | |
281 | ||
282 | static inline void | |
a3ad94ed | 283 | writeval(unsigned char* wv, Valtype v) |
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284 | { |
285 | wv[3] = v >> 24; | |
286 | wv[2] = v >> 16; | |
287 | wv[1] = v >> 8; | |
288 | wv[0] = v; | |
289 | } | |
290 | }; | |
291 | ||
292 | template<> | |
293 | struct Swap_unaligned<32, true> | |
294 | { | |
295 | typedef Valtype_base<32>::Valtype Valtype; | |
296 | ||
297 | static inline Valtype | |
a3ad94ed | 298 | readval(const unsigned char* wv) |
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299 | { |
300 | return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3]; | |
301 | } | |
302 | ||
303 | static inline void | |
a3ad94ed | 304 | writeval(unsigned char* wv, Valtype v) |
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305 | { |
306 | wv[0] = v >> 24; | |
307 | wv[1] = v >> 16; | |
308 | wv[2] = v >> 8; | |
309 | wv[3] = v; | |
310 | } | |
311 | }; | |
312 | ||
313 | template<> | |
314 | struct Swap_unaligned<64, false> | |
315 | { | |
316 | typedef Valtype_base<64>::Valtype Valtype; | |
317 | ||
318 | static inline Valtype | |
a3ad94ed | 319 | readval(const unsigned char* wv) |
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320 | { |
321 | return ((static_cast<Valtype>(wv[7]) << 56) | |
322 | | (static_cast<Valtype>(wv[6]) << 48) | |
323 | | (static_cast<Valtype>(wv[5]) << 40) | |
324 | | (static_cast<Valtype>(wv[4]) << 32) | |
325 | | (static_cast<Valtype>(wv[3]) << 24) | |
326 | | (static_cast<Valtype>(wv[2]) << 16) | |
327 | | (static_cast<Valtype>(wv[1]) << 8) | |
328 | | static_cast<Valtype>(wv[0])); | |
329 | } | |
330 | ||
331 | static inline void | |
a3ad94ed | 332 | writeval(unsigned char* wv, Valtype v) |
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333 | { |
334 | wv[7] = v >> 56; | |
335 | wv[6] = v >> 48; | |
336 | wv[5] = v >> 40; | |
337 | wv[4] = v >> 32; | |
338 | wv[3] = v >> 24; | |
339 | wv[2] = v >> 16; | |
340 | wv[1] = v >> 8; | |
341 | wv[0] = v; | |
342 | } | |
343 | }; | |
344 | ||
345 | template<> | |
346 | struct Swap_unaligned<64, true> | |
347 | { | |
348 | typedef Valtype_base<64>::Valtype Valtype; | |
349 | ||
350 | static inline Valtype | |
a3ad94ed | 351 | readval(const unsigned char* wv) |
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352 | { |
353 | return ((static_cast<Valtype>(wv[0]) << 56) | |
354 | | (static_cast<Valtype>(wv[1]) << 48) | |
355 | | (static_cast<Valtype>(wv[2]) << 40) | |
356 | | (static_cast<Valtype>(wv[3]) << 32) | |
357 | | (static_cast<Valtype>(wv[4]) << 24) | |
358 | | (static_cast<Valtype>(wv[5]) << 16) | |
359 | | (static_cast<Valtype>(wv[6]) << 8) | |
360 | | static_cast<Valtype>(wv[7])); | |
361 | } | |
362 | ||
363 | static inline void | |
a3ad94ed | 364 | writeval(unsigned char* wv, Valtype v) |
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365 | { |
366 | wv[7] = v >> 56; | |
367 | wv[6] = v >> 48; | |
368 | wv[5] = v >> 40; | |
369 | wv[4] = v >> 32; | |
370 | wv[3] = v >> 24; | |
371 | wv[2] = v >> 16; | |
372 | wv[1] = v >> 8; | |
373 | wv[0] = v; | |
374 | } | |
375 | }; | |
376 | ||
377 | } // End namespace elfcpp. | |
378 | ||
379 | #endif // !defined(ELFCPP_SWAP_H) |