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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 | |
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56 | // defines the type Valtype as the unsigned integer, and |
57 | // Signed_valtype as the signed integer, of the specified size. | |
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58 | |
59 | template<int size> | |
60 | struct Valtype_base; | |
61 | ||
62 | template<> | |
63 | struct Valtype_base<8> | |
64 | { | |
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65 | typedef uint8_t Valtype; |
66 | typedef int8_t Signed_valtype; | |
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67 | }; |
68 | ||
69 | template<> | |
70 | struct Valtype_base<16> | |
71 | { | |
72 | typedef uint16_t Valtype; | |
5b3463d9 | 73 | typedef int16_t Signed_valtype; |
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74 | }; |
75 | ||
76 | template<> | |
77 | struct Valtype_base<32> | |
78 | { | |
79 | typedef uint32_t Valtype; | |
5b3463d9 | 80 | typedef int32_t Signed_valtype; |
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81 | }; |
82 | ||
83 | template<> | |
84 | struct Valtype_base<64> | |
85 | { | |
86 | typedef uint64_t Valtype; | |
5b3463d9 | 87 | typedef int64_t Signed_valtype; |
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88 | }; |
89 | ||
90 | // Convert_endian is a template based on size and on whether the host | |
91 | // and target have the same endianness. It defines the type Valtype | |
92 | // as Valtype_base does, and also defines a function convert_host | |
93 | // which takes an argument of type Valtype and returns the same value, | |
94 | // but swapped if the host and target have different endianness. | |
95 | ||
96 | template<int size, bool same_endian> | |
97 | struct Convert_endian; | |
98 | ||
99 | template<int size> | |
100 | struct Convert_endian<size, true> | |
101 | { | |
102 | typedef typename Valtype_base<size>::Valtype Valtype; | |
103 | ||
104 | static inline Valtype | |
105 | convert_host(Valtype v) | |
106 | { return v; } | |
107 | }; | |
108 | ||
109 | template<> | |
110 | struct Convert_endian<8, false> | |
111 | { | |
112 | typedef Valtype_base<8>::Valtype Valtype; | |
113 | ||
114 | static inline Valtype | |
115 | convert_host(Valtype v) | |
116 | { return v; } | |
117 | }; | |
118 | ||
119 | template<> | |
120 | struct Convert_endian<16, false> | |
121 | { | |
122 | typedef Valtype_base<16>::Valtype Valtype; | |
123 | ||
124 | static inline Valtype | |
125 | convert_host(Valtype v) | |
126 | { return bswap_16(v); } | |
127 | }; | |
128 | ||
129 | template<> | |
130 | struct Convert_endian<32, false> | |
131 | { | |
132 | typedef Valtype_base<32>::Valtype Valtype; | |
133 | ||
134 | static inline Valtype | |
135 | convert_host(Valtype v) | |
136 | { return bswap_32(v); } | |
137 | }; | |
138 | ||
139 | template<> | |
140 | struct Convert_endian<64, false> | |
141 | { | |
142 | typedef Valtype_base<64>::Valtype Valtype; | |
143 | ||
144 | static inline Valtype | |
145 | convert_host(Valtype v) | |
146 | { return bswap_64(v); } | |
147 | }; | |
148 | ||
149 | // Convert is a template based on size and on whether the target is | |
150 | // big endian. It defines Valtype and convert_host like | |
151 | // Convert_endian. That is, it is just like Convert_endian except in | |
152 | // the meaning of the second template parameter. | |
153 | ||
154 | template<int size, bool big_endian> | |
155 | struct Convert | |
156 | { | |
157 | typedef typename Valtype_base<size>::Valtype Valtype; | |
158 | ||
159 | static inline Valtype | |
160 | convert_host(Valtype v) | |
161 | { | |
162 | return Convert_endian<size, big_endian == Endian::host_big_endian> | |
163 | ::convert_host(v); | |
164 | } | |
165 | }; | |
166 | ||
167 | // Swap is a template based on size and on whether the target is big | |
168 | // endian. It defines the type Valtype and the functions readval and | |
169 | // writeval. The functions read and write values of the appropriate | |
170 | // size out of buffers, swapping them if necessary. readval and | |
171 | // writeval are overloaded to take pointers to the appropriate type or | |
172 | // pointers to unsigned char. | |
173 | ||
174 | template<int size, bool big_endian> | |
175 | struct Swap | |
176 | { | |
177 | typedef typename Valtype_base<size>::Valtype Valtype; | |
178 | ||
179 | static inline Valtype | |
180 | readval(const Valtype* wv) | |
181 | { return Convert<size, big_endian>::convert_host(*wv); } | |
182 | ||
183 | static inline void | |
184 | writeval(Valtype* wv, Valtype v) | |
185 | { *wv = Convert<size, big_endian>::convert_host(v); } | |
186 | ||
187 | static inline Valtype | |
188 | readval(const unsigned char* wv) | |
189 | { return readval(reinterpret_cast<const Valtype*>(wv)); } | |
190 | ||
191 | static inline void | |
192 | writeval(unsigned char* wv, Valtype v) | |
193 | { writeval(reinterpret_cast<Valtype*>(wv), v); } | |
194 | }; | |
195 | ||
196 | // We need to specialize the 8-bit version of Swap to avoid | |
197 | // conflicting overloads, since both versions of readval and writeval | |
198 | // will have the same type parameters. | |
199 | ||
200 | template<bool big_endian> | |
201 | struct Swap<8, big_endian> | |
202 | { | |
203 | typedef typename Valtype_base<8>::Valtype Valtype; | |
204 | ||
205 | static inline Valtype | |
206 | readval(const Valtype* wv) | |
207 | { return *wv; } | |
208 | ||
209 | static inline void | |
210 | writeval(Valtype* wv, Valtype v) | |
211 | { *wv = v; } | |
212 | }; | |
213 | ||
214 | // Swap_unaligned is a template based on size and on whether the | |
215 | // target is big endian. It defines the type Valtype and the | |
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216 | // functions readval and writeval. The functions read and write |
217 | // values of the appropriate size out of buffers which may be | |
218 | // misaligned. | |
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219 | |
220 | template<int size, bool big_endian> | |
221 | struct Swap_unaligned; | |
222 | ||
223 | template<bool big_endian> | |
224 | struct Swap_unaligned<8, big_endian> | |
225 | { | |
226 | typedef typename Valtype_base<8>::Valtype Valtype; | |
227 | ||
228 | static inline Valtype | |
a3ad94ed | 229 | readval(const unsigned char* wv) |
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230 | { return *wv; } |
231 | ||
232 | static inline void | |
a3ad94ed | 233 | writeval(unsigned char* wv, Valtype v) |
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234 | { *wv = v; } |
235 | }; | |
236 | ||
237 | template<> | |
238 | struct Swap_unaligned<16, false> | |
239 | { | |
240 | typedef Valtype_base<16>::Valtype Valtype; | |
241 | ||
242 | static inline Valtype | |
a3ad94ed | 243 | readval(const unsigned char* wv) |
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244 | { |
245 | return (wv[1] << 8) | wv[0]; | |
246 | } | |
247 | ||
248 | static inline void | |
a3ad94ed | 249 | writeval(unsigned char* wv, Valtype v) |
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250 | { |
251 | wv[1] = v >> 8; | |
252 | wv[0] = v; | |
253 | } | |
254 | }; | |
255 | ||
256 | template<> | |
257 | struct Swap_unaligned<16, true> | |
258 | { | |
259 | typedef Valtype_base<16>::Valtype Valtype; | |
260 | ||
261 | static inline Valtype | |
a3ad94ed | 262 | readval(const unsigned char* wv) |
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263 | { |
264 | return (wv[0] << 8) | wv[1]; | |
265 | } | |
266 | ||
267 | static inline void | |
a3ad94ed | 268 | writeval(unsigned char* wv, Valtype v) |
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269 | { |
270 | wv[0] = v >> 8; | |
271 | wv[1] = v; | |
272 | } | |
273 | }; | |
274 | ||
275 | template<> | |
276 | struct Swap_unaligned<32, false> | |
277 | { | |
278 | typedef Valtype_base<32>::Valtype Valtype; | |
279 | ||
280 | static inline Valtype | |
a3ad94ed | 281 | readval(const unsigned char* wv) |
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282 | { |
283 | return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0]; | |
284 | } | |
285 | ||
286 | static inline void | |
a3ad94ed | 287 | writeval(unsigned char* wv, Valtype v) |
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288 | { |
289 | wv[3] = v >> 24; | |
290 | wv[2] = v >> 16; | |
291 | wv[1] = v >> 8; | |
292 | wv[0] = v; | |
293 | } | |
294 | }; | |
295 | ||
296 | template<> | |
297 | struct Swap_unaligned<32, true> | |
298 | { | |
299 | typedef Valtype_base<32>::Valtype Valtype; | |
300 | ||
301 | static inline Valtype | |
a3ad94ed | 302 | readval(const unsigned char* wv) |
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303 | { |
304 | return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3]; | |
305 | } | |
306 | ||
307 | static inline void | |
a3ad94ed | 308 | writeval(unsigned char* wv, Valtype v) |
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309 | { |
310 | wv[0] = v >> 24; | |
311 | wv[1] = v >> 16; | |
312 | wv[2] = v >> 8; | |
313 | wv[3] = v; | |
314 | } | |
315 | }; | |
316 | ||
317 | template<> | |
318 | struct Swap_unaligned<64, false> | |
319 | { | |
320 | typedef Valtype_base<64>::Valtype Valtype; | |
321 | ||
322 | static inline Valtype | |
a3ad94ed | 323 | readval(const unsigned char* wv) |
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324 | { |
325 | return ((static_cast<Valtype>(wv[7]) << 56) | |
326 | | (static_cast<Valtype>(wv[6]) << 48) | |
327 | | (static_cast<Valtype>(wv[5]) << 40) | |
328 | | (static_cast<Valtype>(wv[4]) << 32) | |
329 | | (static_cast<Valtype>(wv[3]) << 24) | |
330 | | (static_cast<Valtype>(wv[2]) << 16) | |
331 | | (static_cast<Valtype>(wv[1]) << 8) | |
332 | | static_cast<Valtype>(wv[0])); | |
333 | } | |
334 | ||
335 | static inline void | |
a3ad94ed | 336 | writeval(unsigned char* wv, Valtype v) |
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337 | { |
338 | wv[7] = v >> 56; | |
339 | wv[6] = v >> 48; | |
340 | wv[5] = v >> 40; | |
341 | wv[4] = v >> 32; | |
342 | wv[3] = v >> 24; | |
343 | wv[2] = v >> 16; | |
344 | wv[1] = v >> 8; | |
345 | wv[0] = v; | |
346 | } | |
347 | }; | |
348 | ||
349 | template<> | |
350 | struct Swap_unaligned<64, true> | |
351 | { | |
352 | typedef Valtype_base<64>::Valtype Valtype; | |
353 | ||
354 | static inline Valtype | |
a3ad94ed | 355 | readval(const unsigned char* wv) |
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356 | { |
357 | return ((static_cast<Valtype>(wv[0]) << 56) | |
358 | | (static_cast<Valtype>(wv[1]) << 48) | |
359 | | (static_cast<Valtype>(wv[2]) << 40) | |
360 | | (static_cast<Valtype>(wv[3]) << 32) | |
361 | | (static_cast<Valtype>(wv[4]) << 24) | |
362 | | (static_cast<Valtype>(wv[5]) << 16) | |
363 | | (static_cast<Valtype>(wv[6]) << 8) | |
364 | | static_cast<Valtype>(wv[7])); | |
365 | } | |
366 | ||
367 | static inline void | |
a3ad94ed | 368 | writeval(unsigned char* wv, Valtype v) |
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369 | { |
370 | wv[7] = v >> 56; | |
371 | wv[6] = v >> 48; | |
372 | wv[5] = v >> 40; | |
373 | wv[4] = v >> 32; | |
374 | wv[3] = v >> 24; | |
375 | wv[2] = v >> 16; | |
376 | wv[1] = v >> 8; | |
377 | wv[0] = v; | |
378 | } | |
379 | }; | |
380 | ||
381 | } // End namespace elfcpp. | |
382 | ||
383 | #endif // !defined(ELFCPP_SWAP_H) |