aboutsummaryrefslogtreecommitdiff
path: root/elfcpp/elfcpp_swap.h
blob: 06852761588f8d8d345d919187563e174d7d5bba (plain)
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
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
// elfcpp_swap.h -- Handle swapping for elfcpp   -*- C++ -*-

// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of elfcpp.
   
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public License
// as published by the Free Software Foundation; either version 2, or
// (at your option) any later version.

// In addition to the permissions in the GNU Library General Public
// License, the Free Software Foundation gives you unlimited
// permission to link the compiled version of this file into
// combinations with other programs, and to distribute those
// combinations without any restriction coming from the use of this
// file.  (The Library Public License restrictions do apply in other
// respects; for example, they cover modification of the file, and
/// distribution when not linked into a combined executable.)

// This program 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
// Library General Public License for more details.

// You should have received a copy of the GNU Library General Public
// License along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
// 02110-1301, USA.

// This header file defines basic template classes to efficiently swap
// numbers between host form and target form.  When the host and
// target have the same endianness, these turn into no-ops.

#ifndef ELFCPP_SWAP_H
#define ELFCPP_SWAP_H

#include <stdint.h>

// We need an autoconf-generated config.h file for endianness and
// swapping.  We check two macros: WORDS_BIGENDIAN and
// HAVE_BYTESWAP_H.

#include "config.h"

#ifdef HAVE_BYTESWAP_H
#include <byteswap.h>
#else
// Provide our own versions of the byteswap functions.
inline uint16_t
bswap_16(uint16_t v)
{
  return ((v >> 8) & 0xff) | ((v & 0xff) << 8);
}

inline uint32_t
bswap_32(uint32_t v)
{
  return (  ((v & 0xff000000) >> 24)
	  | ((v & 0x00ff0000) >>  8)
	  | ((v & 0x0000ff00) <<  8)
	  | ((v & 0x000000ff) << 24));
}

inline uint64_t
bswap_64(uint64_t v)
{
  return (  ((v & 0xff00000000000000ULL) >> 56)
	  | ((v & 0x00ff000000000000ULL) >> 40)
	  | ((v & 0x0000ff0000000000ULL) >> 24)
	  | ((v & 0x000000ff00000000ULL) >>  8)
	  | ((v & 0x00000000ff000000ULL) <<  8)
	  | ((v & 0x0000000000ff0000ULL) << 24)
	  | ((v & 0x000000000000ff00ULL) << 40)
	  | ((v & 0x00000000000000ffULL) << 56));
}
#endif // !defined(HAVE_BYTESWAP_H)

// gcc 4.3 and later provides __builtin_bswap32 and __builtin_bswap64.

#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
#undef bswap_32
#define bswap_32 __builtin_bswap32
#undef bswap_64
#define bswap_64 __builtin_bswap64
#endif

namespace elfcpp
{

// Endian simply indicates whether the host is big endian or not.

struct Endian
{
 public:
  // Used for template specializations.
  static const bool host_big_endian = 
#ifdef WORDS_BIGENDIAN
    true
#else
    false
#endif
    ;
};

// Valtype_base is a template based on size (8, 16, 32, 64) which
// defines the type Valtype as the unsigned integer, and
// Signed_valtype as the signed integer, of the specified size.

template<int size>
struct Valtype_base;

template<>
struct Valtype_base<8>
{
  typedef uint8_t Valtype;
  typedef int8_t Signed_valtype;
};

template<>
struct Valtype_base<16>
{
  typedef uint16_t Valtype;
  typedef int16_t Signed_valtype;
};

template<>
struct Valtype_base<32>
{
  typedef uint32_t Valtype;
  typedef int32_t Signed_valtype;
};

template<>
struct Valtype_base<64>
{
  typedef uint64_t Valtype;
  typedef int64_t Signed_valtype;
};

// Convert_endian is a template based on size and on whether the host
// and target have the same endianness.  It defines the type Valtype
// as Valtype_base does, and also defines a function convert_host
// which takes an argument of type Valtype and returns the same value,
// but swapped if the host and target have different endianness.

template<int size, bool same_endian>
struct Convert_endian;

template<int size>
struct Convert_endian<size, true>
{
  typedef typename Valtype_base<size>::Valtype Valtype;

  static inline Valtype
  convert_host(Valtype v)
  { return v; }
};

template<>
struct Convert_endian<8, false>
{
  typedef Valtype_base<8>::Valtype Valtype;

  static inline Valtype
  convert_host(Valtype v)
  { return v; }
};

template<>
struct Convert_endian<16, false>
{
  typedef Valtype_base<16>::Valtype Valtype;

  static inline Valtype
  convert_host(Valtype v)
  { return bswap_16(v); }
};

template<>
struct Convert_endian<32, false>
{
  typedef Valtype_base<32>::Valtype Valtype;

  static inline Valtype
  convert_host(Valtype v)
  { return bswap_32(v); }
};

template<>
struct Convert_endian<64, false>
{
  typedef Valtype_base<64>::Valtype Valtype;

  static inline Valtype
  convert_host(Valtype v)
  { return bswap_64(v); }
};

// Convert is a template based on size and on whether the target is
// big endian.  It defines Valtype and convert_host like
// Convert_endian.  That is, it is just like Convert_endian except in
// the meaning of the second template parameter.

template<int size, bool big_endian>
struct Convert
{
  typedef typename Valtype_base<size>::Valtype Valtype;

  static inline Valtype
  convert_host(Valtype v)
  {
    return Convert_endian<size, big_endian == Endian::host_big_endian>
      ::convert_host(v);
  }
};

// Swap is a template based on size and on whether the target is big
// endian.  It defines the type Valtype and the functions readval and
// writeval.  The functions read and write values of the appropriate
// size out of buffers, swapping them if necessary.  readval and
// writeval are overloaded to take pointers to the appropriate type or
// pointers to unsigned char.

template<int size, bool big_endian>
struct Swap
{
  typedef typename Valtype_base<size>::Valtype Valtype;

  static inline Valtype
  readval(const Valtype* wv)
  { return Convert<size, big_endian>::convert_host(*wv); }

  static inline void
  writeval(Valtype* wv, Valtype v)
  { *wv = Convert<size, big_endian>::convert_host(v); }

  static inline Valtype
  readval(const unsigned char* wv)
  { return readval(reinterpret_cast<const Valtype*>(wv)); }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  { writeval(reinterpret_cast<Valtype*>(wv), v); }
};

// We need to specialize the 8-bit version of Swap to avoid
// conflicting overloads, since both versions of readval and writeval
// will have the same type parameters.

template<bool big_endian>
struct Swap<8, big_endian>
{
  typedef typename Valtype_base<8>::Valtype Valtype;

  static inline Valtype
  readval(const Valtype* wv)
  { return *wv; }

  static inline void
  writeval(Valtype* wv, Valtype v)
  { *wv = v; }
};

// Swap_unaligned is a template based on size and on whether the
// target is big endian.  It defines the type Valtype and the
// functions readval and writeval.  The functions read and write
// values of the appropriate size out of buffers which may be
// misaligned.

template<int size, bool big_endian>
struct Swap_unaligned;

template<bool big_endian>
struct Swap_unaligned<8, big_endian>
{
  typedef typename Valtype_base<8>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  { return *wv; }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  { *wv = v; }
};

template<>
struct Swap_unaligned<16, false>
{
  typedef Valtype_base<16>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  {
    return (wv[1] << 8) | wv[0];
  }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  {
    wv[1] = v >> 8;
    wv[0] = v;
  }
};

template<>
struct Swap_unaligned<16, true>
{
  typedef Valtype_base<16>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  {
    return (wv[0] << 8) | wv[1];
  }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  {
    wv[0] = v >> 8;
    wv[1] = v;
  }
};

template<>
struct Swap_unaligned<32, false>
{
  typedef Valtype_base<32>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  {
    return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0];
  }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  {
    wv[3] = v >> 24;
    wv[2] = v >> 16;
    wv[1] = v >> 8;
    wv[0] = v;
  }
};

template<>
struct Swap_unaligned<32, true>
{
  typedef Valtype_base<32>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  {
    return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3];
  }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  {
    wv[0] = v >> 24;
    wv[1] = v >> 16;
    wv[2] = v >> 8;
    wv[3] = v;
  }
};

template<>
struct Swap_unaligned<64, false>
{
  typedef Valtype_base<64>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  {
    return ((static_cast<Valtype>(wv[7]) << 56)
	    | (static_cast<Valtype>(wv[6]) << 48)
	    | (static_cast<Valtype>(wv[5]) << 40)
	    | (static_cast<Valtype>(wv[4]) << 32)
	    | (static_cast<Valtype>(wv[3]) << 24)
	    | (static_cast<Valtype>(wv[2]) << 16)
	    | (static_cast<Valtype>(wv[1]) << 8)
	    | static_cast<Valtype>(wv[0]));
  }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  {
    wv[7] = v >> 56;
    wv[6] = v >> 48;
    wv[5] = v >> 40;
    wv[4] = v >> 32;
    wv[3] = v >> 24;
    wv[2] = v >> 16;
    wv[1] = v >> 8;
    wv[0] = v;
  }
};

template<>
struct Swap_unaligned<64, true>
{
  typedef Valtype_base<64>::Valtype Valtype;

  static inline Valtype
  readval(const unsigned char* wv)
  {
    return ((static_cast<Valtype>(wv[0]) << 56)
	    | (static_cast<Valtype>(wv[1]) << 48)
	    | (static_cast<Valtype>(wv[2]) << 40)
	    | (static_cast<Valtype>(wv[3]) << 32)
	    | (static_cast<Valtype>(wv[4]) << 24)
	    | (static_cast<Valtype>(wv[5]) << 16)
	    | (static_cast<Valtype>(wv[6]) << 8)
	    | static_cast<Valtype>(wv[7]));
  }

  static inline void
  writeval(unsigned char* wv, Valtype v)
  {
    wv[0] = v >> 56;
    wv[1] = v >> 48;
    wv[2] = v >> 40;
    wv[3] = v >> 32;
    wv[4] = v >> 24;
    wv[5] = v >> 16;
    wv[6] = v >> 8;
    wv[7] = v;
  }
};

} // End namespace elfcpp.

#endif // !defined(ELFCPP_SWAP_H)