1 // elfcpp_swap.h -- Handle swapping for elfcpp -*- C++ -*-
3 // Copyright 2006, 2007, Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of elfcpp.
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.
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.)
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.
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
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.
46 // Endian simply indicates whether the host is big endian or not.
51 // Used for template specializations.
52 static const bool host_big_endian
= __BYTE_ORDER
== __BIG_ENDIAN
;
55 // Valtype_base is a template based on size (8, 16, 32, 64) which
56 // defines the type Valtype as the unsigned integer, and
57 // Signed_valtype as the signed integer, of the specified size.
63 struct Valtype_base
<8>
65 typedef uint8_t Valtype
;
66 typedef int8_t Signed_valtype
;
70 struct Valtype_base
<16>
72 typedef uint16_t Valtype
;
73 typedef int16_t Signed_valtype
;
77 struct Valtype_base
<32>
79 typedef uint32_t Valtype
;
80 typedef int32_t Signed_valtype
;
84 struct Valtype_base
<64>
86 typedef uint64_t Valtype
;
87 typedef int64_t Signed_valtype
;
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.
96 template<int size
, bool same_endian
>
97 struct Convert_endian
;
100 struct Convert_endian
<size
, true>
102 typedef typename Valtype_base
<size
>::Valtype Valtype
;
104 static inline Valtype
105 convert_host(Valtype v
)
110 struct Convert_endian
<8, false>
112 typedef Valtype_base
<8>::Valtype Valtype
;
114 static inline Valtype
115 convert_host(Valtype v
)
120 struct Convert_endian
<16, false>
122 typedef Valtype_base
<16>::Valtype Valtype
;
124 static inline Valtype
125 convert_host(Valtype v
)
126 { return bswap_16(v
); }
130 struct Convert_endian
<32, false>
132 typedef Valtype_base
<32>::Valtype Valtype
;
134 static inline Valtype
135 convert_host(Valtype v
)
136 { return bswap_32(v
); }
140 struct Convert_endian
<64, false>
142 typedef Valtype_base
<64>::Valtype Valtype
;
144 static inline Valtype
145 convert_host(Valtype v
)
146 { return bswap_64(v
); }
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.
154 template<int size
, bool big_endian
>
157 typedef typename Valtype_base
<size
>::Valtype Valtype
;
159 static inline Valtype
160 convert_host(Valtype v
)
162 return Convert_endian
<size
, big_endian
== Endian::host_big_endian
>
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.
174 template<int size
, bool big_endian
>
177 typedef typename Valtype_base
<size
>::Valtype Valtype
;
179 static inline Valtype
180 readval(const Valtype
* wv
)
181 { return Convert
<size
, big_endian
>::convert_host(*wv
); }
184 writeval(Valtype
* wv
, Valtype v
)
185 { *wv
= Convert
<size
, big_endian
>::convert_host(v
); }
187 static inline Valtype
188 readval(const unsigned char* wv
)
189 { return readval(reinterpret_cast<const Valtype
*>(wv
)); }
192 writeval(unsigned char* wv
, Valtype v
)
193 { writeval(reinterpret_cast<Valtype
*>(wv
), v
); }
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.
200 template<bool big_endian
>
201 struct Swap
<8, big_endian
>
203 typedef typename Valtype_base
<8>::Valtype Valtype
;
205 static inline Valtype
206 readval(const Valtype
* wv
)
210 writeval(Valtype
* wv
, Valtype v
)
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
216 // functions readval and writeval. The functions read and write
217 // values of the appropriate size out of buffers which may be
220 template<int size
, bool big_endian
>
221 struct Swap_unaligned
;
223 template<bool big_endian
>
224 struct Swap_unaligned
<8, big_endian
>
226 typedef typename Valtype_base
<8>::Valtype Valtype
;
228 static inline Valtype
229 readval(const unsigned char* wv
)
233 writeval(unsigned char* wv
, Valtype v
)
238 struct Swap_unaligned
<16, false>
240 typedef Valtype_base
<16>::Valtype Valtype
;
242 static inline Valtype
243 readval(const unsigned char* wv
)
245 return (wv
[1] << 8) | wv
[0];
249 writeval(unsigned char* wv
, Valtype v
)
257 struct Swap_unaligned
<16, true>
259 typedef Valtype_base
<16>::Valtype Valtype
;
261 static inline Valtype
262 readval(const unsigned char* wv
)
264 return (wv
[0] << 8) | wv
[1];
268 writeval(unsigned char* wv
, Valtype v
)
276 struct Swap_unaligned
<32, false>
278 typedef Valtype_base
<32>::Valtype Valtype
;
280 static inline Valtype
281 readval(const unsigned char* wv
)
283 return (wv
[3] << 24) | (wv
[2] << 16) | (wv
[1] << 8) | wv
[0];
287 writeval(unsigned char* wv
, Valtype v
)
297 struct Swap_unaligned
<32, true>
299 typedef Valtype_base
<32>::Valtype Valtype
;
301 static inline Valtype
302 readval(const unsigned char* wv
)
304 return (wv
[0] << 24) | (wv
[1] << 16) | (wv
[2] << 8) | wv
[3];
308 writeval(unsigned char* wv
, Valtype v
)
318 struct Swap_unaligned
<64, false>
320 typedef Valtype_base
<64>::Valtype Valtype
;
322 static inline Valtype
323 readval(const unsigned char* wv
)
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]));
336 writeval(unsigned char* wv
, Valtype v
)
350 struct Swap_unaligned
<64, true>
352 typedef Valtype_base
<64>::Valtype Valtype
;
354 static inline Valtype
355 readval(const unsigned char* wv
)
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]));
368 writeval(unsigned char* wv
, Valtype v
)
381 } // End namespace elfcpp.
383 #endif // !defined(ELFCPP_SWAP_H)
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