| 1 | // elfcpp_swap.h -- Handle swapping for elfcpp -*- C++ -*- |
| 2 | |
| 3 | // This header file defines basic template classes to efficiently swap |
| 4 | // numbers between host form and target form. When the host and |
| 5 | // target have the same endianness, these turn into no-ops. |
| 6 | |
| 7 | #ifndef ELFCPP_SWAP_H |
| 8 | #define ELFCPP_SWAP_H |
| 9 | |
| 10 | #include <stdint.h> |
| 11 | #include <endian.h> |
| 12 | #include <byteswap.h> |
| 13 | |
| 14 | namespace elfcpp |
| 15 | { |
| 16 | |
| 17 | // Endian simply indicates whether the host is big endian or not. |
| 18 | |
| 19 | struct Endian |
| 20 | { |
| 21 | public: |
| 22 | // Used for template specializations. |
| 23 | static const bool host_big_endian = __BYTE_ORDER == __BIG_ENDIAN; |
| 24 | }; |
| 25 | |
| 26 | // Valtype_base is a template based on size (8, 16, 32, 64) which |
| 27 | // defines the type Valtype as the unsigned integer of the specified |
| 28 | // size. |
| 29 | |
| 30 | template<int size> |
| 31 | struct Valtype_base; |
| 32 | |
| 33 | template<> |
| 34 | struct Valtype_base<8> |
| 35 | { |
| 36 | typedef unsigned char Valtype; |
| 37 | }; |
| 38 | |
| 39 | template<> |
| 40 | struct Valtype_base<16> |
| 41 | { |
| 42 | typedef uint16_t Valtype; |
| 43 | }; |
| 44 | |
| 45 | template<> |
| 46 | struct Valtype_base<32> |
| 47 | { |
| 48 | typedef uint32_t Valtype; |
| 49 | }; |
| 50 | |
| 51 | template<> |
| 52 | struct Valtype_base<64> |
| 53 | { |
| 54 | typedef uint64_t Valtype; |
| 55 | }; |
| 56 | |
| 57 | // Convert_endian is a template based on size and on whether the host |
| 58 | // and target have the same endianness. It defines the type Valtype |
| 59 | // as Valtype_base does, and also defines a function convert_host |
| 60 | // which takes an argument of type Valtype and returns the same value, |
| 61 | // but swapped if the host and target have different endianness. |
| 62 | |
| 63 | template<int size, bool same_endian> |
| 64 | struct Convert_endian; |
| 65 | |
| 66 | template<int size> |
| 67 | struct Convert_endian<size, true> |
| 68 | { |
| 69 | typedef typename Valtype_base<size>::Valtype Valtype; |
| 70 | |
| 71 | static inline Valtype |
| 72 | convert_host(Valtype v) |
| 73 | { return v; } |
| 74 | }; |
| 75 | |
| 76 | template<> |
| 77 | struct Convert_endian<8, false> |
| 78 | { |
| 79 | typedef Valtype_base<8>::Valtype Valtype; |
| 80 | |
| 81 | static inline Valtype |
| 82 | convert_host(Valtype v) |
| 83 | { return v; } |
| 84 | }; |
| 85 | |
| 86 | template<> |
| 87 | struct Convert_endian<16, false> |
| 88 | { |
| 89 | typedef Valtype_base<16>::Valtype Valtype; |
| 90 | |
| 91 | static inline Valtype |
| 92 | convert_host(Valtype v) |
| 93 | { return bswap_16(v); } |
| 94 | }; |
| 95 | |
| 96 | template<> |
| 97 | struct Convert_endian<32, false> |
| 98 | { |
| 99 | typedef Valtype_base<32>::Valtype Valtype; |
| 100 | |
| 101 | static inline Valtype |
| 102 | convert_host(Valtype v) |
| 103 | { return bswap_32(v); } |
| 104 | }; |
| 105 | |
| 106 | template<> |
| 107 | struct Convert_endian<64, false> |
| 108 | { |
| 109 | typedef Valtype_base<64>::Valtype Valtype; |
| 110 | |
| 111 | static inline Valtype |
| 112 | convert_host(Valtype v) |
| 113 | { return bswap_64(v); } |
| 114 | }; |
| 115 | |
| 116 | // Convert is a template based on size and on whether the target is |
| 117 | // big endian. It defines Valtype and convert_host like |
| 118 | // Convert_endian. That is, it is just like Convert_endian except in |
| 119 | // the meaning of the second template parameter. |
| 120 | |
| 121 | template<int size, bool big_endian> |
| 122 | struct Convert |
| 123 | { |
| 124 | typedef typename Valtype_base<size>::Valtype Valtype; |
| 125 | |
| 126 | static inline Valtype |
| 127 | convert_host(Valtype v) |
| 128 | { |
| 129 | return Convert_endian<size, big_endian == Endian::host_big_endian> |
| 130 | ::convert_host(v); |
| 131 | } |
| 132 | }; |
| 133 | |
| 134 | // Swap is a template based on size and on whether the target is big |
| 135 | // endian. It defines the type Valtype and the functions readval and |
| 136 | // writeval. The functions read and write values of the appropriate |
| 137 | // size out of buffers, swapping them if necessary. readval and |
| 138 | // writeval are overloaded to take pointers to the appropriate type or |
| 139 | // pointers to unsigned char. |
| 140 | |
| 141 | template<int size, bool big_endian> |
| 142 | struct Swap |
| 143 | { |
| 144 | typedef typename Valtype_base<size>::Valtype Valtype; |
| 145 | |
| 146 | static inline Valtype |
| 147 | readval(const Valtype* wv) |
| 148 | { return Convert<size, big_endian>::convert_host(*wv); } |
| 149 | |
| 150 | static inline void |
| 151 | writeval(Valtype* wv, Valtype v) |
| 152 | { *wv = Convert<size, big_endian>::convert_host(v); } |
| 153 | |
| 154 | static inline Valtype |
| 155 | readval(const unsigned char* wv) |
| 156 | { return readval(reinterpret_cast<const Valtype*>(wv)); } |
| 157 | |
| 158 | static inline void |
| 159 | writeval(unsigned char* wv, Valtype v) |
| 160 | { writeval(reinterpret_cast<Valtype*>(wv), v); } |
| 161 | }; |
| 162 | |
| 163 | // We need to specialize the 8-bit version of Swap to avoid |
| 164 | // conflicting overloads, since both versions of readval and writeval |
| 165 | // will have the same type parameters. |
| 166 | |
| 167 | template<bool big_endian> |
| 168 | struct Swap<8, big_endian> |
| 169 | { |
| 170 | typedef typename Valtype_base<8>::Valtype Valtype; |
| 171 | |
| 172 | static inline Valtype |
| 173 | readval(const Valtype* wv) |
| 174 | { return *wv; } |
| 175 | |
| 176 | static inline void |
| 177 | writeval(Valtype* wv, Valtype v) |
| 178 | { *wv = v; } |
| 179 | }; |
| 180 | |
| 181 | // Swap_unaligned is a template based on size and on whether the |
| 182 | // target is big endian. It defines the type Valtype and the |
| 183 | // functions readval and writeval. The functions read and write |
| 184 | // values of the appropriate size out of buffers which may be |
| 185 | // misaligned. |
| 186 | |
| 187 | template<int size, bool big_endian> |
| 188 | struct Swap_unaligned; |
| 189 | |
| 190 | template<bool big_endian> |
| 191 | struct Swap_unaligned<8, big_endian> |
| 192 | { |
| 193 | typedef typename Valtype_base<8>::Valtype Valtype; |
| 194 | |
| 195 | static inline Valtype |
| 196 | readval(const unsigned char* wv) |
| 197 | { return *wv; } |
| 198 | |
| 199 | static inline void |
| 200 | writeval(unsigned char* wv, Valtype v) |
| 201 | { *wv = v; } |
| 202 | }; |
| 203 | |
| 204 | template<> |
| 205 | struct Swap_unaligned<16, false> |
| 206 | { |
| 207 | typedef Valtype_base<16>::Valtype Valtype; |
| 208 | |
| 209 | static inline Valtype |
| 210 | readval(const unsigned char* wv) |
| 211 | { |
| 212 | return (wv[1] << 8) | wv[0]; |
| 213 | } |
| 214 | |
| 215 | static inline void |
| 216 | writeval(unsigned char* wv, Valtype v) |
| 217 | { |
| 218 | wv[1] = v >> 8; |
| 219 | wv[0] = v; |
| 220 | } |
| 221 | }; |
| 222 | |
| 223 | template<> |
| 224 | struct Swap_unaligned<16, true> |
| 225 | { |
| 226 | typedef Valtype_base<16>::Valtype Valtype; |
| 227 | |
| 228 | static inline Valtype |
| 229 | readval(const unsigned char* wv) |
| 230 | { |
| 231 | return (wv[0] << 8) | wv[1]; |
| 232 | } |
| 233 | |
| 234 | static inline void |
| 235 | writeval(unsigned char* wv, Valtype v) |
| 236 | { |
| 237 | wv[0] = v >> 8; |
| 238 | wv[1] = v; |
| 239 | } |
| 240 | }; |
| 241 | |
| 242 | template<> |
| 243 | struct Swap_unaligned<32, false> |
| 244 | { |
| 245 | typedef Valtype_base<32>::Valtype Valtype; |
| 246 | |
| 247 | static inline Valtype |
| 248 | readval(const unsigned char* wv) |
| 249 | { |
| 250 | return (wv[3] << 24) | (wv[2] << 16) | (wv[1] << 8) | wv[0]; |
| 251 | } |
| 252 | |
| 253 | static inline void |
| 254 | writeval(unsigned char* wv, Valtype v) |
| 255 | { |
| 256 | wv[3] = v >> 24; |
| 257 | wv[2] = v >> 16; |
| 258 | wv[1] = v >> 8; |
| 259 | wv[0] = v; |
| 260 | } |
| 261 | }; |
| 262 | |
| 263 | template<> |
| 264 | struct Swap_unaligned<32, true> |
| 265 | { |
| 266 | typedef Valtype_base<32>::Valtype Valtype; |
| 267 | |
| 268 | static inline Valtype |
| 269 | readval(const unsigned char* wv) |
| 270 | { |
| 271 | return (wv[0] << 24) | (wv[1] << 16) | (wv[2] << 8) | wv[3]; |
| 272 | } |
| 273 | |
| 274 | static inline void |
| 275 | writeval(unsigned char* wv, Valtype v) |
| 276 | { |
| 277 | wv[0] = v >> 24; |
| 278 | wv[1] = v >> 16; |
| 279 | wv[2] = v >> 8; |
| 280 | wv[3] = v; |
| 281 | } |
| 282 | }; |
| 283 | |
| 284 | template<> |
| 285 | struct Swap_unaligned<64, false> |
| 286 | { |
| 287 | typedef Valtype_base<64>::Valtype Valtype; |
| 288 | |
| 289 | static inline Valtype |
| 290 | readval(const unsigned char* wv) |
| 291 | { |
| 292 | return ((static_cast<Valtype>(wv[7]) << 56) |
| 293 | | (static_cast<Valtype>(wv[6]) << 48) |
| 294 | | (static_cast<Valtype>(wv[5]) << 40) |
| 295 | | (static_cast<Valtype>(wv[4]) << 32) |
| 296 | | (static_cast<Valtype>(wv[3]) << 24) |
| 297 | | (static_cast<Valtype>(wv[2]) << 16) |
| 298 | | (static_cast<Valtype>(wv[1]) << 8) |
| 299 | | static_cast<Valtype>(wv[0])); |
| 300 | } |
| 301 | |
| 302 | static inline void |
| 303 | writeval(unsigned char* wv, Valtype v) |
| 304 | { |
| 305 | wv[7] = v >> 56; |
| 306 | wv[6] = v >> 48; |
| 307 | wv[5] = v >> 40; |
| 308 | wv[4] = v >> 32; |
| 309 | wv[3] = v >> 24; |
| 310 | wv[2] = v >> 16; |
| 311 | wv[1] = v >> 8; |
| 312 | wv[0] = v; |
| 313 | } |
| 314 | }; |
| 315 | |
| 316 | template<> |
| 317 | struct Swap_unaligned<64, true> |
| 318 | { |
| 319 | typedef Valtype_base<64>::Valtype Valtype; |
| 320 | |
| 321 | static inline Valtype |
| 322 | readval(const unsigned char* wv) |
| 323 | { |
| 324 | return ((static_cast<Valtype>(wv[0]) << 56) |
| 325 | | (static_cast<Valtype>(wv[1]) << 48) |
| 326 | | (static_cast<Valtype>(wv[2]) << 40) |
| 327 | | (static_cast<Valtype>(wv[3]) << 32) |
| 328 | | (static_cast<Valtype>(wv[4]) << 24) |
| 329 | | (static_cast<Valtype>(wv[5]) << 16) |
| 330 | | (static_cast<Valtype>(wv[6]) << 8) |
| 331 | | static_cast<Valtype>(wv[7])); |
| 332 | } |
| 333 | |
| 334 | static inline void |
| 335 | writeval(unsigned char* wv, Valtype v) |
| 336 | { |
| 337 | wv[7] = v >> 56; |
| 338 | wv[6] = v >> 48; |
| 339 | wv[5] = v >> 40; |
| 340 | wv[4] = v >> 32; |
| 341 | wv[3] = v >> 24; |
| 342 | wv[2] = v >> 16; |
| 343 | wv[1] = v >> 8; |
| 344 | wv[0] = v; |
| 345 | } |
| 346 | }; |
| 347 | |
| 348 | } // End namespace elfcpp. |
| 349 | |
| 350 | #endif // !defined(ELFCPP_SWAP_H) |