lib/bitfield.h

   1 #ifndef _BABELTRACE_BITFIELD_H
   2 #define _BABELTRACE_BITFIELD_H
   3
   4 /*
   5  * BabelTrace
   6  *
   7  * Bitfields read/write functions.
   8  *
   9  * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this software and associated documentation files (the "Software"), to deal
  13  * in the Software without restriction, including without limitation the rights
  14  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  * copies of the Software, and to permit persons to whom the Software is
  16  * furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  27  * SOFTWARE.
  28  */
  29
  30 #include <lttng-endian.h>
  31
  32 #ifndef CHAR_BIT
  33 #define CHAR_BIT 8
  34 #endif
  35
  36 /* We can't shift a int from 32 bit, >> 32 and << 32 on int is undefined */
  37 #define _bt_piecewise_rshift(_v, _shift)                                \
  38 ({                                                                      \
  39         typeof(_v) ___v = (_v);                                         \
  40         typeof(_shift) ___shift = (_shift);                             \
  41         unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);  \
  42         unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
  43                                                                         \
  44         for (; sb; sb--)                                                \
  45                 ___v >>= sizeof(___v) * CHAR_BIT - 1;                   \
  46         ___v >>= final;                                                 \
  47 })
  48
  49 #define _bt_piecewise_lshift(_v, _shift)                                \
  50 ({                                                                      \
  51         typeof(_v) ___v = (_v);                                         \
  52         typeof(_shift) ___shift = (_shift);                             \
  53         unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);  \
  54         unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
  55                                                                         \
  56         for (; sb; sb--)                                                \
  57                 ___v <<= sizeof(___v) * CHAR_BIT - 1;                   \
  58         ___v <<= final;                                                 \
  59 })
  60
  61 #define _bt_is_signed_type(type)        (((type)(-1)) < 0)
  62
  63 #define _bt_unsigned_cast(type, v)                                      \
  64 ({                                                                      \
  65         (sizeof(v) < sizeof(type)) ?                                    \
  66                 ((type) (v)) & (~(~(type) 0 << (sizeof(v) * CHAR_BIT))) : \
  67                 (type) (v);                                             \
  68 })
  69
  70 /*
  71  * bt_bitfield_write - write integer to a bitfield in native endianness
  72  *
  73  * Save integer to the bitfield, which starts at the "start" bit, has "len"
  74  * bits.
  75  * The inside of a bitfield is from high bits to low bits.
  76  * Uses native endianness.
  77  * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
  78  * For signed "v", sign-extend v if bitfield is larger than v.
  79  *
  80  * On little endian, bytes are placed from the less significant to the most
  81  * significant. Also, consecutive bitfields are placed from lower bits to higher
  82  * bits.
  83  *
  84  * On big endian, bytes are places from most significant to less significant.
  85  * Also, consecutive bitfields are placed from higher to lower bits.
  86  */
  87
  88 #define _bt_bitfield_write_le(_ptr, type, _start, _length, _v)          \
  89 do {                                                                    \
  90         typeof(_v) __v = (_v);                                          \
  91         type *__ptr = (void *) (_ptr);                                  \
  92         unsigned long __start = (_start), __length = (_length);         \
  93         type mask, cmask;                                               \
  94         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
  95         unsigned long start_unit, end_unit, this_unit;                  \
  96         unsigned long end, cshift; /* cshift is "complement shift" */   \
  97                                                                         \
  98         if (!__length)                                                  \
  99                 break;                                                  \
 100                                                                         \
 101         end = __start + __length;                                       \
 102         start_unit = __start / ts;                                      \
 103         end_unit = (end + (ts - 1)) / ts;                               \
 104                                                                         \
 105         /* Trim v high bits */                                          \
 106         if (__length < sizeof(__v) * CHAR_BIT)                          \
 107                 __v &= ~((~(typeof(__v)) 0) << __length);               \
 108                                                                         \
 109         /* We can now append v with a simple "or", shift it piece-wise */ \
 110         this_unit = start_unit;                                         \
 111         if (start_unit == end_unit - 1) {                               \
 112                 mask = ~((~(type) 0) << (__start % ts));                \
 113                 if (end % ts)                                           \
 114                         mask |= (~(type) 0) << (end % ts);              \
 115                 cmask = (type) __v << (__start % ts);                   \
 116                 cmask &= ~mask;                                         \
 117                 __ptr[this_unit] &= mask;                               \
 118                 __ptr[this_unit] |= cmask;                              \
 119                 break;                                                  \
 120         }                                                               \
 121         if (__start % ts) {                                             \
 122                 cshift = __start % ts;                                  \
 123                 mask = ~((~(type) 0) << cshift);                        \
 124                 cmask = (type) __v << cshift;                           \
 125                 cmask &= ~mask;                                         \
 126                 __ptr[this_unit] &= mask;                               \
 127                 __ptr[this_unit] |= cmask;                              \
 128                 __v = _bt_piecewise_rshift(__v, ts - cshift);           \
 129                 __start += ts - cshift;                                 \
 130                 this_unit++;                                            \
 131         }                                                               \
 132         for (; this_unit < end_unit - 1; this_unit++) {                 \
 133                 __ptr[this_unit] = (type) __v;                          \
 134                 __v = _bt_piecewise_rshift(__v, ts);                    \
 135                 __start += ts;                                          \
 136         }                                                               \
 137         if (end % ts) {                                                 \
 138                 mask = (~(type) 0) << (end % ts);                       \
 139                 cmask = (type) __v;                                     \
 140                 cmask &= ~mask;                                         \
 141                 __ptr[this_unit] &= mask;                               \
 142                 __ptr[this_unit] |= cmask;                              \
 143         } else                                                          \
 144                 __ptr[this_unit] = (type) __v;                          \
 145 } while (0)
 146
 147 #define _bt_bitfield_write_be(_ptr, type, _start, _length, _v)          \
 148 do {                                                                    \
 149         typeof(_v) __v = (_v);                                          \
 150         type *__ptr = (void *) (_ptr);                                  \
 151         unsigned long __start = (_start), __length = (_length);         \
 152         type mask, cmask;                                               \
 153         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 154         unsigned long start_unit, end_unit, this_unit;                  \
 155         unsigned long end, cshift; /* cshift is "complement shift" */   \
 156                                                                         \
 157         if (!__length)                                                  \
 158                 break;                                                  \
 159                                                                         \
 160         end = __start + __length;                                       \
 161         start_unit = __start / ts;                                      \
 162         end_unit = (end + (ts - 1)) / ts;                               \
 163                                                                         \
 164         /* Trim v high bits */                                          \
 165         if (__length < sizeof(__v) * CHAR_BIT)                          \
 166                 __v &= ~((~(typeof(__v)) 0) << __length);               \
 167                                                                         \
 168         /* We can now append v with a simple "or", shift it piece-wise */ \
 169         this_unit = end_unit - 1;                                       \
 170         if (start_unit == end_unit - 1) {                               \
 171                 mask = ~((~(type) 0) << ((ts - (end % ts)) % ts));      \
 172                 if (__start % ts)                                       \
 173                         mask |= (~((type) 0)) << (ts - (__start % ts)); \
 174                 cmask = (type) __v << ((ts - (end % ts)) % ts);         \
 175                 cmask &= ~mask;                                         \
 176                 __ptr[this_unit] &= mask;                               \
 177                 __ptr[this_unit] |= cmask;                              \
 178                 break;                                                  \
 179         }                                                               \
 180         if (end % ts) {                                                 \
 181                 cshift = end % ts;                                      \
 182                 mask = ~((~(type) 0) << (ts - cshift));                 \
 183                 cmask = (type) __v << (ts - cshift);                    \
 184                 cmask &= ~mask;                                         \
 185                 __ptr[this_unit] &= mask;                               \
 186                 __ptr[this_unit] |= cmask;                              \
 187                 __v = _bt_piecewise_rshift(__v, cshift);                \
 188                 end -= cshift;                                          \
 189                 this_unit--;                                            \
 190         }                                                               \
 191         for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
 192                 __ptr[this_unit] = (type) __v;                          \
 193                 __v = _bt_piecewise_rshift(__v, ts);                    \
 194                 end -= ts;                                              \
 195         }                                                               \
 196         if (__start % ts) {                                             \
 197                 mask = (~(type) 0) << (ts - (__start % ts));            \
 198                 cmask = (type) __v;                                     \
 199                 cmask &= ~mask;                                         \
 200                 __ptr[this_unit] &= mask;                               \
 201                 __ptr[this_unit] |= cmask;                              \
 202         } else                                                          \
 203                 __ptr[this_unit] = (type) __v;                          \
 204 } while (0)
 205
 206 /*
 207  * bt_bitfield_write - write integer to a bitfield in native endianness
 208  * bt_bitfield_write_le - write integer to a bitfield in little endian
 209  * bt_bitfield_write_be - write integer to a bitfield in big endian
 210  */
 211
 212 #if (__BYTE_ORDER == __LITTLE_ENDIAN)
 213
 214 #define bt_bitfield_write(ptr, type, _start, _length, _v)               \
 215         _bt_bitfield_write_le(ptr, type, _start, _length, _v)
 216
 217 #define bt_bitfield_write_le(ptr, type, _start, _length, _v)            \
 218         _bt_bitfield_write_le(ptr, type, _start, _length, _v)
 219
 220 #define bt_bitfield_write_be(ptr, type, _start, _length, _v)            \
 221         _bt_bitfield_write_be(ptr, unsigned char, _start, _length, _v)
 222
 223 #elif (__BYTE_ORDER == __BIG_ENDIAN)
 224
 225 #define bt_bitfield_write(ptr, type, _start, _length, _v)               \
 226         _bt_bitfield_write_be(ptr, type, _start, _length, _v)
 227
 228 #define bt_bitfield_write_le(ptr, type, _start, _length, _v)            \
 229         _bt_bitfield_write_le(ptr, unsigned char, _start, _length, _v)
 230
 231 #define bt_bitfield_write_be(ptr, type, _start, _length, _v)            \
 232         _bt_bitfield_write_be(ptr, type, _start, _length, _v)
 233
 234 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 235
 236 #error "Byte order not supported"
 237
 238 #endif
 239
 240 #define _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)        \
 241 do {                                                                    \
 242         typeof(*(_vptr)) *__vptr = (_vptr);                             \
 243         typeof(*__vptr) __v;                                            \
 244         type *__ptr = (void *) (_ptr);                                  \
 245         unsigned long __start = (_start), __length = (_length);         \
 246         type mask, cmask;                                               \
 247         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 248         unsigned long start_unit, end_unit, this_unit;                  \
 249         unsigned long end, cshift; /* cshift is "complement shift" */   \
 250                                                                         \
 251         if (!__length) {                                                \
 252                 *__vptr = 0;                                            \
 253                 break;                                                  \
 254         }                                                               \
 255                                                                         \
 256         end = __start + __length;                                       \
 257         start_unit = __start / ts;                                      \
 258         end_unit = (end + (ts - 1)) / ts;                               \
 259                                                                         \
 260         this_unit = end_unit - 1;                                       \
 261         if (_bt_is_signed_type(typeof(__v))                             \
 262             && (__ptr[this_unit] & ((type) 1 << ((end % ts ? : ts) - 1)))) \
 263                 __v = ~(typeof(__v)) 0;                                 \
 264         else                                                            \
 265                 __v = 0;                                                \
 266         if (start_unit == end_unit - 1) {                               \
 267                 cmask = __ptr[this_unit];                               \
 268                 cmask >>= (__start % ts);                               \
 269                 if ((end - __start) % ts) {                             \
 270                         mask = ~((~(type) 0) << (end - __start));       \
 271                         cmask &= mask;                                  \
 272                 }                                                       \
 273                 __v = _bt_piecewise_lshift(__v, end - __start);         \
 274                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 275                 *__vptr = __v;                                          \
 276                 break;                                                  \
 277         }                                                               \
 278         if (end % ts) {                                                 \
 279                 cshift = end % ts;                                      \
 280                 mask = ~((~(type) 0) << cshift);                        \
 281                 cmask = __ptr[this_unit];                               \
 282                 cmask &= mask;                                          \
 283                 __v = _bt_piecewise_lshift(__v, cshift);                \
 284                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 285                 end -= cshift;                                          \
 286                 this_unit--;                                            \
 287         }                                                               \
 288         for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
 289                 __v = _bt_piecewise_lshift(__v, ts);                    \
 290                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 291                 end -= ts;                                              \
 292         }                                                               \
 293         if (__start % ts) {                                             \
 294                 mask = ~((~(type) 0) << (ts - (__start % ts)));         \
 295                 cmask = __ptr[this_unit];                               \
 296                 cmask >>= (__start % ts);                               \
 297                 cmask &= mask;                                          \
 298                 __v = _bt_piecewise_lshift(__v, ts - (__start % ts));   \
 299                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 300         } else {                                                        \
 301                 __v = _bt_piecewise_lshift(__v, ts);                    \
 302                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 303         }                                                               \
 304         *__vptr = __v;                                                  \
 305 } while (0)
 306
 307 #define _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)        \
 308 do {                                                                    \
 309         typeof(*(_vptr)) *__vptr = (_vptr);                             \
 310         typeof(*__vptr) __v;                                            \
 311         type *__ptr = (void *) (_ptr);                                  \
 312         unsigned long __start = (_start), __length = (_length);         \
 313         type mask, cmask;                                               \
 314         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 315         unsigned long start_unit, end_unit, this_unit;                  \
 316         unsigned long end, cshift; /* cshift is "complement shift" */   \
 317                                                                         \
 318         if (!__length) {                                                \
 319                 *__vptr = 0;                                            \
 320                 break;                                                  \
 321         }                                                               \
 322                                                                         \
 323         end = __start + __length;                                       \
 324         start_unit = __start / ts;                                      \
 325         end_unit = (end + (ts - 1)) / ts;                               \
 326                                                                         \
 327         this_unit = start_unit;                                         \
 328         if (_bt_is_signed_type(typeof(__v))                             \
 329             && (__ptr[this_unit] & ((type) 1 << (ts - (__start % ts) - 1)))) \
 330                 __v = ~(typeof(__v)) 0;                                 \
 331         else                                                            \
 332                 __v = 0;                                                \
 333         if (start_unit == end_unit - 1) {                               \
 334                 cmask = __ptr[this_unit];                               \
 335                 cmask >>= (ts - (end % ts)) % ts;                       \
 336                 if ((end - __start) % ts) {                             \
 337                         mask = ~((~(type) 0) << (end - __start));       \
 338                         cmask &= mask;                                  \
 339                 }                                                       \
 340                 __v = _bt_piecewise_lshift(__v, end - __start);         \
 341                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 342                 *__vptr = __v;                                          \
 343                 break;                                                  \
 344         }                                                               \
 345         if (__start % ts) {                                             \
 346                 cshift = __start % ts;                                  \
 347                 mask = ~((~(type) 0) << (ts - cshift));                 \
 348                 cmask = __ptr[this_unit];                               \
 349                 cmask &= mask;                                          \
 350                 __v = _bt_piecewise_lshift(__v, ts - cshift);           \
 351                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 352                 __start += ts - cshift;                                 \
 353                 this_unit++;                                            \
 354         }                                                               \
 355         for (; this_unit < end_unit - 1; this_unit++) {                 \
 356                 __v = _bt_piecewise_lshift(__v, ts);                    \
 357                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 358                 __start += ts;                                          \
 359         }                                                               \
 360         if (end % ts) {                                                 \
 361                 mask = ~((~(type) 0) << (end % ts));                    \
 362                 cmask = __ptr[this_unit];                               \
 363                 cmask >>= ts - (end % ts);                              \
 364                 cmask &= mask;                                          \
 365                 __v = _bt_piecewise_lshift(__v, end % ts);              \
 366                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 367         } else {                                                        \
 368                 __v = _bt_piecewise_lshift(__v, ts);                    \
 369                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 370         }                                                               \
 371         *__vptr = __v;                                                  \
 372 } while (0)
 373
 374 /*
 375  * bt_bitfield_read - read integer from a bitfield in native endianness
 376  * bt_bitfield_read_le - read integer from a bitfield in little endian
 377  * bt_bitfield_read_be - read integer from a bitfield in big endian
 378  */
 379
 380 #if (__BYTE_ORDER == __LITTLE_ENDIAN)
 381
 382 #define bt_bitfield_read(_ptr, type, _start, _length, _vptr)            \
 383         _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
 384
 385 #define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)         \
 386         _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
 387
 388 #define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)         \
 389         _bt_bitfield_read_be(_ptr, unsigned char, _start, _length, _vptr)
 390
 391 #elif (__BYTE_ORDER == __BIG_ENDIAN)
 392
 393 #define bt_bitfield_read(_ptr, type, _start, _length, _vptr)            \
 394         _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
 395
 396 #define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)         \
 397         _bt_bitfield_read_le(_ptr, unsigned char, _start, _length, _vptr)
 398
 399 #define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)         \
 400         _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
 401
 402 #else /* (__BYTE_ORDER == __PDP_ENDIAN) */
 403
 404 #error "Byte order not supported"
 405
 406 #endif
 407
 408 #endif /* _BABELTRACE_BITFIELD_H */