include/babeltrace/bitfield-internal.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 <stdint.h>     /* C99 5.2.4.2 Numerical limits */
  31 #include <babeltrace/compat/limits-internal.h>  /* C99 5.2.4.2 Numerical limits */
  32 #include <babeltrace/endian-internal.h> /* Non-standard BIG_ENDIAN, LITTLE_ENDIAN, BYTE_ORDER */
  33
  34 /* We can't shift a int from 32 bit, >> 32 and << 32 on int is undefined */
  35 #define _bt_piecewise_rshift(_v, _shift)                                \
  36 ({                                                                      \
  37         typeof(_v) ___v = (_v);                                         \
  38         typeof(_shift) ___shift = (_shift);                             \
  39         unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);  \
  40         unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
  41                                                                         \
  42         for (; sb; sb--)                                                \
  43                 ___v >>= sizeof(___v) * CHAR_BIT - 1;                   \
  44         ___v >>= final;                                                 \
  45 })
  46
  47 #define _bt_piecewise_lshift(_v, _shift)                                \
  48 ({                                                                      \
  49         typeof(_v) ___v = (_v);                                         \
  50         typeof(_shift) ___shift = (_shift);                             \
  51         unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);  \
  52         unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
  53                                                                         \
  54         for (; sb; sb--)                                                \
  55                 ___v <<= sizeof(___v) * CHAR_BIT - 1;                   \
  56         ___v <<= final;                                                 \
  57 })
  58
  59 #define _bt_is_signed_type(type)        ((type) -1 < (type) 0)
  60
  61 /*
  62  * NOTE: The cast to (uint64_t) below ensures that we're not casting a
  63  * negative value, which is undefined in C. However, this limits the
  64  * maximum type size of `type` and `v` to 64-bit. The
  65  * _bt_check_max_64bit() is used to check that the users of this header
  66  * do not use types with a size greater than 64-bit.
  67  */
  68 #define _bt_unsigned_cast(type, v)                                      \
  69 ({                                                                      \
  70         (sizeof(v) < sizeof(type)) ?                                    \
  71                 ((type) (v)) & ((type) (~(~(uint64_t) 0 << (sizeof(v) * CHAR_BIT)))) : \
  72                 (type) (v);                                             \
  73 })
  74
  75 #define _bt_check_max_64bit(type)                                       \
  76         char _max_64bit_assertion[sizeof(type) <= sizeof(uint64_t) ? 1 : -1] __attribute__((unused))
  77
  78 /*
  79  * bt_bitfield_write - write integer to a bitfield in native endianness
  80  *
  81  * Save integer to the bitfield, which starts at the "start" bit, has "len"
  82  * bits.
  83  * The inside of a bitfield is from high bits to low bits.
  84  * Uses native endianness.
  85  * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
  86  * For signed "v", sign-extend v if bitfield is larger than v.
  87  *
  88  * On little endian, bytes are placed from the less significant to the most
  89  * significant. Also, consecutive bitfields are placed from lower bits to higher
  90  * bits.
  91  *
  92  * On big endian, bytes are places from most significant to less significant.
  93  * Also, consecutive bitfields are placed from higher to lower bits.
  94  */
  95
  96 #define _bt_bitfield_write_le(_ptr, type, _start, _length, _v)          \
  97 do {                                                                    \
  98         typeof(_v) __v = (_v);                                          \
  99         type *__ptr = (void *) (_ptr);                                  \
 100         unsigned long __start = (_start), __length = (_length);         \
 101         type mask, cmask;                                               \
 102         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 103         unsigned long start_unit, end_unit, this_unit;                  \
 104         unsigned long end, cshift; /* cshift is "complement shift" */   \
 105                                                                         \
 106         if (!__length)                                                  \
 107                 break;                                                  \
 108                                                                         \
 109         end = __start + __length;                                       \
 110         start_unit = __start / ts;                                      \
 111         end_unit = (end + (ts - 1)) / ts;                               \
 112                                                                         \
 113         /* Trim v high bits */                                          \
 114         if (__length < sizeof(__v) * CHAR_BIT)                          \
 115                 __v &= ~((~(typeof(__v)) 0) << __length);               \
 116                                                                         \
 117         /* We can now append v with a simple "or", shift it piece-wise */ \
 118         this_unit = start_unit;                                         \
 119         if (start_unit == end_unit - 1) {                               \
 120                 mask = ~((~(type) 0) << (__start % ts));                \
 121                 if (end % ts)                                           \
 122                         mask |= (~(type) 0) << (end % ts);              \
 123                 cmask = (type) __v << (__start % ts);                   \
 124                 cmask &= ~mask;                                         \
 125                 __ptr[this_unit] &= mask;                               \
 126                 __ptr[this_unit] |= cmask;                              \
 127                 break;                                                  \
 128         }                                                               \
 129         if (__start % ts) {                                             \
 130                 cshift = __start % ts;                                  \
 131                 mask = ~((~(type) 0) << cshift);                        \
 132                 cmask = (type) __v << cshift;                           \
 133                 cmask &= ~mask;                                         \
 134                 __ptr[this_unit] &= mask;                               \
 135                 __ptr[this_unit] |= cmask;                              \
 136                 __v = _bt_piecewise_rshift(__v, ts - cshift);           \
 137                 __start += ts - cshift;                                 \
 138                 this_unit++;                                            \
 139         }                                                               \
 140         for (; this_unit < end_unit - 1; this_unit++) {                 \
 141                 __ptr[this_unit] = (type) __v;                          \
 142                 __v = _bt_piecewise_rshift(__v, ts);                    \
 143                 __start += ts;                                          \
 144         }                                                               \
 145         if (end % ts) {                                                 \
 146                 mask = (~(type) 0) << (end % ts);                       \
 147                 cmask = (type) __v;                                     \
 148                 cmask &= ~mask;                                         \
 149                 __ptr[this_unit] &= mask;                               \
 150                 __ptr[this_unit] |= cmask;                              \
 151         } else                                                          \
 152                 __ptr[this_unit] = (type) __v;                          \
 153 } while (0)
 154
 155 #define _bt_bitfield_write_be(_ptr, type, _start, _length, _v)          \
 156 do {                                                                    \
 157         typeof(_v) __v = (_v);                                          \
 158         type *__ptr = (void *) (_ptr);                                  \
 159         unsigned long __start = (_start), __length = (_length);         \
 160         type mask, cmask;                                               \
 161         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 162         unsigned long start_unit, end_unit, this_unit;                  \
 163         unsigned long end, cshift; /* cshift is "complement shift" */   \
 164                                                                         \
 165         if (!__length)                                                  \
 166                 break;                                                  \
 167                                                                         \
 168         end = __start + __length;                                       \
 169         start_unit = __start / ts;                                      \
 170         end_unit = (end + (ts - 1)) / ts;                               \
 171                                                                         \
 172         /* Trim v high bits */                                          \
 173         if (__length < sizeof(__v) * CHAR_BIT)                          \
 174                 __v &= ~((~(typeof(__v)) 0) << __length);               \
 175                                                                         \
 176         /* We can now append v with a simple "or", shift it piece-wise */ \
 177         this_unit = end_unit - 1;                                       \
 178         if (start_unit == end_unit - 1) {                               \
 179                 mask = ~((~(type) 0) << ((ts - (end % ts)) % ts));      \
 180                 if (__start % ts)                                       \
 181                         mask |= (~((type) 0)) << (ts - (__start % ts)); \
 182                 cmask = (type) __v << ((ts - (end % ts)) % ts);         \
 183                 cmask &= ~mask;                                         \
 184                 __ptr[this_unit] &= mask;                               \
 185                 __ptr[this_unit] |= cmask;                              \
 186                 break;                                                  \
 187         }                                                               \
 188         if (end % ts) {                                                 \
 189                 cshift = end % ts;                                      \
 190                 mask = ~((~(type) 0) << (ts - cshift));                 \
 191                 cmask = (type) __v << (ts - cshift);                    \
 192                 cmask &= ~mask;                                         \
 193                 __ptr[this_unit] &= mask;                               \
 194                 __ptr[this_unit] |= cmask;                              \
 195                 __v = _bt_piecewise_rshift(__v, cshift);                \
 196                 end -= cshift;                                          \
 197                 this_unit--;                                            \
 198         }                                                               \
 199         for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
 200                 __ptr[this_unit] = (type) __v;                          \
 201                 __v = _bt_piecewise_rshift(__v, ts);                    \
 202                 end -= ts;                                              \
 203         }                                                               \
 204         if (__start % ts) {                                             \
 205                 mask = (~(type) 0) << (ts - (__start % ts));            \
 206                 cmask = (type) __v;                                     \
 207                 cmask &= ~mask;                                         \
 208                 __ptr[this_unit] &= mask;                               \
 209                 __ptr[this_unit] |= cmask;                              \
 210         } else                                                          \
 211                 __ptr[this_unit] = (type) __v;                          \
 212 } while (0)
 213
 214 /*
 215  * bt_bitfield_write - write integer to a bitfield in native endianness
 216  * bt_bitfield_write_le - write integer to a bitfield in little endian
 217  * bt_bitfield_write_be - write integer to a bitfield in big endian
 218  */
 219
 220 #if (BYTE_ORDER == LITTLE_ENDIAN)
 221
 222 #define bt_bitfield_write(ptr, type, _start, _length, _v)               \
 223         _bt_bitfield_write_le(ptr, type, _start, _length, _v)
 224
 225 #define bt_bitfield_write_le(ptr, type, _start, _length, _v)            \
 226         _bt_bitfield_write_le(ptr, type, _start, _length, _v)
 227
 228 #define bt_bitfield_write_be(ptr, type, _start, _length, _v)            \
 229         _bt_bitfield_write_be(ptr, unsigned char, _start, _length, _v)
 230
 231 #elif (BYTE_ORDER == BIG_ENDIAN)
 232
 233 #define bt_bitfield_write(ptr, type, _start, _length, _v)               \
 234         _bt_bitfield_write_be(ptr, type, _start, _length, _v)
 235
 236 #define bt_bitfield_write_le(ptr, type, _start, _length, _v)            \
 237         _bt_bitfield_write_le(ptr, unsigned char, _start, _length, _v)
 238
 239 #define bt_bitfield_write_be(ptr, type, _start, _length, _v)            \
 240         _bt_bitfield_write_be(ptr, type, _start, _length, _v)
 241
 242 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 243
 244 #error "Byte order not supported"
 245
 246 #endif
 247
 248 #define _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)        \
 249 do {                                                                    \
 250         typeof(*(_vptr)) *__vptr = (_vptr);                             \
 251         typeof(*__vptr) __v;                                            \
 252         type *__ptr = (void *) (_ptr);                                  \
 253         unsigned long __start = (_start), __length = (_length);         \
 254         type mask, cmask;                                               \
 255         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 256         unsigned long start_unit, end_unit, this_unit;                  \
 257         unsigned long end, cshift; /* cshift is "complement shift" */   \
 258                                                                         \
 259         { _bt_check_max_64bit(type); }                                  \
 260         { _bt_check_max_64bit(typeof(*_vptr)); }                        \
 261         { _bt_check_max_64bit(typeof(*_ptr)); }                         \
 262                                                                         \
 263         if (!__length) {                                                \
 264                 *__vptr = 0;                                            \
 265                 break;                                                  \
 266         }                                                               \
 267                                                                         \
 268         end = __start + __length;                                       \
 269         start_unit = __start / ts;                                      \
 270         end_unit = (end + (ts - 1)) / ts;                               \
 271                                                                         \
 272         this_unit = end_unit - 1;                                       \
 273         if (_bt_is_signed_type(typeof(__v))                             \
 274             && (__ptr[this_unit] & ((type) 1 << ((end % ts ? : ts) - 1)))) \
 275                 __v = ~(typeof(__v)) 0;                                 \
 276         else                                                            \
 277                 __v = 0;                                                \
 278         if (start_unit == end_unit - 1) {                               \
 279                 cmask = __ptr[this_unit];                               \
 280                 cmask >>= (__start % ts);                               \
 281                 if ((end - __start) % ts) {                             \
 282                         mask = ~((~(type) 0) << (end - __start));       \
 283                         cmask &= mask;                                  \
 284                 }                                                       \
 285                 __v = _bt_piecewise_lshift(__v, end - __start);         \
 286                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 287                 *__vptr = __v;                                          \
 288                 break;                                                  \
 289         }                                                               \
 290         if (end % ts) {                                                 \
 291                 cshift = end % ts;                                      \
 292                 mask = ~((~(type) 0) << cshift);                        \
 293                 cmask = __ptr[this_unit];                               \
 294                 cmask &= mask;                                          \
 295                 __v = _bt_piecewise_lshift(__v, cshift);                \
 296                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 297                 end -= cshift;                                          \
 298                 this_unit--;                                            \
 299         }                                                               \
 300         for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
 301                 __v = _bt_piecewise_lshift(__v, ts);                    \
 302                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 303                 end -= ts;                                              \
 304         }                                                               \
 305         if (__start % ts) {                                             \
 306                 mask = ~((~(type) 0) << (ts - (__start % ts)));         \
 307                 cmask = __ptr[this_unit];                               \
 308                 cmask >>= (__start % ts);                               \
 309                 cmask &= mask;                                          \
 310                 __v = _bt_piecewise_lshift(__v, ts - (__start % ts));   \
 311                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 312         } else {                                                        \
 313                 __v = _bt_piecewise_lshift(__v, ts);                    \
 314                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 315         }                                                               \
 316         *__vptr = __v;                                                  \
 317 } while (0)
 318
 319 #define _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)        \
 320 do {                                                                    \
 321         typeof(*(_vptr)) *__vptr = (_vptr);                             \
 322         typeof(*__vptr) __v;                                            \
 323         type *__ptr = (void *) (_ptr);                                  \
 324         unsigned long __start = (_start), __length = (_length);         \
 325         type mask, cmask;                                               \
 326         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 327         unsigned long start_unit, end_unit, this_unit;                  \
 328         unsigned long end, cshift; /* cshift is "complement shift" */   \
 329                                                                         \
 330         { _bt_check_max_64bit(type); }                                  \
 331         { _bt_check_max_64bit(typeof(*_vptr)); }                        \
 332         { _bt_check_max_64bit(typeof(*_ptr)); }                         \
 333                                                                         \
 334         if (!__length) {                                                \
 335                 *__vptr = 0;                                            \
 336                 break;                                                  \
 337         }                                                               \
 338                                                                         \
 339         end = __start + __length;                                       \
 340         start_unit = __start / ts;                                      \
 341         end_unit = (end + (ts - 1)) / ts;                               \
 342                                                                         \
 343         this_unit = start_unit;                                         \
 344         if (_bt_is_signed_type(typeof(__v))                             \
 345             && (__ptr[this_unit] & ((type) 1 << (ts - (__start % ts) - 1)))) \
 346                 __v = ~(typeof(__v)) 0;                                 \
 347         else                                                            \
 348                 __v = 0;                                                \
 349         if (start_unit == end_unit - 1) {                               \
 350                 cmask = __ptr[this_unit];                               \
 351                 cmask >>= (ts - (end % ts)) % ts;                       \
 352                 if ((end - __start) % ts) {                             \
 353                         mask = ~((~(type) 0) << (end - __start));       \
 354                         cmask &= mask;                                  \
 355                 }                                                       \
 356                 __v = _bt_piecewise_lshift(__v, end - __start);         \
 357                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 358                 *__vptr = __v;                                          \
 359                 break;                                                  \
 360         }                                                               \
 361         if (__start % ts) {                                             \
 362                 cshift = __start % ts;                                  \
 363                 mask = ~((~(type) 0) << (ts - cshift));                 \
 364                 cmask = __ptr[this_unit];                               \
 365                 cmask &= mask;                                          \
 366                 __v = _bt_piecewise_lshift(__v, ts - cshift);           \
 367                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 368                 __start += ts - cshift;                                 \
 369                 this_unit++;                                            \
 370         }                                                               \
 371         for (; this_unit < end_unit - 1; this_unit++) {                 \
 372                 __v = _bt_piecewise_lshift(__v, ts);                    \
 373                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 374                 __start += ts;                                          \
 375         }                                                               \
 376         if (end % ts) {                                                 \
 377                 mask = ~((~(type) 0) << (end % ts));                    \
 378                 cmask = __ptr[this_unit];                               \
 379                 cmask >>= ts - (end % ts);                              \
 380                 cmask &= mask;                                          \
 381                 __v = _bt_piecewise_lshift(__v, end % ts);              \
 382                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 383         } else {                                                        \
 384                 __v = _bt_piecewise_lshift(__v, ts);                    \
 385                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 386         }                                                               \
 387         *__vptr = __v;                                                  \
 388 } while (0)
 389
 390 /*
 391  * bt_bitfield_read - read integer from a bitfield in native endianness
 392  * bt_bitfield_read_le - read integer from a bitfield in little endian
 393  * bt_bitfield_read_be - read integer from a bitfield in big endian
 394  */
 395
 396 #if (BYTE_ORDER == LITTLE_ENDIAN)
 397
 398 #define bt_bitfield_read(_ptr, type, _start, _length, _vptr)            \
 399         _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
 400
 401 #define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)         \
 402         _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
 403
 404 #define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)         \
 405         _bt_bitfield_read_be(_ptr, unsigned char, _start, _length, _vptr)
 406
 407 #elif (BYTE_ORDER == BIG_ENDIAN)
 408
 409 #define bt_bitfield_read(_ptr, type, _start, _length, _vptr)            \
 410         _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
 411
 412 #define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)         \
 413         _bt_bitfield_read_le(_ptr, unsigned char, _start, _length, _vptr)
 414
 415 #define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)         \
 416         _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
 417
 418 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 419
 420 #error "Byte order not supported"
 421
 422 #endif
 423
 424 #endif /* _BABELTRACE_BITFIELD_H */