include/babeltrace/bitfield-internal.h

   1 #ifndef _BABELTRACE_BITFIELD_H
   2 #define _BABELTRACE_BITFIELD_H
   3
   4 /*
   5  * Copyright 2010-2019 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE.
  24  */
  25
  26 #include <stdint.h>     /* C99 5.2.4.2 Numerical limits */
  27 #include <stdbool.h>    /* C99 7.16 bool type */
  28 #include <babeltrace/compat/limits-internal.h>  /* C99 5.2.4.2 Numerical limits */
  29 #include <babeltrace/endian-internal.h> /* Non-standard BIG_ENDIAN, LITTLE_ENDIAN, BYTE_ORDER */
  30
  31 /*
  32  * This header strictly follows the C99 standard, except for use of the
  33  * compiler-specific __typeof__.
  34  */
  35
  36 /*
  37  * This bitfield header requires the compiler representation of signed
  38  * integers to be two's complement.
  39  */
  40 #if (-1 != ~0)
  41 #error "bitfield.h requires the compiler representation of signed integers to be two's complement."
  42 #endif
  43
  44 /*
  45  * _bt_is_signed_type() willingly generates comparison of unsigned
  46  * expression < 0, which is always false. Silence compiler warnings.
  47  */
  48 #ifdef __GNUC__
  49 # define _BT_DIAG_PUSH                  _Pragma("GCC diagnostic push")
  50 # define _BT_DIAG_POP                   _Pragma("GCC diagnostic pop")
  51
  52 # define _BT_DIAG_STRINGIFY_1(x)        #x
  53 # define _BT_DIAG_STRINGIFY(x)          _BT_DIAG_STRINGIFY_1(x)
  54
  55 # define _BT_DIAG_IGNORE(option)        \
  56         _Pragma(_BT_DIAG_STRINGIFY(GCC diagnostic ignored option))
  57 # define _BT_DIAG_IGNORE_TYPE_LIMITS    _BT_DIAG_IGNORE("-Wtype-limits")
  58 #else
  59 # define _BT_DIAG_PUSH
  60 # define _BT_DIAG_POP
  61 # define _BT_DIAG_IGNORE
  62 #endif
  63
  64 #define _bt_is_signed_type(type)        ((type) -1 < (type) 0)
  65
  66 /*
  67  * Produce a build-time error if the condition `cond` is non-zero.
  68  * Evaluates as a size_t expression.
  69  */
  70 #define _BT_BUILD_ASSERT(cond)                                  \
  71         sizeof(struct { int f:(2 * !!(cond) - 1); })
  72
  73 /*
  74  * Cast value `v` to an unsigned integer of the same size as `v`.
  75  */
  76 #define _bt_cast_value_to_unsigned(v)                                   \
  77         (sizeof(v) == sizeof(uint8_t) ? (uint8_t) (v) :                 \
  78         sizeof(v) == sizeof(uint16_t) ? (uint16_t) (v) :                \
  79         sizeof(v) == sizeof(uint32_t) ? (uint32_t) (v) :                \
  80         sizeof(v) == sizeof(uint64_t) ? (uint64_t) (v) :                \
  81         _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
  82
  83 /*
  84  * Cast value `v` to an unsigned integer type of the size of type `type`
  85  * *without* sign-extension.
  86  *
  87  * The unsigned cast ensures that we're not shifting a negative value,
  88  * which is undefined in C. However, this limits the maximum type size
  89  * of `type` to 64-bit. Generate a compile-time error if the size of
  90  * `type` is larger than 64-bit.
  91  */
  92 #define _bt_cast_value_to_unsigned_type(type, v)                        \
  93         (sizeof(type) == sizeof(uint8_t) ?                              \
  94                 (uint8_t) _bt_cast_value_to_unsigned(v) :               \
  95         sizeof(type) == sizeof(uint16_t) ?                              \
  96                 (uint16_t) _bt_cast_value_to_unsigned(v) :              \
  97         sizeof(type) == sizeof(uint32_t) ?                              \
  98                 (uint32_t) _bt_cast_value_to_unsigned(v) :              \
  99         sizeof(type) == sizeof(uint64_t) ?                              \
 100                 (uint64_t) _bt_cast_value_to_unsigned(v) :              \
 101         _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
 102
 103 /*
 104  * _bt_fill_mask evaluates to a "type" integer with all bits set.
 105  */
 106 #define _bt_fill_mask(type)     ((type) ~(type) 0)
 107
 108 /*
 109  * Left shift a value `v` of `shift` bits.
 110  *
 111  * The type of `v` can be signed or unsigned integer.
 112  * The value of `shift` must be less than the size of `v` (in bits),
 113  * otherwise the behavior is undefined.
 114  * Evaluates to the result of the shift operation.
 115  *
 116  * According to the C99 standard, left shift of a left hand-side signed
 117  * type is undefined if it has a negative value or if the result cannot
 118  * be represented in the result type. This bitfield header discards the
 119  * bits that are left-shifted beyond the result type representation,
 120  * which is the behavior of an unsigned type left shift operation.
 121  * Therefore, always perform left shift on an unsigned type.
 122  *
 123  * This macro should not be used if `shift` can be greater or equal than
 124  * the bitwidth of `v`. See `_bt_safe_lshift`.
 125  */
 126 #define _bt_lshift(v, shift)                                            \
 127         ((__typeof__(v)) (_bt_cast_value_to_unsigned(v) << (shift)))
 128
 129 /*
 130  * Generate a mask of type `type` with the `length` least significant bits
 131  * cleared, and the most significant bits set.
 132  */
 133 #define _bt_make_mask_complement(type, length)                          \
 134         _bt_lshift(_bt_fill_mask(type), length)
 135
 136 /*
 137  * Generate a mask of type `type` with the `length` least significant bits
 138  * set, and the most significant bits cleared.
 139  */
 140 #define _bt_make_mask(type, length)                                     \
 141         ((type) ~_bt_make_mask_complement(type, length))
 142
 143 /*
 144  * Right shift a value `v` of `shift` bits.
 145  *
 146  * The type of `v` can be signed or unsigned integer.
 147  * The value of `shift` must be less than the size of `v` (in bits),
 148  * otherwise the behavior is undefined.
 149  * Evaluates to the result of the shift operation.
 150  *
 151  * According to the C99 standard, right shift of a left hand-side signed
 152  * type which has a negative value is implementation defined. This
 153  * bitfield header relies on the right shift implementation carrying the
 154  * sign bit. If the compiler implementation has a different behavior,
 155  * emulate carrying the sign bit.
 156  *
 157  * This macro should not be used if `shift` can be greater or equal than
 158  * the bitwidth of `v`. See `_bt_safe_rshift`.
 159  */
 160 #if ((-1 >> 1) == -1)
 161 #define _bt_rshift(v, shift)    ((v) >> (shift))
 162 #else
 163 #define _bt_rshift(v, shift)                                            \
 164         ((__typeof__(v)) ((_bt_cast_value_to_unsigned(v) >> (shift)) |  \
 165                 ((v) < 0 ? _bt_make_mask_complement(__typeof__(v),      \
 166                         sizeof(v) * CHAR_BIT - (shift)) : 0)))
 167 #endif
 168
 169 /*
 170  * Right shift a signed or unsigned integer with `shift` value being an
 171  * arbitrary number of bits. `v` is modified by this macro. The shift
 172  * is transformed into a sequence of `_nr_partial_shifts` consecutive
 173  * shift operations, each of a number of bits smaller than the bitwidth
 174  * of `v`, ending with a shift of the number of left over bits.
 175  */
 176 #define _bt_safe_rshift(v, shift)                                       \
 177 do {                                                                    \
 178         unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
 179         unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
 180                                                                         \
 181         for (; _nr_partial_shifts; _nr_partial_shifts--)                \
 182                 (v) = _bt_rshift(v, sizeof(v) * CHAR_BIT - 1);          \
 183         (v) = _bt_rshift(v, _leftover_bits);                            \
 184 } while (0)
 185
 186 /*
 187  * Left shift a signed or unsigned integer with `shift` value being an
 188  * arbitrary number of bits. `v` is modified by this macro. The shift
 189  * is transformed into a sequence of `_nr_partial_shifts` consecutive
 190  * shift operations, each of a number of bits smaller than the bitwidth
 191  * of `v`, ending with a shift of the number of left over bits.
 192  */
 193 #define _bt_safe_lshift(v, shift)                                       \
 194 do {                                                                    \
 195         unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
 196         unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
 197                                                                         \
 198         for (; _nr_partial_shifts; _nr_partial_shifts--)                \
 199                 (v) = _bt_lshift(v, sizeof(v) * CHAR_BIT - 1);          \
 200         (v) = _bt_lshift(v, _leftover_bits);                            \
 201 } while (0)
 202
 203 /*
 204  * bt_bitfield_write - write integer to a bitfield in native endianness
 205  *
 206  * Save integer to the bitfield, which starts at the "start" bit, has "len"
 207  * bits.
 208  * The inside of a bitfield is from high bits to low bits.
 209  * Uses native endianness.
 210  * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
 211  * For signed "v", sign-extend v if bitfield is larger than v.
 212  *
 213  * On little endian, bytes are placed from the less significant to the most
 214  * significant. Also, consecutive bitfields are placed from lower bits to higher
 215  * bits.
 216  *
 217  * On big endian, bytes are places from most significant to less significant.
 218  * Also, consecutive bitfields are placed from higher to lower bits.
 219  */
 220
 221 #define _bt_bitfield_write_le(ptr, type, start, length, v)              \
 222 do {                                                                    \
 223         __typeof__(v) _v = (v);                                 \
 224         type *_ptr = (void *) (ptr);                                    \
 225         unsigned long _start = (start), _length = (length);             \
 226         type _mask, _cmask;                                             \
 227         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 228         unsigned long _start_unit, _end_unit, _this_unit;               \
 229         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 230                                                                         \
 231         if (!_length)                                                   \
 232                 break;                                                  \
 233                                                                         \
 234         _end = _start + _length;                                        \
 235         _start_unit = _start / _ts;                                     \
 236         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 237                                                                         \
 238         /* Trim v high bits */                                          \
 239         if (_length < sizeof(_v) * CHAR_BIT)                            \
 240                 _v &= _bt_make_mask(__typeof__(_v), _length);           \
 241                                                                         \
 242         /* We can now append v with a simple "or", shift it piece-wise */ \
 243         _this_unit = _start_unit;                                       \
 244         if (_start_unit == _end_unit - 1) {                             \
 245                 _mask = _bt_make_mask(type, _start % _ts);              \
 246                 if (_end % _ts)                                         \
 247                         _mask |= _bt_make_mask_complement(type, _end % _ts); \
 248                 _cmask = _bt_lshift((type) (_v), _start % _ts);         \
 249                 _cmask &= ~_mask;                                       \
 250                 _ptr[_this_unit] &= _mask;                              \
 251                 _ptr[_this_unit] |= _cmask;                             \
 252                 break;                                                  \
 253         }                                                               \
 254         if (_start % _ts) {                                             \
 255                 _cshift = _start % _ts;                                 \
 256                 _mask = _bt_make_mask(type, _cshift);                   \
 257                 _cmask = _bt_lshift((type) (_v), _cshift);              \
 258                 _cmask &= ~_mask;                                       \
 259                 _ptr[_this_unit] &= _mask;                              \
 260                 _ptr[_this_unit] |= _cmask;                             \
 261                 _bt_safe_rshift(_v, _ts - _cshift);                     \
 262                 _start += _ts - _cshift;                                \
 263                 _this_unit++;                                           \
 264         }                                                               \
 265         for (; _this_unit < _end_unit - 1; _this_unit++) {              \
 266                 _ptr[_this_unit] = (type) _v;                           \
 267                 _bt_safe_rshift(_v, _ts);                               \
 268                 _start += _ts;                                          \
 269         }                                                               \
 270         if (_end % _ts) {                                               \
 271                 _mask = _bt_make_mask_complement(type, _end % _ts);     \
 272                 _cmask = (type) _v;                                     \
 273                 _cmask &= ~_mask;                                       \
 274                 _ptr[_this_unit] &= _mask;                              \
 275                 _ptr[_this_unit] |= _cmask;                             \
 276         } else                                                          \
 277                 _ptr[_this_unit] = (type) _v;                           \
 278 } while (0)
 279
 280 #define _bt_bitfield_write_be(ptr, type, start, length, v)              \
 281 do {                                                                    \
 282         __typeof__(v) _v = (v);                                         \
 283         type *_ptr = (void *) (ptr);                                    \
 284         unsigned long _start = (start), _length = (length);             \
 285         type _mask, _cmask;                                             \
 286         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 287         unsigned long _start_unit, _end_unit, _this_unit;               \
 288         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 289                                                                         \
 290         if (!_length)                                                   \
 291                 break;                                                  \
 292                                                                         \
 293         _end = _start + _length;                                        \
 294         _start_unit = _start / _ts;                                     \
 295         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 296                                                                         \
 297         /* Trim v high bits */                                          \
 298         if (_length < sizeof(_v) * CHAR_BIT)                            \
 299                 _v &= _bt_make_mask(__typeof__(_v), _length);           \
 300                                                                         \
 301         /* We can now append v with a simple "or", shift it piece-wise */ \
 302         _this_unit = _end_unit - 1;                                     \
 303         if (_start_unit == _end_unit - 1) {                             \
 304                 _mask = _bt_make_mask(type, (_ts - (_end % _ts)) % _ts); \
 305                 if (_start % _ts)                                       \
 306                         _mask |= _bt_make_mask_complement(type, _ts - (_start % _ts)); \
 307                 _cmask = _bt_lshift((type) (_v), (_ts - (_end % _ts)) % _ts); \
 308                 _cmask &= ~_mask;                                       \
 309                 _ptr[_this_unit] &= _mask;                              \
 310                 _ptr[_this_unit] |= _cmask;                             \
 311                 break;                                                  \
 312         }                                                               \
 313         if (_end % _ts) {                                               \
 314                 _cshift = _end % _ts;                                   \
 315                 _mask = _bt_make_mask(type, _ts - _cshift);             \
 316                 _cmask = _bt_lshift((type) (_v), _ts - _cshift);        \
 317                 _cmask &= ~_mask;                                       \
 318                 _ptr[_this_unit] &= _mask;                              \
 319                 _ptr[_this_unit] |= _cmask;                             \
 320                 _bt_safe_rshift(_v, _cshift);                           \
 321                 _end -= _cshift;                                        \
 322                 _this_unit--;                                           \
 323         }                                                               \
 324         for (; (long) _this_unit >= (long) _start_unit + 1; _this_unit--) { \
 325                 _ptr[_this_unit] = (type) _v;                           \
 326                 _bt_safe_rshift(_v, _ts);                               \
 327                 _end -= _ts;                                            \
 328         }                                                               \
 329         if (_start % _ts) {                                             \
 330                 _mask = _bt_make_mask_complement(type, _ts - (_start % _ts)); \
 331                 _cmask = (type) _v;                                     \
 332                 _cmask &= ~_mask;                                       \
 333                 _ptr[_this_unit] &= _mask;                              \
 334                 _ptr[_this_unit] |= _cmask;                             \
 335         } else                                                          \
 336                 _ptr[_this_unit] = (type) _v;                           \
 337 } while (0)
 338
 339 /*
 340  * bt_bitfield_write - write integer to a bitfield in native endianness
 341  * bt_bitfield_write_le - write integer to a bitfield in little endian
 342  * bt_bitfield_write_be - write integer to a bitfield in big endian
 343  */
 344
 345 #if (BYTE_ORDER == LITTLE_ENDIAN)
 346
 347 #define bt_bitfield_write(ptr, type, start, length, v)                  \
 348         _bt_bitfield_write_le(ptr, type, start, length, v)
 349
 350 #define bt_bitfield_write_le(ptr, type, start, length, v)               \
 351         _bt_bitfield_write_le(ptr, type, start, length, v)
 352
 353 #define bt_bitfield_write_be(ptr, type, start, length, v)               \
 354         _bt_bitfield_write_be(ptr, unsigned char, start, length, v)
 355
 356 #elif (BYTE_ORDER == BIG_ENDIAN)
 357
 358 #define bt_bitfield_write(ptr, type, start, length, v)                  \
 359         _bt_bitfield_write_be(ptr, type, start, length, v)
 360
 361 #define bt_bitfield_write_le(ptr, type, start, length, v)               \
 362         _bt_bitfield_write_le(ptr, unsigned char, start, length, v)
 363
 364 #define bt_bitfield_write_be(ptr, type, start, length, v)               \
 365         _bt_bitfield_write_be(ptr, type, start, length, v)
 366
 367 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 368
 369 #error "Byte order not supported"
 370
 371 #endif
 372
 373 #define _bt_bitfield_read_le(ptr, type, start, length, vptr)            \
 374 do {                                                                    \
 375         __typeof__(*(vptr)) *_vptr = (vptr);                            \
 376         __typeof__(*_vptr) _v;                                          \
 377         type *_ptr = (void *) (ptr);                                    \
 378         unsigned long _start = (start), _length = (length);             \
 379         type _mask, _cmask;                                             \
 380         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 381         unsigned long _start_unit, _end_unit, _this_unit;               \
 382         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 383         bool _is_signed_type;                                           \
 384                                                                         \
 385         if (!_length) {                                                 \
 386                 *_vptr = 0;                                             \
 387                 break;                                                  \
 388         }                                                               \
 389                                                                         \
 390         _end = _start + _length;                                        \
 391         _start_unit = _start / _ts;                                     \
 392         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 393                                                                         \
 394         _this_unit = _end_unit - 1;                                     \
 395         _BT_DIAG_PUSH                                                   \
 396         _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
 397         _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
 398         _BT_DIAG_POP                                                    \
 399         if (_is_signed_type                                             \
 400             && (_ptr[_this_unit] & _bt_lshift((type) 1, (_end % _ts ? _end % _ts : _ts) - 1))) \
 401                 _v = ~(__typeof__(_v)) 0;                               \
 402         else                                                            \
 403                 _v = 0;                                                 \
 404         if (_start_unit == _end_unit - 1) {                             \
 405                 _cmask = _ptr[_this_unit];                              \
 406                 _cmask = _bt_rshift(_cmask, _start % _ts);              \
 407                 if ((_end - _start) % _ts) {                            \
 408                         _mask = _bt_make_mask(type, _end - _start);     \
 409                         _cmask &= _mask;                                \
 410                 }                                                       \
 411                 _bt_safe_lshift(_v, _end - _start);                     \
 412                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 413                 *_vptr = _v;                                            \
 414                 break;                                                  \
 415         }                                                               \
 416         if (_end % _ts) {                                               \
 417                 _cshift = _end % _ts;                                   \
 418                 _mask = _bt_make_mask(type, _cshift);                   \
 419                 _cmask = _ptr[_this_unit];                              \
 420                 _cmask &= _mask;                                        \
 421                 _bt_safe_lshift(_v, _cshift);                           \
 422                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 423                 _end -= _cshift;                                        \
 424                 _this_unit--;                                           \
 425         }                                                               \
 426         for (; (long) _this_unit >= (long) _start_unit + 1; _this_unit--) { \
 427                 _bt_safe_lshift(_v, _ts);                               \
 428                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 429                 _end -= _ts;                                            \
 430         }                                                               \
 431         if (_start % _ts) {                                             \
 432                 _mask = _bt_make_mask(type, _ts - (_start % _ts));      \
 433                 _cmask = _ptr[_this_unit];                              \
 434                 _cmask = _bt_rshift(_cmask, _start % _ts);              \
 435                 _cmask &= _mask;                                        \
 436                 _bt_safe_lshift(_v, _ts - (_start % _ts));              \
 437                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 438         } else {                                                        \
 439                 _bt_safe_lshift(_v, _ts);                               \
 440                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 441         }                                                               \
 442         *_vptr = _v;                                                    \
 443 } while (0)
 444
 445 #define _bt_bitfield_read_be(ptr, type, start, length, vptr)            \
 446 do {                                                                    \
 447         __typeof__(*(vptr)) *_vptr = (vptr);                            \
 448         __typeof__(*_vptr) _v;                                          \
 449         type *_ptr = (void *) (ptr);                                    \
 450         unsigned long _start = (start), _length = (length);             \
 451         type _mask, _cmask;                                             \
 452         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 453         unsigned long _start_unit, _end_unit, _this_unit;               \
 454         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 455         bool _is_signed_type;                                           \
 456                                                                         \
 457         if (!_length) {                                                 \
 458                 *_vptr = 0;                                             \
 459                 break;                                                  \
 460         }                                                               \
 461                                                                         \
 462         _end = _start + _length;                                        \
 463         _start_unit = _start / _ts;                                     \
 464         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 465                                                                         \
 466         _this_unit = _start_unit;                                       \
 467         _BT_DIAG_PUSH                                                   \
 468         _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
 469         _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
 470         _BT_DIAG_POP                                                    \
 471         if (_is_signed_type                                             \
 472             && (_ptr[_this_unit] & _bt_lshift((type) 1, _ts - (_start % _ts) - 1))) \
 473                 _v = ~(__typeof__(_v)) 0;                               \
 474         else                                                            \
 475                 _v = 0;                                                 \
 476         if (_start_unit == _end_unit - 1) {                             \
 477                 _cmask = _ptr[_this_unit];                              \
 478                 _cmask = _bt_rshift(_cmask, (_ts - (_end % _ts)) % _ts); \
 479                 if ((_end - _start) % _ts) {                            \
 480                         _mask = _bt_make_mask(type, _end - _start);     \
 481                         _cmask &= _mask;                                \
 482                 }                                                       \
 483                 _bt_safe_lshift(_v, _end - _start);                     \
 484                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 485                 *_vptr = _v;                                            \
 486                 break;                                                  \
 487         }                                                               \
 488         if (_start % _ts) {                                             \
 489                 _cshift = _start % _ts;                                 \
 490                 _mask = _bt_make_mask(type, _ts - _cshift);             \
 491                 _cmask = _ptr[_this_unit];                              \
 492                 _cmask &= _mask;                                        \
 493                 _bt_safe_lshift(_v, _ts - _cshift);                     \
 494                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 495                 _start += _ts - _cshift;                                \
 496                 _this_unit++;                                           \
 497         }                                                               \
 498         for (; _this_unit < _end_unit - 1; _this_unit++) {              \
 499                 _bt_safe_lshift(_v, _ts);                               \
 500                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 501                 _start += _ts;                                          \
 502         }                                                               \
 503         if (_end % _ts) {                                               \
 504                 _mask = _bt_make_mask(type, _end % _ts);                \
 505                 _cmask = _ptr[_this_unit];                              \
 506                 _cmask = _bt_rshift(_cmask, _ts - (_end % _ts));        \
 507                 _cmask &= _mask;                                        \
 508                 _bt_safe_lshift(_v, _end % _ts);                        \
 509                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 510         } else {                                                        \
 511                 _bt_safe_lshift(_v, _ts);                               \
 512                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 513         }                                                               \
 514         *_vptr = _v;                                                    \
 515 } while (0)
 516
 517 /*
 518  * bt_bitfield_read - read integer from a bitfield in native endianness
 519  * bt_bitfield_read_le - read integer from a bitfield in little endian
 520  * bt_bitfield_read_be - read integer from a bitfield in big endian
 521  */
 522
 523 #if (BYTE_ORDER == LITTLE_ENDIAN)
 524
 525 #define bt_bitfield_read(ptr, type, start, length, vptr)                \
 526         _bt_bitfield_read_le(ptr, type, start, length, vptr)
 527
 528 #define bt_bitfield_read_le(ptr, type, start, length, vptr)             \
 529         _bt_bitfield_read_le(ptr, type, start, length, vptr)
 530
 531 #define bt_bitfield_read_be(ptr, type, start, length, vptr)             \
 532         _bt_bitfield_read_be(ptr, unsigned char, start, length, vptr)
 533
 534 #elif (BYTE_ORDER == BIG_ENDIAN)
 535
 536 #define bt_bitfield_read(ptr, type, start, length, vptr)                \
 537         _bt_bitfield_read_be(ptr, type, start, length, vptr)
 538
 539 #define bt_bitfield_read_le(ptr, type, start, length, vptr)             \
 540         _bt_bitfield_read_le(ptr, unsigned char, start, length, vptr)
 541
 542 #define bt_bitfield_read_be(ptr, type, start, length, vptr)             \
 543         _bt_bitfield_read_be(ptr, type, start, length, vptr)
 544
 545 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 546
 547 #error "Byte order not supported"
 548
 549 #endif
 550
 551 #endif /* _BABELTRACE_BITFIELD_H */