include/lttng/bitfield.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 <limits.h>     /* C99 5.2.4.2 Numerical limits */
  28 #include <stdbool.h>    /* C99 7.16 bool type */
  29 #include <lttng/ust-endian.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 # define _BT_DIAG_IGNORE_TYPE_LIMITS
  63 #endif
  64
  65 #define _bt_is_signed_type(type)        ((type) -1 < (type) 0)
  66
  67 /*
  68  * Produce a build-time error if the condition `cond` is non-zero.
  69  * Evaluates as a size_t expression.
  70  */
  71 #define _BT_BUILD_ASSERT(cond)                                  \
  72         sizeof(struct { int f:(2 * !!(cond) - 1); })
  73
  74 /*
  75  * Cast value `v` to an unsigned integer of the same size as `v`.
  76  */
  77 #define _bt_cast_value_to_unsigned(v)                                   \
  78         (sizeof(v) == sizeof(uint8_t) ? (uint8_t) (v) :                 \
  79         sizeof(v) == sizeof(uint16_t) ? (uint16_t) (v) :                \
  80         sizeof(v) == sizeof(uint32_t) ? (uint32_t) (v) :                \
  81         sizeof(v) == sizeof(uint64_t) ? (uint64_t) (v) :                \
  82         _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
  83
  84 /*
  85  * Cast value `v` to an unsigned integer type of the size of type `type`
  86  * *without* sign-extension.
  87  *
  88  * The unsigned cast ensures that we're not shifting a negative value,
  89  * which is undefined in C. However, this limits the maximum type size
  90  * of `type` to 64-bit. Generate a compile-time error if the size of
  91  * `type` is larger than 64-bit.
  92  */
  93 #define _bt_cast_value_to_unsigned_type(type, v)                        \
  94         (sizeof(type) == sizeof(uint8_t) ?                              \
  95                 (uint8_t) _bt_cast_value_to_unsigned(v) :               \
  96         sizeof(type) == sizeof(uint16_t) ?                              \
  97                 (uint16_t) _bt_cast_value_to_unsigned(v) :              \
  98         sizeof(type) == sizeof(uint32_t) ?                              \
  99                 (uint32_t) _bt_cast_value_to_unsigned(v) :              \
 100         sizeof(type) == sizeof(uint64_t) ?                              \
 101                 (uint64_t) _bt_cast_value_to_unsigned(v) :              \
 102         _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
 103
 104 /*
 105  * _bt_fill_mask evaluates to a "type" integer with all bits set.
 106  */
 107 #define _bt_fill_mask(type)     ((type) ~(type) 0)
 108
 109 /*
 110  * Left shift a value `v` of `shift` bits.
 111  *
 112  * The type of `v` can be signed or unsigned integer.
 113  * The value of `shift` must be less than the size of `v` (in bits),
 114  * otherwise the behavior is undefined.
 115  * Evaluates to the result of the shift operation.
 116  *
 117  * According to the C99 standard, left shift of a left hand-side signed
 118  * type is undefined if it has a negative value or if the result cannot
 119  * be represented in the result type. This bitfield header discards the
 120  * bits that are left-shifted beyond the result type representation,
 121  * which is the behavior of an unsigned type left shift operation.
 122  * Therefore, always perform left shift on an unsigned type.
 123  *
 124  * This macro should not be used if `shift` can be greater or equal than
 125  * the bitwidth of `v`. See `_bt_safe_lshift`.
 126  */
 127 #define _bt_lshift(v, shift)                                            \
 128         ((__typeof__(v)) (_bt_cast_value_to_unsigned(v) << (shift)))
 129
 130 /*
 131  * Generate a mask of type `type` with the `length` least significant bits
 132  * cleared, and the most significant bits set.
 133  */
 134 #define _bt_make_mask_complement(type, length)                          \
 135         _bt_lshift(_bt_fill_mask(type), length)
 136
 137 /*
 138  * Generate a mask of type `type` with the `length` least significant bits
 139  * set, and the most significant bits cleared.
 140  */
 141 #define _bt_make_mask(type, length)                                     \
 142         ((type) ~_bt_make_mask_complement(type, length))
 143
 144 /*
 145  * Right shift a value `v` of `shift` bits.
 146  *
 147  * The type of `v` can be signed or unsigned integer.
 148  * The value of `shift` must be less than the size of `v` (in bits),
 149  * otherwise the behavior is undefined.
 150  * Evaluates to the result of the shift operation.
 151  *
 152  * According to the C99 standard, right shift of a left hand-side signed
 153  * type which has a negative value is implementation defined. This
 154  * bitfield header relies on the right shift implementation carrying the
 155  * sign bit. If the compiler implementation has a different behavior,
 156  * emulate carrying the sign bit.
 157  *
 158  * This macro should not be used if `shift` can be greater or equal than
 159  * the bitwidth of `v`. See `_bt_safe_rshift`.
 160  */
 161 #if ((-1 >> 1) == -1)
 162 #define _bt_rshift(v, shift)    ((v) >> (shift))
 163 #else
 164 #define _bt_rshift(v, shift)                                            \
 165         ((__typeof__(v)) ((_bt_cast_value_to_unsigned(v) >> (shift)) |  \
 166                 ((v) < 0 ? _bt_make_mask_complement(__typeof__(v),      \
 167                         sizeof(v) * CHAR_BIT - (shift)) : 0)))
 168 #endif
 169
 170 /*
 171  * Right shift a signed or unsigned integer with `shift` value being an
 172  * arbitrary number of bits. `v` is modified by this macro. The shift
 173  * is transformed into a sequence of `_nr_partial_shifts` consecutive
 174  * shift operations, each of a number of bits smaller than the bitwidth
 175  * of `v`, ending with a shift of the number of left over bits.
 176  */
 177 #define _bt_safe_rshift(v, shift)                                       \
 178 do {                                                                    \
 179         unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
 180         unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
 181                                                                         \
 182         for (; _nr_partial_shifts; _nr_partial_shifts--)                \
 183                 (v) = _bt_rshift(v, sizeof(v) * CHAR_BIT - 1);          \
 184         (v) = _bt_rshift(v, _leftover_bits);                            \
 185 } while (0)
 186
 187 /*
 188  * Left shift a signed or unsigned integer with `shift` value being an
 189  * arbitrary number of bits. `v` is modified by this macro. The shift
 190  * is transformed into a sequence of `_nr_partial_shifts` consecutive
 191  * shift operations, each of a number of bits smaller than the bitwidth
 192  * of `v`, ending with a shift of the number of left over bits.
 193  */
 194 #define _bt_safe_lshift(v, shift)                                       \
 195 do {                                                                    \
 196         unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
 197         unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
 198                                                                         \
 199         for (; _nr_partial_shifts; _nr_partial_shifts--)                \
 200                 (v) = _bt_lshift(v, sizeof(v) * CHAR_BIT - 1);          \
 201         (v) = _bt_lshift(v, _leftover_bits);                            \
 202 } while (0)
 203
 204 /*
 205  * bt_bitfield_write - write integer to a bitfield in native endianness
 206  *
 207  * Save integer to the bitfield, which starts at the "start" bit, has "len"
 208  * bits.
 209  * The inside of a bitfield is from high bits to low bits.
 210  * Uses native endianness.
 211  * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
 212  * For signed "v", sign-extend v if bitfield is larger than v.
 213  *
 214  * On little endian, bytes are placed from the less significant to the most
 215  * significant. Also, consecutive bitfields are placed from lower bits to higher
 216  * bits.
 217  *
 218  * On big endian, bytes are places from most significant to less significant.
 219  * Also, consecutive bitfields are placed from higher to lower bits.
 220  */
 221
 222 #define _bt_bitfield_write_le(ptr, type, start, length, v)              \
 223 do {                                                                    \
 224         __typeof__(v) _v = (v);                                 \
 225         type *_ptr = (void *) (ptr);                                    \
 226         unsigned long _start = (start), _length = (length);             \
 227         type _mask, _cmask;                                             \
 228         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 229         unsigned long _start_unit, _end_unit, _this_unit;               \
 230         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 231                                                                         \
 232         if (!_length)                                                   \
 233                 break;                                                  \
 234                                                                         \
 235         _end = _start + _length;                                        \
 236         _start_unit = _start / _ts;                                     \
 237         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 238                                                                         \
 239         /* Trim v high bits */                                          \
 240         if (_length < sizeof(_v) * CHAR_BIT)                            \
 241                 _v &= _bt_make_mask(__typeof__(_v), _length);           \
 242                                                                         \
 243         /* We can now append v with a simple "or", shift it piece-wise */ \
 244         _this_unit = _start_unit;                                       \
 245         if (_start_unit == _end_unit - 1) {                             \
 246                 _mask = _bt_make_mask(type, _start % _ts);              \
 247                 if (_end % _ts)                                         \
 248                         _mask |= _bt_make_mask_complement(type, _end % _ts); \
 249                 _cmask = _bt_lshift((type) (_v), _start % _ts);         \
 250                 _cmask &= ~_mask;                                       \
 251                 _ptr[_this_unit] &= _mask;                              \
 252                 _ptr[_this_unit] |= _cmask;                             \
 253                 break;                                                  \
 254         }                                                               \
 255         if (_start % _ts) {                                             \
 256                 _cshift = _start % _ts;                                 \
 257                 _mask = _bt_make_mask(type, _cshift);                   \
 258                 _cmask = _bt_lshift((type) (_v), _cshift);              \
 259                 _cmask &= ~_mask;                                       \
 260                 _ptr[_this_unit] &= _mask;                              \
 261                 _ptr[_this_unit] |= _cmask;                             \
 262                 _bt_safe_rshift(_v, _ts - _cshift);                     \
 263                 _start += _ts - _cshift;                                \
 264                 _this_unit++;                                           \
 265         }                                                               \
 266         for (; _this_unit < _end_unit - 1; _this_unit++) {              \
 267                 _ptr[_this_unit] = (type) _v;                           \
 268                 _bt_safe_rshift(_v, _ts);                               \
 269                 _start += _ts;                                          \
 270         }                                                               \
 271         if (_end % _ts) {                                               \
 272                 _mask = _bt_make_mask_complement(type, _end % _ts);     \
 273                 _cmask = (type) _v;                                     \
 274                 _cmask &= ~_mask;                                       \
 275                 _ptr[_this_unit] &= _mask;                              \
 276                 _ptr[_this_unit] |= _cmask;                             \
 277         } else                                                          \
 278                 _ptr[_this_unit] = (type) _v;                           \
 279 } while (0)
 280
 281 #define _bt_bitfield_write_be(ptr, type, start, length, v)              \
 282 do {                                                                    \
 283         __typeof__(v) _v = (v);                                         \
 284         type *_ptr = (void *) (ptr);                                    \
 285         unsigned long _start = (start), _length = (length);             \
 286         type _mask, _cmask;                                             \
 287         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 288         unsigned long _start_unit, _end_unit, _this_unit;               \
 289         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 290                                                                         \
 291         if (!_length)                                                   \
 292                 break;                                                  \
 293                                                                         \
 294         _end = _start + _length;                                        \
 295         _start_unit = _start / _ts;                                     \
 296         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 297                                                                         \
 298         /* Trim v high bits */                                          \
 299         if (_length < sizeof(_v) * CHAR_BIT)                            \
 300                 _v &= _bt_make_mask(__typeof__(_v), _length);           \
 301                                                                         \
 302         /* We can now append v with a simple "or", shift it piece-wise */ \
 303         _this_unit = _end_unit - 1;                                     \
 304         if (_start_unit == _end_unit - 1) {                             \
 305                 _mask = _bt_make_mask(type, (_ts - (_end % _ts)) % _ts); \
 306                 if (_start % _ts)                                       \
 307                         _mask |= _bt_make_mask_complement(type, _ts - (_start % _ts)); \
 308                 _cmask = _bt_lshift((type) (_v), (_ts - (_end % _ts)) % _ts); \
 309                 _cmask &= ~_mask;                                       \
 310                 _ptr[_this_unit] &= _mask;                              \
 311                 _ptr[_this_unit] |= _cmask;                             \
 312                 break;                                                  \
 313         }                                                               \
 314         if (_end % _ts) {                                               \
 315                 _cshift = _end % _ts;                                   \
 316                 _mask = _bt_make_mask(type, _ts - _cshift);             \
 317                 _cmask = _bt_lshift((type) (_v), _ts - _cshift);        \
 318                 _cmask &= ~_mask;                                       \
 319                 _ptr[_this_unit] &= _mask;                              \
 320                 _ptr[_this_unit] |= _cmask;                             \
 321                 _bt_safe_rshift(_v, _cshift);                           \
 322                 _end -= _cshift;                                        \
 323                 _this_unit--;                                           \
 324         }                                                               \
 325         for (; (long) _this_unit >= (long) _start_unit + 1; _this_unit--) { \
 326                 _ptr[_this_unit] = (type) _v;                           \
 327                 _bt_safe_rshift(_v, _ts);                               \
 328                 _end -= _ts;                                            \
 329         }                                                               \
 330         if (_start % _ts) {                                             \
 331                 _mask = _bt_make_mask_complement(type, _ts - (_start % _ts)); \
 332                 _cmask = (type) _v;                                     \
 333                 _cmask &= ~_mask;                                       \
 334                 _ptr[_this_unit] &= _mask;                              \
 335                 _ptr[_this_unit] |= _cmask;                             \
 336         } else                                                          \
 337                 _ptr[_this_unit] = (type) _v;                           \
 338 } while (0)
 339
 340 /*
 341  * bt_bitfield_write - write integer to a bitfield in native endianness
 342  * bt_bitfield_write_le - write integer to a bitfield in little endian
 343  * bt_bitfield_write_be - write integer to a bitfield in big endian
 344  */
 345
 346 #if (BYTE_ORDER == LITTLE_ENDIAN)
 347
 348 #define bt_bitfield_write(ptr, type, start, length, v)                  \
 349         _bt_bitfield_write_le(ptr, type, start, length, v)
 350
 351 #define bt_bitfield_write_le(ptr, type, start, length, v)               \
 352         _bt_bitfield_write_le(ptr, type, start, length, v)
 353
 354 #define bt_bitfield_write_be(ptr, type, start, length, v)               \
 355         _bt_bitfield_write_be(ptr, unsigned char, start, length, v)
 356
 357 #elif (BYTE_ORDER == BIG_ENDIAN)
 358
 359 #define bt_bitfield_write(ptr, type, start, length, v)                  \
 360         _bt_bitfield_write_be(ptr, type, start, length, v)
 361
 362 #define bt_bitfield_write_le(ptr, type, start, length, v)               \
 363         _bt_bitfield_write_le(ptr, unsigned char, start, length, v)
 364
 365 #define bt_bitfield_write_be(ptr, type, start, length, v)               \
 366         _bt_bitfield_write_be(ptr, type, start, length, v)
 367
 368 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 369
 370 #error "Byte order not supported"
 371
 372 #endif
 373
 374 #define _bt_bitfield_read_le(ptr, type, start, length, vptr)            \
 375 do {                                                                    \
 376         __typeof__(*(vptr)) *_vptr = (vptr);                            \
 377         __typeof__(*_vptr) _v;                                          \
 378         type *_ptr = (void *) (ptr);                                    \
 379         unsigned long _start = (start), _length = (length);             \
 380         type _mask, _cmask;                                             \
 381         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 382         unsigned long _start_unit, _end_unit, _this_unit;               \
 383         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 384         bool _is_signed_type;                                           \
 385                                                                         \
 386         if (!_length) {                                                 \
 387                 *_vptr = 0;                                             \
 388                 break;                                                  \
 389         }                                                               \
 390                                                                         \
 391         _end = _start + _length;                                        \
 392         _start_unit = _start / _ts;                                     \
 393         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 394                                                                         \
 395         _this_unit = _end_unit - 1;                                     \
 396         _BT_DIAG_PUSH                                                   \
 397         _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
 398         _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
 399         _BT_DIAG_POP                                                    \
 400         if (_is_signed_type                                             \
 401             && (_ptr[_this_unit] & _bt_lshift((type) 1, (_end % _ts ? _end % _ts : _ts) - 1))) \
 402                 _v = ~(__typeof__(_v)) 0;                               \
 403         else                                                            \
 404                 _v = 0;                                                 \
 405         if (_start_unit == _end_unit - 1) {                             \
 406                 _cmask = _ptr[_this_unit];                              \
 407                 _cmask = _bt_rshift(_cmask, _start % _ts);              \
 408                 if ((_end - _start) % _ts) {                            \
 409                         _mask = _bt_make_mask(type, _end - _start);     \
 410                         _cmask &= _mask;                                \
 411                 }                                                       \
 412                 _bt_safe_lshift(_v, _end - _start);                     \
 413                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 414                 *_vptr = _v;                                            \
 415                 break;                                                  \
 416         }                                                               \
 417         if (_end % _ts) {                                               \
 418                 _cshift = _end % _ts;                                   \
 419                 _mask = _bt_make_mask(type, _cshift);                   \
 420                 _cmask = _ptr[_this_unit];                              \
 421                 _cmask &= _mask;                                        \
 422                 _bt_safe_lshift(_v, _cshift);                           \
 423                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 424                 _end -= _cshift;                                        \
 425                 _this_unit--;                                           \
 426         }                                                               \
 427         for (; (long) _this_unit >= (long) _start_unit + 1; _this_unit--) { \
 428                 _bt_safe_lshift(_v, _ts);                               \
 429                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 430                 _end -= _ts;                                            \
 431         }                                                               \
 432         if (_start % _ts) {                                             \
 433                 _mask = _bt_make_mask(type, _ts - (_start % _ts));      \
 434                 _cmask = _ptr[_this_unit];                              \
 435                 _cmask = _bt_rshift(_cmask, _start % _ts);              \
 436                 _cmask &= _mask;                                        \
 437                 _bt_safe_lshift(_v, _ts - (_start % _ts));              \
 438                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 439         } else {                                                        \
 440                 _bt_safe_lshift(_v, _ts);                               \
 441                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 442         }                                                               \
 443         *_vptr = _v;                                                    \
 444 } while (0)
 445
 446 #define _bt_bitfield_read_be(ptr, type, start, length, vptr)            \
 447 do {                                                                    \
 448         __typeof__(*(vptr)) *_vptr = (vptr);                            \
 449         __typeof__(*_vptr) _v;                                          \
 450         type *_ptr = (void *) (ptr);                                    \
 451         unsigned long _start = (start), _length = (length);             \
 452         type _mask, _cmask;                                             \
 453         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 454         unsigned long _start_unit, _end_unit, _this_unit;               \
 455         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 456         bool _is_signed_type;                                           \
 457                                                                         \
 458         if (!_length) {                                                 \
 459                 *_vptr = 0;                                             \
 460                 break;                                                  \
 461         }                                                               \
 462                                                                         \
 463         _end = _start + _length;                                        \
 464         _start_unit = _start / _ts;                                     \
 465         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 466                                                                         \
 467         _this_unit = _start_unit;                                       \
 468         _BT_DIAG_PUSH                                                   \
 469         _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
 470         _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
 471         _BT_DIAG_POP                                                    \
 472         if (_is_signed_type                                             \
 473             && (_ptr[_this_unit] & _bt_lshift((type) 1, _ts - (_start % _ts) - 1))) \
 474                 _v = ~(__typeof__(_v)) 0;                               \
 475         else                                                            \
 476                 _v = 0;                                                 \
 477         if (_start_unit == _end_unit - 1) {                             \
 478                 _cmask = _ptr[_this_unit];                              \
 479                 _cmask = _bt_rshift(_cmask, (_ts - (_end % _ts)) % _ts); \
 480                 if ((_end - _start) % _ts) {                            \
 481                         _mask = _bt_make_mask(type, _end - _start);     \
 482                         _cmask &= _mask;                                \
 483                 }                                                       \
 484                 _bt_safe_lshift(_v, _end - _start);                     \
 485                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 486                 *_vptr = _v;                                            \
 487                 break;                                                  \
 488         }                                                               \
 489         if (_start % _ts) {                                             \
 490                 _cshift = _start % _ts;                                 \
 491                 _mask = _bt_make_mask(type, _ts - _cshift);             \
 492                 _cmask = _ptr[_this_unit];                              \
 493                 _cmask &= _mask;                                        \
 494                 _bt_safe_lshift(_v, _ts - _cshift);                     \
 495                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 496                 _start += _ts - _cshift;                                \
 497                 _this_unit++;                                           \
 498         }                                                               \
 499         for (; _this_unit < _end_unit - 1; _this_unit++) {              \
 500                 _bt_safe_lshift(_v, _ts);                               \
 501                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 502                 _start += _ts;                                          \
 503         }                                                               \
 504         if (_end % _ts) {                                               \
 505                 _mask = _bt_make_mask(type, _end % _ts);                \
 506                 _cmask = _ptr[_this_unit];                              \
 507                 _cmask = _bt_rshift(_cmask, _ts - (_end % _ts));        \
 508                 _cmask &= _mask;                                        \
 509                 _bt_safe_lshift(_v, _end % _ts);                        \
 510                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 511         } else {                                                        \
 512                 _bt_safe_lshift(_v, _ts);                               \
 513                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 514         }                                                               \
 515         *_vptr = _v;                                                    \
 516 } while (0)
 517
 518 /*
 519  * bt_bitfield_read - read integer from a bitfield in native endianness
 520  * bt_bitfield_read_le - read integer from a bitfield in little endian
 521  * bt_bitfield_read_be - read integer from a bitfield in big endian
 522  */
 523
 524 #if (BYTE_ORDER == LITTLE_ENDIAN)
 525
 526 #define bt_bitfield_read(ptr, type, start, length, vptr)                \
 527         _bt_bitfield_read_le(ptr, type, start, length, vptr)
 528
 529 #define bt_bitfield_read_le(ptr, type, start, length, vptr)             \
 530         _bt_bitfield_read_le(ptr, type, start, length, vptr)
 531
 532 #define bt_bitfield_read_be(ptr, type, start, length, vptr)             \
 533         _bt_bitfield_read_be(ptr, unsigned char, start, length, vptr)
 534
 535 #elif (BYTE_ORDER == BIG_ENDIAN)
 536
 537 #define bt_bitfield_read(ptr, type, start, length, vptr)                \
 538         _bt_bitfield_read_be(ptr, type, start, length, vptr)
 539
 540 #define bt_bitfield_read_le(ptr, type, start, length, vptr)             \
 541         _bt_bitfield_read_le(ptr, unsigned char, start, length, vptr)
 542
 543 #define bt_bitfield_read_be(ptr, type, start, length, vptr)             \
 544         _bt_bitfield_read_be(ptr, type, start, length, vptr)
 545
 546 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 547
 548 #error "Byte order not supported"
 549
 550 #endif
 551
 552 #endif /* _BABELTRACE_BITFIELD_H */