lib/bitfield.h

   1 /* SPDX-License-Identifier: MIT
   2  *
   3  * Copyright 2010-2019 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  */
   5
   6 #ifndef _BABELTRACE_BITFIELD_H
   7 #define _BABELTRACE_BITFIELD_H
   8
   9 #include <linux/types.h>
  10 #include <lttng-endian.h>
  11
  12 #ifndef CHAR_BIT
  13 #define CHAR_BIT 8
  14 #endif
  15
  16 /*
  17  * This header strictly follows the C99 standard, except for use of the
  18  * compiler-specific __typeof__.
  19  */
  20
  21 /*
  22  * This bitfield header requires the compiler representation of signed
  23  * integers to be two's complement.
  24  */
  25 #if (-1 != ~0)
  26 #error "bitfield.h requires the compiler representation of signed integers to be two's complement."
  27 #endif
  28
  29 /*
  30  * _bt_is_signed_type() willingly generates comparison of unsigned
  31  * expression < 0, which is always false. Silence compiler warnings.
  32  * GCC versions lower than 4.6.0 do not accept diagnostic pragma inside
  33  * functions.
  34  */
  35 #if defined(__GNUC__) && (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) >= 40600
  36 # define _BT_DIAG_PUSH                  _Pragma("GCC diagnostic push")
  37 # define _BT_DIAG_POP                   _Pragma("GCC diagnostic pop")
  38
  39 # define _BT_DIAG_STRINGIFY_1(x)        #x
  40 # define _BT_DIAG_STRINGIFY(x)          _BT_DIAG_STRINGIFY_1(x)
  41
  42 # define _BT_DIAG_IGNORE(option)        \
  43         _Pragma(_BT_DIAG_STRINGIFY(GCC diagnostic ignored option))
  44 # define _BT_DIAG_IGNORE_TYPE_LIMITS    _BT_DIAG_IGNORE("-Wtype-limits")
  45 #else
  46 # define _BT_DIAG_PUSH
  47 # define _BT_DIAG_POP
  48 # define _BT_DIAG_IGNORE
  49 # define _BT_DIAG_IGNORE_TYPE_LIMITS
  50 #endif
  51
  52 #define _bt_is_signed_type(type)        ((type) -1 < (type) 0)
  53
  54 /*
  55  * Produce a build-time error if the condition `cond` is non-zero.
  56  * Evaluates as a size_t expression.
  57  */
  58 #define _BT_BUILD_ASSERT(cond)                                  \
  59         sizeof(struct { int f:(2 * !!(cond) - 1); })
  60
  61 /*
  62  * Cast value `v` to an unsigned integer of the same size as `v`.
  63  */
  64 #define _bt_cast_value_to_unsigned(v)                                   \
  65         (sizeof(v) == sizeof(uint8_t) ? (uint8_t) (v) :                 \
  66         sizeof(v) == sizeof(uint16_t) ? (uint16_t) (v) :                \
  67         sizeof(v) == sizeof(uint32_t) ? (uint32_t) (v) :                \
  68         sizeof(v) == sizeof(uint64_t) ? (uint64_t) (v) :                \
  69         _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
  70
  71 /*
  72  * Cast value `v` to an unsigned integer type of the size of type `type`
  73  * *without* sign-extension.
  74  *
  75  * The unsigned cast ensures that we're not shifting a negative value,
  76  * which is undefined in C. However, this limits the maximum type size
  77  * of `type` to 64-bit. Generate a compile-time error if the size of
  78  * `type` is larger than 64-bit.
  79  */
  80 #define _bt_cast_value_to_unsigned_type(type, v)                        \
  81         (sizeof(type) == sizeof(uint8_t) ?                              \
  82                 (uint8_t) _bt_cast_value_to_unsigned(v) :               \
  83         sizeof(type) == sizeof(uint16_t) ?                              \
  84                 (uint16_t) _bt_cast_value_to_unsigned(v) :              \
  85         sizeof(type) == sizeof(uint32_t) ?                              \
  86                 (uint32_t) _bt_cast_value_to_unsigned(v) :              \
  87         sizeof(type) == sizeof(uint64_t) ?                              \
  88                 (uint64_t) _bt_cast_value_to_unsigned(v) :              \
  89         _BT_BUILD_ASSERT(sizeof(v) <= sizeof(uint64_t)))
  90
  91 /*
  92  * _bt_fill_mask evaluates to a "type" integer with all bits set.
  93  */
  94 #define _bt_fill_mask(type)     ((type) ~(type) 0)
  95
  96 /*
  97  * Left shift a value `v` of `shift` bits.
  98  *
  99  * The type of `v` can be signed or unsigned integer.
 100  * The value of `shift` must be less than the size of `v` (in bits),
 101  * otherwise the behavior is undefined.
 102  * Evaluates to the result of the shift operation.
 103  *
 104  * According to the C99 standard, left shift of a left hand-side signed
 105  * type is undefined if it has a negative value or if the result cannot
 106  * be represented in the result type. This bitfield header discards the
 107  * bits that are left-shifted beyond the result type representation,
 108  * which is the behavior of an unsigned type left shift operation.
 109  * Therefore, always perform left shift on an unsigned type.
 110  *
 111  * This macro should not be used if `shift` can be greater or equal than
 112  * the bitwidth of `v`. See `_bt_safe_lshift`.
 113  */
 114 #define _bt_lshift(v, shift)                                            \
 115         ((__typeof__(v)) (_bt_cast_value_to_unsigned(v) << (shift)))
 116
 117 /*
 118  * Generate a mask of type `type` with the `length` least significant bits
 119  * cleared, and the most significant bits set.
 120  */
 121 #define _bt_make_mask_complement(type, length)                          \
 122         _bt_lshift(_bt_fill_mask(type), length)
 123
 124 /*
 125  * Generate a mask of type `type` with the `length` least significant bits
 126  * set, and the most significant bits cleared.
 127  */
 128 #define _bt_make_mask(type, length)                                     \
 129         ((type) ~_bt_make_mask_complement(type, length))
 130
 131 /*
 132  * Right shift a value `v` of `shift` bits.
 133  *
 134  * The type of `v` can be signed or unsigned integer.
 135  * The value of `shift` must be less than the size of `v` (in bits),
 136  * otherwise the behavior is undefined.
 137  * Evaluates to the result of the shift operation.
 138  *
 139  * According to the C99 standard, right shift of a left hand-side signed
 140  * type which has a negative value is implementation defined. This
 141  * bitfield header relies on the right shift implementation carrying the
 142  * sign bit. If the compiler implementation has a different behavior,
 143  * emulate carrying the sign bit.
 144  *
 145  * This macro should not be used if `shift` can be greater or equal than
 146  * the bitwidth of `v`. See `_bt_safe_rshift`.
 147  */
 148 #if ((-1 >> 1) == -1)
 149 #define _bt_rshift(v, shift)    ((v) >> (shift))
 150 #else
 151 #define _bt_rshift(v, shift)                                            \
 152         ((__typeof__(v)) ((_bt_cast_value_to_unsigned(v) >> (shift)) |  \
 153                 ((v) < 0 ? _bt_make_mask_complement(__typeof__(v),      \
 154                         sizeof(v) * CHAR_BIT - (shift)) : 0)))
 155 #endif
 156
 157 /*
 158  * Right shift a signed or unsigned integer with `shift` value being an
 159  * arbitrary number of bits. `v` is modified by this macro. The shift
 160  * is transformed into a sequence of `_nr_partial_shifts` consecutive
 161  * shift operations, each of a number of bits smaller than the bitwidth
 162  * of `v`, ending with a shift of the number of left over bits.
 163  */
 164 #define _bt_safe_rshift(v, shift)                                       \
 165 do {                                                                    \
 166         unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
 167         unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
 168                                                                         \
 169         for (; _nr_partial_shifts; _nr_partial_shifts--)                \
 170                 (v) = _bt_rshift(v, sizeof(v) * CHAR_BIT - 1);          \
 171         (v) = _bt_rshift(v, _leftover_bits);                            \
 172 } while (0)
 173
 174 /*
 175  * Left shift a signed or unsigned integer with `shift` value being an
 176  * arbitrary number of bits. `v` is modified by this macro. The shift
 177  * is transformed into a sequence of `_nr_partial_shifts` consecutive
 178  * shift operations, each of a number of bits smaller than the bitwidth
 179  * of `v`, ending with a shift of the number of left over bits.
 180  */
 181 #define _bt_safe_lshift(v, shift)                                       \
 182 do {                                                                    \
 183         unsigned long _nr_partial_shifts = (shift) / (sizeof(v) * CHAR_BIT - 1); \
 184         unsigned long _leftover_bits = (shift) % (sizeof(v) * CHAR_BIT - 1); \
 185                                                                         \
 186         for (; _nr_partial_shifts; _nr_partial_shifts--)                \
 187                 (v) = _bt_lshift(v, sizeof(v) * CHAR_BIT - 1);          \
 188         (v) = _bt_lshift(v, _leftover_bits);                            \
 189 } while (0)
 190
 191 /*
 192  * bt_bitfield_write - write integer to a bitfield in native endianness
 193  *
 194  * Save integer to the bitfield, which starts at the "start" bit, has "len"
 195  * bits.
 196  * The inside of a bitfield is from high bits to low bits.
 197  * Uses native endianness.
 198  * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
 199  * For signed "v", sign-extend v if bitfield is larger than v.
 200  *
 201  * On little endian, bytes are placed from the less significant to the most
 202  * significant. Also, consecutive bitfields are placed from lower bits to higher
 203  * bits.
 204  *
 205  * On big endian, bytes are places from most significant to less significant.
 206  * Also, consecutive bitfields are placed from higher to lower bits.
 207  */
 208
 209 #define _bt_bitfield_write_le(ptr, type, start, length, v)              \
 210 do {                                                                    \
 211         __typeof__(v) _v = (v);                                 \
 212         type *_ptr = (void *) (ptr);                                    \
 213         unsigned long _start = (start), _length = (length);             \
 214         type _mask, _cmask;                                             \
 215         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 216         unsigned long _start_unit, _end_unit, _this_unit;               \
 217         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 218                                                                         \
 219         if (!_length)                                                   \
 220                 break;                                                  \
 221                                                                         \
 222         _end = _start + _length;                                        \
 223         _start_unit = _start / _ts;                                     \
 224         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 225                                                                         \
 226         /* Trim v high bits */                                          \
 227         if (_length < sizeof(_v) * CHAR_BIT)                            \
 228                 _v &= _bt_make_mask(__typeof__(_v), _length);           \
 229                                                                         \
 230         /* We can now append v with a simple "or", shift it piece-wise */ \
 231         _this_unit = _start_unit;                                       \
 232         if (_start_unit == _end_unit - 1) {                             \
 233                 _mask = _bt_make_mask(type, _start % _ts);              \
 234                 if (_end % _ts)                                         \
 235                         _mask |= _bt_make_mask_complement(type, _end % _ts); \
 236                 _cmask = _bt_lshift((type) (_v), _start % _ts);         \
 237                 _cmask &= ~_mask;                                       \
 238                 _ptr[_this_unit] &= _mask;                              \
 239                 _ptr[_this_unit] |= _cmask;                             \
 240                 break;                                                  \
 241         }                                                               \
 242         if (_start % _ts) {                                             \
 243                 _cshift = _start % _ts;                                 \
 244                 _mask = _bt_make_mask(type, _cshift);                   \
 245                 _cmask = _bt_lshift((type) (_v), _cshift);              \
 246                 _cmask &= ~_mask;                                       \
 247                 _ptr[_this_unit] &= _mask;                              \
 248                 _ptr[_this_unit] |= _cmask;                             \
 249                 _bt_safe_rshift(_v, _ts - _cshift);                     \
 250                 _start += _ts - _cshift;                                \
 251                 _this_unit++;                                           \
 252         }                                                               \
 253         for (; _this_unit < _end_unit - 1; _this_unit++) {              \
 254                 _ptr[_this_unit] = (type) _v;                           \
 255                 _bt_safe_rshift(_v, _ts);                               \
 256                 _start += _ts;                                          \
 257         }                                                               \
 258         if (_end % _ts) {                                               \
 259                 _mask = _bt_make_mask_complement(type, _end % _ts);     \
 260                 _cmask = (type) _v;                                     \
 261                 _cmask &= ~_mask;                                       \
 262                 _ptr[_this_unit] &= _mask;                              \
 263                 _ptr[_this_unit] |= _cmask;                             \
 264         } else                                                          \
 265                 _ptr[_this_unit] = (type) _v;                           \
 266 } while (0)
 267
 268 #define _bt_bitfield_write_be(ptr, type, start, length, v)              \
 269 do {                                                                    \
 270         __typeof__(v) _v = (v);                                         \
 271         type *_ptr = (void *) (ptr);                                    \
 272         unsigned long _start = (start), _length = (length);             \
 273         type _mask, _cmask;                                             \
 274         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 275         unsigned long _start_unit, _end_unit, _this_unit;               \
 276         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 277                                                                         \
 278         if (!_length)                                                   \
 279                 break;                                                  \
 280                                                                         \
 281         _end = _start + _length;                                        \
 282         _start_unit = _start / _ts;                                     \
 283         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 284                                                                         \
 285         /* Trim v high bits */                                          \
 286         if (_length < sizeof(_v) * CHAR_BIT)                            \
 287                 _v &= _bt_make_mask(__typeof__(_v), _length);           \
 288                                                                         \
 289         /* We can now append v with a simple "or", shift it piece-wise */ \
 290         _this_unit = _end_unit - 1;                                     \
 291         if (_start_unit == _end_unit - 1) {                             \
 292                 _mask = _bt_make_mask(type, (_ts - (_end % _ts)) % _ts); \
 293                 if (_start % _ts)                                       \
 294                         _mask |= _bt_make_mask_complement(type, _ts - (_start % _ts)); \
 295                 _cmask = _bt_lshift((type) (_v), (_ts - (_end % _ts)) % _ts); \
 296                 _cmask &= ~_mask;                                       \
 297                 _ptr[_this_unit] &= _mask;                              \
 298                 _ptr[_this_unit] |= _cmask;                             \
 299                 break;                                                  \
 300         }                                                               \
 301         if (_end % _ts) {                                               \
 302                 _cshift = _end % _ts;                                   \
 303                 _mask = _bt_make_mask(type, _ts - _cshift);             \
 304                 _cmask = _bt_lshift((type) (_v), _ts - _cshift);        \
 305                 _cmask &= ~_mask;                                       \
 306                 _ptr[_this_unit] &= _mask;                              \
 307                 _ptr[_this_unit] |= _cmask;                             \
 308                 _bt_safe_rshift(_v, _cshift);                           \
 309                 _end -= _cshift;                                        \
 310                 _this_unit--;                                           \
 311         }                                                               \
 312         for (; (long) _this_unit >= (long) _start_unit + 1; _this_unit--) { \
 313                 _ptr[_this_unit] = (type) _v;                           \
 314                 _bt_safe_rshift(_v, _ts);                               \
 315                 _end -= _ts;                                            \
 316         }                                                               \
 317         if (_start % _ts) {                                             \
 318                 _mask = _bt_make_mask_complement(type, _ts - (_start % _ts)); \
 319                 _cmask = (type) _v;                                     \
 320                 _cmask &= ~_mask;                                       \
 321                 _ptr[_this_unit] &= _mask;                              \
 322                 _ptr[_this_unit] |= _cmask;                             \
 323         } else                                                          \
 324                 _ptr[_this_unit] = (type) _v;                           \
 325 } while (0)
 326
 327 /*
 328  * bt_bitfield_write - write integer to a bitfield in native endianness
 329  * bt_bitfield_write_le - write integer to a bitfield in little endian
 330  * bt_bitfield_write_be - write integer to a bitfield in big endian
 331  */
 332
 333 #if (__BYTE_ORDER == __LITTLE_ENDIAN)
 334
 335 #define bt_bitfield_write(ptr, type, start, length, v)                  \
 336         _bt_bitfield_write_le(ptr, type, start, length, v)
 337
 338 #define bt_bitfield_write_le(ptr, type, start, length, v)               \
 339         _bt_bitfield_write_le(ptr, type, start, length, v)
 340
 341 #define bt_bitfield_write_be(ptr, type, start, length, v)               \
 342         _bt_bitfield_write_be(ptr, unsigned char, start, length, v)
 343
 344 #elif (__BYTE_ORDER == __BIG_ENDIAN)
 345
 346 #define bt_bitfield_write(ptr, type, start, length, v)                  \
 347         _bt_bitfield_write_be(ptr, type, start, length, v)
 348
 349 #define bt_bitfield_write_le(ptr, type, start, length, v)               \
 350         _bt_bitfield_write_le(ptr, unsigned char, start, length, v)
 351
 352 #define bt_bitfield_write_be(ptr, type, start, length, v)               \
 353         _bt_bitfield_write_be(ptr, type, start, length, v)
 354
 355 #else /* (__BYTE_ORDER == __PDP_ENDIAN) */
 356
 357 #error "Byte order not supported"
 358
 359 #endif
 360
 361 #define _bt_bitfield_read_le(ptr, type, start, length, vptr)            \
 362 do {                                                                    \
 363         __typeof__(*(vptr)) *_vptr = (vptr);                            \
 364         __typeof__(*_vptr) _v;                                          \
 365         type *_ptr = (void *) (ptr);                                    \
 366         unsigned long _start = (start), _length = (length);             \
 367         type _mask, _cmask;                                             \
 368         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 369         unsigned long _start_unit, _end_unit, _this_unit;               \
 370         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 371         bool _is_signed_type;                                           \
 372                                                                         \
 373         if (!_length) {                                                 \
 374                 *_vptr = 0;                                             \
 375                 break;                                                  \
 376         }                                                               \
 377                                                                         \
 378         _end = _start + _length;                                        \
 379         _start_unit = _start / _ts;                                     \
 380         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 381                                                                         \
 382         _this_unit = _end_unit - 1;                                     \
 383         _BT_DIAG_PUSH                                                   \
 384         _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
 385         _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
 386         _BT_DIAG_POP                                                    \
 387         if (_is_signed_type                                             \
 388             && (_ptr[_this_unit] & _bt_lshift((type) 1, (_end % _ts ? _end % _ts : _ts) - 1))) \
 389                 _v = ~(__typeof__(_v)) 0;                               \
 390         else                                                            \
 391                 _v = 0;                                                 \
 392         if (_start_unit == _end_unit - 1) {                             \
 393                 _cmask = _ptr[_this_unit];                              \
 394                 _cmask = _bt_rshift(_cmask, _start % _ts);              \
 395                 if ((_end - _start) % _ts) {                            \
 396                         _mask = _bt_make_mask(type, _end - _start);     \
 397                         _cmask &= _mask;                                \
 398                 }                                                       \
 399                 _bt_safe_lshift(_v, _end - _start);                     \
 400                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 401                 *_vptr = _v;                                            \
 402                 break;                                                  \
 403         }                                                               \
 404         if (_end % _ts) {                                               \
 405                 _cshift = _end % _ts;                                   \
 406                 _mask = _bt_make_mask(type, _cshift);                   \
 407                 _cmask = _ptr[_this_unit];                              \
 408                 _cmask &= _mask;                                        \
 409                 _bt_safe_lshift(_v, _cshift);                           \
 410                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 411                 _end -= _cshift;                                        \
 412                 _this_unit--;                                           \
 413         }                                                               \
 414         for (; (long) _this_unit >= (long) _start_unit + 1; _this_unit--) { \
 415                 _bt_safe_lshift(_v, _ts);                               \
 416                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 417                 _end -= _ts;                                            \
 418         }                                                               \
 419         if (_start % _ts) {                                             \
 420                 _mask = _bt_make_mask(type, _ts - (_start % _ts));      \
 421                 _cmask = _ptr[_this_unit];                              \
 422                 _cmask = _bt_rshift(_cmask, _start % _ts);              \
 423                 _cmask &= _mask;                                        \
 424                 _bt_safe_lshift(_v, _ts - (_start % _ts));              \
 425                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 426         } else {                                                        \
 427                 _bt_safe_lshift(_v, _ts);                               \
 428                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 429         }                                                               \
 430         *_vptr = _v;                                                    \
 431 } while (0)
 432
 433 #define _bt_bitfield_read_be(ptr, type, start, length, vptr)            \
 434 do {                                                                    \
 435         __typeof__(*(vptr)) *_vptr = (vptr);                            \
 436         __typeof__(*_vptr) _v;                                          \
 437         type *_ptr = (void *) (ptr);                                    \
 438         unsigned long _start = (start), _length = (length);             \
 439         type _mask, _cmask;                                             \
 440         unsigned long _ts = sizeof(type) * CHAR_BIT; /* type size */    \
 441         unsigned long _start_unit, _end_unit, _this_unit;               \
 442         unsigned long _end, _cshift; /* _cshift is "complement shift" */ \
 443         bool _is_signed_type;                                           \
 444                                                                         \
 445         if (!_length) {                                                 \
 446                 *_vptr = 0;                                             \
 447                 break;                                                  \
 448         }                                                               \
 449                                                                         \
 450         _end = _start + _length;                                        \
 451         _start_unit = _start / _ts;                                     \
 452         _end_unit = (_end + (_ts - 1)) / _ts;                           \
 453                                                                         \
 454         _this_unit = _start_unit;                                       \
 455         _BT_DIAG_PUSH                                                   \
 456         _BT_DIAG_IGNORE_TYPE_LIMITS                                     \
 457         _is_signed_type = _bt_is_signed_type(__typeof__(_v));           \
 458         _BT_DIAG_POP                                                    \
 459         if (_is_signed_type                                             \
 460             && (_ptr[_this_unit] & _bt_lshift((type) 1, _ts - (_start % _ts) - 1))) \
 461                 _v = ~(__typeof__(_v)) 0;                               \
 462         else                                                            \
 463                 _v = 0;                                                 \
 464         if (_start_unit == _end_unit - 1) {                             \
 465                 _cmask = _ptr[_this_unit];                              \
 466                 _cmask = _bt_rshift(_cmask, (_ts - (_end % _ts)) % _ts); \
 467                 if ((_end - _start) % _ts) {                            \
 468                         _mask = _bt_make_mask(type, _end - _start);     \
 469                         _cmask &= _mask;                                \
 470                 }                                                       \
 471                 _bt_safe_lshift(_v, _end - _start);                     \
 472                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 473                 *_vptr = _v;                                            \
 474                 break;                                                  \
 475         }                                                               \
 476         if (_start % _ts) {                                             \
 477                 _cshift = _start % _ts;                                 \
 478                 _mask = _bt_make_mask(type, _ts - _cshift);             \
 479                 _cmask = _ptr[_this_unit];                              \
 480                 _cmask &= _mask;                                        \
 481                 _bt_safe_lshift(_v, _ts - _cshift);                     \
 482                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 483                 _start += _ts - _cshift;                                \
 484                 _this_unit++;                                           \
 485         }                                                               \
 486         for (; _this_unit < _end_unit - 1; _this_unit++) {              \
 487                 _bt_safe_lshift(_v, _ts);                               \
 488                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 489                 _start += _ts;                                          \
 490         }                                                               \
 491         if (_end % _ts) {                                               \
 492                 _mask = _bt_make_mask(type, _end % _ts);                \
 493                 _cmask = _ptr[_this_unit];                              \
 494                 _cmask = _bt_rshift(_cmask, _ts - (_end % _ts));        \
 495                 _cmask &= _mask;                                        \
 496                 _bt_safe_lshift(_v, _end % _ts);                        \
 497                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _cmask); \
 498         } else {                                                        \
 499                 _bt_safe_lshift(_v, _ts);                               \
 500                 _v |= _bt_cast_value_to_unsigned_type(__typeof__(_v), _ptr[_this_unit]); \
 501         }                                                               \
 502         *_vptr = _v;                                                    \
 503 } while (0)
 504
 505 /*
 506  * bt_bitfield_read - read integer from a bitfield in native endianness
 507  * bt_bitfield_read_le - read integer from a bitfield in little endian
 508  * bt_bitfield_read_be - read integer from a bitfield in big endian
 509  */
 510
 511 #if (__BYTE_ORDER == __LITTLE_ENDIAN)
 512
 513 #define bt_bitfield_read(ptr, type, start, length, vptr)                \
 514         _bt_bitfield_read_le(ptr, type, start, length, vptr)
 515
 516 #define bt_bitfield_read_le(ptr, type, start, length, vptr)             \
 517         _bt_bitfield_read_le(ptr, type, start, length, vptr)
 518
 519 #define bt_bitfield_read_be(ptr, type, start, length, vptr)             \
 520         _bt_bitfield_read_be(ptr, unsigned char, start, length, vptr)
 521
 522 #elif (__BYTE_ORDER == __BIG_ENDIAN)
 523
 524 #define bt_bitfield_read(ptr, type, start, length, vptr)                \
 525         _bt_bitfield_read_be(ptr, type, start, length, vptr)
 526
 527 #define bt_bitfield_read_le(ptr, type, start, length, vptr)             \
 528         _bt_bitfield_read_le(ptr, unsigned char, start, length, vptr)
 529
 530 #define bt_bitfield_read_be(ptr, type, start, length, vptr)             \
 531         _bt_bitfield_read_be(ptr, type, start, length, vptr)
 532
 533 #else /* (__BYTE_ORDER == __PDP_ENDIAN) */
 534
 535 #error "Byte order not supported"
 536
 537 #endif
 538
 539 #endif /* _BABELTRACE_BITFIELD_H */