include/babeltrace/bitfield.h

   1 #ifndef _BABELTRACE_BITFIELD_H
   2 #define _BABELTRACE_BITFIELD_H
   3
   4 /*
   5  * BabelTrace
   6  *
   7  * Bitfields read/write functions.
   8  *
   9  * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this software and associated documentation files (the "Software"), to deal
  13  * in the Software without restriction, including without limitation the rights
  14  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15  * copies of the Software, and to permit persons to whom the Software is
  16  * furnished to do so, subject to the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  */
  21
  22 #include <stdint.h>     /* C99 5.2.4.2 Numerical limits */
  23 #include <limits.h>     /* C99 5.2.4.2 Numerical limits */
  24 #include <assert.h>
  25 #include <babeltrace/endian.h>  /* Non-standard BIG_ENDIAN, LITTLE_ENDIAN, BYTE_ORDER */
  26
  27 /* We can't shift a int from 32 bit, >> 32 and << 32 on int is undefined */
  28 #define _bt_piecewise_rshift(_v, _shift)                                \
  29 ({                                                                      \
  30         typeof(_v) ___v = (_v);                                         \
  31         typeof(_shift) ___shift = (_shift);                             \
  32         unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);  \
  33         unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
  34                                                                         \
  35         for (; sb; sb--)                                                \
  36                 ___v >>= sizeof(___v) * CHAR_BIT - 1;                   \
  37         ___v >>= final;                                                 \
  38 })
  39
  40 #define _bt_piecewise_lshift(_v, _shift)                                \
  41 ({                                                                      \
  42         typeof(_v) ___v = (_v);                                         \
  43         typeof(_shift) ___shift = (_shift);                             \
  44         unsigned long sb = (___shift) / (sizeof(___v) * CHAR_BIT - 1);  \
  45         unsigned long final = (___shift) % (sizeof(___v) * CHAR_BIT - 1); \
  46                                                                         \
  47         for (; sb; sb--)                                                \
  48                 ___v <<= sizeof(___v) * CHAR_BIT - 1;                   \
  49         ___v <<= final;                                                 \
  50 })
  51
  52 #define _bt_is_signed_type(type)        (((type)(-1)) < 0)
  53
  54 #define _bt_unsigned_cast(type, v)                                      \
  55 ({                                                                      \
  56         (sizeof(v) < sizeof(type)) ?                                    \
  57                 ((type) (v)) & (~(~(type) 0 << (sizeof(v) * CHAR_BIT))) : \
  58                 (type) (v);                                             \
  59 })
  60
  61 /*
  62  * bt_bitfield_write - write integer to a bitfield in native endianness
  63  *
  64  * Save integer to the bitfield, which starts at the "start" bit, has "len"
  65  * bits.
  66  * The inside of a bitfield is from high bits to low bits.
  67  * Uses native endianness.
  68  * For unsigned "v", pad MSB with 0 if bitfield is larger than v.
  69  * For signed "v", sign-extend v if bitfield is larger than v.
  70  *
  71  * On little endian, bytes are placed from the less significant to the most
  72  * significant. Also, consecutive bitfields are placed from lower bits to higher
  73  * bits.
  74  *
  75  * On big endian, bytes are places from most significant to less significant.
  76  * Also, consecutive bitfields are placed from higher to lower bits.
  77  */
  78
  79 #define _bt_bitfield_write_le(_ptr, type, _start, _length, _v)          \
  80 do {                                                                    \
  81         typeof(_v) __v = (_v);                                          \
  82         type *__ptr = (void *) (_ptr);                                  \
  83         unsigned long __start = (_start), __length = (_length);         \
  84         type mask, cmask;                                               \
  85         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
  86         unsigned long start_unit, end_unit, this_unit;                  \
  87         unsigned long end, cshift; /* cshift is "complement shift" */   \
  88                                                                         \
  89         if (!__length)                                                  \
  90                 break;                                                  \
  91                                                                         \
  92         end = __start + __length;                                       \
  93         start_unit = __start / ts;                                      \
  94         end_unit = (end + (ts - 1)) / ts;                               \
  95                                                                         \
  96         /* Trim v high bits */                                          \
  97         if (__length < sizeof(__v) * CHAR_BIT)                          \
  98                 __v &= ~((~(typeof(__v)) 0) << __length);               \
  99                                                                         \
 100         /* We can now append v with a simple "or", shift it piece-wise */ \
 101         this_unit = start_unit;                                         \
 102         if (start_unit == end_unit - 1) {                               \
 103                 mask = ~((~(type) 0) << (__start % ts));                \
 104                 if (end % ts)                                           \
 105                         mask |= (~(type) 0) << (end % ts);              \
 106                 cmask = (type) __v << (__start % ts);                   \
 107                 cmask &= ~mask;                                         \
 108                 __ptr[this_unit] &= mask;                               \
 109                 __ptr[this_unit] |= cmask;                              \
 110                 break;                                                  \
 111         }                                                               \
 112         if (__start % ts) {                                             \
 113                 cshift = __start % ts;                                  \
 114                 mask = ~((~(type) 0) << cshift);                        \
 115                 cmask = (type) __v << cshift;                           \
 116                 cmask &= ~mask;                                         \
 117                 __ptr[this_unit] &= mask;                               \
 118                 __ptr[this_unit] |= cmask;                              \
 119                 __v = _bt_piecewise_rshift(__v, ts - cshift);           \
 120                 __start += ts - cshift;                                 \
 121                 this_unit++;                                            \
 122         }                                                               \
 123         for (; this_unit < end_unit - 1; this_unit++) {                 \
 124                 __ptr[this_unit] = (type) __v;                          \
 125                 __v = _bt_piecewise_rshift(__v, ts);                    \
 126                 __start += ts;                                          \
 127         }                                                               \
 128         if (end % ts) {                                                 \
 129                 mask = (~(type) 0) << (end % ts);                       \
 130                 cmask = (type) __v;                                     \
 131                 cmask &= ~mask;                                         \
 132                 __ptr[this_unit] &= mask;                               \
 133                 __ptr[this_unit] |= cmask;                              \
 134         } else                                                          \
 135                 __ptr[this_unit] = (type) __v;                          \
 136 } while (0)
 137
 138 #define _bt_bitfield_write_be(_ptr, type, _start, _length, _v)          \
 139 do {                                                                    \
 140         typeof(_v) __v = (_v);                                          \
 141         type *__ptr = (void *) (_ptr);                                  \
 142         unsigned long __start = (_start), __length = (_length);         \
 143         type mask, cmask;                                               \
 144         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 145         unsigned long start_unit, end_unit, this_unit;                  \
 146         unsigned long end, cshift; /* cshift is "complement shift" */   \
 147                                                                         \
 148         if (!__length)                                                  \
 149                 break;                                                  \
 150                                                                         \
 151         end = __start + __length;                                       \
 152         start_unit = __start / ts;                                      \
 153         end_unit = (end + (ts - 1)) / ts;                               \
 154                                                                         \
 155         /* Trim v high bits */                                          \
 156         if (__length < sizeof(__v) * CHAR_BIT)                          \
 157                 __v &= ~((~(typeof(__v)) 0) << __length);               \
 158                                                                         \
 159         /* We can now append v with a simple "or", shift it piece-wise */ \
 160         this_unit = end_unit - 1;                                       \
 161         if (start_unit == end_unit - 1) {                               \
 162                 mask = ~((~(type) 0) << ((ts - (end % ts)) % ts));      \
 163                 if (__start % ts)                                       \
 164                         mask |= (~((type) 0)) << (ts - (__start % ts)); \
 165                 cmask = (type) __v << ((ts - (end % ts)) % ts);         \
 166                 cmask &= ~mask;                                         \
 167                 __ptr[this_unit] &= mask;                               \
 168                 __ptr[this_unit] |= cmask;                              \
 169                 break;                                                  \
 170         }                                                               \
 171         if (end % ts) {                                                 \
 172                 cshift = end % ts;                                      \
 173                 mask = ~((~(type) 0) << (ts - cshift));                 \
 174                 cmask = (type) __v << (ts - cshift);                    \
 175                 cmask &= ~mask;                                         \
 176                 __ptr[this_unit] &= mask;                               \
 177                 __ptr[this_unit] |= cmask;                              \
 178                 __v = _bt_piecewise_rshift(__v, cshift);                \
 179                 end -= cshift;                                          \
 180                 this_unit--;                                            \
 181         }                                                               \
 182         for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
 183                 __ptr[this_unit] = (type) __v;                          \
 184                 __v = _bt_piecewise_rshift(__v, ts);                    \
 185                 end -= ts;                                              \
 186         }                                                               \
 187         if (__start % ts) {                                             \
 188                 mask = (~(type) 0) << (ts - (__start % ts));            \
 189                 cmask = (type) __v;                                     \
 190                 cmask &= ~mask;                                         \
 191                 __ptr[this_unit] &= mask;                               \
 192                 __ptr[this_unit] |= cmask;                              \
 193         } else                                                          \
 194                 __ptr[this_unit] = (type) __v;                          \
 195 } while (0)
 196
 197 /*
 198  * bt_bitfield_write - write integer to a bitfield in native endianness
 199  * bt_bitfield_write_le - write integer to a bitfield in little endian
 200  * bt_bitfield_write_be - write integer to a bitfield in big endian
 201  */
 202
 203 #if (BYTE_ORDER == LITTLE_ENDIAN)
 204
 205 #define bt_bitfield_write(ptr, type, _start, _length, _v)               \
 206         _bt_bitfield_write_le(ptr, type, _start, _length, _v)
 207
 208 #define bt_bitfield_write_le(ptr, type, _start, _length, _v)            \
 209         _bt_bitfield_write_le(ptr, type, _start, _length, _v)
 210
 211 #define bt_bitfield_write_be(ptr, type, _start, _length, _v)            \
 212         _bt_bitfield_write_be(ptr, unsigned char, _start, _length, _v)
 213
 214 #elif (BYTE_ORDER == BIG_ENDIAN)
 215
 216 #define bt_bitfield_write(ptr, type, _start, _length, _v)               \
 217         _bt_bitfield_write_be(ptr, type, _start, _length, _v)
 218
 219 #define bt_bitfield_write_le(ptr, type, _start, _length, _v)            \
 220         _bt_bitfield_write_le(ptr, unsigned char, _start, _length, _v)
 221
 222 #define bt_bitfield_write_be(ptr, type, _start, _length, _v)            \
 223         _bt_bitfield_write_be(ptr, type, _start, _length, _v)
 224
 225 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 226
 227 #error "Byte order not supported"
 228
 229 #endif
 230
 231 #define _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)        \
 232 do {                                                                    \
 233         typeof(*(_vptr)) *__vptr = (_vptr);                             \
 234         typeof(*__vptr) __v;                                            \
 235         type *__ptr = (void *) (_ptr);                                  \
 236         unsigned long __start = (_start), __length = (_length);         \
 237         type mask, cmask;                                               \
 238         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 239         unsigned long start_unit, end_unit, this_unit;                  \
 240         unsigned long end, cshift; /* cshift is "complement shift" */   \
 241                                                                         \
 242         if (!__length) {                                                \
 243                 *__vptr = 0;                                            \
 244                 break;                                                  \
 245         }                                                               \
 246                                                                         \
 247         end = __start + __length;                                       \
 248         start_unit = __start / ts;                                      \
 249         end_unit = (end + (ts - 1)) / ts;                               \
 250                                                                         \
 251         this_unit = end_unit - 1;                                       \
 252         if (_bt_is_signed_type(typeof(__v))                             \
 253             && (__ptr[this_unit] & ((type) 1 << ((end % ts ? : ts) - 1)))) \
 254                 __v = ~(typeof(__v)) 0;                                 \
 255         else                                                            \
 256                 __v = 0;                                                \
 257         if (start_unit == end_unit - 1) {                               \
 258                 cmask = __ptr[this_unit];                               \
 259                 cmask >>= (__start % ts);                               \
 260                 if ((end - __start) % ts) {                             \
 261                         mask = ~((~(type) 0) << (end - __start));       \
 262                         cmask &= mask;                                  \
 263                 }                                                       \
 264                 __v = _bt_piecewise_lshift(__v, end - __start);         \
 265                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 266                 *__vptr = __v;                                          \
 267                 break;                                                  \
 268         }                                                               \
 269         if (end % ts) {                                                 \
 270                 cshift = end % ts;                                      \
 271                 mask = ~((~(type) 0) << cshift);                        \
 272                 cmask = __ptr[this_unit];                               \
 273                 cmask &= mask;                                          \
 274                 __v = _bt_piecewise_lshift(__v, cshift);                \
 275                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 276                 end -= cshift;                                          \
 277                 this_unit--;                                            \
 278         }                                                               \
 279         for (; (long) this_unit >= (long) start_unit + 1; this_unit--) { \
 280                 __v = _bt_piecewise_lshift(__v, ts);                    \
 281                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 282                 end -= ts;                                              \
 283         }                                                               \
 284         if (__start % ts) {                                             \
 285                 mask = ~((~(type) 0) << (ts - (__start % ts)));         \
 286                 cmask = __ptr[this_unit];                               \
 287                 cmask >>= (__start % ts);                               \
 288                 cmask &= mask;                                          \
 289                 __v = _bt_piecewise_lshift(__v, ts - (__start % ts));   \
 290                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 291         } else {                                                        \
 292                 __v = _bt_piecewise_lshift(__v, ts);                    \
 293                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 294         }                                                               \
 295         *__vptr = __v;                                                  \
 296 } while (0)
 297
 298 #define _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)        \
 299 do {                                                                    \
 300         typeof(*(_vptr)) *__vptr = (_vptr);                             \
 301         typeof(*__vptr) __v;                                            \
 302         type *__ptr = (void *) (_ptr);                                  \
 303         unsigned long __start = (_start), __length = (_length);         \
 304         type mask, cmask;                                               \
 305         unsigned long ts = sizeof(type) * CHAR_BIT; /* type size */     \
 306         unsigned long start_unit, end_unit, this_unit;                  \
 307         unsigned long end, cshift; /* cshift is "complement shift" */   \
 308                                                                         \
 309         if (!__length) {                                                \
 310                 *__vptr = 0;                                            \
 311                 break;                                                  \
 312         }                                                               \
 313                                                                         \
 314         end = __start + __length;                                       \
 315         start_unit = __start / ts;                                      \
 316         end_unit = (end + (ts - 1)) / ts;                               \
 317                                                                         \
 318         this_unit = start_unit;                                         \
 319         if (_bt_is_signed_type(typeof(__v))                             \
 320             && (__ptr[this_unit] & ((type) 1 << (ts - (__start % ts) - 1)))) \
 321                 __v = ~(typeof(__v)) 0;                                 \
 322         else                                                            \
 323                 __v = 0;                                                \
 324         if (start_unit == end_unit - 1) {                               \
 325                 cmask = __ptr[this_unit];                               \
 326                 cmask >>= (ts - (end % ts)) % ts;                       \
 327                 if ((end - __start) % ts) {                             \
 328                         mask = ~((~(type) 0) << (end - __start));       \
 329                         cmask &= mask;                                  \
 330                 }                                                       \
 331                 __v = _bt_piecewise_lshift(__v, end - __start);         \
 332                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 333                 *__vptr = __v;                                          \
 334                 break;                                                  \
 335         }                                                               \
 336         if (__start % ts) {                                             \
 337                 cshift = __start % ts;                                  \
 338                 mask = ~((~(type) 0) << (ts - cshift));                 \
 339                 cmask = __ptr[this_unit];                               \
 340                 cmask &= mask;                                          \
 341                 __v = _bt_piecewise_lshift(__v, ts - cshift);           \
 342                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 343                 __start += ts - cshift;                                 \
 344                 this_unit++;                                            \
 345         }                                                               \
 346         for (; this_unit < end_unit - 1; this_unit++) {                 \
 347                 __v = _bt_piecewise_lshift(__v, ts);                    \
 348                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 349                 __start += ts;                                          \
 350         }                                                               \
 351         if (end % ts) {                                                 \
 352                 mask = ~((~(type) 0) << (end % ts));                    \
 353                 cmask = __ptr[this_unit];                               \
 354                 cmask >>= ts - (end % ts);                              \
 355                 cmask &= mask;                                          \
 356                 __v = _bt_piecewise_lshift(__v, end % ts);              \
 357                 __v |= _bt_unsigned_cast(typeof(__v), cmask);           \
 358         } else {                                                        \
 359                 __v = _bt_piecewise_lshift(__v, ts);                    \
 360                 __v |= _bt_unsigned_cast(typeof(__v), __ptr[this_unit]);\
 361         }                                                               \
 362         *__vptr = __v;                                                  \
 363 } while (0)
 364
 365 /*
 366  * bt_bitfield_read - read integer from a bitfield in native endianness
 367  * bt_bitfield_read_le - read integer from a bitfield in little endian
 368  * bt_bitfield_read_be - read integer from a bitfield in big endian
 369  */
 370
 371 #if (BYTE_ORDER == LITTLE_ENDIAN)
 372
 373 #define bt_bitfield_read(_ptr, type, _start, _length, _vptr)            \
 374         _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
 375
 376 #define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)         \
 377         _bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)
 378
 379 #define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)         \
 380         _bt_bitfield_read_be(_ptr, unsigned char, _start, _length, _vptr)
 381
 382 #elif (BYTE_ORDER == BIG_ENDIAN)
 383
 384 #define bt_bitfield_read(_ptr, type, _start, _length, _vptr)            \
 385         _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
 386
 387 #define bt_bitfield_read_le(_ptr, type, _start, _length, _vptr)         \
 388         _bt_bitfield_read_le(_ptr, unsigned char, _start, _length, _vptr)
 389
 390 #define bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)         \
 391         _bt_bitfield_read_be(_ptr, type, _start, _length, _vptr)
 392
 393 #else /* (BYTE_ORDER == PDP_ENDIAN) */
 394
 395 #error "Byte order not supported"
 396
 397 #endif
 398
 399 #endif /* _BABELTRACE_BITFIELD_H */