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