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e0e53b2f CC |
1 | /* |
2 | * Bitops Module | |
3 | * | |
4 | * Copyright (C) 2010 Corentin Chary <corentin.chary@gmail.com> | |
5 | * | |
6 | * Mostly inspired by (stolen from) linux/bitmap.h and linux/bitops.h | |
7 | * | |
8 | * This work is licensed under the terms of the GNU LGPL, version 2.1 or later. | |
9 | * See the COPYING.LIB file in the top-level directory. | |
10 | */ | |
11 | ||
12 | #ifndef BITOPS_H | |
13 | #define BITOPS_H | |
14 | ||
afeeead1 | 15 | |
fbeadf50 | 16 | #include "host-utils.h" |
9f02cfc8 | 17 | #include "atomic.h" |
e0e53b2f CC |
18 | |
19 | #define BITS_PER_BYTE CHAR_BIT | |
20 | #define BITS_PER_LONG (sizeof (unsigned long) * BITS_PER_BYTE) | |
21 | ||
4188e390 | 22 | #define BIT(nr) (1UL << (nr)) |
0df9142d | 23 | #define BIT_ULL(nr) (1ULL << (nr)) |
4188e390 CMC |
24 | #define BIT_MASK(nr) (1UL << ((nr) % BITS_PER_LONG)) |
25 | #define BIT_WORD(nr) ((nr) / BITS_PER_LONG) | |
26 | #define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long)) | |
e0e53b2f | 27 | |
ae2923b5 AF |
28 | #define MAKE_64BIT_MASK(shift, length) \ |
29 | (((~0ULL) >> (64 - (length))) << (shift)) | |
30 | ||
e0e53b2f CC |
31 | /** |
32 | * set_bit - Set a bit in memory | |
33 | * @nr: the bit to set | |
34 | * @addr: the address to start counting from | |
35 | */ | |
9c22687e | 36 | static inline void set_bit(long nr, unsigned long *addr) |
e0e53b2f | 37 | { |
4188e390 CMC |
38 | unsigned long mask = BIT_MASK(nr); |
39 | unsigned long *p = addr + BIT_WORD(nr); | |
e0e53b2f | 40 | |
4188e390 | 41 | *p |= mask; |
e0e53b2f CC |
42 | } |
43 | ||
9f02cfc8 SH |
44 | /** |
45 | * set_bit_atomic - Set a bit in memory atomically | |
46 | * @nr: the bit to set | |
47 | * @addr: the address to start counting from | |
48 | */ | |
49 | static inline void set_bit_atomic(long nr, unsigned long *addr) | |
50 | { | |
51 | unsigned long mask = BIT_MASK(nr); | |
52 | unsigned long *p = addr + BIT_WORD(nr); | |
53 | ||
d73415a3 | 54 | qatomic_or(p, mask); |
9f02cfc8 SH |
55 | } |
56 | ||
e0e53b2f CC |
57 | /** |
58 | * clear_bit - Clears a bit in memory | |
59 | * @nr: Bit to clear | |
60 | * @addr: Address to start counting from | |
61 | */ | |
9c22687e | 62 | static inline void clear_bit(long nr, unsigned long *addr) |
e0e53b2f | 63 | { |
4188e390 CMC |
64 | unsigned long mask = BIT_MASK(nr); |
65 | unsigned long *p = addr + BIT_WORD(nr); | |
e0e53b2f | 66 | |
4188e390 | 67 | *p &= ~mask; |
e0e53b2f CC |
68 | } |
69 | ||
70 | /** | |
71 | * change_bit - Toggle a bit in memory | |
72 | * @nr: Bit to change | |
73 | * @addr: Address to start counting from | |
74 | */ | |
9c22687e | 75 | static inline void change_bit(long nr, unsigned long *addr) |
e0e53b2f | 76 | { |
4188e390 CMC |
77 | unsigned long mask = BIT_MASK(nr); |
78 | unsigned long *p = addr + BIT_WORD(nr); | |
e0e53b2f | 79 | |
4188e390 | 80 | *p ^= mask; |
e0e53b2f CC |
81 | } |
82 | ||
83 | /** | |
84 | * test_and_set_bit - Set a bit and return its old value | |
85 | * @nr: Bit to set | |
86 | * @addr: Address to count from | |
87 | */ | |
9c22687e | 88 | static inline int test_and_set_bit(long nr, unsigned long *addr) |
e0e53b2f | 89 | { |
4188e390 CMC |
90 | unsigned long mask = BIT_MASK(nr); |
91 | unsigned long *p = addr + BIT_WORD(nr); | |
92 | unsigned long old = *p; | |
e0e53b2f | 93 | |
4188e390 CMC |
94 | *p = old | mask; |
95 | return (old & mask) != 0; | |
e0e53b2f CC |
96 | } |
97 | ||
98 | /** | |
99 | * test_and_clear_bit - Clear a bit and return its old value | |
100 | * @nr: Bit to clear | |
101 | * @addr: Address to count from | |
102 | */ | |
9c22687e | 103 | static inline int test_and_clear_bit(long nr, unsigned long *addr) |
e0e53b2f | 104 | { |
4188e390 CMC |
105 | unsigned long mask = BIT_MASK(nr); |
106 | unsigned long *p = addr + BIT_WORD(nr); | |
107 | unsigned long old = *p; | |
e0e53b2f | 108 | |
4188e390 CMC |
109 | *p = old & ~mask; |
110 | return (old & mask) != 0; | |
e0e53b2f CC |
111 | } |
112 | ||
113 | /** | |
114 | * test_and_change_bit - Change a bit and return its old value | |
115 | * @nr: Bit to change | |
116 | * @addr: Address to count from | |
117 | */ | |
9c22687e | 118 | static inline int test_and_change_bit(long nr, unsigned long *addr) |
e0e53b2f | 119 | { |
4188e390 CMC |
120 | unsigned long mask = BIT_MASK(nr); |
121 | unsigned long *p = addr + BIT_WORD(nr); | |
122 | unsigned long old = *p; | |
e0e53b2f | 123 | |
4188e390 CMC |
124 | *p = old ^ mask; |
125 | return (old & mask) != 0; | |
e0e53b2f CC |
126 | } |
127 | ||
128 | /** | |
129 | * test_bit - Determine whether a bit is set | |
130 | * @nr: bit number to test | |
131 | * @addr: Address to start counting from | |
132 | */ | |
9c22687e | 133 | static inline int test_bit(long nr, const unsigned long *addr) |
e0e53b2f | 134 | { |
4188e390 | 135 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1))); |
e0e53b2f CC |
136 | } |
137 | ||
138 | /** | |
139 | * find_last_bit - find the last set bit in a memory region | |
140 | * @addr: The address to start the search at | |
141 | * @size: The maximum size to search | |
142 | * | |
5c6ae58d PMD |
143 | * Returns the bit number of the last set bit, |
144 | * or @size if there is no set bit in the bitmap. | |
e0e53b2f CC |
145 | */ |
146 | unsigned long find_last_bit(const unsigned long *addr, | |
147 | unsigned long size); | |
148 | ||
149 | /** | |
150 | * find_next_bit - find the next set bit in a memory region | |
151 | * @addr: The address to base the search on | |
152 | * @offset: The bitnumber to start searching at | |
153 | * @size: The bitmap size in bits | |
5c6ae58d PMD |
154 | * |
155 | * Returns the bit number of the next set bit, | |
156 | * or @size if there are no further set bits in the bitmap. | |
e0e53b2f CC |
157 | */ |
158 | unsigned long find_next_bit(const unsigned long *addr, | |
4188e390 CMC |
159 | unsigned long size, |
160 | unsigned long offset); | |
e0e53b2f CC |
161 | |
162 | /** | |
163 | * find_next_zero_bit - find the next cleared bit in a memory region | |
164 | * @addr: The address to base the search on | |
165 | * @offset: The bitnumber to start searching at | |
166 | * @size: The bitmap size in bits | |
5c6ae58d PMD |
167 | * |
168 | * Returns the bit number of the next cleared bit, | |
169 | * or @size if there are no further clear bits in the bitmap. | |
e0e53b2f CC |
170 | */ |
171 | ||
172 | unsigned long find_next_zero_bit(const unsigned long *addr, | |
173 | unsigned long size, | |
174 | unsigned long offset); | |
175 | ||
176 | /** | |
177 | * find_first_bit - find the first set bit in a memory region | |
178 | * @addr: The address to start the search at | |
179 | * @size: The maximum size to search | |
180 | * | |
5c6ae58d PMD |
181 | * Returns the bit number of the first set bit, |
182 | * or @size if there is no set bit in the bitmap. | |
e0e53b2f CC |
183 | */ |
184 | static inline unsigned long find_first_bit(const unsigned long *addr, | |
185 | unsigned long size) | |
186 | { | |
739b7a90 AJ |
187 | unsigned long result, tmp; |
188 | ||
189 | for (result = 0; result < size; result += BITS_PER_LONG) { | |
190 | tmp = *addr++; | |
191 | if (tmp) { | |
192 | result += ctzl(tmp); | |
193 | return result < size ? result : size; | |
194 | } | |
195 | } | |
196 | /* Not found */ | |
197 | return size; | |
e0e53b2f CC |
198 | } |
199 | ||
200 | /** | |
201 | * find_first_zero_bit - find the first cleared bit in a memory region | |
202 | * @addr: The address to start the search at | |
203 | * @size: The maximum size to search | |
204 | * | |
5c6ae58d PMD |
205 | * Returns the bit number of the first cleared bit, |
206 | * or @size if there is no clear bit in the bitmap. | |
e0e53b2f CC |
207 | */ |
208 | static inline unsigned long find_first_zero_bit(const unsigned long *addr, | |
209 | unsigned long size) | |
210 | { | |
211 | return find_next_zero_bit(addr, size, 0); | |
212 | } | |
213 | ||
6aa25b4a SW |
214 | /** |
215 | * rol8 - rotate an 8-bit value left | |
216 | * @word: value to rotate | |
217 | * @shift: bits to roll | |
218 | */ | |
219 | static inline uint8_t rol8(uint8_t word, unsigned int shift) | |
220 | { | |
8841c815 | 221 | return (word << (shift & 7)) | (word >> (-shift & 7)); |
6aa25b4a SW |
222 | } |
223 | ||
224 | /** | |
225 | * ror8 - rotate an 8-bit value right | |
226 | * @word: value to rotate | |
227 | * @shift: bits to roll | |
228 | */ | |
229 | static inline uint8_t ror8(uint8_t word, unsigned int shift) | |
230 | { | |
8841c815 | 231 | return (word >> (shift & 7)) | (word << (-shift & 7)); |
6aa25b4a SW |
232 | } |
233 | ||
234 | /** | |
235 | * rol16 - rotate a 16-bit value left | |
236 | * @word: value to rotate | |
237 | * @shift: bits to roll | |
238 | */ | |
239 | static inline uint16_t rol16(uint16_t word, unsigned int shift) | |
240 | { | |
8841c815 | 241 | return (word << (shift & 15)) | (word >> (-shift & 15)); |
6aa25b4a SW |
242 | } |
243 | ||
244 | /** | |
245 | * ror16 - rotate a 16-bit value right | |
246 | * @word: value to rotate | |
247 | * @shift: bits to roll | |
248 | */ | |
249 | static inline uint16_t ror16(uint16_t word, unsigned int shift) | |
250 | { | |
8841c815 | 251 | return (word >> (shift & 15)) | (word << (-shift & 15)); |
6aa25b4a SW |
252 | } |
253 | ||
254 | /** | |
255 | * rol32 - rotate a 32-bit value left | |
256 | * @word: value to rotate | |
257 | * @shift: bits to roll | |
258 | */ | |
259 | static inline uint32_t rol32(uint32_t word, unsigned int shift) | |
260 | { | |
8841c815 | 261 | return (word << (shift & 31)) | (word >> (-shift & 31)); |
6aa25b4a SW |
262 | } |
263 | ||
264 | /** | |
265 | * ror32 - rotate a 32-bit value right | |
266 | * @word: value to rotate | |
267 | * @shift: bits to roll | |
268 | */ | |
269 | static inline uint32_t ror32(uint32_t word, unsigned int shift) | |
270 | { | |
8841c815 | 271 | return (word >> (shift & 31)) | (word << (-shift & 31)); |
6aa25b4a SW |
272 | } |
273 | ||
274 | /** | |
275 | * rol64 - rotate a 64-bit value left | |
276 | * @word: value to rotate | |
277 | * @shift: bits to roll | |
278 | */ | |
279 | static inline uint64_t rol64(uint64_t word, unsigned int shift) | |
280 | { | |
8841c815 | 281 | return (word << (shift & 63)) | (word >> (-shift & 63)); |
6aa25b4a SW |
282 | } |
283 | ||
284 | /** | |
285 | * ror64 - rotate a 64-bit value right | |
286 | * @word: value to rotate | |
287 | * @shift: bits to roll | |
288 | */ | |
289 | static inline uint64_t ror64(uint64_t word, unsigned int shift) | |
290 | { | |
8841c815 | 291 | return (word >> (shift & 63)) | (word << (-shift & 63)); |
6aa25b4a SW |
292 | } |
293 | ||
dbcf6f93 PM |
294 | /** |
295 | * hswap32 - swap 16-bit halfwords within a 32-bit value | |
296 | * @h: value to swap | |
297 | */ | |
298 | static inline uint32_t hswap32(uint32_t h) | |
299 | { | |
300 | return rol32(h, 16); | |
301 | } | |
302 | ||
303 | /** | |
304 | * hswap64 - swap 16-bit halfwords within a 64-bit value | |
305 | * @h: value to swap | |
306 | */ | |
307 | static inline uint64_t hswap64(uint64_t h) | |
308 | { | |
309 | uint64_t m = 0x0000ffff0000ffffull; | |
310 | h = rol64(h, 32); | |
311 | return ((h & m) << 16) | ((h >> 16) & m); | |
312 | } | |
313 | ||
314 | /** | |
315 | * wswap64 - swap 32-bit words within a 64-bit value | |
316 | * @h: value to swap | |
317 | */ | |
318 | static inline uint64_t wswap64(uint64_t h) | |
319 | { | |
320 | return rol64(h, 32); | |
321 | } | |
322 | ||
84988cf9 PM |
323 | /** |
324 | * extract32: | |
325 | * @value: the value to extract the bit field from | |
326 | * @start: the lowest bit in the bit field (numbered from 0) | |
327 | * @length: the length of the bit field | |
328 | * | |
329 | * Extract from the 32 bit input @value the bit field specified by the | |
330 | * @start and @length parameters, and return it. The bit field must | |
331 | * lie entirely within the 32 bit word. It is valid to request that | |
332 | * all 32 bits are returned (ie @length 32 and @start 0). | |
333 | * | |
334 | * Returns: the value of the bit field extracted from the input value. | |
335 | */ | |
336 | static inline uint32_t extract32(uint32_t value, int start, int length) | |
337 | { | |
338 | assert(start >= 0 && length > 0 && length <= 32 - start); | |
339 | return (value >> start) & (~0U >> (32 - length)); | |
340 | } | |
341 | ||
ed04c8b1 YS |
342 | /** |
343 | * extract8: | |
344 | * @value: the value to extract the bit field from | |
345 | * @start: the lowest bit in the bit field (numbered from 0) | |
346 | * @length: the length of the bit field | |
347 | * | |
348 | * Extract from the 8 bit input @value the bit field specified by the | |
349 | * @start and @length parameters, and return it. The bit field must | |
350 | * lie entirely within the 8 bit word. It is valid to request that | |
351 | * all 8 bits are returned (ie @length 8 and @start 0). | |
352 | * | |
353 | * Returns: the value of the bit field extracted from the input value. | |
354 | */ | |
355 | static inline uint8_t extract8(uint8_t value, int start, int length) | |
356 | { | |
357 | assert(start >= 0 && length > 0 && length <= 8 - start); | |
358 | return extract32(value, start, length); | |
359 | } | |
360 | ||
361 | /** | |
362 | * extract16: | |
363 | * @value: the value to extract the bit field from | |
364 | * @start: the lowest bit in the bit field (numbered from 0) | |
365 | * @length: the length of the bit field | |
366 | * | |
367 | * Extract from the 16 bit input @value the bit field specified by the | |
368 | * @start and @length parameters, and return it. The bit field must | |
369 | * lie entirely within the 16 bit word. It is valid to request that | |
370 | * all 16 bits are returned (ie @length 16 and @start 0). | |
371 | * | |
372 | * Returns: the value of the bit field extracted from the input value. | |
373 | */ | |
374 | static inline uint16_t extract16(uint16_t value, int start, int length) | |
375 | { | |
376 | assert(start >= 0 && length > 0 && length <= 16 - start); | |
377 | return extract32(value, start, length); | |
378 | } | |
379 | ||
84988cf9 PM |
380 | /** |
381 | * extract64: | |
382 | * @value: the value to extract the bit field from | |
383 | * @start: the lowest bit in the bit field (numbered from 0) | |
384 | * @length: the length of the bit field | |
385 | * | |
386 | * Extract from the 64 bit input @value the bit field specified by the | |
387 | * @start and @length parameters, and return it. The bit field must | |
388 | * lie entirely within the 64 bit word. It is valid to request that | |
389 | * all 64 bits are returned (ie @length 64 and @start 0). | |
390 | * | |
391 | * Returns: the value of the bit field extracted from the input value. | |
392 | */ | |
393 | static inline uint64_t extract64(uint64_t value, int start, int length) | |
394 | { | |
395 | assert(start >= 0 && length > 0 && length <= 64 - start); | |
396 | return (value >> start) & (~0ULL >> (64 - length)); | |
397 | } | |
398 | ||
2dc6bebd PM |
399 | /** |
400 | * sextract32: | |
401 | * @value: the value to extract the bit field from | |
402 | * @start: the lowest bit in the bit field (numbered from 0) | |
403 | * @length: the length of the bit field | |
404 | * | |
405 | * Extract from the 32 bit input @value the bit field specified by the | |
406 | * @start and @length parameters, and return it, sign extended to | |
407 | * an int32_t (ie with the most significant bit of the field propagated | |
408 | * to all the upper bits of the return value). The bit field must lie | |
409 | * entirely within the 32 bit word. It is valid to request that | |
410 | * all 32 bits are returned (ie @length 32 and @start 0). | |
411 | * | |
412 | * Returns: the sign extended value of the bit field extracted from the | |
413 | * input value. | |
414 | */ | |
415 | static inline int32_t sextract32(uint32_t value, int start, int length) | |
416 | { | |
417 | assert(start >= 0 && length > 0 && length <= 32 - start); | |
418 | /* Note that this implementation relies on right shift of signed | |
419 | * integers being an arithmetic shift. | |
420 | */ | |
421 | return ((int32_t)(value << (32 - length - start))) >> (32 - length); | |
422 | } | |
423 | ||
424 | /** | |
425 | * sextract64: | |
426 | * @value: the value to extract the bit field from | |
427 | * @start: the lowest bit in the bit field (numbered from 0) | |
428 | * @length: the length of the bit field | |
429 | * | |
430 | * Extract from the 64 bit input @value the bit field specified by the | |
431 | * @start and @length parameters, and return it, sign extended to | |
432 | * an int64_t (ie with the most significant bit of the field propagated | |
433 | * to all the upper bits of the return value). The bit field must lie | |
434 | * entirely within the 64 bit word. It is valid to request that | |
435 | * all 64 bits are returned (ie @length 64 and @start 0). | |
436 | * | |
437 | * Returns: the sign extended value of the bit field extracted from the | |
438 | * input value. | |
439 | */ | |
4f995052 | 440 | static inline int64_t sextract64(uint64_t value, int start, int length) |
2dc6bebd PM |
441 | { |
442 | assert(start >= 0 && length > 0 && length <= 64 - start); | |
443 | /* Note that this implementation relies on right shift of signed | |
444 | * integers being an arithmetic shift. | |
445 | */ | |
446 | return ((int64_t)(value << (64 - length - start))) >> (64 - length); | |
447 | } | |
448 | ||
84988cf9 PM |
449 | /** |
450 | * deposit32: | |
451 | * @value: initial value to insert bit field into | |
452 | * @start: the lowest bit in the bit field (numbered from 0) | |
453 | * @length: the length of the bit field | |
454 | * @fieldval: the value to insert into the bit field | |
455 | * | |
456 | * Deposit @fieldval into the 32 bit @value at the bit field specified | |
457 | * by the @start and @length parameters, and return the modified | |
458 | * @value. Bits of @value outside the bit field are not modified. | |
459 | * Bits of @fieldval above the least significant @length bits are | |
460 | * ignored. The bit field must lie entirely within the 32 bit word. | |
ab411770 SW |
461 | * It is valid to request that all 32 bits are modified (ie @length |
462 | * 32 and @start 0). | |
84988cf9 PM |
463 | * |
464 | * Returns: the modified @value. | |
465 | */ | |
466 | static inline uint32_t deposit32(uint32_t value, int start, int length, | |
467 | uint32_t fieldval) | |
468 | { | |
469 | uint32_t mask; | |
470 | assert(start >= 0 && length > 0 && length <= 32 - start); | |
471 | mask = (~0U >> (32 - length)) << start; | |
472 | return (value & ~mask) | ((fieldval << start) & mask); | |
473 | } | |
474 | ||
475 | /** | |
ab411770 | 476 | * deposit64: |
84988cf9 PM |
477 | * @value: initial value to insert bit field into |
478 | * @start: the lowest bit in the bit field (numbered from 0) | |
479 | * @length: the length of the bit field | |
480 | * @fieldval: the value to insert into the bit field | |
481 | * | |
482 | * Deposit @fieldval into the 64 bit @value at the bit field specified | |
483 | * by the @start and @length parameters, and return the modified | |
484 | * @value. Bits of @value outside the bit field are not modified. | |
485 | * Bits of @fieldval above the least significant @length bits are | |
ab411770 | 486 | * ignored. The bit field must lie entirely within the 64 bit word. |
84988cf9 PM |
487 | * It is valid to request that all 64 bits are modified (ie @length |
488 | * 64 and @start 0). | |
489 | * | |
490 | * Returns: the modified @value. | |
491 | */ | |
492 | static inline uint64_t deposit64(uint64_t value, int start, int length, | |
493 | uint64_t fieldval) | |
494 | { | |
495 | uint64_t mask; | |
496 | assert(start >= 0 && length > 0 && length <= 64 - start); | |
497 | mask = (~0ULL >> (64 - length)) << start; | |
498 | return (value & ~mask) | ((fieldval << start) & mask); | |
499 | } | |
500 | ||
b355438d PM |
501 | /** |
502 | * half_shuffle32: | |
7d41d764 PM |
503 | * @x: 32-bit value (of which only the bottom 16 bits are of interest) |
504 | * | |
505 | * Given an input value:: | |
506 | * | |
507 | * xxxx xxxx xxxx xxxx ABCD EFGH IJKL MNOP | |
b355438d | 508 | * |
b355438d | 509 | * return the value where the bottom 16 bits are spread out into |
7d41d764 PM |
510 | * the odd bits in the word, and the even bits are zeroed:: |
511 | * | |
512 | * 0A0B 0C0D 0E0F 0G0H 0I0J 0K0L 0M0N 0O0P | |
b355438d PM |
513 | * |
514 | * Any bits set in the top half of the input are ignored. | |
515 | * | |
516 | * Returns: the shuffled bits. | |
517 | */ | |
518 | static inline uint32_t half_shuffle32(uint32_t x) | |
519 | { | |
520 | /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". | |
521 | * It ignores any bits set in the top half of the input. | |
522 | */ | |
523 | x = ((x & 0xFF00) << 8) | (x & 0x00FF); | |
524 | x = ((x << 4) | x) & 0x0F0F0F0F; | |
525 | x = ((x << 2) | x) & 0x33333333; | |
526 | x = ((x << 1) | x) & 0x55555555; | |
527 | return x; | |
528 | } | |
529 | ||
530 | /** | |
531 | * half_shuffle64: | |
7d41d764 PM |
532 | * @x: 64-bit value (of which only the bottom 32 bits are of interest) |
533 | * | |
534 | * Given an input value:: | |
535 | * | |
536 | * xxxx xxxx xxxx .... xxxx xxxx ABCD EFGH IJKL MNOP QRST UVWX YZab cdef | |
b355438d | 537 | * |
b355438d | 538 | * return the value where the bottom 32 bits are spread out into |
7d41d764 PM |
539 | * the odd bits in the word, and the even bits are zeroed:: |
540 | * | |
541 | * 0A0B 0C0D 0E0F 0G0H 0I0J 0K0L 0M0N .... 0U0V 0W0X 0Y0Z 0a0b 0c0d 0e0f | |
b355438d PM |
542 | * |
543 | * Any bits set in the top half of the input are ignored. | |
544 | * | |
545 | * Returns: the shuffled bits. | |
546 | */ | |
547 | static inline uint64_t half_shuffle64(uint64_t x) | |
548 | { | |
549 | /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". | |
550 | * It ignores any bits set in the top half of the input. | |
551 | */ | |
552 | x = ((x & 0xFFFF0000ULL) << 16) | (x & 0xFFFF); | |
553 | x = ((x << 8) | x) & 0x00FF00FF00FF00FFULL; | |
554 | x = ((x << 4) | x) & 0x0F0F0F0F0F0F0F0FULL; | |
555 | x = ((x << 2) | x) & 0x3333333333333333ULL; | |
556 | x = ((x << 1) | x) & 0x5555555555555555ULL; | |
557 | return x; | |
558 | } | |
559 | ||
560 | /** | |
561 | * half_unshuffle32: | |
7d41d764 PM |
562 | * @x: 32-bit value (of which only the odd bits are of interest) |
563 | * | |
564 | * Given an input value:: | |
565 | * | |
566 | * xAxB xCxD xExF xGxH xIxJ xKxL xMxN xOxP | |
b355438d | 567 | * |
b355438d | 568 | * return the value where all the odd bits are compressed down |
7d41d764 PM |
569 | * into the low half of the word, and the high half is zeroed:: |
570 | * | |
571 | * 0000 0000 0000 0000 ABCD EFGH IJKL MNOP | |
b355438d PM |
572 | * |
573 | * Any even bits set in the input are ignored. | |
574 | * | |
575 | * Returns: the unshuffled bits. | |
576 | */ | |
577 | static inline uint32_t half_unshuffle32(uint32_t x) | |
578 | { | |
579 | /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". | |
580 | * where it is called an inverse half shuffle. | |
581 | */ | |
582 | x &= 0x55555555; | |
583 | x = ((x >> 1) | x) & 0x33333333; | |
584 | x = ((x >> 2) | x) & 0x0F0F0F0F; | |
585 | x = ((x >> 4) | x) & 0x00FF00FF; | |
586 | x = ((x >> 8) | x) & 0x0000FFFF; | |
587 | return x; | |
588 | } | |
589 | ||
590 | /** | |
591 | * half_unshuffle64: | |
7d41d764 PM |
592 | * @x: 64-bit value (of which only the odd bits are of interest) |
593 | * | |
594 | * Given an input value:: | |
595 | * | |
596 | * xAxB xCxD xExF xGxH xIxJ xKxL xMxN .... xUxV xWxX xYxZ xaxb xcxd xexf | |
b355438d | 597 | * |
b355438d | 598 | * return the value where all the odd bits are compressed down |
7d41d764 PM |
599 | * into the low half of the word, and the high half is zeroed:: |
600 | * | |
601 | * 0000 0000 0000 .... 0000 0000 ABCD EFGH IJKL MNOP QRST UVWX YZab cdef | |
b355438d PM |
602 | * |
603 | * Any even bits set in the input are ignored. | |
604 | * | |
605 | * Returns: the unshuffled bits. | |
606 | */ | |
607 | static inline uint64_t half_unshuffle64(uint64_t x) | |
608 | { | |
609 | /* This algorithm is from _Hacker's Delight_ section 7-2 "Shuffling Bits". | |
610 | * where it is called an inverse half shuffle. | |
611 | */ | |
612 | x &= 0x5555555555555555ULL; | |
613 | x = ((x >> 1) | x) & 0x3333333333333333ULL; | |
614 | x = ((x >> 2) | x) & 0x0F0F0F0F0F0F0F0FULL; | |
615 | x = ((x >> 4) | x) & 0x00FF00FF00FF00FFULL; | |
616 | x = ((x >> 8) | x) & 0x0000FFFF0000FFFFULL; | |
617 | x = ((x >> 16) | x) & 0x00000000FFFFFFFFULL; | |
618 | return x; | |
619 | } | |
620 | ||
e0e53b2f | 621 | #endif |