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basic/bitfield: add bitfield operations

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Add macros to manage bits in a bitfield (e.g. uint32_t, uint64_t, etc),
such as setting, clearing, checking bits, and iterating all set bits.

These are similiar to the bitmap operations, but operate on basic types
instead of requiring a Bitmap object.
This commit is contained in:
Dan Streetman
2023-02-02 15:58:10 -05:00
parent 326ef26700
commit 33d9beed07
1 changed files with 73 additions and 0 deletions
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73
src/basic/bitfield.h Normal file
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "macro.h"
/* Bit index (0-based) to mask of specified type. Assertion failure if index is out of range. */
#define _INDEX_TO_MASK(type, i, uniq) \
({ \
int UNIQ_T(_i, uniq) = (i); \
assert(UNIQ_T(_i, uniq) < (int)sizeof(type) * 8); \
((type)1) << UNIQ_T(_i, uniq); \
})
#define INDEX_TO_MASK(type, i) \
({ \
assert_cc(sizeof(type) <= sizeof(unsigned long long)); \
assert_cc(__builtin_choose_expr(__builtin_constant_p(i), i, 0) < (int)(sizeof(type) * 8)); \
__builtin_choose_expr(__builtin_constant_p(i), \
((type)1) << (i), \
_INDEX_TO_MASK(type, i, UNIQ)); \
})
/* Builds a mask of specified type with multiple bits set. Note the result will not be constant, even if all
* indexes are constant. */
#define INDEXES_TO_MASK(type, ...) \
UNIQ_INDEXES_TO_MASK(type, UNIQ, ##__VA_ARGS__)
#define UNIQ_INDEXES_TO_MASK(type, uniq, ...) \
({ \
typeof(type) UNIQ_T(_mask, uniq) = (type)0; \
int UNIQ_T(_i, uniq); \
VA_ARGS_FOREACH(UNIQ_T(_i, uniq), ##__VA_ARGS__) \
UNIQ_T(_mask, uniq) |= INDEX_TO_MASK(type, UNIQ_T(_i, uniq)); \
UNIQ_T(_mask, uniq); \
})
/* Same as the FLAG macros, but accept a 0-based bit index instead of a mask. Results in assertion failure if
* index is out of range for the type. */
#define SET_BIT(bits, i) SET_FLAG(bits, INDEX_TO_MASK(typeof(bits), i), true)
#define CLEAR_BIT(bits, i) SET_FLAG(bits, INDEX_TO_MASK(typeof(bits), i), false)
#define BIT_SET(bits, i) FLAGS_SET(bits, INDEX_TO_MASK(typeof(bits), i))
/* As above, but accepts multiple indexes. Note the result will not be constant, even if all indexes are
* constant. */
#define SET_BITS(bits, ...) SET_FLAG(bits, INDEXES_TO_MASK(typeof(bits), ##__VA_ARGS__), true)
#define CLEAR_BITS(bits, ...) SET_FLAG(bits, INDEXES_TO_MASK(typeof(bits), ##__VA_ARGS__), false)
#define BITS_SET(bits, ...) FLAGS_SET(bits, INDEXES_TO_MASK(typeof(bits), ##__VA_ARGS__))
/* Iterate through each set bit. Index is 0-based and type int. */
#define BIT_FOREACH(index, bits) _BIT_FOREACH(index, bits, UNIQ)
#define _BIT_FOREACH(index, bits, uniq) \
for (int UNIQ_T(_last, uniq) = -1, index; \
(index = BIT_NEXT_SET(bits, UNIQ_T(_last, uniq))) >= 0; \
UNIQ_T(_last, uniq) = index)
/* Find the next set bit after 0-based index 'prev'. Result is 0-based index of next set bit, or -1 if no
* more bits are set. */
#define BIT_FIRST_SET(bits) BIT_NEXT_SET(bits, -1)
#define BIT_NEXT_SET(bits, prev) \
UNIQ_BIT_NEXT_SET(bits, prev, UNIQ)
#define UNIQ_BIT_NEXT_SET(bits, prev, uniq) \
({ \
typeof(bits) UNIQ_T(_bits, uniq) = (bits); \
int UNIQ_T(_prev, uniq) = (prev); \
int UNIQ_T(_next, uniq); \
_BIT_NEXT_SET(UNIQ_T(_bits, uniq), \
UNIQ_T(_prev, uniq), \
UNIQ_T(_next, uniq)); \
})
#define _BIT_NEXT_SET(bits, prev, next) \
((int)(prev + 1) == (int)sizeof(bits) * 8 \
? -1 /* Prev index was msb. */ \
: ((next = __builtin_ffsll(((unsigned long long)(bits)) >> (prev + 1))) == 0 \
? -1 /* No more bits set. */ \
: prev + next))