77 lines
1.9 KiB
C
77 lines
1.9 KiB
C
/*
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* SPDX-License-Identifier: LicenseRef-CSSL-1.0
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*/
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#ifndef BITS_H_
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#define BITS_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#include "assertions.h"
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uint64_t reverse_bits(uint64_t in, int n_bits);
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void reverse_bits_u8(uint8_t const* in, size_t sz, uint8_t* out);
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static inline int get_last_bit_index(const uint32_t *arr, int sz)
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{
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AssertFatal(sz > 0, "Invalid size %d to get the first bit of array\n", sz);
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for (int i = sz - 1; i >= 0; i--) {
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if (arr[i] != 0) {
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// 31 - clz gives the index of the highest bit (0-31)
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return (i * 32) + (31 - __builtin_clz(arr[i]));
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}
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}
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return -1;
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}
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static uint32_t bit_mask(int from_bit, int num_bits)
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{
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int total = from_bit + num_bits;
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uint32_t right_mask = total < 32 ? (0xFFFFFFFF >> (32 - total)) : 0xFFFFFFFF;
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return (0xFFFFFFFF << from_bit) & right_mask;
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}
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static inline int get_first_bit_index_mask(const uint32_t *arr, int sz, int from_bit, int num_bits)
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{
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// start i from first_bit
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int i = from_bit / 32;
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from_bit %= 32;
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for (; i < sz && num_bits > 0; i++) {
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uint32_t a = arr[i] & bit_mask(from_bit, num_bits);
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if (a != 0) {
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// Find the first set bit in this 32-bit word
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return (i * 32) + __builtin_ctz(a);
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}
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num_bits -= 32 - from_bit;
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from_bit = 0;
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}
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return -1;
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}
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static inline int get_first_bit_index(const uint32_t *arr, int sz)
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{
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return get_first_bit_index_mask(arr, sz, 0, sz * 32);
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}
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static inline int count_bits(const uint32_t *arr, int sz)
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{
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int ret = 0;
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// sz is the number of uint32_t elements
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for (int i = 0; i < sz; i++)
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ret += __builtin_popcount(arr[i]);
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return ret;
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}
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static __attribute__((always_inline)) inline int count_bits64(uint64_t v)
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{
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return __builtin_popcountll(v);
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}
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static __attribute__((always_inline)) inline int count_bits64_with_mask(uint64_t v, int start, int num)
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{
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uint64_t mask = ((1LL << num) - 1) << start;
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return count_bits64(v & mask);
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}
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#endif /* BITS_H_ */
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