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/* SPDX-License-Identifier: GPL-3.0-or-later */
/* Copyright 2021 - 2022, Kim Kuparinen < kimi.h.kuparinen@gmail.com > */
/**
* @file bits.c
* Bit manipulation helper implementations, currently just byte swaps.
*/
#include <kmi/types.h>
#include <kmi/attrs.h>
#include <kmi/bits.h>
#include <kmi/builtin.h>
#undef __bswap16
__weak uint16_t __bswap16(const uint16_t u)
{
return (u & 0xff00) >> 8 | (u & 0x00ff) << 8;
}
#undef __bswap32
__weak uint32_t __bswap32(const uint32_t u)
{
return (u & 0xff000000) >> 24 | (u & 0x00ff0000) >> 8 |
(u & 0x0000ff00) << 8 | (u & 0x000000ff) << 24;
}
#undef __bswap64
__weak uint64_t __bswap64(const uint64_t u)
{
return (u & 0xff00000000000000ULL) >> 56 |
(u & 0x00ff000000000000ULL) >> 40 |
(u & 0x0000ff0000000000ULL) >> 24 |
(u & 0x000000ff00000000ULL) >> 8 |
(u & 0x00000000ff000000ULL) << 8 |
(u & 0x0000000000ff0000ULL) << 24 |
(u & 0x000000000000ff00ULL) << 40 |
(u & 0x00000000000000ffULL) << 56;
}
#undef ffs
__weak int ffs(int v)
{
/* http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel */
if (v == 0)
return 0;
/* silence ubsan warning */
if (v == INT_MIN)
return 32;
int c = 32;
v &= -v;
if (v) c--;
if (v & 0x0000FFFF) c -= 16;
if (v & 0x00FF00FF) c -= 8;
if (v & 0x0F0F0F0F) c -= 4;
if (v & 0x33333333) c -= 2;
if (v & 0x55555555) c -= 1;
return c + 1;
}
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