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/*
* Bit operations
*
* Copyright (c) 2020 Michael Buesch <m@bues.ch>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "bitops.h"
#include "compat.h"
/* Find most significant (last) bit set. */
uint8_t fls16(uint16_t value)
{
uint8_t ret = 16u;
if (value == 0u)
return 0u;
if ((value & 0xFF00u) == 0u) {
value = (uint16_t)(value << 8);
ret = (uint8_t)(ret - 8u);
}
if ((value & 0xF000u) == 0u) {
value = (uint16_t)(value << 4);
ret = (uint8_t)(ret - 4u);
}
if ((value & 0xC000u) == 0u) {
value = (uint16_t)(value << 2);
ret = (uint8_t)(ret - 2u);
}
if ((value & 0x8000u) == 0u) {
value = (uint16_t)(value << 1);
ret = (uint8_t)(ret - 1u);
}
return ret;
}
/* Find most significant (last) bit set. */
uint8_t fls8(uint8_t value)
{
uint8_t ret = 8u;
if (value == 0u)
return 0u;
if ((value & 0xF0u) == 0u) {
value = (uint8_t)(value << 4);
ret = (uint8_t)(ret - 4u);
}
if ((value & 0xC0u) == 0u) {
value = (uint8_t)(value << 2);
ret = (uint8_t)(ret - 2u);
}
if ((value & 0x80u) == 0u) {
value = (uint8_t)(value << 1);
ret = (uint8_t)(ret - 1u);
}
return ret;
}
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