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/*
Copyright 2011 Jun Wako <wakojun@gmail.com>
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, see <http://www.gnu.org/licenses/>.
*/
#include "util.h"
// bit population - return number of on-bit
__attribute__((noinline)) uint8_t bitpop(uint8_t bits) {
uint8_t c;
for (c = 0; bits; c++)
bits &= bits - 1;
return c;
/*
const uint8_t bit_count[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
return bit_count[bits>>4] + bit_count[bits&0x0F]
*/
}
uint8_t bitpop16(uint16_t bits) {
uint8_t c;
for (c = 0; bits; c++)
bits &= bits - 1;
return c;
}
uint8_t bitpop32(uint32_t bits) {
uint8_t c;
for (c = 0; bits; c++)
bits &= bits - 1;
return c;
}
// most significant on-bit - return highest location of on-bit
// NOTE: return 0 when bit0 is on or all bits are off
__attribute__((noinline)) uint8_t biton(uint8_t bits) {
uint8_t n = 0;
if (bits >> 4) {
bits >>= 4;
n += 4;
}
if (bits >> 2) {
bits >>= 2;
n += 2;
}
if (bits >> 1) {
bits >>= 1;
n += 1;
}
return n;
}
uint8_t biton16(uint16_t bits) {
uint8_t n = 0;
if (bits >> 8) {
bits >>= 8;
n += 8;
}
if (bits >> 4) {
bits >>= 4;
n += 4;
}
if (bits >> 2) {
bits >>= 2;
n += 2;
}
if (bits >> 1) {
bits >>= 1;
n += 1;
}
return n;
}
uint8_t biton32(uint32_t bits) {
uint8_t n = 0;
if (bits >> 16) {
bits >>= 16;
n += 16;
}
if (bits >> 8) {
bits >>= 8;
n += 8;
}
if (bits >> 4) {
bits >>= 4;
n += 4;
}
if (bits >> 2) {
bits >>= 2;
n += 2;
}
if (bits >> 1) {
bits >>= 1;
n += 1;
}
return n;
}
__attribute__((noinline)) uint8_t bitrev(uint8_t bits) {
bits = (bits & 0x0f) << 4 | (bits & 0xf0) >> 4;
bits = (bits & 0b00110011) << 2 | (bits & 0b11001100) >> 2;
bits = (bits & 0b01010101) << 1 | (bits & 0b10101010) >> 1;
return bits;
}
uint16_t bitrev16(uint16_t bits) {
bits = bitrev(bits & 0x00ff) << 8 | bitrev((bits & 0xff00) >> 8);
return bits;
}
uint32_t bitrev32(uint32_t bits) {
bits = (uint32_t)bitrev16(bits & 0x0000ffff) << 16 | bitrev16((bits & 0xffff0000) >> 16);
return bits;
}
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