124 lines
2.8 KiB
C
124 lines
2.8 KiB
C
/*
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Copyright 2011 Jun Wako <wakojun@gmail.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "util.h"
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// bit population - return number of on-bit
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__attribute__((noinline)) uint8_t bitpop(uint8_t bits) {
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uint8_t c;
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for (c = 0; bits; c++) bits &= bits - 1;
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return c;
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/*
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const uint8_t bit_count[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
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return bit_count[bits>>4] + bit_count[bits&0x0F]
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*/
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}
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uint8_t bitpop16(uint16_t bits) {
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uint8_t c;
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for (c = 0; bits; c++) bits &= bits - 1;
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return c;
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}
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uint8_t bitpop32(uint32_t bits) {
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uint8_t c;
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for (c = 0; bits; c++) bits &= bits - 1;
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return c;
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}
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// most significant on-bit - return highest location of on-bit
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// NOTE: return 0 when bit0 is on or all bits are off
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__attribute__((noinline)) uint8_t biton(uint8_t bits) {
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uint8_t n = 0;
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if (bits >> 4) {
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bits >>= 4;
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n += 4;
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}
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if (bits >> 2) {
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bits >>= 2;
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n += 2;
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}
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if (bits >> 1) {
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bits >>= 1;
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n += 1;
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}
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return n;
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}
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uint8_t biton16(uint16_t bits) {
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uint8_t n = 0;
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if (bits >> 8) {
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bits >>= 8;
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n += 8;
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}
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if (bits >> 4) {
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bits >>= 4;
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n += 4;
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}
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if (bits >> 2) {
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bits >>= 2;
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n += 2;
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}
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if (bits >> 1) {
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bits >>= 1;
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n += 1;
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}
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return n;
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}
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uint8_t biton32(uint32_t bits) {
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uint8_t n = 0;
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if (bits >> 16) {
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bits >>= 16;
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n += 16;
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}
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if (bits >> 8) {
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bits >>= 8;
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n += 8;
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}
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if (bits >> 4) {
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bits >>= 4;
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n += 4;
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}
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if (bits >> 2) {
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bits >>= 2;
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n += 2;
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}
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if (bits >> 1) {
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bits >>= 1;
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n += 1;
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}
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return n;
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}
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__attribute__((noinline)) uint8_t bitrev(uint8_t bits) {
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bits = (bits & 0x0f) << 4 | (bits & 0xf0) >> 4;
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bits = (bits & 0b00110011) << 2 | (bits & 0b11001100) >> 2;
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bits = (bits & 0b01010101) << 1 | (bits & 0b10101010) >> 1;
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return bits;
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}
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uint16_t bitrev16(uint16_t bits) {
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bits = bitrev(bits & 0x00ff) << 8 | bitrev((bits & 0xff00) >> 8);
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return bits;
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}
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uint32_t bitrev32(uint32_t bits) {
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bits = (uint32_t)bitrev16(bits & 0x0000ffff) << 16 | bitrev16((bits & 0xffff0000) >> 16);
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return bits;
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}
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