/*
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
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
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;
}



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;
}
