/**
 * Copyright (c) 2012 Anup Patel.
 * All rights reserved.
 *
 * 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, 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * @file mathlib.c
 * @author Anup Patel (anup@brainfault.org)
 * @brief Software implementation common math operations
 */

#include <libs/bitops.h>
#include <libs/mathlib.h>

#if !defined(ARCH_HAS_DIVISON_OPERATION)

static const unsigned char byte_reverse_table[] = 
{
  0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, 0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0, 
  0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, 0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8, 
  0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, 0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4, 
  0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC, 0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC, 
  0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, 0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2, 
  0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA, 0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
  0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, 0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6, 
  0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, 0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
  0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1, 0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
  0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, 0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9, 
  0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5, 0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
  0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED, 0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
  0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3, 0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3, 
  0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, 0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
  0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7, 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7, 
  0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, 0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
};

static inline u32 do_fls64(u64 value) 
{
	u32 num_bits = 0;
	if (value & 0xFFFF000000000000ULL) {
		num_bits += 16;
		value = value >> 16;
	}
	if (value & 0x0000FFFF00000000ULL) {
		num_bits += 16;
		value = value >> 16;
	}
	if (value & 0x00000000FFFF0000ULL) {
		num_bits += 16;
		value = value >> 16;
	}
	if (value & 0x000000000000FF00ULL) {
		num_bits += 8;
		value = value >> 8;
	}
	if (value & 0x00000000000000F0ULL) {
		num_bits += 4;
		value = value >> 4;
	}
	if (value & 0x000000000000000CULL) {
		num_bits += 2;
		value = value >> 2;
	}
	if (value & 0x0000000000000003ULL) {
		num_bits += 2;
		value = value >> 2;
	}
	return num_bits;
}

u64 do_udiv64(u64 dividend, u64 divisor, u64 * remainder)
{
	u32 num_bits;
	register u8 *p, *q;
	u64 quotient, remaind;

	if (divisor == 0) {
		while (1);
	}

	if (dividend <= divisor) {
		remaind = divisor - dividend;
		if (remainder) {
			*remainder = (remaind) ? dividend : 0;
		}
		return (remaind) ? 0 : 1;
	}

	remaind = 0;
	num_bits = do_fls64(dividend);
	dividend = dividend << (64 - num_bits);
	p = (u8 *)&dividend;
	q = (u8 *)&quotient;
	q[7] = byte_reverse_table[p[0]]; 
	q[6] = byte_reverse_table[p[1]]; 
	q[5] = byte_reverse_table[p[2]]; 
	q[4] = byte_reverse_table[p[3]];
	q[3] = byte_reverse_table[p[4]]; 
	q[2] = byte_reverse_table[p[5]]; 
	q[1] = byte_reverse_table[p[6]]; 
	q[0] = byte_reverse_table[p[7]];
	dividend = quotient;
	quotient = 0;

	while (num_bits) {
		remaind = (remaind << 1) | (dividend & 0x1);
		dividend = dividend >> 1;
		if (remaind < divisor) {
			quotient = ((quotient) << 1) | 0;
		} else {
			quotient = ((quotient) << 1) | 1;
			remaind = remaind - divisor;
		}
		num_bits--;
	}

	if (remainder) {
		*remainder = remaind;
	}

	return quotient;
}

static inline u32 do_fls32(u32 value) 
{
	u32 num_bits = 0;
	if (value & 0xFFFF0000) {
		num_bits += 16;
		value = value >> 16;
	}
	if (value & 0x0000FF00) {
		num_bits += 8;
		value = value >> 8;
	}
	if (value & 0x000000F0) {
		num_bits += 4;
		value = value >> 4;
	}
	if (value & 0x0000000C) {
		num_bits += 2;
		value = value >> 2;
	}
	if (value & 0x00000003) {
		num_bits += 2;
		value = value >> 2;
	}
	return num_bits;
}

u32 do_udiv32(u32 dividend, u32 divisor, u32 * remainder)
{
	register u8 *p, *q;
	u32 num_bits, quotient, remaind;

	if (divisor == 0) {
		while (1);
	}

	if (dividend <= divisor) {
		remaind = divisor - dividend;
		if (remainder) {
			*remainder = (remaind) ? dividend : 0;
		}
		return (remaind) ? 0 : 1;
	}

	remaind = 0;
	num_bits = do_fls32(dividend);
	dividend = dividend << (32 - num_bits);
	p = (u8 *)&dividend;
	q = (u8 *)&quotient;
	q[3] = byte_reverse_table[p[0]]; 
	q[2] = byte_reverse_table[p[1]]; 
	q[1] = byte_reverse_table[p[2]]; 
	q[0] = byte_reverse_table[p[3]];
	dividend = quotient;
	quotient = 0;

	while (num_bits) {
		remaind = (remaind << 1) | (dividend & 0x1);
		dividend = dividend >> 1;
		if (remaind < divisor) {
			quotient = ((quotient) << 1) | 0;
		} else {
			quotient = ((quotient) << 1) | 1;
			remaind = remaind - divisor;
		}
		num_bits--;
	}

	if (remainder) {
		*remainder = remaind;
	}

	return quotient;
}

#endif

unsigned long int_sqrt(unsigned long x)
{
	unsigned long op, res, one;

	op = x;
	res = 0;

	one = 1UL << (BITS_PER_LONG - 2);
	while (one > op)
		one >>= 2;

	while (one != 0) {
		if (op >= res + one) {
			op = op - (res + one);
			res = res +  2 * one;
		}
		res /= 2;
		one /= 4;
	}
	return res;
}

