96 lines
3.0 KiB
C
96 lines
3.0 KiB
C
/*
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* Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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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, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <stdint.h>
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#include <string.h>
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#include <ipxe/bigint.h>
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/** @file
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*
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* Big integer support
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*/
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/**
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* Multiply big integers
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*
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* @v multiplicand0 Element 0 of big integer to be multiplied
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* @v multiplier0 Element 0 of big integer to be multiplied
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* @v result0 Element 0 of big integer to hold result
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* @v size Number of elements
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*/
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void bigint_multiply_raw ( const uint32_t *multiplicand0,
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const uint32_t *multiplier0,
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uint32_t *result0, unsigned int size ) {
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const bigint_t ( size ) __attribute__ (( may_alias )) *multiplicand =
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( ( const void * ) multiplicand0 );
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const bigint_t ( size ) __attribute__ (( may_alias )) *multiplier =
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( ( const void * ) multiplier0 );
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bigint_t ( size * 2 ) __attribute__ (( may_alias )) *result =
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( ( void * ) result0 );
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unsigned int i;
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unsigned int j;
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uint32_t multiplicand_element;
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uint32_t multiplier_element;
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uint32_t *result_elements;
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uint32_t discard_a;
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uint32_t discard_d;
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long index;
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/* Zero result */
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memset ( result, 0, sizeof ( *result ) );
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/* Multiply integers one element at a time */
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for ( i = 0 ; i < size ; i++ ) {
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multiplicand_element = multiplicand->element[i];
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for ( j = 0 ; j < size ; j++ ) {
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multiplier_element = multiplier->element[j];
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result_elements = &result->element[ i + j ];
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/* Perform a single multiply, and add the
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* resulting double-element into the result,
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* carrying as necessary. The carry can
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* never overflow beyond the end of the
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* result, since:
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*
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* a < 2^{n}, b < 2^{n} => ab < 2^{2n}
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*/
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__asm__ __volatile__ ( "mull %4\n\t"
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"addl %%eax, (%5,%2,4)\n\t"
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"adcl %%edx, 4(%5,%2,4)\n\t"
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"\n1:\n\t"
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"adcl $0, 8(%5,%2,4)\n\t"
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"inc %2\n\t"
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/* Does not affect CF */
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"jc 1b\n\t"
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: "=&a" ( discard_a ),
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"=&d" ( discard_d ),
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"=&r" ( index )
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: "0" ( multiplicand_element ),
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"g" ( multiplier_element ),
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"r" ( result_elements ),
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"2" ( 0 ) );
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}
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}
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}
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