x86_bigint.c File Reference

Big integer support. More...

#include <stdint.h>
#include <string.h>
#include <ipxe/bigint.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
void	bigint_multiply_raw (const uint32_t *multiplicand0, unsigned int multiplicand_size, const uint32_t *multiplier0, unsigned int multiplier_size, uint32_t *result0)
	Multiply big integers. More...

Detailed Description

Big integer support.

Definition in file x86_bigint.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

bigint_multiply_raw()

void bigint_multiply_raw	(	const uint32_t *	multiplicand0,
		unsigned int	multiplicand_size,
		const uint32_t *	multiplier0,
		unsigned int	multiplier_size,
		uint32_t *	result0
	)

Multiply big integers.

Parameters

multiplicand0	Element 0 of big integer to be multiplied
multiplicand_size	Number of elements in multiplicand
multiplier0	Element 0 of big integer to be multiplied
multiplier_size	Number of elements in multiplier
result0	Element 0 of big integer to hold result

Definition at line 44 of file x86_bigint.c.

                                               {
        unsigned int result_size = ( multiplicand_size + multiplier_size );
        const bigint_t ( multiplicand_size ) __attribute__ (( may_alias ))
                *multiplicand = ( ( const void * ) multiplicand0 );
        const bigint_t ( multiplier_size ) __attribute__ (( may_alias ))
                *multiplier = ( ( const void * ) multiplier0 );
        bigint_t ( result_size ) __attribute__ (( may_alias ))
                *result = ( ( void * ) result0 );
        unsigned int i;
        unsigned int j;
        uint32_t multiplicand_element;
        uint32_t multiplier_element;
        uint32_t *result_elements;
        uint32_t discard_a;
        uint32_t discard_d;
        long index;

        /* Zero result */
        memset ( result, 0, sizeof ( *result ) );

        /* Multiply integers one element at a time */
        for ( i = 0 ; i < multiplicand_size ; i++ ) {
                multiplicand_element = multiplicand->element[i];
                for ( j = 0 ; j < multiplier_size ; j++ ) {
                        multiplier_element = multiplier->element[j];
                        result_elements = &result->element[ i + j ];
                        /* Perform a single multiply, and add the
                         * resulting double-element into the result,
                         * carrying as necessary.  The carry can
                         * never overflow beyond the end of the
                         * result, since:
                         *
                         *     a < 2^{n}, b < 2^{m} => ab < 2^{n+m}
                         */
                        __asm__ __volatile__ ( "mull %5\n\t"
                                               "addl %%eax, (%6,%2,4)\n\t"
                                               "adcl %%edx, 4(%6,%2,4)\n\t"
                                               "\n1:\n\t"
                                               "adcl $0, 8(%6,%2,4)\n\t"
                                               "inc %2\n\t"
                                                       /* Does not affect CF */
                                               "jc 1b\n\t"
                                               : "=&a" ( discard_a ),
                                                 "=&d" ( discard_d ),
                                                 "=&r" ( index ),
                                                 "+m" ( *result )
                                               : "0" ( multiplicand_element ),
                                                 "g" ( multiplier_element ),
                                                 "r" ( result_elements ),
                                                 "2" ( 0 ) );
                }
        }
}

References __asm__(), __attribute__, __volatile__(), bigint_t(), index, memset(), multiplier, and result.