mirror of
https://github.com/ipxe/ipxe
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5056e8ad93
Expose the bit shifted out as a result of shifting a big integer left or right. Signed-off-by: Michael Brown <mcb30@ipxe.org>
339 lines
9.0 KiB
C
339 lines
9.0 KiB
C
#ifndef _BITS_BIGINT_H
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#define _BITS_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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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 <strings.h>
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/** Element of a big integer */
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typedef uint64_t bigint_element_t;
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/**
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* Initialise big integer
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*
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* @v value0 Element 0 of big integer to initialise
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* @v size Number of elements
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* @v data Raw data
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* @v len Length of raw data
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*/
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static inline __attribute__ (( always_inline )) void
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bigint_init_raw ( uint64_t *value0, unsigned int size,
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const void *data, size_t len ) {
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size_t pad_len = ( sizeof ( bigint_t ( size ) ) - len );
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uint8_t *value_byte = ( ( void * ) value0 );
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const uint8_t *data_byte = ( data + len );
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/* Copy raw data in reverse order, padding with zeros */
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while ( len-- )
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*(value_byte++) = *(--data_byte);
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while ( pad_len-- )
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*(value_byte++) = 0;
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}
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/**
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* Add big integers
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*
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* @v addend0 Element 0 of big integer to add
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* @v value0 Element 0 of big integer to be added to
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* @v size Number of elements
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* @ret carry Carry out
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*/
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static inline __attribute__ (( always_inline )) int
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bigint_add_raw ( const uint64_t *addend0, uint64_t *value0,
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unsigned int size ) {
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bigint_t ( size ) __attribute__ (( may_alias )) *value =
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( ( void * ) value0 );
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uint64_t *discard_addend;
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uint64_t *discard_value;
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uint64_t discard_addend_i;
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uint64_t discard_value_i;
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unsigned int discard_size;
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int carry;
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__asm__ __volatile__ ( "cmn xzr, xzr\n\t" /* clear CF */
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"\n1:\n\t"
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"ldr %3, [%0], #8\n\t"
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"ldr %4, [%1]\n\t"
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"adcs %4, %4, %3\n\t"
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"str %4, [%1], #8\n\t"
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"sub %w2, %w2, #1\n\t"
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"cbnz %w2, 1b\n\t"
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: "=r" ( discard_addend ),
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"=r" ( discard_value ),
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"=r" ( discard_size ),
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"=r" ( discard_addend_i ),
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"=r" ( discard_value_i ),
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"=@cccs" ( carry ),
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"+m" ( *value )
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: "0" ( addend0 ), "1" ( value0 ),
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"2" ( size ) );
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return carry;
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}
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/**
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* Subtract big integers
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*
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* @v subtrahend0 Element 0 of big integer to subtract
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* @v value0 Element 0 of big integer to be subtracted from
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* @v size Number of elements
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* @ret borrow Borrow out
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*/
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static inline __attribute__ (( always_inline )) int
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bigint_subtract_raw ( const uint64_t *subtrahend0, uint64_t *value0,
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unsigned int size ) {
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bigint_t ( size ) __attribute__ (( may_alias )) *value =
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( ( void * ) value0 );
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uint64_t *discard_subtrahend;
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uint64_t *discard_value;
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uint64_t discard_subtrahend_i;
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uint64_t discard_value_i;
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unsigned int discard_size;
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int borrow;
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__asm__ __volatile__ ( "cmp xzr, xzr\n\t" /* set CF */
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"\n1:\n\t"
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"ldr %3, [%0], #8\n\t"
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"ldr %4, [%1]\n\t"
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"sbcs %4, %4, %3\n\t"
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"str %4, [%1], #8\n\t"
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"sub %w2, %w2, #1\n\t"
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"cbnz %w2, 1b\n\t"
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: "=r" ( discard_subtrahend ),
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"=r" ( discard_value ),
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"=r" ( discard_size ),
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"=r" ( discard_subtrahend_i ),
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"=r" ( discard_value_i ),
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"=@cccc" ( borrow ),
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"+m" ( *value )
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: "0" ( subtrahend0 ), "1" ( value0 ),
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"2" ( size ) );
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return borrow;
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}
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/**
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* Shift big integer left
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*
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* @v value0 Element 0 of big integer
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* @v size Number of elements
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* @ret out Bit shifted out
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*/
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static inline __attribute__ (( always_inline )) int
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bigint_shl_raw ( uint64_t *value0, unsigned int size ) {
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bigint_t ( size ) __attribute__ (( may_alias )) *value =
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( ( void * ) value0 );
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uint64_t *discard_value;
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uint64_t discard_value_i;
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unsigned int discard_size;
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int carry;
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__asm__ __volatile__ ( "cmn xzr, xzr\n\t" /* clear CF */
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"\n1:\n\t"
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"ldr %2, [%0]\n\t"
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"adcs %2, %2, %2\n\t"
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"str %2, [%0], #8\n\t"
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"sub %w1, %w1, #1\n\t"
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"cbnz %w1, 1b\n\t"
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: "=r" ( discard_value ),
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"=r" ( discard_size ),
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"=r" ( discard_value_i ),
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"=@cccs" ( carry ),
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"+m" ( *value )
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: "0" ( value0 ), "1" ( size ) );
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return carry;
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}
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/**
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* Shift big integer right
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*
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* @v value0 Element 0 of big integer
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* @v size Number of elements
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* @ret out Bit shifted out
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*/
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static inline __attribute__ (( always_inline )) int
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bigint_shr_raw ( uint64_t *value0, unsigned int size ) {
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bigint_t ( size ) __attribute__ (( may_alias )) *value =
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( ( void * ) value0 );
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uint64_t *discard_value;
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uint64_t discard_high;
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unsigned int discard_size;
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uint64_t low;
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__asm__ __volatile__ ( "mov %2, #0\n\t"
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"\n1:\n\t"
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"sub %w1, %w1, #1\n\t"
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"ldr %3, [%0, %1, lsl #3]\n\t"
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"extr %2, %2, %3, #1\n\t"
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"str %2, [%0, %1, lsl #3]\n\t"
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"mov %2, %3\n\t"
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"cbnz %w1, 1b\n\t"
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: "=r" ( discard_value ),
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"=r" ( discard_size ),
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"=r" ( discard_high ),
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"=r" ( low ),
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"+m" ( *value )
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: "0" ( value0 ), "1" ( size ) );
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return ( low & 1 );
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}
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/**
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* Test if big integer is equal to zero
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*
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* @v value0 Element 0 of big integer
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* @v size Number of elements
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* @ret is_zero Big integer is equal to zero
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*/
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static inline __attribute__ (( always_inline, pure )) int
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bigint_is_zero_raw ( const uint64_t *value0, unsigned int size ) {
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const uint64_t *value = value0;
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uint64_t value_i;
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do {
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value_i = *(value++);
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if ( value_i )
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break;
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} while ( --size );
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return ( value_i == 0 );
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}
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/**
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* Compare big integers
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*
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* @v value0 Element 0 of big integer
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* @v reference0 Element 0 of reference big integer
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* @v size Number of elements
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* @ret geq Big integer is greater than or equal to the reference
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*/
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static inline __attribute__ (( always_inline, pure )) int
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bigint_is_geq_raw ( const uint64_t *value0, const uint64_t *reference0,
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unsigned int size ) {
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const uint64_t *value = ( value0 + size );
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const uint64_t *reference = ( reference0 + size );
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uint64_t value_i;
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uint64_t reference_i;
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do {
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value_i = *(--value);
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reference_i = *(--reference);
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if ( value_i != reference_i )
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break;
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} while ( --size );
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return ( value_i >= reference_i );
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}
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/**
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* Find highest bit set in big integer
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*
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* @v value0 Element 0 of big integer
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* @v size Number of elements
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* @ret max_bit Highest bit set + 1 (or 0 if no bits set)
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*/
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static inline __attribute__ (( always_inline )) int
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bigint_max_set_bit_raw ( const uint64_t *value0, unsigned int size ) {
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const uint64_t *value = ( value0 + size );
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int max_bit = ( 8 * sizeof ( bigint_t ( size ) ) );
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uint64_t value_i;
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do {
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value_i = *(--value);
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max_bit -= ( 64 - fls ( value_i ) );
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if ( value_i )
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break;
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} while ( --size );
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return max_bit;
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}
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/**
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* Grow big integer
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*
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* @v source0 Element 0 of source big integer
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* @v source_size Number of elements in source big integer
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* @v dest0 Element 0 of destination big integer
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* @v dest_size Number of elements in destination big integer
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*/
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static inline __attribute__ (( always_inline )) void
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bigint_grow_raw ( const uint64_t *source0, unsigned int source_size,
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uint64_t *dest0, unsigned int dest_size ) {
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unsigned int pad_size = ( dest_size - source_size );
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memcpy ( dest0, source0, sizeof ( bigint_t ( source_size ) ) );
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memset ( ( dest0 + source_size ), 0, sizeof ( bigint_t ( pad_size ) ) );
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}
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/**
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* Shrink big integer
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*
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* @v source0 Element 0 of source big integer
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* @v source_size Number of elements in source big integer
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* @v dest0 Element 0 of destination big integer
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* @v dest_size Number of elements in destination big integer
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*/
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static inline __attribute__ (( always_inline )) void
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bigint_shrink_raw ( const uint64_t *source0, unsigned int source_size __unused,
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uint64_t *dest0, unsigned int dest_size ) {
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memcpy ( dest0, source0, sizeof ( bigint_t ( dest_size ) ) );
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}
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/**
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* Finalise big integer
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*
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* @v value0 Element 0 of big integer to finalise
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* @v size Number of elements
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* @v out Output buffer
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* @v len Length of output buffer
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*/
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static inline __attribute__ (( always_inline )) void
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bigint_done_raw ( const uint64_t *value0, unsigned int size __unused,
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void *out, size_t len ) {
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const uint8_t *value_byte = ( ( const void * ) value0 );
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uint8_t *out_byte = ( out + len );
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/* Copy raw data in reverse order */
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while ( len-- )
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*(--out_byte) = *(value_byte++);
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}
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/**
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* Multiply big integer elements
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*
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* @v multiplicand Multiplicand element
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* @v multiplier Multiplier element
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* @v result Result element
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* @v carry Carry element
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*/
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static inline __attribute__ (( always_inline )) void
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bigint_multiply_one ( const uint64_t multiplicand, const uint64_t multiplier,
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uint64_t *result, uint64_t *carry ) {
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uint64_t discard_low;
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uint64_t discard_high;
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__asm__ __volatile__ ( /* Perform multiplication */
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"mul %0, %4, %5\n\t"
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"umulh %1, %4, %5\n\t"
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/* Accumulate result */
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"adds %2, %2, %0\n\t"
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"adc %1, %1, xzr\n\t"
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/* Accumulate carry (cannot overflow) */
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"adds %2, %2, %3\n\t"
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"adc %3, %1, xzr\n\t"
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: "=&r" ( discard_low ),
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"=r" ( discard_high ),
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"+r" ( *result ),
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"+r" ( *carry )
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: "r" ( multiplicand ),
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"r" ( multiplier )
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: "cc" );
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}
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#endif /* _BITS_BIGINT_H */
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