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/*-------------------------------------------------------------------------
_moduint.c - routine for unsigned int (16 bit) modulus
Copyright (C) 1999, Sandeep Dutta . sandeep.dutta@usa.net
Bug fixes by Martijn van Balen, aed@iae.nl
This library 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 library 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 library; see the file COPYING. If not, write to the
Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA.
As a special exception, if you link this library with other files,
some of which are compiled with SDCC, to produce an executable,
this library does not by itself cause the resulting executable to
be covered by the GNU General Public License. This exception does
not however invalidate any other reasons why the executable file
might be covered by the GNU General Public License.
-------------------------------------------------------------------------*/
/* Assembler-functions are provided for:
mcs51 small
mcs51 small stack-auto
*/
#if !defined(__SDCC_USE_XSTACK) && !defined(_SDCC_NO_ASM_LIB_FUNCS)
# if defined(__SDCC_mcs51)
# if defined(__SDCC_MODEL_SMALL)
# if defined(__SDCC_STACK_AUTO)
# define _MODUINT_ASM_SMALL_AUTO
# else
# define _MODUINT_ASM_SMALL
# endif
# endif
# endif
#endif
#if defined _MODUINT_ASM_SMALL || defined _MODUINT_ASM_SMALL_AUTO
static void
_moduint_dummy (void) __naked
{
__asm
.globl __moduint
__moduint:
#define count r2
#define al dpl
#define ah dph
#if defined(__SDCC_STACK_AUTO) && !defined(__SDCC_PARMS_IN_BANK1)
ar0 = 0 ; BUG register set is not considered
ar1 = 1
.globl __modint
mov a,sp
add a,#-2 ; 2 bytes return address
mov r0,a ; r0 points to bh
mov ar1,@r0 ; load bh
dec r0
mov ar0,@r0 ; load bl
#define bl r0
#define bh r1
__modint: ; entry point for __modsint
#else // __SDCC_STACK_AUTO
#if !defined(__SDCC_PARMS_IN_BANK1)
#if defined(__SDCC_NOOVERLAY)
.area DSEG (DATA)
#else
.area OSEG (OVR,DATA)
#endif
.globl __moduint_PARM_2
.globl __modsint_PARM_2
__moduint_PARM_2:
__modsint_PARM_2:
.ds 2
.area CSEG (CODE)
#define bl (__moduint_PARM_2)
#define bh (__moduint_PARM_2 + 1)
#else
#define bl (b1_0)
#define bh (b1_1)
#endif
#endif // __SDCC_STACK_AUTO
mov a,bl ; avoid endless loop
orl a,bh
jz div_by_0
mov count,#1
loop1: mov a,bl ; b <<= 1
add a,acc
mov bl,a
mov a,bh
rlc a
jc msbset
mov bh,a
mov a,al ; a - b
subb a,bl ; here carry is always clear
mov a,ah
subb a,bh
jc start
inc count
sjmp loop1
start: clr c
mov a,bh ; b >>= 1;
msbset: rrc a
mov bh,a
mov a,bl
rrc a
mov bl,a
loop2: clr c
mov a,al ; a - b
subb a,bl
mov b,a
mov a,ah
subb a,bh
jc smaller ; a >= b?
mov ah,a ; -> yes; a = a - b;
mov al,b
smaller: ; -> no
clr c
mov a,bh ; b >>= 1;
rrc a
mov bh,a
mov a,bl
rrc a
mov bl,a
djnz count,loop2
div_by_0:
ret
__endasm;
}
#else // defined _MODUINT_ASM_SMALL || defined _MODUINT_ASM_SMALL_AUTO
#define MSB_SET(x) ((x >> (8*sizeof(x)-1)) & 1)
unsigned int
_moduint (unsigned int a, unsigned int b)
{
unsigned char count = 0;
while (!MSB_SET(b))
{
b <<= 1;
if (b > a)
{
b >>=1;
break;
}
count++;
}
do
{
if (a >= b)
a -= b;
b >>= 1;
}
while (count--);
return a;
}
#endif // defined _MODUINT_ASM_SMALL || defined _MODUINT_ASM_SMALL_AUTO
|
