smalldiv

#!/usr/bin/perl
# SPDX-License-Identifier: Apache-2.0
# Copyright 2020 Western Digital Corporation or its affiliates.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

use Getopt::Long;

use integer;

$helpusage = "placeholder";

GetOptions ('len=s'       => \$len,
            'num=s'       => \$num,
            'den=s'       => \$den,
            'skip'   => \$skip)  || die("$helpusage");

if (!defined($len)) { $len=8; }
$LEN=$len;

$n=d2b($num);  # numerator - quotient
$m=d2b($den);  # denominator - divisor


printf(".i 8\n");
printf(".o 4\n");
printf(".ilb q_ff[3] q_ff[2] q_ff[1] q_ff[0] m_ff[3] m_ff[2] m_ff[1] m_ff[0]\n");
printf(".ob smallnum[3] smallnum[2] smallnum[1] smallnum[0]\n");
printf(".type fr\n");
for ($q=0; $q<16; $q++) {
    for ($m=0; $m<16; $m++) {
        if ($m==0) { next; }
        $result=int($q/$m);
        printf("%s %s %s\n",d2bl($q,4),d2bl($m,4),d2bl($result,4));
    }
}

exit;

#$LEN=length($n);

$a="0"x$LEN;
$q=$n;

#printf("n=%s, m=%s\n",$n,$m);
#printf("a=%s, q=%s\n",$a,$q);

for ($i=1; $i<=$LEN; $i++) {

    #printf("iteration $n:\n");

    printf("$i: a=%s q=%s\n",$a,$q);


    $signa = substr($a,0,1);


    $a = substr($a.$q,1,$LEN);  # new a with q shifted in

    if ($signa==0) { $a=b2d($a)-b2d($m); }
    else           { $a=b2d($a)+b2d($m); }

    $a=d2b($a);


    $signa = substr($a,0,1);
    if ($signa==0) { $q=substr($q,1,$LEN-1)."1"; }
    else           { $q=substr($q,1,$LEN-1)."0"; }

}


#printf("a=$a\n");
$signa = substr($a,0,1);
if ($signa==1 && !defined($skip)) {
    printf("correction:\n");
    $a=b2d($a)+b2d($m);
    $a=d2b($a);
}
#printf("a=$a\n");
printf("%d / %d = %d R %d ",b2d($n),b2d($m),b2d($q),b2d($a));
if ($a eq $n) { printf("-> remainder equal numerator\n"); }
else          { printf("\n"); }

sub b2d {
    my ($v) = @_;

    $v = oct("0b" . $v);

    return($v);
}

sub d2b {
    my ($v) = @_;

    my $repeat;

    $v = sprintf "%b",$v;
    if (length($v)<$LEN) {
        $repeat=$LEN-length($v);
        $v="0"x$repeat.$v;
    }
    elsif (length($v)>$LEN) {
        $v=substr($v,length($v)-$LEN,$LEN);
    }

    return($v);
}

sub d2bl {
    my ($v,$LEN) = @_;

    my $repeat;

    $v = sprintf "%b",$v;
    if (length($v)<$LEN) {
        $repeat=$LEN-length($v);
        $v="0"x$repeat.$v;
    }
    elsif (length($v)>$LEN) {
        $v=substr($v,length($v)-$LEN,$LEN);
    }

    return($v);
}