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use v6;
use experimental :pack;
use Crypt::Misc:from<Perl5> <decode_b58b>;
use Digest::SHA256::Native;
my Sub $decode_b58b := &Crypt::Misc::decode_b58b;
my constant %ADDR-FORMATS =
(1 => 'P2PKH', 3 => 'P2SH', bc1 => 'Bech32');
my Str constant $DEFAULT-ADDR =
'1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2';
my Regex constant $INVALID-CHARS =
rx{ ( <-[1..9A..HJ..NP..Za..km..z]> ) };
my UInt constant $MAX-CHARS = 35;
my UInt constant $MIN-CHARS = 26;
my Str constant $TAB = ' ';
sub MAIN(Str:D $address = $DEFAULT-ADDR)
{
print "\nBitcoin address: \"$address\"\n";
my Str:D $format = '';
if my $error = validate-format($address, $format)
{
print "{$TAB}Format validation FAILED: $error\n";
}
elsif $format eq 'Bech32'
{
print "{$TAB}Bech32 format not currently supported\n";
}
else
{
print "{$TAB}Format is \"$format\"\n";
if $error = validate-chars($address)
{
print "{$TAB}Character validation FAILED: $error\n";
}
elsif validate-checksum($address)
{
print "{$TAB}Checksum validation PASSED\n";
}
else
{
print "{$TAB}Checksum validation FAILED\n";
}
}
}
sub validate-format(Str:D $address, Str:D $format is rw)
{
my Str $error;
for keys %ADDR-FORMATS -> Str $prefix
{
if $address ~~ /^$prefix/
{
$format = %ADDR-FORMATS{$prefix};
last;
}
}
unless $format
{
my UInt $len = $address.substr(0, 1) eq 'b' ??
$address.substr(1, 1) eq 'c' ?? 3 !! 2 !! 1;
$error = 'invalid prefix "' ~ $address.substr(0, $len) ~
'", unknown format';
}
return $error;
}
sub validate-chars(Str:D $address)
{
my $chars = $address.chars;
my Str $error;
if $chars < $MIN-CHARS
{
$error = "invalid length $chars (minimum is $MIN-CHARS)";
}
elsif $chars > $MAX-CHARS
{
$error = "invalid length $chars (maximum is $MAX-CHARS)";
}
elsif $address ~~ $INVALID-CHARS
{
$error = "invalid character \"$0\"";
}
return $error;
}
sub validate-checksum(Str:D $address)
{
my Blob[uint8] $raw-data = $decode_b58b($address);
my Str $hex-data = $raw-data.unpack('H*');
my Str $hex-checksum1 = $hex-data.substr(*-8);
my Str $hex-payload = $hex-data.substr(0, *-8);
my Blob[uint8] $raw-payload = pack('H*', $hex-payload);
my Str $hex-digest1 = sha256-hex($raw-payload);
my Blob[uint8] $raw_digest1 = pack('H*', $hex-digest1);
my Str $hex-digest2 = sha256-hex($raw_digest1);
my Str $hex-checksum2 = $hex-digest2.substr(0, 8);
return $hex-checksum1 eq $hex-checksum2;
}
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