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Decoder.pm
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Decoder.pm
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package MaxMind::DB::Reader::Decoder;
use strict;
use warnings;
use namespace::autoclean;
use autodie;
our $VERSION = '1.000015';
use Carp qw( confess );
use Data::IEEE754 qw( unpack_double_be unpack_float_be );
use Encode ();
use Math::BigInt qw();
use MaxMind::DB::Common 0.040001 qw( %TypeNumToName );
use MaxMind::DB::Reader::Data::Container;
use MaxMind::DB::Reader::Data::EndMarker;
use MaxMind::DB::Types qw( Int );
use Moo;
use MooX::StrictConstructor;
with 'MaxMind::DB::Role::Debugs', 'MaxMind::DB::Reader::Role::Sysreader';
use constant DEBUG => $ENV{MAXMIND_DB_DECODER_DEBUG};
# This is a constant so that outside of testing any references to it can be
# optimised away by the compiler.
use constant POINTER_TEST_HACK => $ENV{MAXMIND_DB_POINTER_TEST_HACK};
binmode STDERR, ':utf8'
if DEBUG;
has _pointer_base => (
is => 'ro',
isa => Int,
init_arg => 'pointer_base',
default => 0,
);
sub decode {
my $self = shift;
my $offset = shift;
confess 'You must provide an offset to decode from when calling ->decode'
unless defined $offset;
confess
q{The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)}
if $offset >= $self->_data_source_size;
if (DEBUG) {
$self->_debug_newline;
$self->_debug_string( 'Offset', $offset );
}
my $ctrl_byte;
$self->_read( \$ctrl_byte, $offset, 1 );
$offset++;
$self->_debug_binary( 'Control byte', $ctrl_byte )
if DEBUG;
$ctrl_byte = unpack( C => $ctrl_byte );
# The type is encoded in the first 3 bits of the byte.
my $type = $TypeNumToName{ $ctrl_byte >> 5 };
$self->_debug_string( 'Type', $type )
if DEBUG;
# Pointers are a special case, we don't read the next $size bytes, we use
# the size to determine the length of the pointer and then follow it.
if ( $type eq 'pointer' ) {
my ( $pointer, $new_offset )
= $self->_decode_pointer( $ctrl_byte, $offset );
return $pointer if POINTER_TEST_HACK;
my $value = $self->decode($pointer);
return wantarray
? ( $value, $new_offset )
: $value;
}
if ( $type eq 'extended' ) {
my $next_byte;
$self->_read( \$next_byte, $offset, 1 );
$self->_debug_binary( 'Next byte', $next_byte )
if DEBUG;
my $type_num = unpack( C => $next_byte ) + 7;
confess
"Something went horribly wrong in the decoder. An extended type resolved to a type number < 8 ($type_num)"
if $type_num < 8;
$type = $TypeNumToName{$type_num};
$offset++;
}
( my $size, $offset )
= $self->_size_from_ctrl_byte( $ctrl_byte, $offset );
$self->_debug_string( 'Size', $size )
if DEBUG;
# The map and array types are special cases, since we don't read the next
# $size bytes. For all other types, we do.
return $self->_decode_map( $size, $offset )
if $type eq 'map';
return $self->_decode_array( $size, $offset )
if $type eq 'array';
return $self->_decode_boolean( $size, $offset )
if $type eq 'boolean';
my $buffer;
$self->_read( \$buffer, $offset, $size )
if $size;
$self->_debug_binary( 'Buffer', $buffer )
if DEBUG;
my $method = '_decode_' . ( $type =~ /^uint/ ? 'uint' : $type );
return wantarray
? ( $self->$method( $buffer, $size ), $offset + $size )
: $self->$method( $buffer, $size );
}
my %pointer_value_offset = (
1 => 0,
2 => 2**11,
3 => 2**19 + 2**11,
4 => 0,
);
sub _decode_pointer {
my $self = shift;
my $ctrl_byte = shift;
my $offset = shift;
my $pointer_size = ( ( $ctrl_byte >> 3 ) & 0b00000011 ) + 1;
$self->_debug_string( 'Pointer size', $pointer_size )
if DEBUG;
my $buffer;
$self->_read( \$buffer, $offset, $pointer_size );
$self->_debug_binary( 'Buffer', $buffer )
if DEBUG;
my $packed
= $pointer_size == 4
? $buffer
: ( pack( C => $ctrl_byte & 0b00000111 ) ) . $buffer;
$packed = $self->_zero_pad_left( $packed, 4 );
$self->_debug_binary( 'Packed pointer', $packed )
if DEBUG;
my $pointer = unpack( 'N' => $packed ) + $self->_pointer_base;
$pointer += $pointer_value_offset{$pointer_size};
$self->_debug_string( 'Pointer to', $pointer )
if DEBUG;
return ( $pointer, $offset + $pointer_size );
}
## no critic (Subroutines::ProhibitUnusedPrivateSubroutines)
sub _decode_utf8_string {
my $self = shift;
my $buffer = shift;
my $size = shift;
return q{} if $size == 0;
## no critic (Subroutines::ProhibitCallsToUnexportedSubs)
return Encode::decode( 'utf-8', $buffer, Encode::FB_CROAK );
}
sub _decode_double {
my $self = shift;
my $buffer = shift;
my $size = shift;
$self->_verify_size( 8, $size );
return unpack_double_be($buffer);
}
sub _decode_float {
my $self = shift;
my $buffer = shift;
my $size = shift;
$self->_verify_size( 4, $size );
return unpack_float_be($buffer);
}
sub _decode_bytes {
my $self = shift;
my $buffer = shift;
my $size = shift;
return q{} if $size == 0;
return $buffer;
}
sub _decode_map {
my $self = shift;
my $size = shift;
my $offset = shift;
$self->_debug_string( 'Map size', $size )
if DEBUG;
my %map;
for ( 1 .. $size ) {
( my $key, $offset ) = $self->decode($offset);
( my $val, $offset ) = $self->decode($offset);
if (DEBUG) {
$self->_debug_string( "Key $_", $key );
$self->_debug_string( "Value $_", $val );
}
$map{$key} = $val;
}
$self->_debug_structure( 'Decoded map', \%map )
if DEBUG;
return wantarray ? ( \%map, $offset ) : \%map;
}
sub _decode_int32 {
my $self = shift;
my $buffer = shift;
my $size = shift;
return 0 if $size == 0;
return unpack( 'N!' => $self->_zero_pad_left( $buffer, 4 ) );
}
{
my $max_int_bytes = log( ~0 ) / ( 8 * log(2) );
sub _decode_uint {
my $self = shift;
my $buffer = shift;
my $size = shift;
if (DEBUG) {
$self->_debug_string( 'UINT size', $size );
$self->_debug_binary( 'Buffer', $buffer );
}
my $int = $size <= $max_int_bytes ? 0 : Math::BigInt->bzero;
return $int if $size == 0;
my @unpacked = unpack( 'C*', $buffer );
for my $piece (@unpacked) {
$int = ( $int << 8 ) | $piece;
}
return $int;
}
}
sub _decode_array {
my $self = shift;
my $size = shift;
my $offset = shift;
$self->_debug_string( 'Array size', $size )
if DEBUG;
my @array;
for ( 1 .. $size ) {
( my $val, $offset ) = $self->decode($offset);
if (DEBUG) {
$self->_debug_string( "Value $_", $val );
}
push @array, $val;
}
$self->_debug_structure( 'Decoded array', \@array )
if DEBUG;
return wantarray ? ( \@array, $offset ) : \@array;
}
sub _decode_container {
return MaxMind::DB::Reader::Data::Container->new;
}
sub _decode_end_marker {
return MaxMind::DB::Reader::Data::EndMarker->new;
}
sub _decode_boolean {
my $self = shift;
my $size = shift;
my $offset = shift;
return wantarray ? ( $size, $offset ) : $size;
}
## use critic
sub _verify_size {
my $self = shift;
my $expected = shift;
my $actual = shift;
confess
q{The MaxMind DB file's data section contains bad data (unknown data type or corrupt data)}
unless $expected == $actual;
}
sub _size_from_ctrl_byte {
my $self = shift;
my $ctrl_byte = shift;
my $offset = shift;
my $size = $ctrl_byte & 0b00011111;
return ( $size, $offset )
if $size < 29;
my $bytes_to_read = $size - 28;
my $buffer;
$self->_read( \$buffer, $offset, $bytes_to_read );
if ( $size == 29 ) {
$size = 29 + unpack( 'C', $buffer );
}
elsif ( $size == 30 ) {
$size = 285 + unpack( 'n', $buffer );
}
else {
$size = 65821 + unpack( 'N', $self->_zero_pad_left( $buffer, 4 ) );
}
return ( $size, $offset + $bytes_to_read );
}
sub _zero_pad_left {
my $self = shift;
my $content = shift;
my $desired_length = shift;
return ( "\x00" x ( $desired_length - length($content) ) ) . $content;
}
1;