Convert-BER
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=back=head1 OPLISTAn I<opList> is a list of I<operator>-I<value> pairs. An operator canbe any of those defined below, or any defined by sub-classingC<Convert::BER>, which will probably be derived from the primitivesgiven here.The I<value>s depend on whether BER is being encoded or decoded:=over 4=item EncodingIf the I<value> is a scalar, just encode it. If the I<value> is areference to a list, then encode each item in the list in turn. If theI<value> is a code reference, then execute the code. If the returnedvalue is a scalar, encode that value. If the returned value is areference to a list, encode each item in the list in turn.
The I<value> is testedforboolean truth, and encoded appropriately.# Encode a TRUE value$ber->encode(BOOLEAN=> 1,) ordie;=item DecodingThe decoded I<value>s will be either 1 or 0.# Decode a boolean value into $bval$ber->decode(BOOLEAN => \$bval,) or die;=back=head2 INTEGER
=item EncodingThe I<value> is the integer value to be encoded.$ber->encode(INTEGER => -123456,) or die;=item DecodingThe I<value> will be the decoded integer value.$ber->decode(INTEGER => \$ival,) or die;=back=head2 STRINGThis is an OCTET STRING, which is an arbitrarily long binary value.
The I<value> should be the packed bits to encode, B<not> a string ofC<0> and C<1> characters.$ber->encode(BIT_STRING8=>pack('B8','10110101'),) ordie;=item DecodingThe I<value> will be the decoded packed bits.$ber->decode(BIT_STRING8 => \$bval,) or die;=back=head2 REALThe REAL type encodes an floating-point number. It requires the POSIX
=item EncodingThe I<value> should be the number to encode.$ber->encode(REAL => 3.14159265358979,) or die;=item DecodingThe I<value> will be the decoded floating-point value.$ber->decode(REAL => \$rval,);=head2 ObjectDescriptorThe ObjectDescriptor type encodes an ObjectDescriptor string. It is asub-class of C<STRING>.
is 2-bytes wide. It is asub-class of C<STRING>.=head1 CONSTRUCTED OPERATORSThese operators are used to build constructed types, which containvalues in different types, like a C structure.=head2 SEQUENCEA SEQUENCE is a complex type that contains other types, a bit like a Cstructure. Elements inside a SEQUENCE are encoded and decoded in theorder given.=over 4=item EncodingThe I<value> should be a reference to an array containing anotherI<opList> which defines the elements inside the SEQUENCE.$ber->encode(
);$ber->encode(BER=>$tmp,BOOLEAN=> 1);=item DecodingI<value> should be a reference to a scalar, which will contain aC<Convert::BER> object. This object will contain the remainder of thecurrent sequence or set being decoded.# After this, ber2 will contain the encoded INTEGER B<and> STRING.# sval will be ignored and left undefined, but bval will be decoded. The# decode of ber2 will return the integer and string values.$ber->decode(SEQUENCE => [BER => \$ber2,STRING => \$sval,],BOOLEAN => \$bval,);$ber2->decode(INTEGER => \$ival,STRING => \$sval2,);=back=head2 ANYThis is like the C<BER> operator except that when decoding only thenext item is decoded and placed into the C<Convert::BER> objectreturned. There is no difference when encoding.=over 4=item DecodingI<value> should be a reference to a scalar, which will contain aC<Convert::BER> object. This object will only contain the next singleitem in the current sequence being decoded.# After this, ber2 will decode further, and ival and sval# will be decoded.$ber->decode(INTEGER = \$ival,ANY => \$ber2,STRING => \$sval,);=back=head2 OPTIONAL
INTEGER=> 16,# Will be encodedOPTIONAL=> [INTEGER=>undef,# Will not be encoded],STRING=>'Foo',# Will be encoded]);=item DecodingThe contents of I<value> are decoded if possible, if not then decodecontinues at the next I<operator>-I<value> pair.$ber->decode(SEQUENCE => [INTEGER => \$ival1,OPTIONAL => [INTEGER => \$ival2,],STRING => \$sval,]);=back=head2 CHOICEThe I<opList> is a list of alternate I<operator>-I<value> pairs. Onlyone will be encoded, and only one will be decoded.=over 4=item EncodingA scalar at the start of the I<opList> identifies which I<opList>alternative to use for encoding the value. A value of 0 means thefirst one is used, 1 means the second one, etc.# Encode the BMPString alternate of the CHOICE
PrintableString=>'Printable',TeletexString=>'Teletex/T61',BMPString=>'BMP/Unicode',UniversalString=>'Universal/ISO10646',]) ordie;=item DecodingA reference to a scalar at the start of the I<opList> is used to storewhich alternative is decoded (0 for the first one, 1 for the secondone, etc.) Pass undef instead of the ref if you don't care about this,or you store all the alternate values in different variables.# Decode the above.# Afterwards, $alt will be set to 2, $str will be set to 'BMP/Unicode'.$ber->decode(CHOICE => [ \$alt,PrintableString => \$str,TeletexString => \$str,BMPString => \$str,
);Which will encode or decode the data using the formats and tagsdefinedin the C<Net::LDAP::BER>sub-class. It also helps to make thecode more readable.=head2 DEFINING NEW PACKING OPERATORSAs well as defining new operators which inherit from existingoperators it is also possible to define a new operator and how data isencoded and decoded. The interface for doing this is still changingbut will be documented here when it is done. To be continued ...=head1 LIMITATIONSConvert::BER cannot support tags that contain more bits than can bestored in a scalar variable, typically this is 32 bits.Convert::BER cannot support items that have a packed length whichcannot be stored in 32 bits.
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