BER(3pm) | User Contributed Perl Documentation | BER(3pm) |
NAME¶
BER - Basic Encoding Rules (BER) of Abstract Syntax Notation One (ASN.1)
SYNOPSIS¶
use BER; $encoded = encode_sequence (encode_int (123), encode_string ("foo")); ($i, $s) = decode_by_template ($encoded, "%{%i%s"); # $i will now be 123, $s the string "foo".
DESCRIPTION¶
This is a simple library to encode and decode data using the Basic Encoding Rules (BER) of Abstract Syntax Notation One (ASN.1). It does not claim to be a complete implementation of the standard, but implements enough of the BER standard to encode and decode SNMP messages.
VARIABLES¶
$pretty_print_timeticks (default: 1)¶
If non-zero (the default), "pretty_print" will convert TimeTicks to "human readable" strings containing days, hours, minutes and seconds.
If the variable is zero, "pretty_print" will simply return an unsigned integer representing hundredths of seconds. If you prefer this, bind $pretty_print_timeticks to zero.
$errmsg - error message from last failed operation.¶
When they encounter errors, the routines in this module will generally return "undef") and leave an informative error message in $errmsg).
METHODS¶
encode_int_0() - encode the integer 0.¶
This is functionally identical to encode_int(0).
encode_int() - encode an integer using the generic "integer" type tag.¶
encode_uinteger32() - encode an integer using the SNMP UInteger32 tag.¶
encode_counter32() - encode an integer using the SNMP Counter32 tag.¶
encode_counter64() - encode an integer using the SNMP Counter64 tag.¶
encode_gauge32() - encode an integer using the SNMP Gauge32 tag.¶
encode_oid() - encode an object ID, passed as a list of sub-IDs.¶
$encoded = encode_oid (1,3,6,1,...);
encode_null() - encode a null object.¶
This is used e.g. in binding lists for variables that don't have a value (yet)
encode_sequence()¶
encode_tagged_sequence()¶
$encoded = encode_sequence (encoded1, encoded2, ...); $encoded = encode_tagged_sequence (tag, encoded1, encoded2, ...);
Take already encoded values, and extend them to an encoded sequence. "encoded_sequence" uses the generic sequence tag, while with "encode_tagged_sequence" you can specify your own tag.
encode_string() - encode a Perl string as an OCTET STRING.¶
encode_ip_address() - encode an IPv4 address.¶
This can either be passed as a four-octet sequence in network byte order, or as a text string in dotted-quad notation, e.g. "192.0.2.234".
encode_timeticks() - encode an integer as a "TimeTicks" object.¶
The integer should count hundredths of a second since the epoch defined by "sysUpTime.0".
pretty_print() - convert an encoded byte sequence into human-readable form.¶
This function can be extended by registering pretty-printing methods for specific type codes. Most BER type codes used in SNMP already have such methods pre-registered by default. See "register_pretty_printer" for how new methods can be added.
hex_string() - convert OCTET STRING to hexadecimal notation.¶
hex_string_of_type() - convert octet string to hex, and check type against given tag.¶
decode_by_template() - decode complex object according to a template.¶
($var1, ...) = decode_by_template ($pdu, $template, ...);
The template can contain various %X directives. Some directives consume additional arguments following the template itself. Most directives will cause values to be returned. The values are returned as a sequence in the order of the directives that generated them.
- %{ - decode sequence.
- This doesn't assign any return value, just checks and skips the tag/length fields of the sequence. By default, the tag should be the generic sequence tag, but a tag can also be specified in the directive. The directive can either specify the tag as a prefix, e.g. "%99{" will require a sequence tag of 99, or if the directive is given as "%*{", the tag will be taken from the next argument.
- %s - decode string
- %i - decode integer
- %u - decode unsigned integer
- %O - decode Object ID (OID)
- %A - decode IPv4 address
- %@ - assigns the remaining undecoded part of the PDU to the next return value.
decode_sequence() - Split sequence into components.¶
($first, $rest) = decode_sequence ($pdu);
Checks whether the PDU has a sequence type tag and a plausible length field. Splits the initial element off the list, and returns both this and the remainder of the PDU.
register_pretty_printer() - register pretty-printing methods for typecodes.¶
This function takes a hashref that specifies functions to call when the specified value type is being printed. It returns the number of functions that were registered.
AUTHORS¶
Created by: Simon Leinen <simon.leinen@switch.ch>
Contributions and fixes by:
- Andrzej Tobola <san@iem.pw.edu.pl>: Added long String decode
- Tobias Oetiker <tobi@oetiker.ch>: Added 5 Byte Integer decode ...
- Dave Rand <dlr@Bungi.com>: Added "SysUpTime" decode
- Philippe Simonet <sip00@vg.swissptt.ch>: Support larger subids
- Yufang HU <yhu@casc.com>: Support even larger subids
- Mike Mitchell <Mike.Mitchell@sas.com>: New generalized "encode_int()"
- Mike Diehn <mdiehn@mindspring.net>: "encode_ip_address()"
- Rik Hoorelbeke <rik.hoorelbeke@pandora.be>: "encode_oid()" fix
- Brett T Warden <wardenb@eluminant.com>: pretty "UInteger32"
- Bert Driehuis <driehuis@playbeing.org>: Handle SNMPv2 exception codes
- Jakob Ilves (/IlvJa) <jakob.ilves@oracle.com>: PDU decoding
- Jan Kasprzak <kas@informatics.muni.cz>: Fix for PDU syntax check
- Milen Pavlov <milen@batmbg.com>: Recognize variant length for ints
COPYRIGHT¶
Copyright (c) 1995-2009, Simon Leinen.
This program is free software; you can redistribute it under the "Artistic License 2.0" included in this distribution (file "Artistic").
2023-06-16 | perl v5.36.0 |