View Source megaco_encoder behaviour (megaco v4.6)

Megaco encoder behaviour.

The following functions should be exported from a megaco_encoder callback module:

DATA TYPES

Note

Note that the actual definition of (some of) these records depend on the megaco protocol version used. For instance, the 'TransactionReply' record has two more fields in version 3, so a simple erlang type definition cannot be made here.

protocol_version() = integer()
segment_no()       = integer()
megaco_message() = #'MegacoMessage{}'
transaction() = {transactionRequest,     transaction_request()}      |
                {transactionPending,     transaction_reply()}        |
                {transactionReply,       transaction_pending()}      |
                {transactionResponseAck, transaction_response_ack()} |
                {segmentReply,           segment_reply()}
transaction_request() = #'TransactionRequest'{}
transaction_pending() = #'TransactionPending'{}
transaction_reply() = #'TransactionReply'{}
transaction_response_ack() = [transaction_ack()]
transaction_ack() = #'TransactionAck'{}
segment_reply() = #'SegmentReply'{}
action_request() = #'ActionRequest'{}
action_reply() = #'ActionReply'{}
command_request() = #'CommandRequest'{}
error_desc()   = #'ErrorDescriptor'{}

Summary

Types

Alpha Numeric characters: A..Z | a..z

Decimal digits: 0..9

There is no way to properly express this type in the Erlang type system, so this is the best we can do.

There is no way to properly express this type in the Erlang type system, so this is the best we can do. The minimum length is 1 and the maximum length is 64.

The problem with TransactionReply is that its definition depend on which version of the protocol we are using. As of version 3, it has two more fields.

Callbacks

Perform a minimal decode of a megaco message.

Encode a megaco action reply. If this, for whatever reason, is not supported, the function should return the error reason not_implemented.

Encode megaco action requests. This function is called when the user calls the function encode_actions/3. If that function is never used or if the codec cannot support this (the encoding of individual actions), then return with error reason not_implemented.

Encode a megaco transaction. If this, for whatever reason, is not supported, the function should return the error reason not_implemented.

Types

-type action_reply() :: {'ActionReply', _, _, _}.
-type action_request() :: {'ActionRequest', _, _, _, _}.
-type alpha() :: 65..90 | 97..122.

Alpha Numeric characters: A..Z | a..z

-type command_request() :: {'CommandRequest', _, _, _}.
-type deviceName() :: pathName().
-type digit() :: 48..57.

Decimal digits: 0..9

-type domainName() :: #'DomainName'{name :: term(), portNumber :: term()}.
-type error_desc() :: #'ErrorDescriptor'{errorCode :: term(), errorText :: term()}.
-type ip4Address() :: #'IP4Address'{address :: term(), portNumber :: term()}.
-type ip6Address() :: #'IP6Address'{address :: term(), portNumber :: term()}.
-type megaco_message() :: #'MegacoMessage'{authHeader :: term(), mess :: term()}.
-type mtpAddress() :: octet_string().

There is no way to properly express this type in the Erlang type system, so this is the best we can do.

A proper definition would be: -type mtpAddress() :: octet_string(2..4).

-type octet() :: 0..255.
-type octet_string() :: [octet()].
-type pathName() :: [$* | alpha() | digit() | $_ | $/ | $$ | $@ | $- | $.].

There is no way to properly express this type in the Erlang type system, so this is the best we can do. The minimum length is 1 and the maximum length is 64.

Here is the ABNF (copied from the megaco standard) to fill in the blanks:

# Total length of pathNAME must not exceed 64 chars.

pathNAME = ["*"] NAME *("/" / "*"/ ALPHA / DIGIT /"_" / "$" ) ["@" pathDomainName ]

# ABNF allows two or more consecutive "." although it is meaningless in a path domain name.

pathDomainName = (ALPHA / DIGIT / "*" ) *63(ALPHA / DIGIT / "-" / "*" / ".")

NAME = ALPHA *63(ALPHA / DIGIT / "_" )

-type protocol_version() :: pos_integer().
-type segment_no() :: 0..65535.
-type segment_reply() ::
    #'SegmentReply'{transactionId :: term(),
                    segmentNumber :: term(),
                    segmentationComplete :: term()}.
-type transaction() ::
    {transactionRequest, transaction_request()} |
    {transactionPending, transaction_reply()} |
    {transactionReply, transaction_pending()} |
    {transactionResponseAck, transaction_response_ack()} |
    {segmentReply, segment_reply()}.
-type transaction_ack() :: #'TransactionAck'{firstAck :: term(), lastAck :: term()}.
-type transaction_pending() :: #'TransactionPending'{transactionId :: term()}.
-type transaction_reply() :: {'TransactionReply', _, _} | {'TransactionReply', _, _, _, _}.

The problem with TransactionReply is that its definition depend on which version of the protocol we are using. As of version 3, it has two more fields.

-type transaction_request() :: #'TransactionRequest'{transactionId :: term(), actions :: term()}.
Link to this type

transaction_response_ack()

View Source
-type transaction_response_ack() :: [transaction_ack()].

Callbacks

Link to this callback

decode_message(EncodingConfig, Version, Bin)

View Source
-callback decode_message(EncodingConfig, Version, Bin) -> {ok, Message} | Error
                  when
                      EncodingConfig :: list(),
                      Version :: protocol_version() | dynamic,
                      Bin :: binary(),
                      Message :: megaco_message(),
                      Error :: term().

Decode a megaco message.

Note that if the Version argument is dynamic, the decoder should try to figure out the actual version from the message itself and then use the proper decoder, e.g. version 1.
If on the other hand the Version argument is an integer, it means that this is the expected version of the message and the decoder for that version should be used.

Link to this callback

decode_mini_message(EncodingConfig, Version, Bin)

View Source
-callback decode_mini_message(EncodingConfig, Version, Bin) -> {ok, Message} | Error
                       when
                           EncodingConfig :: list(),
                           Version :: protocol_version() | dynamic,
                           Bin :: binary(),
                           Message :: megaco_message(),
                           Error :: term().

Perform a minimal decode of a megaco message.

The purpose of this function is to do a minimal decode of Megaco message. A successfull result is a 'MegacoMessage' in which only version and mid has been initiated. This function is used by the megaco_messenger module when the decode_message/3 function fails to figure out the mid (the actual sender) of the message.

Note again that a successfull decode only returns a partially initiated message.

Link to this callback

encode_action_reply(EncodingConfig, Version, AR)

View Source (optional)
-callback encode_action_reply(EncodingConfig, Version, AR) -> {ok, Bin} | {error, Reason}
                       when
                           EncodingConfig :: list(),
                           Version :: protocol_version(),
                           AR :: action_reply(),
                           Bin :: binary(),
                           Reason :: not_implemented | term().

Encode a megaco action reply. If this, for whatever reason, is not supported, the function should return the error reason not_implemented.

This function is used when segmentation has been configured. So, for this to work, this function must be fully supported!

Link to this callback

encode_action_requests(EncodingConfig, Version, ARs)

View Source
-callback encode_action_requests(EncodingConfig, Version, ARs) -> {ok, Bin} | {error, Reason}
                          when
                              EncodingConfig :: list(),
                              Version :: protocol_version(),
                              ARs :: [action_request()],
                              Bin :: binary(),
                              Reason :: not_implemented | term().

Encode megaco action requests. This function is called when the user calls the function encode_actions/3. If that function is never used or if the codec cannot support this (the encoding of individual actions), then return with error reason not_implemented.

Link to this callback

encode_message(EncodingConfig, Version, Message)

View Source
-callback encode_message(EncodingConfig, Version, Message) -> {ok, Bin} | Error
                  when
                      EncodingConfig :: list(),
                      Version :: protocol_version(),
                      Message :: megaco_message(),
                      Bin :: binary(),
                      Error :: term().

Encode a megaco message.

Link to this callback

encode_transaction(EncodingConfig, Version, Transaction)

View Source
-callback encode_transaction(EncodingConfig, Version, Transaction) -> {ok, Bin} | {error, Reason}
                      when
                          EncodingConfig :: list(),
                          Version :: protocol_version(),
                          Transaction :: transaction(),
                          Bin :: binary(),
                          Reason :: not_implemented | term().

Encode a megaco transaction. If this, for whatever reason, is not supported, the function should return the error reason not_implemented.

This functionality is used both when the transaction sender is used and for segmentation. So, for either of those to work, this function must be fully supported!