Re: [ASN1] SEQUENCE OF CHOICE with auto tagging

[WangHao]

I think that A1 xx             a1 �             ax ..             . may be right.   According to X.680, "automatic tagging is a syntactical transformation which is applied to the ComponentTypeLists and AlternativeTypeLists productions occurring within the defintion of the module". Therefore, "Transaction" following the SEQUENCE OF has no automaitc tag, but transactionXXXs within the Transaction CHOICE have automatic tags.   So, when the encoder encoding the value of type Transaction it actually encode the the value of alternative type selected within the Transsaction. Decoder can identify the encoding unambiguously since automaitc tagging can ensure that.     Author Name: Wang Hao Phone:+86-755-89650628 EMail:[EMAIL PROTECTED] ***************************************************************** This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! ***************************************************************** ----- Original Message ----- From: Robert Hewitt To: [EMAIL PROTECTED] Sent: Tuesday, September 28, 2004 4:08 PM Subject: [ASN1] SEQUENCE OF CHOICE with auto tagging     The Megaco spec H.248.1 defines :         transactions    SEQUENCE OF Transaction   where Transaction ::= CHOICE {     transactionRequest      TransactionRequest,     transactionPending  TransactionPending,     transactionReply    TransactionReply,     transactionResponseAck  TransactionResponseAck,           -- use of response acks is dependent on underlying transport     ... }   and it uses AUTOMATIC TAGS.   My question is over the encoding: for each transaction is there a tag for the CHOICE (followed by the tag for the transaction), or just a tag for the type of transaction. If the former presumably the tag is context 0?   Ie is it: A1 xx a0 xx a1 �.. //a request a0 xx ax �//some other . .     or A1 xx             a1 �             ax ..             .             . ??? Thanks Robert Hewitt _______________________________________________ ASN1 mailing list [EMAIL PROTECTED] http://lists.asn1.org/mailman/listinfo/asn1

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