[anna.git] / include / anna / diameter / codec / Message.hpp

// ANNA - Anna is Not Nothingness Anymore                                                         //
//                                                                                                //
// (c) Copyright 2005-2015 Eduardo Ramos Testillano & Francisco Ruiz Rayo                         //
//                                                                                                //
// See project site at http://redmine.teslayout.com/projects/anna-suite                           //
// See accompanying file LICENSE or copy at http://www.teslayout.com/projects/public/anna.LICENSE //


#ifndef anna_diameter_codec_Message_hpp
#define anna_diameter_codec_Message_hpp


// Local
#include <anna/config/defines.hpp>
#include <anna/diameter/defines.hpp>
#include <anna/diameter/codec/Avp.hpp>
#include <anna/diameter/helpers/base/defines.hpp>

#include <anna/core/DataBlock.hpp>
#include <anna/core/RuntimeException.hpp>

// STL
#include <string>

//------------------------------------------------------------------------------
//---------------------------------------------------------------------- #define
//------------------------------------------------------------------------------

namespace anna {
class Node;
}

namespace anna {

namespace diameter {

namespace stack {
class Dictionary;
class Format;
class Command;
}

namespace codec {

class Avp;
class Engine;

/**
* Diameter message generic container
* <pre>
*    RFC 3588                Diameter Based Protocol           September 2003
*    3.  Diameter Header
*
*       A summary of the Diameter header format is shown below.  The fields
*       are transmitted in network byte order.
*
*        0                   1                   2                   3
*        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
*       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*       |    Version    |                 Message Length                |
*       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*       | command flags |                  Command-Code                 |
*       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*       |                         Application-ID                        |
*       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*       |                      Hop-by-Hop Identifier                    |
*       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*       |                      End-to-End Identifier                    |
*       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*       |  AVPs ...
*       +-+-+-+-+-+-+-+-+-+-+-+-+-
* </pre>
*/
class Message {

  U8 a_version;
  CommandId a_id;          // code and request indicator
  U8 a_flags;
  U32 a_applicationId;
  U32 a_hopByHop;
  U32 a_endToEnd;
  avp_container a_avps; // childrens
  find_container a_finds; // fast access for message first-level avps

  // auxiliary
  int a_insertionPositionForChilds; // used with childrens
  anna::DataBlock a_forCode;

  const Avp* _getAvp(const char *name, int ocurrence, anna::Exception::Mode::_v emode) const throw(anna::RuntimeException);

  // --- Developer notes ---
  // 'AVP Length' does not include posible data padding. Thanks to this, 'Data Length'
  // is the difference between 'AVP Length' and sum of code, length, flags and
  // optionally the vendor-ID (all of them are 32-bit boundary), that is to say:
  // 8 or 12 (vendor-specific avps).
  //
  // Grouped avps 'AVP Length' includes own headers plus the total length of all
  //  underlying AVPs, including their headers and padding, then 'AVP Length' is
  //  always multiple of 4 (library will check this), and smae for 'Data Length'
  //  which is an 'whole avp Length with padding' itself.


  // Children helpers

  // Own
  avp_iterator avp_begin() throw() { return a_avps.begin(); }
  avp_iterator avp_end() throw() { return a_avps.end(); }
  const_avp_iterator avp_begin() const throw() { return a_avps.begin(); }
  const_avp_iterator avp_end() const throw() { return a_avps.end(); }

  /**
  * Gets avp total message length.
  */
  U24 getLength() const throw();


  // Internal
  bool flagsOK(int &rc) const throw(); // flags coherence regarding dictionary. Only must be called when Message is identified at the dictionary.
  int addChild(Avp *avp) throw() { return Avp::addChild(a_avps, a_insertionPositionForChilds, avp); }
  const anna::diameter::stack::Command *getStackCommand(CommandId id) const throw(anna::RuntimeException);

  void setFailedAvp(const parent_t &parent, AvpId wrong, const char *wrongName = NULL) throw(anna::RuntimeException);
  // During message decoding and validation, the first wrong avp is stored and all the tracking is managed to find out its
  //  nested path for the case of grouped avps with wrong avps inside. Remember the RFC 6733, section 7.5:
  //
  //           In the case where the offending AVP is embedded within a Grouped AVP,
  //           the Failed-AVP MAY contain the grouped AVP, which in turn contains
  //           the single offending AVP.  The same method MAY be employed if the
  //           grouped AVP itself is embedded in yet another grouped AVP and so on.
  //           In this case, the Failed-AVP MAY contain the grouped AVP hierarchy up
  //           to the single offending AVP.  This enables the recipient to detect
  //           the location of the offending AVP when embedded in a group.
  //
  // The first wrong avp found will set the final result code, as the RFC recommends:
  //
  //           The value of the Result-Code AVP will provide information on the reason
  //           for the Failed-AVP AVP.  A Diameter answer message SHOULD contain an
  //           instance of the Failed-AVP AVP that corresponds to the error
  //           indicated by the Result-Code AVP.  For practical purposes, this
  //           Failed-AVP would typically refer to the first AVP processing error
  //           that a Diameter node encounters.
  //
  // The message keeps the list (reverse order) of avps hierarchy (in case of grouping) for the final Failed-AVP construction,
  // which is done at the end of decoding or validation, and only the first wrong avp is stored with its corresponding path.


protected:

  /** Codec Engine */
  mutable Engine *a_engine;

  /** Codec Engine getter: avoids have to create base engine when using its child */
  virtual Engine * getEngine() const throw(anna::RuntimeException);

  /**
  * Initializes Message class information.
  * Any reimplementation must first invoke base class method.
  */
  virtual void initialize() throw();


public:

  /**
  * Default constructor
  * @param engine Codec engine used
  */
  Message(Engine *engine = NULL);

  /**
  * Identified constructor
  * @param id Command identifier as pair (code,request-indicator).
  * @param engine Codec engine used
  */
  Message(CommandId id, Engine *engine = NULL);


  /**
  * Sets the codec engine.
  *
  * Once assigned (here or at constructor), this method SHALL NOT be used anymore.
  * Also, the associated dictionary SHOULD NOT BE CHANGED through the engine,
  * unless you know what are you doing.
  * Setting a new different engine with different stack, even same engine where the
  * stack has been dynamically changed, could cause a bad behaviour depending on the
  * changes: in general, if the dictionary grows, nothing bad will happen, but if
  * you remove or modified some elements which were processed with a certain format,
  * will be interpreted as 'unknown' with the new dictionary, and then some problems
  * may occur. If you add elements (vendors, avps, messages) is not a problem.
  *
  * IMPORTANT NOTES:
  * 1) if you want to reuse the message, as a recommendation, you should #clear the
  * message. In that way, next operation will adjust automatically the needed engine.
  * 2) if you have dedicated message objects for each interface (application id), then
  * you could set the corresponding engine on constructor (or setEngine), and forget
  * about #clear. The needed cleanup will be done automatically from decoding and xml
  * loading procedures, and initialized engine will be kept along message operations.
  */
  void setEngine(Engine *engine) throw();


  // Length references
  static const int HeaderLength;


  //    Command Flags
  //    +-+-+-+-+-+-+-+-+
  //    |R P E T r r r r|
  //    +-+-+-+-+-+-+-+-+
  //
  //      R(equest)
  //      P(roxiable)
  //      E(rror)
  //      T(Potentially re-transmitted message)
  //      r(eserved)  - these flag bits are reserved for future use, and
  //                    MUST be set to zero, and ignored by the receiver.
  static const U8 RBitMask;
  static const U8 PBitMask;
  static const U8 EBitMask;
  static const U8 TBitMask;


  /**
  * Destructor
  */
  ~Message();
  // Virtual destructors are useful when you can delete an instance of a derived class through a pointer to base class:
  // This destructor is not virtual, then a pointer to base class (even pointing to a children one) will invoke this destructor, not the derived one.
  // My current solution: virtualizing method 'clear'
  //
  // Recommendation:
  // To sum up, always make base classes' destructors virtual when they're meant to be manipulated polymorphically.

  // setters

  /**
     Sets the command identifier and clear the former content.

     @param id Command identifier as pair (code,request-indicator).
  */
  void setId(CommandId id) throw(anna::RuntimeException);

  /**
     Same as #setId but providing dictionary logical name for Avp searched
  */
  void setId(const char *name) throw(anna::RuntimeException);

  /**
     Sets the command version. By default, messages initializes with value 1.

     @param version Version provided
  */
  void setVersion(U8 version) throw() { a_version = version; }

  /**
     Sets/unsets P bit activation.
     Application should not have to use this because dictionary information is used in order to configure flags when Message identifier is stored.

     @param activate Activates/deactivates the bit. True by default.
  */
  void setProxiableBit(bool activate = true) throw() { if(activate) a_flags |= PBitMask; else a_flags &= (~PBitMask); }

  /**
     Sets/unsets E bit activation.
     Application should not have to use this because dictionary information is used in order to configure flags when Message identifier is stored.
     This flag MUST NOT be set in request messages (in this case, it will be ignored).

     @param activate Activates/deactivates the bit. True by default.
  */
  void setErrorBit(bool activate = true) throw() { if(isRequest()) return; if(activate) a_flags |= EBitMask; else a_flags &= (~EBitMask); }

  /**
     Sets/unsets T bit activation.
     Application should not have to use this because dictionary information is used in order to configure flags when Message identifier is stored.
     This flag MUST NOT be set in answer messages (in this case, it will be ignored).

     @param activate Activates/deactivates the bit. True by default.
  */
  void setPotentiallyReTransmittedMessageBit(bool activate = true) throw() { if(isAnswer()) return; if(activate) a_flags |= TBitMask; else a_flags &= (~TBitMask); }

  /**
     Sets the message application id.

     The codec engine could be configured to force a stack selection based in this field value: see #selectStackWithApplicationId.
     In multistack applications (in case of being monothread), you only have to take care about how to apply this method: the thing
     is that you must not interleave message builds which belongs to different stacks. For example, you could think about setting the
     message header for message A using stack A. Then, start to add the message header fields for a second message B using another stack B.
     Following you would add the message A avps, but then, the stack is not going to be automatically changed (this is only done through this
     method). The result could be unexpected when adding/encoding messages with a dictionary which does not correspond.

     @warning do not interleave build/encode operations between different messages which uses different stacks over the same codec engine.
     It seems common sense, but it is not bad to advice about this.

     @param aid Application-id.
  */
  void setApplicationId(U32 aid) throw(anna::RuntimeException);

  /**
     Sets the message hop-by-hop
     @param hbh Hop-by-hop identifier.
  */
  void setHopByHop(U32 hbh) throw() { a_hopByHop = hbh; }

  /**
     Sets the message end-to-end
     @param ete End-to-end identifier.
  */
  void setEndToEnd(U32 ete) throw() { a_endToEnd = ete; }


  /**
     Sets header to be an answer regarding provided request message code.
     Internally, updates command identifier (indeed request flag), promotes version, application identifier, hop-by-hop and end-to-end fields.

     @param request Message to be answered.

     @warning Request provided must be a request, in other case method do nothing.
  */
  void setHeaderToAnswer(const Message &request) throw(anna::RuntimeException) {
    if(!request.getId().second) return;

    a_engine = request.getEngine(); // we know this will be

    setId(CommandId(request.getId().first, !request.getId().second));
    setVersion(request.getVersion());
    setApplicationId(request.getApplicationId());
    setHopByHop(request.getHopByHop()); // The same Hop-by-Hop Identifier in the request is used in the answer (RFC 6733 Section 6.2).
    setEndToEnd(request.getEndToEnd()); // The same End-to-End Identifier in the request is used in the answer (RFC 6733 Section 6.2).
    setProxiableBit(request.proxiableBit()); // The 'P' bit is set to the same value as the one in the request (RFC 6733 Section 6.2).
  }


  /**
    Standard minimum-answer building from requests. Adds Session-Id (mirrored from request if present), Origin-Host and Origin-Realm
    (which could be configured, extracted from optional Destination AVPs, etc.), and all the Proxy-Info AVPs (added in same order as
    appear on the request). Of course, answer message header is built from request information through #setHeaderToAnswer. Finally,
    message is fixed regarding dictionary elements order (#fix).

    Summing up, as RFC 6733 Section 6.2, says:

    <pre>

        6.2.  Diameter Answer Processing

           When a request is locally processed, the following procedures MUST be
           applied to create the associated answer, in addition to any
           additional procedures that MAY be discussed in the Diameter
           application defining the command:

           o  The same Hop-by-Hop Identifier in the request is used in the
              answer.

           o  The local host's identity is encoded in the Origin-Host AVP.

           o  The Destination-Host and Destination-Realm AVPs MUST NOT be
              present in the answer message.

           o  The Result-Code AVP is added with its value indicating success or
              failure.

           o  If the Session-Id is present in the request, it MUST be included
              in the answer.

           o  Any Proxy-Info AVPs in the request MUST be added to the answer
              message, in the same order they were present in the request.

           o  The 'P' bit is set to the same value as the one in the request.

           o  The same End-to-End identifier in the request is used in the
              answer.

           Note that the error messages (see Section 7) are also subjected to
           the above processing rules.

   Regarding errors, is recommended to use this over automatic answer built at #decode and/or #valid procedures, which would had added
   Result-Code and/or Failed-AVP AVPs if proceed, but be aware of DIAMETER_COMMAND_UNSUPPORTED Result-Code, because becomes impossible
   to fix (Session-Id SHOULD appear immediately following the Diameter header, and #fix do this manually even if no information about
   the command structure is known, but perhaps another fixed AVPs could not comply... use #getResultCode to find out this situation before
   using #setStandardToAnswer). Anyway, application could add another Failed-AVP content no detected internally, for example:
   DIAMETER_CONTRADICTING_AVPS or DIAMETER_INVALID_AVP_BIT_COMBO). Also, application could add more Failed-AVP avps with other
   wrong avps, or accumulate wrong avps inside the one and only Failed-AVP managed by the stack. The standard is open to add multiple
   avps inside Failed-AVP or multiple Failed-AVP avps with single or multiple avps inside. This depends on application criteria regarding
   other nodes. However, internally the Anna::diameter stack only provides one Failed-AVP with the first wrong avp found, as RFC 6733 says
   in section 7.5.

   If application decoding and/or validation operations are ok, user may search for other problems and put the appropiate Result-Code.
   For example, DIAMETER_TOO_BUSY (3004) depends on congestion issues at business layer and cannot be decided with the only message
   information automatically (not all the Result-Code values are taken into account, only those which correspond to anomalies managed
   by anna::diameter::codec). Application Result-Codes could be provided in this prototype, being DIAMETER_SUCCESS the default value if missing.

   </pre>
   @param request Message to be answered.
   @param originHost Mandatory Origin-Host diameter identity value provided by application. If answer has already an Origin-Host, this will be ignored.
   @param originRealm Mandatory Origin-Realm diameter identity value provided by application. If answer has already an Origin-Realm, this will be ignored.
   @param resultCode Result-Code value assigned by application. If non-success value is already assigned, this will be ignored. DIAMETER_SUCCESS is provided by default.

   @warning Request provided must be a request, in other case method do nothing.
  */
  void setStandardToAnswer(const Message &request, const std::string &originHost, const std::string &originRealm, int resultCode = helpers::base::AVPVALUES__Result_Code::DIAMETER_SUCCESS) throw(anna::RuntimeException);


  /**
     Sets a Result-Code AVP over an answer message (for requests, do nothing).
     If Result-Code AVP doesn't exists, is added and then filled with the value provided.
     If Result-Code AVP already exists, value detected is replaced if was DIAMETER_SUCCESS (non success codes are unchanged).
     When provided value corresponds to an protocol error, that is to say within range [3001,3010], message (E)rror bit is
     automatically activated.

     This method is internally used during #decode and/or #valid procedures in order to build automatic answers, but application
     could call this for set another Result-Code no detected by these methods within its category or for other one (application
     layer). These are the Result-Codes implemented (detected) by ANNA::diameter::codec:

     <pre>
        Protocol Errors:

           DIAMETER_COMMAND_UNSUPPORTED
           DIAMETER_INVALID_HDR_BITS
           DIAMETER_INVALID_AVP_BITS

        Permanent Failures:

           DIAMETER_AVP_UNSUPPORTED (F)
           DIAMETER_INVALID_AVP_VALUE (F)
           DIAMETER_MISSING_AVP (F)
           DIAMETER_AVP_NOT_ALLOWED (F)
           DIAMETER_AVP_OCCURS_TOO_MANY_TIMES (F)
           DIAMETER_INVALID_BIT_IN_HEADER
           DIAMETER_INVALID_AVP_LENGTH (F)
           DIAMETER_INVALID_MESSAGE_LENGTH

           (F) Generates Failed-AVP (also DIAMETER_CONTRADICTING_AVPS and DIAMETER_INVALID_AVP_BIT_COMBO
                                     values does, but these are not managed by anna::diameter::codec).
     </pre>

     @param rc Result-Code value. DIAMETER_SUCCESS by default.
  */
  void setResultCode(int rc = helpers::base::AVPVALUES__Result_Code::DIAMETER_SUCCESS) throw(anna::RuntimeException);


  /**
     Gets the Result-Code AVP value from an answer message (for requests, returns -1).
     If missing, -1 value is returned.

     @return Result-Code value for answers, -1 for request and answers without Result-Code AVP inside
  */
  int getResultCode() const throw();


  /**
     Adds an avp child providing its identifier and reserve internal memory it.

     @param id Avp identifier as pair (code,vendor-id).

     @return Pointer to the new created avp.
  */
  Avp * addAvp(AvpId id) throw(anna::RuntimeException) { return Avp::addAvp(a_avps, a_insertionPositionForChilds, id, getEngine()); }


  /**
     Same as #addAvp but providing dictionary logical name for Avp searched
  */
  Avp * addAvp(const char *name) throw(anna::RuntimeException);


  /**
     Adds an avp child providing a persistent pointer (must be maintained by application).
     It is not allowed to add an avp with no codec engine configured, neither if the engine
     is not the same.

     @param avp Avp external pointer. If NULL provided, nothing is done and NULL returned.
     Also NULL returned for bad engine configuration.

     @return Pointer to the added avp (again).
  */
  Avp * addAvp(Avp * avp) throw();


  /**
     Removes an Avp within message (first level) and free resources.

     @param id Avp identifier (pair code + vendor-id).
     @param ocurrence Order of appearance for the searched avp. Zero value means remove all avps with provided identifier at first level (no recursiveness would be allowed in the API in order to avoid unexpected behaviour).
     Negative values could be used to reverse access positions: i.e. -1 is the last ocurrence, -2 is the second to last (penultimate), etc.

     @return Returns true if something was removed. False in other cases (including i.e. when this message is empty).
  */
  bool removeAvp(AvpId id, int ocurrence = 1) throw(anna::RuntimeException) { return Avp::removeAvp(a_avps, (find_container&)a_finds, id, ocurrence, getEngine()); }


  /**
     Same as #removeAvp but providing dictionary logical name for Avp searched
  */
  bool removeAvp(const char *name, int ocurrence = 1) throw(anna::RuntimeException);


  /**
  * Clears and initializes Message class information.
  * Application must clear auxiliary message objects before adding Avps in a new context if the same object is reused.
  * Application don't need to clear a message object before decode operation (decode invokes #clear before any other task).
  * Any reimplementation must first invoke base class method.
  *
  * @param resetEngine Sets to NULL the codec engine (true, default) or respect its current value (false). If you are going
  * to reuse the message instance it is better to clear all the information (default) to manage different stacks, because if
  * you don't initialize the engine to NULL, the second use of the message will keep the same engine deduced from the first
  * decoding/loading operation, which could be wrong if the second message belongs to a different application identifier.
  */
  virtual void clear(bool resetEngine = true) throw(anna::RuntimeException);

  /**
     Decodes buffer provided over class content. If an error ocurred, decoding will stop launching exception (fatal error) or a warning trace (perhaps the achieved
     message is valid against all odds then validation will go on). In case that validation is enabled (codec::Engine::ValidationMode) an exception will be launched
     in a moment which depends on validation depth (codec::Engine::ValidationDepth).

     You could decode multiple times over the same object. A basic cleanup is done respecting the codec engine.

     @param db buffer data block processed. Before decoding, the whole message instance will be cleared (no need to invoke #clear before #decode).
     @param ptrAnswer Answer set by application (could be empty or not), who is responsible for its memory reservation,
     and automatically built regarding standard. If message analyzed realizes to be an answer, internal reference becomes
     NULL because no answer is built for answers. By default, automatic answer is not built.
  */
  void decode(const anna::DataBlock &db, Message *ptrAnswer = NULL) throw(anna::RuntimeException);

  /**
    Fix childrens content regarding dictionary avp positions.
    Message could remain invalid because of possible fixed/mandatory avps.
    This is useful to give flexibility to the application during message construction before encoding or representing the data.
    Is not recommended to fix a recently decoded message because possible validation problems will be hidden.
  */
  void fix() throw();

  /**
     Validates the message regarding dictionary rules like enumerated range, flags coherence, mandatory and fixed types, cardinality qualifiers, etc.
     @return Boolean indicating validation result
     @param ptrAnswer Answer set by application (could be empty or not), who is responsible for its memory reservation,
     and automatically built regarding standard. If message analyzed realizes to be an answer, internal reference becomes
     NULL because no answer is built for answers. By default, automatic answer is not built.
  */
  bool valid(Message *ptrAnswer = NULL) const throw(anna::RuntimeException);

  /**
     Interpret xml data in order to dump over the class content.
     You could apply this multiple times over the same object. A basic cleanup is done respecting the codec engine.
     \param messageNode Message root node obtained from @functions::xmlFileTo
  */
  void fromXML(const anna::xml::Node* messageNode) throw(anna::RuntimeException);

  /**
   * Interpret a xml file in order to create a diameter message
   * You could apply this multiple times over the same object. A basic cleanup is done respecting the codec engine.
   *
   * @see functions::messageXmlDocumentFromXmlFile
   * @see fromXML
   *
   * @param xmlPathFile Complete path file to the xml document which represents the diameter message
   */
  void loadXML(const std::string &xmlPathFile) throw(anna::RuntimeException);


  // getters

  /**
     Gets Message identifier as pair (code, request indicator).
  */
  const CommandId & getId() const throw() { return a_id; }

  /**
     Gets the command version. By default, messages initializes with value 1.

     @return version Message version
  */
  U8 getVersion() const throw() { return a_version; }

  /**
     Gets Message request indicator.
  */
  bool isRequest() const throw() { return a_id.second; }

  /**
     Gets Message answer indicator.
  */
  bool isAnswer() const throw() { return !isRequest(); }

  /**
     Gets the message application id
     @return aid Application-id.
  */
  const U32 & getApplicationId() const throw() { return a_applicationId; }

  /**
     Gets the message hop-by-hop
     @return hbh Hop-by-hop identifier.
  */
  const U32 & getHopByHop() const throw() { return a_hopByHop; }

  /**
     Gets the message end-to-end
     @return ete End-to-end identifier.
  */
  const U32 & getEndToEnd() const throw() { return a_endToEnd; }

  /**
     Gets stack command (dictionary command reference).
  */
  const anna::diameter::stack::Command *getStackCommand() const throw(anna::RuntimeException) { return getStackCommand(a_id); }

  /** Returns R bit activation state */
  bool requestBit() const throw() { return ((a_flags & RBitMask) != 0x00); }

  /** Returns P bit activation state */
  bool proxiableBit() const throw() { return ((a_flags & PBitMask) != 0x00); }

  /** Returns E bit activation state */
  bool errorBit() const throw() { return ((a_flags & EBitMask) != 0x00); }

  /** Returns T bit activation state */
  bool potentiallyReTransmittedMessageBit() const throw() { return ((a_flags & TBitMask) != 0x00); }


  /**
     Access content for internal Avps. Exception mode allows different combinations like cascade access:
     <pre>

        try {
           message->getAvp(anna::diameter::helpers::base::AVP__Multiple_Services_Credit_Control, anna::Exception::Mode::Throw)
                  ->getAvp(anna::diameter::helpers::base::AVP__Rating_Group, anna::Exception::Mode::Throw);
        }
        catch(anna::RuntimeException) {;}
     </pre>

     Or step access:

     <pre>
        const Avp *mscc = message->getAvp(anna::diameter::helpers::base::AVP__Multiple_Services_Credit_Control);
        const Avp *rg;
        if (mscc) rg = mscc->getAvp(anna::diameter::helpers::base::AVP__Rating_Group);
     </pre>

     Replacing procedures becomes easy because an Avp can be searched and its pointer reconfigured by mean #setId and data part setters.
     Deleting procedures must use #removeAvp.
     Access is internally cached to speed up the search operations. This cache is reset after calling #fix or #removeAvp methods.

     @param id Avp identifier (pair code + vendor-id).
     @param ocurrence Order of appearance for the searched avp. Zero position is rejected, but negative values could be used to reverse
     access positions: i.e. -1 is the last ocurrence, -2 is the second to last (penultimate), etc.
     @param emode Excepcion mode handling: Ignore (no action is taken), Throw (excepcion when missing avp), Trace (trace situation as warning).
  */
  const Avp* getAvp(AvpId id, int ocurrence = 1, anna::Exception::Mode::_v emode = anna::Exception::Mode::Throw) const throw(anna::RuntimeException) {
    return Avp::getAvp(a_avps, (find_container&)a_finds, id, ocurrence, getEngine(), emode);
  }

  Avp* getAvp(AvpId id, int ocurrence = 1, anna::Exception::Mode::_v emode = anna::Exception::Mode::Throw) throw(anna::RuntimeException) {
    return const_cast<Avp*>(Avp::getAvp(a_avps, (find_container&)a_finds, id, ocurrence, getEngine(), emode));
  }


  /**
     Same as #getAvp but providing dictionary logical name for Avp searched
  */
  const Avp* getAvp(const char *name, int ocurrence = 1, anna::Exception::Mode::_v emode = anna::Exception::Mode::Throw) const throw(anna::RuntimeException) {
    return _getAvp(name, ocurrence, emode);
  }

  Avp* getAvp(const char *name, int ocurrence = 1, anna::Exception::Mode::_v emode = anna::Exception::Mode::Throw) throw(anna::RuntimeException) {
    return const_cast<Avp*>(_getAvp(name, ocurrence, emode));
  }

// Helpers

  /**
     Counts the number of ocurrences of Avps (first level) with the identifier provided

     @param id Avp identifier (pair code + vendor-id).
  */
  int countAvp(AvpId id) const throw() { return Avp::countAvp(a_avps, id); }

  /**
     Same as #countAvp but providing dictionary logical name for Avp searched
  */
  int countAvp(const char *name) const throw(anna::RuntimeException);

  /**
     Counts the number of children

     @param id Avp identifier (pair code + vendor-id).
  */
  int countChilds() const throw() { return Avp::countChilds(a_avps); }

  /**
     Encodes datablock with the class content. In case that validation is enabled (codec::Engine::ValidationMode) an exception will be launched
     in a moment which depends on validation depth (codec::Engine::ValidationDepth). If you want to see validation errors but go on with encoding,
     you should try/catch #valid() procedure out of #code.

     @return DataBlock encoded (internal memory used)
  */
  const anna::DataBlock & code() throw(anna::RuntimeException);

  /**
     Class xml representation
     \param parent Parent XML node on which hold this instance information.
     \return XML document with relevant information for this instance.
  */
  anna::xml::Node* asXML(anna::xml::Node* parent) const throw();

  /**
     Class xml string representation
     \return XML string representation with relevant information for this instance.
  */
  std::string asXMLString() const throw();

  /**
     Comparison operator by mean serialization

     @param m1 Instance 1 for Message class
     @param m2 Instance 2 for Message class

     @return Comparison result
  */
  friend bool operator == (const Message & m1, const Message & m2) throw() { return (m1.asXMLString() == m2.asXMLString()); }

  /**
     Match a regular expression (string pattern) regarding xml string serialization for this message.
     Using a complex pattern (many avps, grouped ones) it could be necessary to fix the message before
     using the method in order to perform a more controlled comparison. In the same way, flags could be
     ignored to simplify message xml presentation.
     This powerful tool could be used to program traffic analysis and decide future behaviour (routing,
     traslation, etc.).

     <pre>
     Examples:

     The pattern '<avp name="Service-Context-Id" data="(.)*32251@3gpp.org"/>' detects PS charging contexts
     because of data suffix specification '32251@3gpp.org' for that AVP.

     The pattern '<message version="1" name="Capabilities-Exchange-Request"' detects a CER message.

     The pattern (string including carriage returns):

     '<avp name="Subscription-Id">
        <avp name="Subscription-Id-Type" data="0" alias="END_USER_E164"/>
        <avp name="Subscription-Id-Data" data="606000106"/>
     </avp>'

     detects MSISDN (not IMSI) equal to 606000106

     It would seems strange or 'creative' to use regular expressions within an hex string representation,
     but anyway you could also do such kind of things to check non-printable data parts within the message:
     for example, the pattern '<avp name="Framed-IP-Address" hex-data="0a[A-Fa-f0-9][A-Fa-f0-9]0a0a"/>'
     matchs IP addresses for '10.x.10.10' where x = [0..255].

     Note that string pattern could also be generated via #loadXML and then #asXML, that is to say, you
     could get patterns through xml files which act as conditional triggers over message. In that case,
     it is not possible to specify regular expressions within xml 'hex-data' fields because parser will fail
     during hexadecimal read. Normally only printable 'data' fields are used for matching issues.

     For example, imagine a 'pattern.xml' file like:
     <message version="1" name="Credit-Control-Request" application-id="16777236" hop-by-hop-id="0" end-to-end-id="0">
        <avp name="Subscription-Id">
           <avp name="Subscription-Id-Type" data="0" alias="END_USER_E164"/>
           <avp name="Subscription-Id-Data" data="616[0-9]{6,6}"/>
        </avp>
     </message>

     Then you could do:

     anna::diameter::codec::Message patternMessage;
     patternMessage.loadXML("pattern.xml");
     std::string pattern = patternMessage.getAvp("Subscription-Id")->getAvp("Subscription-Id-Type")->asXMLString();
     // Former is '<avp name="Subscription-Id-Data" data="616[0-9]{6,6}"/>'
     bool match = incomingMessage.isLike(pattern);

     Then, messages having MSISDN numbers starting with '616' will match the pattern.
     Note, that any other message codes (and not only Credit-Control-Request ones), could pass the test...
     You could also build that string manually:

     Example 1:
     std::string pattern = "<avp name=\"Subscription-Id\">\n";
     pattern += ANNA_XML_COMPILER_TAB; pattern += "<avp name=\"Subscription-Id-Type\" data=\"0\" alias=\"END_USER_E164\"/>\n"
     pattern += ANNA_XML_COMPILER_TAB; pattern += "<avp name=\"Subscription-Id-Data\" data=\"616[0-9]{6,6}\"/>"

     Example 2:
     std::string pattern = "name=\"Subscription-Id\"(.)*name=\"Subscription-Id-Type\" data=\"0\"(.)*name=\"Subscription-Id-Data\" data=\"616[0-9]{6,6}\"";
     </pre>

     \return Returns the match result
  */
  bool isLike(const std::string &pattern) const throw();


//friend class Engine;
  friend class Avp;
};

}
}
}


#endif