1 #ifndef ALIMUONTRIGGERDDLDECODER_H
2 #define ALIMUONTRIGGERDDLDECODER_H
3 /**************************************************************************
4 * This file is property of and copyright by the ALICE HLT Project *
5 * All rights reserved. *
8 * Artur Szostak <artursz@iafrica.com> *
10 * Permission to use, copy, modify and distribute this software and its *
11 * documentation strictly for non-commercial purposes is hereby granted *
12 * without fee, provided that the above copyright notice appears in all *
13 * copies and that both the copyright notice and this permission notice *
14 * appear in the supporting documentation. The authors make no claims *
15 * about the suitability of this software for any purpose. It is *
16 * provided "as is" without express or implied warranty. *
17 **************************************************************************/
22 /// \file AliMUONTriggerDDLDecoder.h
23 /// \author Artur Szostak <artursz@iafrica.com>
25 /// \brief Implementation of a high performance DDL decoder for the muon trigger.
27 /// This file implementes the AliMUONTriggerDDLDecoder class, which contains
28 /// the core logic for decoding the payload in DDL streams comming from the muon
29 /// spectrometer's hardware trigger in a very efficient manner.
31 /// This implementation is derived from work done by Christian Finck for the
32 /// AliMUONPayloadTrigger class.
34 /// Note to maintainers: Please remember that this file is used by the online
35 /// dHLT system. As an online system, the dHLT requires the fastest code possible
36 /// in the decoders to satisfy its timing constraints. The performance impact
37 /// must be checked before any proposed modification is made to this file.
40 #include "AliMUONTriggerDDLDecoderEventHandler.h"
43 /// \class AliMUONTriggerDDLDecoder
44 /// \brief A high performance decoder class for MUON trigger DDL data.
46 /// This class implements a high performance decoder for decoding DDL payload
47 /// data coming from the muon spectrometers trigger stations.
48 /// It has been implemented using the event driven paradigm with templates,
49 /// which allows us to minimise the number of method calls made in the inner
50 /// loops of the algorithm and minimise the memory footprint.
51 /// At least for optimised production compilations.
52 /// The decoder class only contains the basic decoding and error checking logic.
53 /// It calls methods such as OnNewBuffer, OnDarcHeader, OnNewRegionalStruct,
54 /// OnLocalStruct etc in the event handler during the decoding to return the
55 /// decoded data and headers.
56 /// The event handler class is nothing more than a callback interface to deliver
57 /// the next chunks of decoded data.
58 /// To actually do something with the data, one needs to implement a custom
59 /// event handler (callback) class by inheriting from AliMUONTriggerDDLDecoderEventHandler
60 /// and overriding the callback methods like so:
62 /// class MyCustomHandler : public AliMUONTriggerDDLDecoderEventHandler
65 /// void OnLocalStruct(const AliMUONLocalInfoStruct* localStruct,
66 /// const AliMUONLocalScalarsStruct* scalars)
68 /// // I can do something with the data in 'localStruct' here.
69 /// // and the 'scalars' if they are not NULL.
74 /// Once the custom handler is written then the decoder is instantiated as
75 /// shown below, to use your new custom handler. Also to start decoding one needs
76 /// to call the Decode() method of the decoder.
78 /// AliMUONTriggerDDLDecoder<MyCustomHandler> myDecoder;
79 /// muDecoder.Decoder(buffer, bufferSize);
82 /// Note that this class was written as a template on purpose. To maximise the
83 /// compilers chance to make optimisations and inline the code we must use a template.
84 /// Depending on exactly what you do inside your handler, the decoder could be
85 /// significantly slower if run time polymorphism was used, i.e. making the class
86 /// AliMUONTriggerDDLDecoderEventHandler abstract and using virtual methods.
88 template <class EventHandler>
89 class AliMUONTriggerDDLDecoder
93 /// Default contructor.
94 AliMUONTriggerDDLDecoder() :
95 fExitOnError(true), fTryRecover(false),
96 fAutoDetectScalars(false), fHadError(false),
97 fNoRegionals(0), fMaxRegionals(8), fMaxLocals(16),
101 /// Constant method to return the event handler instance.
102 const EventHandler& GetHandler() const { return fHandler; }
104 /// Returns the event handler instance.
105 EventHandler& GetHandler() { return fHandler; }
107 /// Returns the "exit on error" flag.
108 /// i.e. should the decoder stop on the very first error found.
109 bool ExitOnError() const { return fExitOnError; }
111 /// Sets the "exit on error" flag.
112 /// i.e. should the decoder stop on the very first error found.
113 void ExitOnError(bool value) { fExitOnError = value; }
115 /// Returns the "try to recover from errors" flag.
116 /// i.e. should the decoder try to recover from errors found in the
118 bool TryRecover() const { return fTryRecover; }
120 /// Sets the "try to recover from errors" flag.
121 /// i.e. should the decoder try to recover from errors found in the
123 void TryRecover(bool value) { fTryRecover = value; }
125 /// Returns the flag indicating if we should check for the scalars of
126 /// software triggers automatically or not.
127 bool AutoDetectScalars() const { return fAutoDetectScalars; }
129 /// Sets the flag indicating if we should check for the scalars of
130 /// software triggers automatically or not. If set to true then the
131 /// scalarEvent parameter of the Decode method is ignored.
132 void AutoDetectScalars(bool value) { fAutoDetectScalars = value; }
134 /// Returns the maximum regional structure count expected in the DDL payload.
135 UInt_t MaxRegionals() const { return fMaxRegionals; }
137 /// Sets the maximum regional structure count expected in the DDL payload.
138 void MaxRegionals(UInt_t n) { fMaxRegionals = n; }
140 /// Returns the number of regional structures we actually attempted to decode.
141 UInt_t RegionalsDecoded() const { return fNoRegionals; }
143 /// Returns the maximum local structure count expected in any given regional
144 /// card structure within the DDL payload.
145 UInt_t MaxLocals() const { return fMaxLocals; }
147 /// Sets the maximum local structure count expected in any given regional
148 /// card structure within the DDL payload.
149 void MaxLocals(UInt_t n) { fMaxLocals = n; }
151 /// This method decodes the DDL payload contained in the buffer.
152 bool Decode(const void* buffer, UInt_t bufferSize, bool scalarEvent = false);
154 /// Returns the end of DARC marker key.
155 static UInt_t EndOfDarcWord() { return fgkEndOfDarc; }
157 /// Returns the end of global header marker key.
158 static UInt_t EndOfGlobalWord() { return fgkEndOfGlobal; }
160 /// Returns the end of regional structure marker key.
161 static UInt_t EndOfRegionalWord() { return fgkEndOfReg; }
163 /// Returns the regional error word.
164 static UInt_t RegionalErrorWord() { return fgkErrorWord; }
166 /// Returns the end of local structure marker key.
167 static UInt_t EndOfLocalWord() { return fgkEndOfLocal; }
169 /// Returns the local card disable word.
170 static UInt_t LocalDisableWord() { return fgkDisableWord; }
172 /// Returns value of default DARC type.
173 static UInt_t DarcDefaultType() { return fgkDarcDefaultType; }
175 /// Returns value of Vadorh DARC type.
176 static UInt_t DarcVadorhType() { return fgkDarcVadorhType; }
180 bool fExitOnError; ///< Indicates if we should exit on the very first error.
181 bool fTryRecover; ///< Indicates if we should try recover from a corrupt structures.
182 bool fAutoDetectScalars; ///< Flag to indicate if we should auto-detect if there are scalars in the data.
183 bool fHadError; ///< Indicates if we had an error decoding the data.
184 UInt_t fNoRegionals; ///< The number of regional card structures actually decoded.
185 UInt_t fMaxRegionals; ///< Maximum number of regional card structures allowed in a DDL stream.
186 UInt_t fMaxLocals; ///< Maximum number of local card structures per regional structure allowed in a DDL stream.
187 EventHandler fHandler; ///< The event handler which deals with the generated parsing events.
189 void DecodeBuffer(const UChar_t* start, const UChar_t* end, bool scalarEvent);
190 void DecodeRegionalStructs(const UChar_t* start, const UChar_t* end, bool scalarEvent);
191 const UChar_t* DecodeLocalStructs(const UChar_t* start, const UChar_t* end, bool scalarEvent);
193 const UChar_t* FindKey(
194 UInt_t key, const UChar_t* start, const UChar_t* end
197 static const UInt_t fgkEndOfDarc; ///< Indicates the end of the DARC header.
198 static const UInt_t fgkEndOfGlobal; ///< Indicates the end of the global header just after the DARC header.
199 static const UInt_t fgkEndOfReg; ///< Indicates the end of a regional card structure.
200 static const UInt_t fgkErrorWord; ///< The error word when a regional board is missing.
201 static const UInt_t fgkEndOfLocal; ///< Indicates the end of a local card structure.
202 static const UInt_t fgkDisableWord; ///< Word used to fill "empty" slots.
203 static const UInt_t fgkDarcDefaultType; ///< default type for DARC def.
204 static const UInt_t fgkDarcVadorhType; ///< default type for DARC vadorh
207 //_____________________________________________________________________________
209 // The following are the structure key words which are used to demarcate (identify
210 // the end) of the structures within the raw trigger data.
211 template <class EventHandler>
212 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkEndOfDarc = 0xDEADFACE;
213 template <class EventHandler>
214 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkEndOfGlobal = 0xDEADBEEF;
215 template <class EventHandler>
216 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkEndOfReg = 0xBEEFFACE;
217 template <class EventHandler>
218 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkErrorWord = 0xCAFEDEAD;
219 template <class EventHandler>
220 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkEndOfLocal = 0xCAFEFADE;
221 template <class EventHandler>
222 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkDisableWord = 0x010CDEAD;
223 template <class EventHandler>
224 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkDarcDefaultType = 0x6;
225 template <class EventHandler>
226 const UInt_t AliMUONTriggerDDLDecoder<EventHandler>::fgkDarcVadorhType = 0x4;
229 template <class EventHandler>
230 bool AliMUONTriggerDDLDecoder<EventHandler>::Decode(
231 const void* buffer, UInt_t bufferSize, bool scalarEvent
234 /// This method should be called to actually decode the DDL payload
235 /// contained in a memory buffer. The payload should be in the muon trigger
236 /// system DDL stream format otherwise it will be recognised as corrupt.
237 /// As the decoder progresses it will make method calls to the event handler
238 /// instance (which can be accessed with the GetHandler() method) to indicate
239 /// the start of the DARC header, global header, new regional structures and
240 /// local card structures.
242 /// If an error occurs during the parse, because the data is corrupt, then
243 /// the OnError method is called indicating what the problem was.
244 /// Decoding will stop at this point unless the fExitOnError flag is set
245 /// to false. There is an optional flag fTryRecover which can enable logic
246 /// which will attempt to recover from corruption of the data structures
247 /// in the DDL payload, if they are found to be inconsistent (assumed corrupt).
248 /// The recovery procedure simply involves trying to find in the DDL stream
249 /// the location of the expected end of header/structure marker/key or the
250 /// next expected key, and then continue decoding from there. This kind of
251 /// recovery logic is (and should be) turned off by default and only
252 /// enabled when trying to recover corrupted data.
254 /// \param buffer This is the pointer to the start of the memory buffer
255 /// containing the DDL payload. Remember that this must be the start of
256 /// the payload and not the DDL stream. That is, this pointer should be
257 /// equal to: DDL start pointer + 8 * sizeof(UInt_t).
258 /// \param bufferSize This is the pointer to the first byte just past the
259 /// end of the block structure.
260 /// \param scalarEvent Set to true if this DDL contains a scalar event
261 /// and false if it is a normal physics event. If the fAutoDetectScalars
262 /// flag is true then we ignore this parameter.
263 /// \return Returns false if there was any problem with decoding the data,
264 /// and true otherwise. Note: the data may have been partially decoded
265 /// even if false was returned, which would be indicated by at least one
266 /// call to the event handler's OnLocalStruct or OnNewRegionalStruct methods.
268 assert( buffer != NULL );
272 // We are basically implementing something like a recursive decent parser.
273 // So start by marking the start of buffer position and end of buffer.
274 const UChar_t* start = reinterpret_cast<const UChar_t*>(buffer);
275 const UChar_t* end = start + bufferSize;
277 fHandler.OnNewBuffer(buffer, bufferSize);
278 DecodeBuffer(start, end, scalarEvent);
279 fHandler.OnEndOfBuffer(buffer, bufferSize);
280 return not fHadError;
284 template <class EventHandler>
285 void AliMUONTriggerDDLDecoder<EventHandler>::DecodeBuffer(
286 const UChar_t* start, const UChar_t* end, bool scalarEvent
289 /// This method does the work to decode the buffer's payload data. It
290 /// unpacks the DARC header, the global header, then calls the
291 /// DecodeRegionalStructs() method to decode the regional structures.
292 /// For the DARC and global headers the methods OnDarcHeader and
293 /// OnGlobalHeader of the event handler object are called respectively.
294 /// \param start This is the pointer to the start of the buffer to decode.
295 /// \param end This is the pointer to the first byte just past the
296 /// end of the buffer.
297 /// \param scalarEvent Set to true if this DDL contains a scalar event
298 /// and false if it is a normal physics event.
300 /// fHadError is set to true if there were any errors decoding the buffer
301 /// and the OnError method of the callback event handler is called for
304 const UChar_t* current = start;
306 // Mark the DARC header, but check that we do not overrun the buffer.
307 const UInt_t* darcHeader = reinterpret_cast<const UInt_t*>(current);
308 current += sizeof(UInt_t);
311 // Indicate we had an error and stop the decoding because we
312 // hit the end of the buffer already.
313 fHandler.OnError(EventHandler::kNoDarcHeader, darcHeader);
318 // Check if we need to figure out if this is a scalar event.
319 // If we do, then we do this by checking the event type in the DARC header
320 // and double checking this by checking if the fgkEndOfDarc key is in the
321 // expected location for a scalar event DDL payload.
322 if (fAutoDetectScalars)
324 const UInt_t* expectedEndOfDarc = reinterpret_cast<const UInt_t*>(
325 current + sizeof(AliMUONDarcScalarsStruct)
328 // First make sure not to read past the end of buffer. Then check
329 // the value of the event type in the DARC header.
330 // Physics events are indicated by the two trigger bits of the
331 // DARC header set to 01b. Everything else is a software trigger
333 if (reinterpret_cast<const UChar_t*>(expectedEndOfDarc+1) <= end and
334 EventHandler::GetDarcEventType(*darcHeader) != 0x1
335 and *expectedEndOfDarc == fgkEndOfDarc
346 // Detect how many regional blocks we expect. If we have no idea then
347 // just use what the maximum setting is.
348 switch (EventHandler::GetDarcType(*darcHeader))
350 case fgkDarcVadorhType: fNoRegionals = 1; break;
351 case fgkDarcDefaultType: fNoRegionals = 8; break;
352 default: fNoRegionals = fMaxRegionals; break;
355 // Check if the DARC header indicates we expect more regionals than we
356 // are allowed to decode according to our max regional structures count.
357 // If we do then this is an error and we should indicate it and exit
358 // if so requested by the user. Also we can fix the number of regionals
359 // to expect if we are trying to recover from errors.
360 if (fNoRegionals > fMaxRegionals)
362 fHandler.OnError(EventHandler::kTooManyRegionals, darcHeader);
364 if (fExitOnError) return;
367 fNoRegionals = fMaxRegionals;
371 // Check that the DARC header indicates correctly if we are a scalar event or not.
372 bool darcShowsScalar = (EventHandler::GetDarcEventType(*darcHeader) != 0x1);
373 if (darcShowsScalar != scalarEvent)
375 // Indicate we had an error and stop the decoding if so requested
377 fHandler.OnError(EventHandler::kWrongEventType, darcHeader);
379 if (fExitOnError) return;
382 // Decode the DARC scalars if this is a scalar event.
383 const AliMUONDarcScalarsStruct* darcScalars = NULL;
386 darcScalars = reinterpret_cast<const AliMUONDarcScalarsStruct*>(current);
387 current += sizeof(AliMUONDarcScalarsStruct);
390 // Indicate we had an error and stop the decoding because we
391 // hit the end of the buffer already.
392 fHandler.OnError(EventHandler::kNoDarcScalars, darcScalars);
398 // Now check that the end of DARC header marker is OK.
399 const UInt_t* endOfDarc = reinterpret_cast<const UInt_t*>(current);
400 current += sizeof(UInt_t);
403 // Indicate we had an error and stop the decoding because we
404 // hit the end of the buffer already.
405 fHandler.OnError(EventHandler::kNoEndOfDarc, endOfDarc);
409 if (*endOfDarc != fgkEndOfDarc)
411 // Indicate we had an error and stop the decoding if so requested
413 fHandler.OnError(EventHandler::kBadEndOfDarc, endOfDarc);
415 if (fExitOnError) return;
417 // If the user requested for us to try and recover from structure
418 // errors then we need to try locate the key in the data stream
419 // and continue decoding from there.
422 const UChar_t* keypos = FindKey(fgkEndOfDarc,
423 reinterpret_cast<const UChar_t*>(darcHeader),
428 // remember to continue decoding just past the key.
429 current = keypos + sizeof(UInt_t);
434 fHandler.OnDarcHeader(*darcHeader, darcScalars, current);
436 // Next, we mark the Global header and check that we do not overrun the buffer.
437 const AliMUONGlobalHeaderStruct* globalHeader =
438 reinterpret_cast<const AliMUONGlobalHeaderStruct*>(current);
439 current += sizeof(AliMUONGlobalHeaderStruct);
442 // Indicate we had an error and stop the decoding because we
443 // hit the end of the buffer already.
444 fHandler.OnError(EventHandler::kNoGlobalHeader, globalHeader);
449 // Decode the global scalars if this is a scalar event.
450 const AliMUONGlobalScalarsStruct* globalScalars = NULL;
453 globalScalars = reinterpret_cast<const AliMUONGlobalScalarsStruct*>(current);
454 current += sizeof(AliMUONGlobalScalarsStruct);
457 // Indicate we had an error and stop the decoding because we
458 // hit the end of the buffer already.
459 fHandler.OnError(EventHandler::kNoGlobalScalars, globalScalars);
465 // Now check that the end of global header marker is OK.
466 const UInt_t* endOfGlobal = reinterpret_cast<const UInt_t*>(current);
467 current += sizeof(UInt_t);
470 // Indicate we had an error and stop the decoding because we
471 // hit the end of the buffer already.
472 fHandler.OnError(EventHandler::kNoEndOfGlobal, endOfGlobal);
476 if (*endOfGlobal != fgkEndOfGlobal)
478 // Indicate we had an error and stop the decoding if so requested
480 fHandler.OnError(EventHandler::kBadEndOfGlobal, endOfGlobal);
482 if (fExitOnError) return;
484 // If the user requested for us to try and recover from structure
485 // errors then we need to try locate the key in the data stream
486 // and continue decoding from there.
489 const UChar_t* keypos = FindKey(fgkEndOfGlobal,
490 reinterpret_cast<const UChar_t*>(globalHeader),
495 // remember to continue decoding just past the key.
496 current = keypos + sizeof(UInt_t);
501 fHandler.OnGlobalHeader(globalHeader, globalScalars, current);
503 DecodeRegionalStructs(current, end, scalarEvent);
507 template <class EventHandler>
508 void AliMUONTriggerDDLDecoder<EventHandler>::DecodeRegionalStructs(
509 const UChar_t* start, const UChar_t* end, bool scalarEvent
512 /// This method decodes the regional structures in the DDL data.
513 /// For each regional header found, the OnNewRegionalStruct method of
514 /// the event handler is called, to signal the start of each
515 /// new regional structure. The DecodeLocalStructs() method is then
516 /// called to decode the local trigger structures. Finally, a symmetrical
517 /// call to OnEndOfRegionalStruct of the event handler is called to
518 /// signal that the regional structure has been decoded.
519 /// \param start This is the pointer to the start of the buffer.
520 /// \param end This is the pointer to the first byte just past the
521 /// end of the buffer.
522 /// \param scalarEvent Set to true if this DDL contains a scalar event
523 /// and false if it is a normal physics event.
525 /// fHadError is set to true if there were any errors decoding the buffer
526 /// and the OnError method of the callback event handler is called for
529 const UChar_t* current = start;
531 for (UInt_t iReg = 0; iReg < fNoRegionals; iReg++)
533 const AliMUONRegionalHeaderStruct* regionalHeader =
534 reinterpret_cast<const AliMUONRegionalHeaderStruct*>(current);
535 current += sizeof(AliMUONRegionalHeaderStruct);
539 // So we only got part of a regional header, nothing to do but
540 // report the error and exit.
541 fHandler.OnError(EventHandler::kNoRegionalHeader, regionalHeader);
546 // Skip empty regional board (not connected or with error reading).
547 if (regionalHeader->fDarcWord == fgkErrorWord)
549 //current += sizeof(AliMUONRegionalHeaderStruct); // already done above
551 current += sizeof(AliMUONRegionalScalarsStruct);
552 current += sizeof(UInt_t); // skip the end of regional structure key.
554 // now also skip the local structure part:
555 current += fMaxLocals * sizeof(AliMUONLocalInfoStruct);
557 current += fMaxLocals * sizeof(AliMUONLocalScalarsStruct);
558 current += fMaxLocals * sizeof(UInt_t); // skip all the end of local structure keys.
563 // Decode the regional scalar words if this is a scalar event.
564 const AliMUONRegionalScalarsStruct* regionalScalars = NULL;
567 regionalScalars = reinterpret_cast<const AliMUONRegionalScalarsStruct*>(current);
568 current += sizeof(AliMUONRegionalScalarsStruct);
571 // Indicate we had an error and stop the decoding because we
572 // hit the end of the buffer already.
573 fHandler.OnError(EventHandler::kNoRegionalScalars, regionalScalars);
579 // Now check that the end of regional header marker is OK.
580 const UInt_t* endOfRegional = reinterpret_cast<const UInt_t*>(current);
581 current += sizeof(UInt_t);
584 // Indicate we had an error and stop the decoding because we
585 // hit the end of the buffer already.
586 fHandler.OnError(EventHandler::kNoEndOfRegional, endOfRegional);
590 if (*endOfRegional != fgkEndOfReg)
592 // Indicate we had an error and stop the decoding if so requested
594 fHandler.OnError(EventHandler::kBadEndOfRegional, endOfRegional);
596 if (fExitOnError) return;
598 // If the user requested for us to try and recover from structure
599 // errors then we need to try locate the key in the data stream
600 // and continue decoding from there.
603 const UChar_t* keypos = FindKey(fgkEndOfReg,
604 reinterpret_cast<const UChar_t*>(regionalHeader),
608 // If the fgkEndOfReg key was found exactly one regional
609 // structure later then we should not adjust the current
610 // decoding position because it is more likely that the
611 // end of regional structure key was just corrupt rather
613 // If we could not find another good key then just continue.
614 size_t sizeOfRegional = sizeof(AliMUONRegionalHeaderStruct) + sizeof(UInt_t)
615 + fMaxLocals * (sizeof(AliMUONLocalInfoStruct) + sizeof(UInt_t));
618 sizeOfRegional += sizeof(AliMUONRegionalScalarsStruct)
619 + fMaxLocals * sizeof(AliMUONLocalScalarsStruct);
622 if (keypos != NULL and keypos != current + sizeOfRegional)
624 current = keypos + sizeof(UInt_t);
629 // Tell the handler that we have a new regional block and decode it.
630 // When done, tell the handler again.
631 const UChar_t* startOfLocals = current;
632 fHandler.OnNewRegionalStruct(regionalHeader, regionalScalars, startOfLocals);
633 current = DecodeLocalStructs(current, end, scalarEvent);
634 fHandler.OnEndOfRegionalStruct(regionalHeader, regionalScalars, startOfLocals);
637 // Now just check that there is no extra rubbish at the end of the DDL.
640 fHandler.OnError(EventHandler::kBufferTooBig, current);
646 template <class EventHandler>
647 const UChar_t* AliMUONTriggerDDLDecoder<EventHandler>::DecodeLocalStructs(
648 const UChar_t* start, const UChar_t* end, bool scalarEvent
651 /// This method decodes the local structures in the DDL data for a
652 /// single regional structure. For each local trigger structure found,
653 /// the OnLocalStruct method of the event handler is called.
654 /// \param start This is the pointer to the start of the regional structure
655 /// payload (The pointer just past the regional header key).
656 /// \param end This is the pointer to the first byte just past the
657 /// end of the buffer.
658 /// \param scalarEvent Set to true if this DDL contains a scalar event
659 /// and false if it is a normal physics event.
660 /// \returns The position in the buffer where this method stopped decoding.
662 /// fHadError is set to true if there were any errors decoding the buffer
663 /// and the OnError method of the callback event handler is called for
666 const UChar_t* current = start;
668 for (UInt_t iLocal = 0; iLocal < fMaxLocals; iLocal++)
670 const AliMUONLocalInfoStruct* localStruct =
671 reinterpret_cast<const AliMUONLocalInfoStruct*>(current);
672 current += sizeof(AliMUONLocalInfoStruct);
676 // So we only got part of a local structure, nothing to do but
677 // report the error and exit.
678 fHandler.OnError(EventHandler::kNoLocalStruct, localStruct);
683 // Skip empty local board if card not notified.
684 if (localStruct->fX2X1 == fgkDisableWord and
685 localStruct->fX4X3 == fgkDisableWord and
686 localStruct->fY2Y1 == fgkDisableWord and
687 localStruct->fY4Y3 == fgkDisableWord and
688 localStruct->fTriggerBits == fgkDisableWord
691 //current += sizeof(AliMUONLocalInfoStruct); // already done above
693 current += sizeof(AliMUONLocalScalarsStruct);
694 current += sizeof(UInt_t); // skip the end of local structure key.
698 // Decode the regional scalar words if this is a scalar event.
699 const AliMUONLocalScalarsStruct* localScalars = NULL;
702 localScalars = reinterpret_cast<const AliMUONLocalScalarsStruct*>(current);
703 current += sizeof(AliMUONLocalScalarsStruct);
706 // Indicate we had an error and stop the decoding because we
707 // hit the end of the buffer already.
708 fHandler.OnError(EventHandler::kNoLocalScalars, localScalars);
714 // Now check that the end of regional header marker is OK.
715 const UInt_t* endOfLocal = reinterpret_cast<const UInt_t*>(current);
716 current += sizeof(UInt_t);
719 // Indicate we had an error and stop the decoding because we
720 // hit the end of the buffer already. We can however signal that
721 // we got a local structure, because the buffer contains enough
722 // data to potencially contain the real data of the structure.
723 fHandler.OnError(EventHandler::kNoEndOfLocal, endOfLocal);
724 if (not fExitOnError)
726 fHandler.OnLocalStruct(localStruct, localScalars);
731 if (*endOfLocal != fgkEndOfLocal)
733 // Indicate we had an error and stop the decoding if so requested
735 fHandler.OnError(EventHandler::kBadEndOfLocal, endOfLocal);
737 if (fExitOnError) return current;
739 // If the user requested for us to try and recover from structure
740 // errors then we need to try locate the key in the data stream
741 // and continue decoding from there.
744 const UChar_t* searchPos = reinterpret_cast<const UChar_t*>(localStruct);
745 const UChar_t* firstLocalKey = FindKey(fgkEndOfLocal, searchPos, end);
746 const UChar_t* firstRegionalKey = FindKey(fgkEndOfReg, searchPos, end);
748 // If a regional key was found first, then give up on
749 // anymore local structures from this regional block and
750 // continue decoding from the next regional block.
751 // Also if the fgkEndOfLocal key was found exactly one
752 // local structure later then we should not adjust the
753 // current decoding position because it is more likely that
754 // the end of local structure key was just corrupt rather
756 if (firstLocalKey != NULL and firstRegionalKey != NULL)
758 if (firstLocalKey < firstRegionalKey)
760 size_t sizeOflocalStruct = sizeof(AliMUONLocalInfoStruct) + sizeof(UInt_t);
762 sizeOflocalStruct += sizeof(AliMUONLocalScalarsStruct);
764 if (firstLocalKey != current + sizeOflocalStruct)
765 current = firstLocalKey + sizeof(UInt_t);
769 // Adjust back to the start of the regional header.
770 current = firstRegionalKey - sizeof(AliMUONRegionalHeaderStruct);
772 current -= sizeof(AliMUONRegionalScalarsStruct);
777 // If we could not find another good key then just continue.
781 fHandler.OnLocalStruct(localStruct, localScalars);
788 template <class EventHandler>
789 const UChar_t* AliMUONTriggerDDLDecoder<EventHandler>::FindKey(
790 UInt_t key, const UChar_t* start, const UChar_t* end
793 /// Searches for the first occurrence of the key value in the buffer
794 /// marked by 'start' and 'end'. 'start' should point to the start of
795 /// the buffer and 'end' should point to 'start + bufferSize'.
796 /// \param key The 32 bit word to look for.
797 /// \param start The start location to begin the search at.
798 /// \param end The pointer to the first byte just past end of the
800 /// \returns The location of the first occurance of key in the buffer,
801 /// otherwise NULL is returned if nothing was found.
803 const UChar_t* current = start;
804 while (current + sizeof(UInt_t) <= end)
806 UInt_t data = * reinterpret_cast<const UInt_t*>(current);
807 if (data == key) return current;
813 #endif // ALIMUONTRIGGERDDLDECODER_H