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ROOT
Reference Guide |
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Format of StreamerInfo record in release 3.02.06. It is probably not accessed by its key, but from its offset given in the file header. The StreamerInfo record DATA consists of a TList (list) object containing elements of class TStreamerInfo.
----------TKey-(never compressed)---------------------- byte 0->3 Nbytes = Number of bytes in compressed record (TKey+data) TKey::fNbytes 4->5 Version = TKey class version identifier TKey::fVersion 6->9 ObjLen = Number of bytes of uncompressed data TKey::fObjLen 10->13 Datime = Date and time when record was written to file TKey::fDatime | (year-1995)<<26|month<<22|day<<17|hour<<12|minute<<6|second 14->15 KeyLen = Number of bytes in key structure (TKey) (64) TKey::fKeyLen 16->17 Cycle = Cycle of key TKey::fCycle 18->21 SeekKey = Byte offset of record itself (consistency check) TKey::fSeekKey 22->25 SeekPdir = Byte offset of parent directory record (TFile) TKey::fSeekPdir 26->26 lname = Number of bytes in the class name (5) TKey::fClassName 27->31 ClassName = Object Class Name ("TList") TKey::fClassName 32->32 lname = Number of bytes in the object name (12) TNamed::fName 33->44 Name = lName bytes with the name of the object ("StreamerInfo") TNamed::fName 45->45 lTitle = Number of bytes in the object title (18) TNamed::fTitle 46->63 Title = lTitle bytes with the title of the object TNamed::fTitle | ("Doubly linked list")
----------TList-(always compressed at level 1 (even if compression level 0))----
The DATA is a TList collection object containing TStreamerInfo objects. Below is the format of this TList data.
Here is the format of a TList object in Release 3.02.06. Comments and offsets refer specifically to its use in the StreamerInfo record.
--------
0->3 ByteCount = Number of remaining bytes in TList object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->5 Version = Version of TList Class
6->15 = TObject object (a base class of TList) (see Format of the DATA for a TObject object).
| Objects in StreamerInfo record are not referenced.
| Would be two bytes longer (6->17) if object were referenced.
16->16 fName = Number of bytes in name of TList object, followed by the
| name itself. (TCollection::fName). The TList object in
| StreamerInfo record is unnamed, so byte contains 0.
17->20 nObjects = Number of objects in list.
21->.. objects = Sequentially, TStreamerInfo Objects in the list.
| In the StreamerInfo record, the objects in the list are
| TStreamerInfo objects. There will be one TStreamerInfo
| object for every class used in data records other than
| core records and the StreamerInfo record itself.
-------
Here is the format of a TStreamerInfo object in Release 3.02.06. Note: Although TStreamerInfo does not use the default streamer, it has the same format as if it did. (compare with Format of a class object in DATA)
0->3 ByteCount = Number of remaining bytes in TStreamerInfo object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->.. ClassInfo = Information about TStreamerInfo class
| If this is the first occurrence of a TStreamerInfo object in the record
| 4->7 -1 = New class tag (constant kNewClassTag = 0xffffffff)
| 8->21 Classname = Object Class Name "TStreamerInfo" (null terminated)
| Otherwise
| 4->7 clIdx = Byte offset of new class tag in record, plus 2.
| OR'd with kClassMask (0x80000000)
0->3 ByteCount = Number of remaining bytes in TStreamerInfo object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->5 Version = Version of TStreamerInfo Class
-Begin TNamed object (Base class of TStreamerInfo)
6->9 ByteCount = Number of remaining bytes in TNamed object
| OR'd with kByteCountMask (0x40000000)
10->11 Version = Version of TNamed Class
12->21 = TObject object (Base class of TNamed) (see Format of the DATA for a TObject object).
| Objects in StreamerInfo record are not referenced.
| Would be two bytes longer (12->23) if object were referenced.
22->.. fName = Number of bytes in name of class that this TStreamerInfo object
| describes, followed by the class name itself. (TNamed::fName).
0->.. fTitle = Number of bytes in title of class that this TStreamerInfo object
| describes, followed by the class title itself. (TNamed::fTitle).
| (Class title may be zero length)
-End TNamed object
0->3 fCheckSum = Check sum for class that this TStreamerInfo object describes.
| This checksum is over all base classes and all persistent
| non-static data members. It is computed by TClass::GetCheckSum().
| (TStreamerInfo::fCheckSum)
4->7 fClassVersion = Version of class that this TStreamerInfo object describes.
| (TStreamerInfo::fClassVersion)
-Begin TObjArray object (Data member of TStreamerInfo)
0->3 ByteCount = Number of remaining bytes in TObjArray object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->.. ClassInfo = Information about TObjArray class
| If this is the first occurrence of a TObjArray object in the record
| 4->7 -1 = New class tag (constant kNewClassTag = 0xffffffff)
| 8->17 Classname = Object Class Name "TObjArray" (null terminated)
| Otherwise
| 4->7 clIdx = Byte offset of new class tag in record, plus 2.
| OR'd with kClassMask (0x80000000)
0->3 ByteCount = Number of remaining bytes in TObjArray object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->5 Version = Version of TObjArray Class
6->15 = TObject object (a base class of TObjArray) (see Format of the DATA for a TObject object).
| Objects in StreamerInfo record are not referenced.
| Would be two bytes longer (6->17) if object were referenced.
16->16 fName = Number of bytes in name of TObjArray object, followed by the
| name itself. (TCollection::fName). TObjArray objects in
| StreamerInfo record are unnamed, so byte contains 0.
17->20 nObjects = Number of objects (derived from TStreamerElement) in array.
21->24 fLowerBound = Lower bound of array. Will always be 0 in StreamerInfo record.
25->.. objects = Sequentially, TStreamerElement objects in the array.
| In a TStreamerInfo object, the objects in the TObjArray are
| of various types (described below), all of which inherit
| directly from TStreamerElement objects. There will be one
| such object for every base class of the class that the
| TStreamerInfo object describes, and also one such object for
| each persistent non-static data member of the class that the
| TStreamerInfo object describes.
-End TObjArray object and TStreamerInfo object
-------
The objects stored in the TObjectArray in TStreamerInfo are of various classes, each of which inherits directly from the TStreamerElement class. The possible classes (which we refer to collectively as TStreamer<XXX>) are:
TStreamerBase: Used for a base class. All others below used for data members. TStreamerBasicType: For a basic type TStreamerString: For type TString TStreamerBasicPointer: For pointer to array of basic types TStreamerObject: For an object derived from TObject TStreamerObjectPointer: For pointer to an object derived from TObject TStreamerLoop: For pointer to an array of objects TStreamerObjectAny: For an object not derived from TObject TStreamerSTL: For an STL container (not yet used??) TStreamerSTLString: For an STL string (not yet used??) -------
Here is the format of a TStreamer<XXX> object in Release 3.02.06. In description below,
0->3 ByteCount = Number of remaining bytes in TStreamer<XXX> object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->.. ClassInfo = Information about the specific TStreamer<XXX> class
| If this is the first occurrence of a TStreamerXXX object in the record
| 4->7 -1 = New class tag (constant kNewClassTag = 0xffffffff)
| 8->.. Classname = Object Class Name "TStreamer<XXX>" (null terminated)
| Otherwise
| 4->7 clIdx = Byte offset of new class tag in record, plus 2.
| OR'd with kClassMask (0x80000000)
0->3 ByteCount = Number of remaining bytes in TStreamer<XXX> object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->5 Version = Version of TStreamer<XXX> Class
-Begin TStreamerElement object (Base class of TStreamerXXX)
0->3 ByteCount = Number of remaining bytes in TStreamerElement object (uncompressed)
| OR'd with kByteCountMask (0x40000000)
4->5 Version = Version of TStreamerElement Class
-Begin TNamed object (Base class of TStreamerElement)
6->9 ByteCount = Number of remaining bytes in TNamed object
| OR'd with kByteCountMask (0x40000000)
10->11 Version = Version of TNamed Class
12->21 = TObject object (Base class of TNamed) (see Format of the DATA for a TObject object).
| Objects in StreamerInfo record are not referenced.
| Would be two bytes longer (12->23) if object were referenced.
22->.. fName = Number of bytes in class name of base class or member name of
| data member that this TStreamerElement object describes,
| followed by the name itself. (TNamed::fName).
0->.. fTitle = Number of bytes in title of base class or data member that this
| TStreamerElement object describes, followed by the title itself.
| (TNamed::fTitle).
-End TNamed object
0->3 fType = Type of data described by this TStreamerElement.
| (TStreamerElement::fType)
| Built in types:
| 1:char, 2:short, 3:int, 4:long, 5:float, 8:double
| 11, 12, 13, 14:unsigned char, short, int, long respectively
| 6: an array dimension (counter)
| 15: bit mask (used for fBits field)
|
| Pointers to built in types:
| 40 + fType of built in type (e.g. 43: pointer to int)
|
| Objects:
| 65:TString, 66:TObject, 67:TNamed
| 0: base class (other than TObject or TNamed)
| 61: object data member derived from TObject (other than TObject or TNamed)
| 62: object data member not derived from TObject
| 63: pointer to object derived from TObject (pointer can't be null)
| 64: pointer to object derived from TObject (pointer may be null)
| 501: pointer to an array of objects
| 500: an STL string or container
|
| Arrays:
| 20 + fType of array element (e.g. 23: array of int)
|
4->7 fSize = Size of built in type or of pointer to built in type. 0 otherwise.
| (TStreamerElement::fSize).
8->11 fArrayLength = Size of array (0 if not array)
| (TStreamerElement::fArrayLength).
12->15 fArrayDim = Number of dimensions of array (0 if not an array)
| (TStreamerElement::fArrayDim).
16->35 fMaxIndex = Five integers giving the array dimensions (0 if not applicable)
| (TStreamerElement::fMaxIndex).
36->.. fTypeName = Number of bytes in name of the data type of the data member that
| the TStreamerElement object describes, followed by the name
| itself. If this TStreamerElement object defines a base class
| rather than a data member, the name used is 'BASE'.
| (TStreamerElement::fTypeName).
-End TStreamerElement object
The remaining data is specific to the type of TStreamer<XXX> class.
For TStreamerInfoBase:
0->3 fBaseVersion = Version of base class that this TStreamerElement describes.
For TStreamerBasicType:
No specific data
For TStreamerString:
No specific data
For TStreamerBasicPointer:
0->3 fCountVersion = Version of class with the count (array dimension)
4->.. fCountName= Number of bytes in the name of the data member holding
| the count, followed by the name itself.
0->.. fCountName= Number of bytes in the name of the class holding the
| count, followed by the name itself.
For TStreamerObject:
No specific data
For TStreamerObjectPointer:
No specific data
For TStreamerLoop:
0->3 fCountVersion = Version of class with the count (array dimension)
4->.. fCountName= Number of bytes in the name of the data member holding
| the count, followed by the name itself.
0->.. fCountClass= Number of bytes in the name of the class holding the
| count, followed by the name itself.
For TStreamerObjectAny:
No specific data
For TStreamerSTL:
0->3 fSTLtype = Type of STL container:
| 1:vector, 2:list, 3:deque, 4:map, 5:set, 6:multimap, 7:multiset
4->7 fCType = Type contained in STL container:
| Same values as for fType above, with one addition: 365:STL string
For TStreamerSTLString:
No specific data
