add local fEvolution flag in TMessage. It will be initialized by the value

of fgEvolution at the time of message creation. This to:
1) allow some message to have schema evolution while others not
2) to avoid that the changing of the global fgEvolution during the life-time
   of a message to cause problems


git-svn-id: http://root.cern.ch/svn/root/trunk@24432 27541ba8-7e3a-0410-8455-c3a389f83636

net/net/inc/TMessage.h

@@ -44,16 +44,17 @@ friend class TXSocket;
 
 private:
    TList   *fInfos;       //Array of TStreamerInfo used in WriteObject
-   TBits    fBitsPIDs;    //Array of bits to mark the TProcessIDs uids written to the mesasge
+   TBits    fBitsPIDs;    //Array of bits to mark the TProcessIDs uids written to the message
    UInt_t   fWhat;        //Message type
    TClass  *fClass;       //If message is kMESS_OBJECT pointer to object's class
    Int_t    fCompress;    //Compression level from 0 (not compressed) to 9 (max compression)
    char    *fBufComp;     //Compressed buffer
    char    *fBufCompCur;  //Current position in compressed buffer
    char    *fCompPos;     //Position of fBufCur when message was compressed
-   
-   static Bool_t   fgEvolution;  //True if support for schema evolution required
-   
+   Bool_t   fEvolution;   //True if support for schema evolution required
+
+   static Bool_t fgEvolution;  //True if global support for schema evolution required
+
    // TMessage objects cannot be copied or assigned
    TMessage(const TMessage &);           // not implemented
    void operator=(const TMessage &);     // not implemented
@@ -66,17 +67,17 @@ public:
    TMessage(UInt_t what = kMESS_ANY);
    virtual ~TMessage();
 
-   static void EnableSchemaEvolution(Bool_t enable=kTRUE);
-   
    void     ForceWriteInfo(TVirtualStreamerInfo *info, Bool_t force);
    void     Forward();
-   TClass  *GetClass() const { return fClass;} 
+   TClass  *GetClass() const { return fClass;}
    void     IncrementLevel(TVirtualStreamerInfo* info);
    void     Reset();
    void     Reset(UInt_t what) { SetWhat(what); Reset(); }
    UInt_t   What() const { return fWhat; }
    void     SetWhat(UInt_t what);
 
+   void     EnableSchemaEvolution(Bool_t enable = kTRUE) { fEvolution = enable; }
+   Bool_t   UsesSchemaEvolution() const { return fEvolution; }
    void     SetCompressionLevel(Int_t level = 1);
    Int_t    GetCompressionLevel() const { return fCompress; }
    Int_t    Compress();
@@ -87,6 +88,9 @@ public:
    void     WriteObject(const TObject *obj);
    UShort_t WriteProcessID(TProcessID *pid);
 
+   static void   EnableSchemaEvolutionForAll(Bool_t enable = kTRUE);
+   static Bool_t UsesSchemaEvolutionForAll();
+
    ClassDef(TMessage,0)  // Message buffer class
 };
 

net/net/src/TMessage.cxx

@@ -60,7 +60,7 @@ TMessage::TMessage(UInt_t what) : TBufferFile(TBuffer::kWrite)
    fBufCompCur = 0;
    fCompPos    = 0;
    fInfos      = 0;
-   
+   fEvolution  = kFALSE;
 }
 
 //______________________________________________________________________________
@@ -79,6 +79,7 @@ TMessage::TMessage(void *buf, Int_t bufsize) : TBufferFile(TBuffer::kRead, bufsi
    fBufCompCur = 0;
    fCompPos    = 0;
    fInfos      = 0;
+   fEvolution  = kFALSE;
 
    if (fWhat & kMESS_ZIP) {
       // if buffer has kMESS_ZIP set, move it to fBufComp and uncompress
@@ -108,19 +109,27 @@ TMessage::~TMessage()
 }
 
 //______________________________________________________________________________
-void TMessage::EnableSchemaEvolution(Bool_t enable)
+void TMessage::EnableSchemaEvolutionForAll(Bool_t enable)
 {
-   //static function enabling or disabling the automatic schema evolution
-   //by default schema evolution support is off
-   
+   // Static function enabling or disabling the automatic schema evolution.
+   // By default schema evolution support is off.
+
    fgEvolution = enable;
 }
 
+//______________________________________________________________________________
+Bool_t TMessage::UsesSchemaEvolutionForAll()
+{
+   // Static function returning status of global schema evolution.
+
+   return fgEvolution;
+}
+
 //______________________________________________________________________________
 void TMessage::ForceWriteInfo(TVirtualStreamerInfo *info, Bool_t /* force */)
 {
    // force writing the TStreamerInfo to the message
-   
+
    if (fgEvolution) fInfos->Add(info);
 }
 
@@ -146,7 +155,7 @@ void TMessage::IncrementLevel(TVirtualStreamerInfo* info)
    // Increment level.
 
    TBufferFile::IncrementLevel(info);
-  
+
    if (fgEvolution) fInfos->Add(info);
 }