<!-- TBuffer.md --- 
;; 
;; Description: 
;; Author: Hongyi Wu(吴鸿毅)
;; Email: wuhongyi@qq.com 
;; Created: 二 9月 13 20:54:28 2016 (+0800)
;; Last-Updated: 三 9月 16 10:37:33 2020 (+0800)
;;           By: Hongyi Wu(吴鸿毅)
;;     Update #: 2
;; URL: http://wuhongyi.cn -->

# TBuffer+

继承 TObject

Buffer base class used for serializing objects. 

## class

```cpp
   enum EMode { kRead = 0, kWrite = 1 };
   enum { kIsOwner = BIT(16) };                        //if set TBuffer owns fBuffer
   enum { kCannotHandleMemberWiseStreaming = BIT(17)}; //if set TClonesArray should not use member wise streaming
   enum { kInitialSize = 1024, kMinimalSize = 128 };

   TBuffer(EMode mode);
   TBuffer(EMode mode, Int_t bufsiz);
   TBuffer(EMode mode, Int_t bufsiz, void *buf, Bool_t adopt = kTRUE, ReAllocCharFun_t reallocfunc = 0);
   virtual ~TBuffer();

   Int_t    GetBufferVersion() const { return fVersion; }
   Bool_t   IsReading() const { return (fMode & kWrite) == 0; }
   Bool_t   IsWriting() const { return (fMode & kWrite) != 0; }
   void     SetReadMode();
   void     SetWriteMode();
   void     SetBuffer(void *buf, UInt_t bufsiz = 0, Bool_t adopt = kTRUE, ReAllocCharFun_t reallocfunc = 0);
   ReAllocCharFun_t GetReAllocFunc() const;
   void     SetReAllocFunc(ReAllocCharFun_t reallocfunc = 0);
   void     SetBufferOffset(Int_t offset = 0) { fBufCur = fBuffer+offset; }
   void     SetParent(TObject *parent);
   TObject *GetParent()  const;
   char    *Buffer()     const { return fBuffer; }
   Int_t    BufferSize() const { return fBufSize; }
   void     DetachBuffer() { fBuffer = 0; }
   Int_t    Length()     const { return (Int_t)(fBufCur - fBuffer); }
   void     Expand(Int_t newsize, Bool_t copy = kTRUE);  // expand buffer to newsize
   void     AutoExpand(Int_t size_needed);  // expand buffer to newsize

   virtual Bool_t     CheckObject(const TObject *obj) = 0;
   virtual Bool_t     CheckObject(const void *obj, const TClass *ptrClass) = 0;

   virtual Int_t      ReadBuf(void *buf, Int_t max) = 0;
   virtual void       WriteBuf(const void *buf, Int_t max) = 0;

   virtual char      *ReadString(char *s, Int_t max) = 0;
   virtual void       WriteString(const char *s) = 0;

   virtual Int_t      GetVersionOwner() const  = 0;
   virtual Int_t      GetMapCount() const  = 0;
   virtual void       GetMappedObject(UInt_t tag, void* &ptr, TClass* &ClassPtr) const = 0;
   virtual void       MapObject(const TObject *obj, UInt_t offset = 1) = 0;
   virtual void       MapObject(const void *obj, const TClass *cl, UInt_t offset = 1) = 0;
   virtual void       Reset() = 0;
   virtual void       InitMap() = 0;
   virtual void       ResetMap() = 0;
   virtual void       SetReadParam(Int_t mapsize) = 0;
   virtual void       SetWriteParam(Int_t mapsize) = 0;

   virtual Int_t      CheckByteCount(UInt_t startpos, UInt_t bcnt, const TClass *clss) = 0;
   virtual Int_t      CheckByteCount(UInt_t startpos, UInt_t bcnt, const char *classname) = 0;
   virtual void       SetByteCount(UInt_t cntpos, Bool_t packInVersion = kFALSE)= 0;

   virtual void       SkipVersion(const TClass *cl = 0) = 0;
   virtual Version_t  ReadVersion(UInt_t *start = 0, UInt_t *bcnt = 0, const TClass *cl = 0) = 0;
   virtual Version_t  ReadVersionNoCheckSum(UInt_t *start = 0, UInt_t *bcnt = 0) = 0;
   virtual Version_t  ReadVersionForMemberWise(const TClass *cl = 0) = 0;
   virtual UInt_t     WriteVersion(const TClass *cl, Bool_t useBcnt = kFALSE) = 0;
   virtual UInt_t     WriteVersionMemberWise(const TClass *cl, Bool_t useBcnt = kFALSE) = 0;

   virtual void      *ReadObjectAny(const TClass* cast) = 0;
   virtual void       SkipObjectAny() = 0;

   virtual void       TagStreamerInfo(TVirtualStreamerInfo* info) = 0;
   virtual void       IncrementLevel(TVirtualStreamerInfo* info) = 0;
   virtual void       SetStreamerElementNumber(TStreamerElement *elem, Int_t comp_type) = 0;
   virtual void       DecrementLevel(TVirtualStreamerInfo*) = 0;

   virtual void       ClassBegin(const TClass*, Version_t = -1) = 0;
   virtual void       ClassEnd(const TClass*) = 0;
   virtual void       ClassMember(const char*, const char* = 0, Int_t = -1, Int_t = -1) = 0;
   virtual TVirtualStreamerInfo *GetInfo() = 0;

   virtual TVirtualArray *PeekDataCache() const;
   virtual TVirtualArray *PopDataCache();
   virtual void           PushDataCache(TVirtualArray *);

   virtual TClass    *ReadClass(const TClass *cl = 0, UInt_t *objTag = 0) = 0;
   virtual void       WriteClass(const TClass *cl) = 0;

   virtual TObject   *ReadObject(const TClass *cl) = 0;
   virtual void       WriteObject(const TObject *obj) = 0;

   virtual Int_t      WriteObjectAny(const void *obj, const TClass *ptrClass) = 0;

   virtual UShort_t   GetPidOffset() const  = 0;
   virtual void       SetPidOffset(UShort_t offset) = 0;
   virtual Int_t      GetBufferDisplacement() const  = 0;
   virtual void       SetBufferDisplacement() = 0;
   virtual void       SetBufferDisplacement(Int_t skipped) = 0;

   // basic types and arrays of basic types
   virtual   void     ReadFloat16 (Float_t *f, TStreamerElement *ele=0) = 0;
   virtual   void     WriteFloat16(Float_t *f, TStreamerElement *ele=0) = 0;
   virtual   void     ReadDouble32 (Double_t *d, TStreamerElement *ele=0) = 0;
   virtual   void     WriteDouble32(Double_t *d, TStreamerElement *ele=0) = 0;
   virtual   void     ReadWithFactor(Float_t *ptr, Double_t factor, Double_t minvalue) = 0;
   virtual   void     ReadWithNbits(Float_t *ptr, Int_t nbits) = 0;
   virtual   void     ReadWithFactor(Double_t *ptr, Double_t factor, Double_t minvalue) = 0;
   virtual   void     ReadWithNbits(Double_t *ptr, Int_t nbits) = 0;

   virtual   Int_t    ReadArray(Bool_t    *&b) = 0;
   virtual   Int_t    ReadArray(Char_t    *&c) = 0;
   virtual   Int_t    ReadArray(UChar_t   *&c) = 0;
   virtual   Int_t    ReadArray(Short_t   *&h) = 0;
   virtual   Int_t    ReadArray(UShort_t  *&h) = 0;
   virtual   Int_t    ReadArray(Int_t     *&i) = 0;
   virtual   Int_t    ReadArray(UInt_t    *&i) = 0;
   virtual   Int_t    ReadArray(Long_t    *&l) = 0;
   virtual   Int_t    ReadArray(ULong_t   *&l) = 0;
   virtual   Int_t    ReadArray(Long64_t  *&l) = 0;
   virtual   Int_t    ReadArray(ULong64_t *&l) = 0;
   virtual   Int_t    ReadArray(Float_t   *&f) = 0;
   virtual   Int_t    ReadArray(Double_t  *&d) = 0;
   virtual   Int_t    ReadArrayFloat16(Float_t *&f, TStreamerElement *ele=0) = 0;
   virtual   Int_t    ReadArrayDouble32(Double_t *&d, TStreamerElement *ele=0) = 0;

   virtual   Int_t    ReadStaticArray(Bool_t    *b) = 0;
   virtual   Int_t    ReadStaticArray(Char_t    *c) = 0;
   virtual   Int_t    ReadStaticArray(UChar_t   *c) = 0;
   virtual   Int_t    ReadStaticArray(Short_t   *h) = 0;
   virtual   Int_t    ReadStaticArray(UShort_t  *h) = 0;
   virtual   Int_t    ReadStaticArray(Int_t     *i) = 0;
   virtual   Int_t    ReadStaticArray(UInt_t    *i) = 0;
   virtual   Int_t    ReadStaticArray(Long_t    *l) = 0;
   virtual   Int_t    ReadStaticArray(ULong_t   *l) = 0;
   virtual   Int_t    ReadStaticArray(Long64_t  *l) = 0;
   virtual   Int_t    ReadStaticArray(ULong64_t *l) = 0;
   virtual   Int_t    ReadStaticArray(Float_t   *f) = 0;
   virtual   Int_t    ReadStaticArray(Double_t  *d) = 0;
   virtual   Int_t    ReadStaticArrayFloat16(Float_t  *f, TStreamerElement *ele=0) = 0;
   virtual   Int_t    ReadStaticArrayDouble32(Double_t  *d, TStreamerElement *ele=0) = 0;

   virtual   void     ReadFastArray(Bool_t    *b, Int_t n) = 0;
   virtual   void     ReadFastArray(Char_t    *c, Int_t n) = 0;
   virtual   void     ReadFastArrayString(Char_t *c, Int_t n) = 0;
   virtual   void     ReadFastArray(UChar_t   *c, Int_t n) = 0;
   virtual   void     ReadFastArray(Short_t   *h, Int_t n) = 0;
   virtual   void     ReadFastArray(UShort_t  *h, Int_t n) = 0;
   virtual   void     ReadFastArray(Int_t     *i, Int_t n) = 0;
   virtual   void     ReadFastArray(UInt_t    *i, Int_t n) = 0;
   virtual   void     ReadFastArray(Long_t    *l, Int_t n) = 0;
   virtual   void     ReadFastArray(ULong_t   *l, Int_t n) = 0;
   virtual   void     ReadFastArray(Long64_t  *l, Int_t n) = 0;
   virtual   void     ReadFastArray(ULong64_t *l, Int_t n) = 0;
   virtual   void     ReadFastArray(Float_t   *f, Int_t n) = 0;
   virtual   void     ReadFastArray(Double_t  *d, Int_t n) = 0;
   virtual   void     ReadFastArrayFloat16(Float_t  *f, Int_t n, TStreamerElement *ele=0) = 0;
   virtual   void     ReadFastArrayDouble32(Double_t  *d, Int_t n, TStreamerElement *ele=0) = 0;
   virtual   void     ReadFastArrayWithFactor(Float_t *ptr, Int_t n, Double_t factor, Double_t minvalue) = 0;
   virtual   void     ReadFastArrayWithNbits(Float_t *ptr, Int_t n, Int_t nbits) = 0;
   virtual   void     ReadFastArrayWithFactor(Double_t *ptr, Int_t n, Double_t factor, Double_t minvalue) = 0;
   virtual   void     ReadFastArrayWithNbits(Double_t *ptr, Int_t n, Int_t nbits) = 0;
   virtual   void     ReadFastArray(void  *start , const TClass *cl, Int_t n=1, TMemberStreamer *s=0, const TClass *onFileClass=0) = 0;
   virtual   void     ReadFastArray(void **startp, const TClass *cl, Int_t n=1, Bool_t isPreAlloc=kFALSE, TMemberStreamer *s=0, const TClass *onFileClass=0) = 0;

   virtual   void     WriteArray(const Bool_t    *b, Int_t n) = 0;
   virtual   void     WriteArray(const Char_t    *c, Int_t n) = 0;
   virtual   void     WriteArray(const UChar_t   *c, Int_t n) = 0;
   virtual   void     WriteArray(const Short_t   *h, Int_t n) = 0;
   virtual   void     WriteArray(const UShort_t  *h, Int_t n) = 0;
   virtual   void     WriteArray(const Int_t     *i, Int_t n) = 0;
   virtual   void     WriteArray(const UInt_t    *i, Int_t n) = 0;
   virtual   void     WriteArray(const Long_t    *l, Int_t n) = 0;
   virtual   void     WriteArray(const ULong_t   *l, Int_t n) = 0;
   virtual   void     WriteArray(const Long64_t  *l, Int_t n) = 0;
   virtual   void     WriteArray(const ULong64_t *l, Int_t n) = 0;
   virtual   void     WriteArray(const Float_t   *f, Int_t n) = 0;
   virtual   void     WriteArray(const Double_t  *d, Int_t n) = 0;
   virtual   void     WriteArrayFloat16(const Float_t  *f, Int_t n, TStreamerElement *ele=0) = 0;
   virtual   void     WriteArrayDouble32(const Double_t  *d, Int_t n, TStreamerElement *ele=0) = 0;

   virtual   void     WriteFastArray(const Bool_t    *b, Int_t n) = 0;
   virtual   void     WriteFastArray(const Char_t    *c, Int_t n) = 0;
   virtual   void     WriteFastArrayString(const Char_t    *c, Int_t n) = 0;
   virtual   void     WriteFastArray(const UChar_t   *c, Int_t n) = 0;
   virtual   void     WriteFastArray(const Short_t   *h, Int_t n) = 0;
   virtual   void     WriteFastArray(const UShort_t  *h, Int_t n) = 0;
   virtual   void     WriteFastArray(const Int_t     *i, Int_t n) = 0;
   virtual   void     WriteFastArray(const UInt_t    *i, Int_t n) = 0;
   virtual   void     WriteFastArray(const Long_t    *l, Int_t n) = 0;
   virtual   void     WriteFastArray(const ULong_t   *l, Int_t n) = 0;
   virtual   void     WriteFastArray(const Long64_t  *l, Int_t n) = 0;
   virtual   void     WriteFastArray(const ULong64_t *l, Int_t n) = 0;
   virtual   void     WriteFastArray(const Float_t   *f, Int_t n) = 0;
   virtual   void     WriteFastArray(const Double_t  *d, Int_t n) = 0;
   virtual   void     WriteFastArrayFloat16(const Float_t  *f, Int_t n, TStreamerElement *ele=0) = 0;
   virtual   void     WriteFastArrayDouble32(const Double_t  *d, Int_t n, TStreamerElement *ele=0) = 0;
   virtual   void     WriteFastArray(void  *start,  const TClass *cl, Int_t n=1, TMemberStreamer *s=0) = 0;
   virtual   Int_t    WriteFastArray(void **startp, const TClass *cl, Int_t n=1, Bool_t isPreAlloc=kFALSE, TMemberStreamer *s=0) = 0;

   virtual   void     StreamObject(void *obj, const type_info &typeinfo, const TClass* onFileClass = 0 ) = 0;
   virtual   void     StreamObject(void *obj, const char *className, const TClass* onFileClass = 0 ) = 0;
   virtual   void     StreamObject(void *obj, const TClass *cl, const TClass* onFileClass = 0 ) = 0;
   virtual   void     StreamObject(TObject *obj) = 0;

   virtual   void     ReadBool(Bool_t       &b) = 0;
   virtual   void     ReadChar(Char_t       &c) = 0;
   virtual   void     ReadUChar(UChar_t     &c) = 0;
   virtual   void     ReadShort(Short_t     &s) = 0;
   virtual   void     ReadUShort(UShort_t   &s) = 0;
   virtual   void     ReadInt(Int_t         &i) = 0;
   virtual   void     ReadUInt(UInt_t       &i) = 0;
   virtual   void     ReadLong(Long_t       &l) = 0;
   virtual   void     ReadULong(ULong_t     &l) = 0;
   virtual   void     ReadLong64(Long64_t   &l) = 0;
   virtual   void     ReadULong64(ULong64_t &l) = 0;
   virtual   void     ReadFloat(Float_t     &f) = 0;
   virtual   void     ReadDouble(Double_t   &d) = 0;
   virtual   void     ReadCharP(Char_t      *c) = 0;
   virtual   void     ReadTString(TString   &s) = 0;
   virtual   void     ReadStdString(std::string &s) = 0;

   virtual   void     WriteBool(Bool_t       b) = 0;
   virtual   void     WriteChar(Char_t       c) = 0;
   virtual   void     WriteUChar(UChar_t     c) = 0;
   virtual   void     WriteShort(Short_t     s) = 0;
   virtual   void     WriteUShort(UShort_t   s) = 0;
   virtual   void     WriteInt(Int_t         i) = 0;
   virtual   void     WriteUInt(UInt_t       i) = 0;
   virtual   void     WriteLong(Long_t       l) = 0;
   virtual   void     WriteULong(ULong_t     l) = 0;
   virtual   void     WriteLong64(Long64_t   l) = 0;
   virtual   void     WriteULong64(ULong64_t l) = 0;
   virtual   void     WriteFloat(Float_t     f) = 0;
   virtual   void     WriteDouble(Double_t   d) = 0;
   virtual   void     WriteCharP(const Char_t *c) = 0;
   virtual   void     WriteTString(const TString &s) = 0;
   virtual   void     WriteStdString(const std::string &s) = 0;

   // Special basic ROOT objects and collections
   virtual   TProcessID *GetLastProcessID(TRefTable *reftable) const = 0;
   virtual   UInt_t      GetTRefExecId() = 0;
   virtual   TProcessID *ReadProcessID(UShort_t pidf) = 0;
   virtual   UShort_t    WriteProcessID(TProcessID *pid) = 0;

   // Utilities for TStreamerInfo
   virtual   void     ForceWriteInfo(TVirtualStreamerInfo *info, Bool_t force) = 0;
   virtual   void     ForceWriteInfoClones(TClonesArray *a) = 0;
   virtual   Int_t    ReadClones (TClonesArray *a, Int_t nobjects, Version_t objvers) = 0;
   virtual   Int_t    WriteClones(TClonesArray *a, Int_t nobjects) = 0;

   // Utilities for TClass
   virtual   Int_t    ReadClassEmulated(const TClass *cl, void *object, const TClass *onfile_class = 0) = 0;
   virtual   Int_t    ReadClassBuffer(const TClass *cl, void *pointer, const TClass *onfile_class = 0) = 0;
   virtual   Int_t    ReadClassBuffer(const TClass *cl, void *pointer, Int_t version, UInt_t start, UInt_t count, const TClass *onfile_class = 0) = 0;
   virtual   Int_t    WriteClassBuffer(const TClass *cl, void *pointer) = 0;

   // Utilites to streamer using sequences.
   virtual Int_t ApplySequence(const TStreamerInfoActions::TActionSequence &sequence, void *object) = 0;
   virtual Int_t ApplySequenceVecPtr(const TStreamerInfoActions::TActionSequence &sequence, void *start_collection, void *end_collection) = 0;
   virtual Int_t ApplySequence(const TStreamerInfoActions::TActionSequence &sequence, void *start_collection, void *end_collection) = 0;

   static TClass *GetClass(const type_info &typeinfo);
   static TClass *GetClass(const char *className);
```


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