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Reference Guide
TMemFile.h
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1 // @(#)root/io:$Id$
2 // Author: Philippe Canal, May 2011
3 
4 /*************************************************************************
5  * Copyright (C) 1995-2009, Rene Brun and Fons Rademakers. *
6  * All rights reserved. *
7  * *
8  * For the licensing terms see $ROOTSYS/LICENSE. *
9  * For the list of contributors see $ROOTSYS/README/CREDITS. *
10  *************************************************************************/
11 
12 #ifndef ROOT_TMemFile
13 #define ROOT_TMemFile
14 
15 #include "TFile.h"
16 #include <vector>
17 #include <memory>
18 
19 class TMemFile : public TFile {
20 public:
21  using ExternalDataPtr_t = std::shared_ptr<const std::vector<char>>;
22 
23 private:
24  struct TMemBlock {
25  private:
26  TMemBlock(const TMemBlock&); // Not implemented
27  TMemBlock &operator=(const TMemBlock&); // Not implemented.
28  public:
29  TMemBlock();
30  TMemBlock(Long64_t size, TMemBlock *previous = 0);
31  TMemBlock(UChar_t* externalBuffer, Long64_t size);
32  ~TMemBlock();
33 
34  void CreateNext(Long64_t size);
35 
40  };
41  TMemBlock fBlockList; ///< Collection of memory blocks of size fgDefaultBlockSize
42  const ExternalDataPtr_t fExternalData; ///< shared file data / content
43  Long64_t fSize; ///< Total file size (sum of the size of the chunks)
44  Long64_t fSysOffset; ///< Seek offset in file
45  TMemBlock *fBlockSeek; ///< Pointer to the block we seeked to.
46  Long64_t fBlockOffset; ///< Seek offset within the block
47 
49 
50  Long64_t MemRead(Int_t fd, void *buf, Long64_t len) const;
51 
52  // Overload TFile interfaces.
53  Int_t SysOpen(const char *pathname, Int_t flags, UInt_t mode);
54  Int_t SysClose(Int_t fd);
55  Int_t SysReadImpl(Int_t fd, void *buf, Long64_t len);
56  Int_t SysWriteImpl(Int_t fd, const void *buf, Long64_t len);
57  Int_t SysRead(Int_t fd, void *buf, Int_t len);
58  Int_t SysWrite(Int_t fd, const void *buf, Int_t len);
59  Long64_t SysSeek(Int_t fd, Long64_t offset, Int_t whence);
60  Int_t SysStat(Int_t fd, Long_t *id, Long64_t *size, Long_t *flags, Long_t *modtime);
61  Int_t SysSync(Int_t fd);
62 
64 
65  enum class EMode {
66  kCreate,
67  kRecreate,
68  kUpdate,
69  kRead
70  };
71 
72  bool NeedsToWrite(EMode mode) const { return mode != EMode::kRead; }
73  bool NeedsExistingFile(EMode mode) const { return mode == EMode::kUpdate || mode == EMode::kRead; }
74 
75  EMode ParseOption(Option_t *option);
76 
77  TMemFile &operator=(const TMemFile&); // Not implemented.
78 
79 public:
80  TMemFile(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=1);
81  TMemFile(const char *name, char *buffer, Long64_t size, Option_t *option="", const char *ftitle="", Int_t compress=1);
82  TMemFile(const char *name, ExternalDataPtr_t data);
83  TMemFile(const TMemFile &orig);
84  virtual ~TMemFile();
85 
86  virtual Long64_t CopyTo(void *to, Long64_t maxsize) const;
87  virtual void CopyTo(TBuffer &tobuf) const;
88  virtual Long64_t GetSize() const;
89 
91  void ResetErrno() const;
92 
93  virtual void Print(Option_t *option="") const;
94 
95  ClassDef(TMemFile, 0) // A ROOT file that reads/writes on a chunk of memory
96 };
97 
98 #endif
void ResetAfterMerge(TFileMergeInfo *)
Wipe all the data from the permanent buffer but keep, the in-memory object alive. ...
Definition: TMemFile.cxx:298
~TMemBlock()
Usual destructors. Delete the block memory.
Definition: TMemFile.cxx:80
Int_t SysOpen(const char *pathname, Int_t flags, UInt_t mode)
Open a file in &#39;MemFile&#39;.
Definition: TMemFile.cxx:551
Long64_t fSysOffset
Seek offset in file.
Definition: TMemFile.h:44
Long64_t fSize
Total file size (sum of the size of the chunks)
Definition: TMemFile.h:43
long long Long64_t
Definition: RtypesCore.h:69
const char Option_t
Definition: RtypesCore.h:62
Int_t SysClose(Int_t fd)
Close the mem file.
Definition: TMemFile.cxx:568
Long64_t fBlockOffset
Seek offset within the block.
Definition: TMemFile.h:46
UChar_t * fBuffer
Definition: TMemFile.h:38
TMemBlock * fPrevious
Definition: TMemFile.h:36
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format...
Definition: TFile.h:47
Buffer base class used for serializing objects.
Definition: TBuffer.h:40
Int_t SysWrite(Int_t fd, const void *buf, Int_t len)
Write a buffer into the file.
Definition: TMemFile.cxx:640
int Int_t
Definition: RtypesCore.h:41
virtual void Print(Option_t *option="") const
Print all objects in the file.
Definition: TMemFile.cxx:276
A TMemFile is like a normal TFile except that it reads and writes only from memory.
Definition: TMemFile.h:19
#define ClassDef(name, id)
Definition: Rtypes.h:320
void ResetErrno() const
Simply calls TSystem::ResetErrno().
Definition: TMemFile.cxx:666
TMemBlock()
Default constructor.
Definition: TMemFile.cxx:48
Int_t SysSync(Int_t fd)
Sync remaining data to disk.
Definition: TMemFile.cxx:658
Long64_t MemRead(Int_t fd, void *buf, Long64_t len) const
void tobuf(char *&buf, Bool_t x)
Definition: Bytes.h:57
const ExternalDataPtr_t fExternalData
shared file data / content
Definition: TMemFile.h:42
bool NeedsToWrite(EMode mode) const
Definition: TMemFile.h:72
virtual Long64_t GetSize() const
Return the current size of the memory file.
Definition: TMemFile.cxx:268
Int_t SysRead(Int_t fd, void *buf, Int_t len)
Read specified number of bytes from current offset into the buffer.
Definition: TMemFile.cxx:466
A ROOT file is structured in Directories (like a file system).
std::shared_ptr< const std::vector< char > > ExternalDataPtr_t
Definition: TMemFile.h:21
TMemBlock * fBlockSeek
Pointer to the block we seeked to.
Definition: TMemFile.h:45
TMemBlock * fNext
Definition: TMemFile.h:37
unsigned int UInt_t
Definition: RtypesCore.h:42
Int_t SysStat(Int_t fd, Long_t *id, Long64_t *size, Long_t *flags, Long_t *modtime)
Perform a stat on the HDFS file; see TFile::SysStat().
Definition: TMemFile.cxx:648
TMemBlock fBlockList
Collection of memory blocks of size fgDefaultBlockSize.
Definition: TMemFile.h:41
virtual ~TMemFile()
Close and clean-up file.
Definition: TMemFile.cxx:214
void ResetObjects(TDirectoryFile *, TFileMergeInfo *) const
Wipe all the data from the permanent buffer but keep, the in-memory object alive. ...
Definition: TMemFile.cxx:365
long Long_t
Definition: RtypesCore.h:50
Long64_t SysSeek(Int_t fd, Long64_t offset, Int_t whence)
Seek to a specified position in the file.
Definition: TMemFile.cxx:475
static Long64_t fgDefaultBlockSize
Definition: TMemFile.h:48
void CreateNext(Long64_t size)
Definition: TMemFile.cxx:88
Long64_t fSize
Definition: TMemFile.h:39
EMode ParseOption(Option_t *option)
Parse option strings and set fOption.
Definition: TMemFile.cxx:96
Int_t SysReadImpl(Int_t fd, void *buf, Long64_t len)
Read specified number of bytes from current offset into the buffer.
Definition: TMemFile.cxx:408
bool NeedsExistingFile(EMode mode) const
Definition: TMemFile.h:73
TMemFile(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=1)
Usual Constructor. See the TFile constructor for details.
Definition: TMemFile.cxx:142
unsigned char UChar_t
Definition: RtypesCore.h:34
virtual Long64_t CopyTo(void *to, Long64_t maxsize) const
Copy the binary representation of the TMemFile into the memory area starting at &#39;to&#39; and of length at...
Definition: TMemFile.cxx:233
char name[80]
Definition: TGX11.cxx:109
TMemBlock & operator=(const TMemBlock &)
Int_t SysWriteImpl(Int_t fd, const void *buf, Long64_t len)
Write a buffer into the file.
Definition: TMemFile.cxx:576